Potential applications of alginate oligosaccharides for biomedicine – A mini review

Carbohydrate Polymers 271 (2021) 118408

Contents lists available at ScienceDirect

Carbohydrate Polymers
journal homepage: www.elsevier.com/locate/carbpol

Potential applications of alginate oligosaccharides for biomedicine – A
mini review
Mingpeng Wang a, Lei Chen a, *, Zhaojie Zhang b
a
b

College of Life Science, Qufu Normal University, Qufu 273100, China
Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, USA

A R T I C L E I N F O

A B S T R A C T

Keywords:
Alginate oligosaccharides
Brown algae
Health-promoting
Biomedicine

Extensive research on marine algae, especially on their health-promoting properties, has been conducted.
Various ingredients with potential biomedical applications have been discovered and extracted from marine
algae. Alginate oligosaccharides are low molecular weight alginate polysaccharides present in cell walls of brown
algae. They exhibit various health benefits such as anti-inflammatory, anti-microbial, anti-oxidant, anti-tumor
and immunomodulation. Their low-toxicity, non-immunogenicity, and biodegradability make them an excellent

material in biomedicine. Alginate oligosaccharides can be chemically or biochemically modified to enhance their
biological activity and potential in pharmaceutical applications. This paper provides a brief overview on alginate
oligosaccharides characteristics, modification patterns and highlights their vital health promoting properties.

1. Introduction
Brown algae are a large group of multicellular algae and one of the
essential and integral components of the marine ecosystem (Lavaud &
Goss, 2014). They are biologically diverse, with thousands of different
species, forming the dominant vegetation in the intertidal and subtidal
zone of rocky shores (Bartsch et al., 2008). They live from coastalestuarine to deep-sea regions and have many unique features, such as
fast growth, distinctive structure, strong adaptiveness, and wide distri­
bution. Their ecological significance is based in part on their contribu­
tions to marine biomass and marine carbon cycling (Lavaud & Goss,
2014). Brown algae provide food and habitats for many other organisms
and promote the prosperity of the entire marine biosphere (de Mesquita
et al., 2018; Santelices, 2007). Brown algae are also economically
important for human beings as a kind of food, especially in Asian
countries. In addition, they are used as natural feed or fertilizer due to
their high mineral and trace elements, and as a source of biological
products such as alginates, mannitol and iodine (Afonso et al., 2019;
Arioli et al., 2015; Overland et al., 2019; Salehi et al., 2019). Brown
algae have tremendous potential as a source of novel functional com­
ponents that are not present in terrestrial plants. More recently, the
valuable ingredients extracted from brown algae, e.g. alginates, fucoi­
dan and laminaran, have been explored for nutrient and drug develop­
ment (Ford et al., 2020; Garcia-Vaquero et al., 2018; Generali´c Mekini´c

et al., 2019; Gunathilaka et al., 2020; Saraswati et al., 2019; Thanh et al.,
2013; Zou et al., 2019).
Alginate is a linear acidic polysaccharide distributed widely in cell

walls of brown algae (Sari-Chmayssem et al., 2015; Synytsya et al.,
2015). Alginate consists of hexuronic acid residues β-D-mannuronic acid
(M) and α-L-guluronic acid (G) with exclusively 1 → 4 glycosidic link­
ages. Its chelation, gelation, and hydrophilic properties have led to its
wide application in food, cosmetic and biomedical industries (Donati &
Paoletti, 2009; Lee & Mooney, 2012). Increasing evidence indicates that,
when used as a therapeutic adjuvant, drug carrier, wound healing ma­
terial and biological scaffold, alginate could improve antitumor immune
efficacy in ovarian cancer, melanoma, liver cancer, and breast cancer
(Fan et al., 2019). However, the direct therapeutic effects of alginate in
biomedical applications have been greatly limited due to its macromo­
lecular structure, poor solubility and low bioavailability (Zhu et al.,
2020). Alginate can be digested chemically or enzymatically, producing
alginate oligosaccharides (AOS), which have lower molecular weights
and lower viscosity. AOS have better solubility and bioavailability
(Trincone, 2015). As a consequence, particular interest has been focused
on AOS due to their better pharmacological activities and beneficial
effects in biomedicine.
In this paper, we present an overview of the structure, biological
activities and modification patterns of AOS. We also discuss the recent
developments of using AOS in treating chronic and degenerative

* Corresponding author at: Qufu Normal University, 57 Jingxuan West Road, Qufu, China.
E-mail address: (L. Chen).
/>Received 7 April 2021; Received in revised form 23 June 2021; Accepted 3 July 2021
Available online 8 July 2021
0144-8617/© 2021 The Author(s).
Published by Elsevier Ltd.
This
( />

is

an

open

access

article

under

the

CC

BY-NC-ND

license


M. Wang et al.

Carbohydrate Polymers 271 (2021) 118408

Fig. 1. The structure of alginate and AOS: monomers; chain conformation and fragments of AOS product. 2 ≤ n ≤ 25.

diseases, modulating human gut microbiota and promoting curative
effect of traditional drugs as therapeutic adjuvant or drug carrier.

formation of poly G (Mackie et al., 1983; Plazinski, 2011). Generally, the
poly G involving axial linkage is more rigid than the equatorially linked
poly M.

2. Structure and modification patterns of alginate
oligosaccharides

2.2. Production of AOS from alignate

2.1. Structure of AOS

At present, the three main methods for AOS production are acid
hydrolysis (AH), oxidative degradation (OD) and enzymatic digestion
(ED). Each method has its own advantages and limitations.
The main feature of acid hydrolysis of alginate is that it results in
random cleavage along the polysaccharide chains and produces AOS
fragments with unmodified hexuronic acid residues at both termini
(Fig. 2). Therefore, the AOS produced by acid hydrolysis can maintain
the inherent structure of alginate. Acid hydrolysis has been widely used
for producing a series of AOS with different degrees of polymerization
because of its low cost, ease of control, simplicity and availability.
However, only under high temperature and pressure conditions can AOS
with molecular weight below 4000 be obtained through acid hydrolysis.
In addition, a large number of inorganic salts are generated during the
final neutralization stage of acid hydrolysis. The application of acid
hydrolysis has been limited due to equipment corrosion, high energy
consumption and residue waste pollution.
Another chemical degradation method is oxidative degradation,
which has higher reaction efficiency and high yield compared to acid
hydrolysis. As an easily degradable reagent that creates only water as an

oxidation by-product, hydrogen peroxide (H2O2) has been widely used
to produce functional AOS with high purity and quality. As shown in
Fig. 2, AOS residues are easily ring-opened at the reducing end to form
carboxyl group during the oxidative degradation. This additional
carboxyl radical could induce novel bioactivities of oxidative AOS. Zhou
et al. reported that guluronate oligosaccharide (GOS) prepared by
oxidative degradation (GOS-OD), but not GOS produced by acid hy­
drolysis or enzymatic digestion, significantly reduced the lipopolysac­
charide (LPS)-stimulated overproduction of nitric oxide (NO) in RAW

As a degradation product of alginate, AOS are a mixture of linear
oligomers, which consist of β-D-mannuronic acid (M) and α-L-guluronic
acid (G) (Fig. 1) at different ratios and degrees of polymerization (DP)
(Rioux & Turgeon, 2015). The overall composition of the two uronic
acids and their distribution along the oligomer chain vary widely
depending on the species of algae and influence the properties of AOS.
As shown in Fig. 1, three types of oligomer blocks (2 ≤ DP ≤ 25) are
typically obtained: M, G, and mixed MG blocks, according to different
source and degradation methods.
Structurally, the monomeric units M and G are a pair of C-5 epimers
due to their different orientation of carboxyl group at the C-5 position
(Grasdalen, 1983). The molecular formula of M or G units is C6H10O7
and the conversion relationships of AOS relative molecular weight (Mr)
and the degree of polymerization can be described as shown in Eq. (1):
Mr = DP⋅Mr (C6 H10 O7 ) − (DP − 1)⋅Mr (H2 O)

(1)

When the atomic weights of carbon, hydrogen and oxygen, and the
molecular weights of H2O are plugged into the formula, the DP can be

calculated using Eq. (2):
DP = (Mr − 18)/176

(2)

Finally, the epimerization at C-5 results in significant differences in
spatial structure and physicochemical properties of their oligomers,
respectively. The equatorial configuration of the β-1,4-glycosidic bond
predestines a stretched chain conformation of poly M while the axial
linkage of the α-1,4-glycosidic bond implicates the tendency to helix
2


M. Wang et al.

Carbohydrate Polymers 271 (2021) 118408

Fig. 2. The different structures of AOS fragments produced by three degradation methods and hypothetical structure of modified AOS.

264.7 cells (Zhou et al., 2015). The existence of the additional carboxyl
group may play an important role in the NO-inhibitory and subsequent
anti-inflammation effect of GOS-OD.
The enzymatic digestion may be the most promising method for
producing AOS due to its key advantages such as site-specific cleavage
reaction, mild reaction conditions, efficient reaction rate, and high re­
action yields. Alginate lyases are key enzymes that specially catalyze the
degradation of alginate. They break the O–C4 bond to uronic acid
residues through a β-elimination reaction that leads to formation of the
4,5-unsaturated hexuronic acid residue at the non-reducing terminus
(Fig. 2). This unsaturated terminal structure with a C4–C5 double bond

can be detected at 230 nm. The unsaturated AOS have various novel
bioactivities such as antioxidant, anti-tumor, neuroprotective and
immuno-stimulation (Iwamoto et al., 2003; Iwamoto et al., 2005; Tusi
et al., 2011). Compared with saturated AOS, the unsaturated AOS
showed efficient anti-obesity effects in high-fat diet (HFD)-fed mice
through activating the AMPK signaling pathway (Li et al., 2019).
Although the enzymatic digestion of alginate has various advantages
and bright application prospects, most studies are still at laboratory
level. The discovery and development of novel enzymes with high yield,

activity and stability is still in high demand for the achievement of in­
dustrial production of AOS.
2.3. Modification of AOS
Recently, various approaches, i.e. vanadylation, sulfation, selenyla­
tion or oxidation, have been used to modify the backbone of AOS and
improve their physicochemical and biological properties. For example,
vanadyl AOS (VAOS) presents a higher antioxidant activity than un­
modified AOS in hydroxyl and DPPH radical scavenging systems (Liu
et al., 2015). In addition, VAOS exhibited strong anti-proliferation ac­
tivities against human hepatoma cell line BEL-7402. VAOS could
markedly inhibit tumor progression in non-small cell lung cancer
(NSCLC) (Zhou et al., 2018). It was synthesized through slowly adding
vanadium (IV) oxide sulfate hydrate into the AOS solution under con­
dition of constant stirring and pH 12 during whole process. The vana­
dium content of VAOS could reach to about 3.0%. According to FT-IR
spectral analysis, introduction of vanadyl groups changed the absorp­
tion peak of different functional groups of the oligosaccharide chain
– O and C–O. A similar infrared shift has also been
such as C–O–C, C–
3

M. Wang et al.

Carbohydrate Polymers 271 (2021) 118408

found in FT-IR spectra of vanadyl (IV)/chondroitin sulfate A (CSA)
complex (Etcheverry et al., 1994). Although the exact structure of VAOS
remains to be determined, it is believed that VAOS is a new type of
coordination compound rather than a covalent compound based on the
available data. As previously reported, the FT-IR spectra in this study
indicate the hypothetical structure of VAOS in the form of coordination
through the hydroxyl oxygen of carboxylate group and the glycosidic
oxygen of G or M moieties (Etcheverry et al., 1994; Etcheverry et al.,
– C–O occupy
1997). As shown in Fig. 2, both the C–O–C and the O–
two coordination positions. This speculated coordination structure may
play a key role in improving the bioavailability of vanadium and
bioactivity of AOS. The definite structure-function relationship of VAOS
requires further investigation.
A recent study of selenium-containing alginate oligosaccharides (Bi
et al., 2020) showed that the modification of AOS was driven by two
reaction steps: Poly M and SO3-Py were each suspended in dimethyl
methanamide, and then the two solutions were mixed and reacted to
obtain the sulfonated Poly M (S-PM) in the sulfonation step; while in the
selenylation step, the sulfur in S-PM was partially replaced by Se
through reacting with Na2SeO3 in the presence of excess barium chloride
(BaCl2) in 5% HNO3 at 60 ◦ C for 8 h. According to the FT-IR spectra of
– O and C–O–S
PM, S-PM, and Se-PM, the specific absorption of S–

detected only in S-PM and Se-PM, confirming that the sulfation substi­
tution was successfully prepared. Furthermore, the spectrum of Se-PM is
similar to that of S-PM, which suggests that their carbon-skeleton
structure was the same. In addition, the measured S content in Se-PM
decreased to about 60% of that in S-PM, implying that some S bound
is replaced by Se. Therefore, they speculated that Se might be in the form
of -SeO3 covalently bound to sites that were originally occupied by S
(Fig. 2). As a new covalent compound, Se-PM combines the advantages
of Se and AOS and exhibits various bioactivities including antioxidation, anti-inflammation and neuroprotection that are superior to
those of Se itself or Se-free oligosaccharides (Bi et al., 2019; Bi, Lai, Cai,
et al., 2018; Bi, Lai, Han, et al., 2018). The resultant low molecular
weight Se-PM exhibited enhanced neuroimmunoregulatory activity in
LPS-induced BV2 microglia probably due to the covalent structure
formed during the replacement process that could attenuate the nitric
oxide (NO) and prostaglandin E2 (PGE2) secretion, as well as the
inducible NO synthase-20 (iNOS) and cyclooxygenase-2 (COX-2)
expression, depending on the treatment dose.
A different kind of sulfated mannuronate oligosaccharides (S-MOS)
were developed by reacting mannuronate oligomers with ClSO3H in
formamide (Liu et al., 2005). 13C-nuclear magnetic resonance (NMR)
analysis suggested that sulfate modification of mannuronate occurs at
the hydroxyl groups of C-2 and partial C-3 with different degrees of
substitution.

by the same degradation patterns, still exhibited distinct biological ac­
tivities. Interestingly, AOS with anti-obesity effects tend to have a lower
average DP, usually no more than 4 in many reports (Guo et al., 2016,
2017; Li et al., 2019; Nakazono et al., 2016; Wang et al., 2020).
2.4.2. G/M ratio
Xu et al. reported that the unsaturated guluronate oligosaccharides

(GOS) prepared by enzymatic digestion exhibited macrophagesactivating effect in mouse immune response while GOS prepared by
other methods or mannuronate oligosaccharides (MOS) showed very
low or no such effects (Xu, Wu, et al., 2014). A series of studies have
shown the potential of the guluronate rich alginate OligoG CF-5/20
(containing >85% G residues) as an effective treatment in chronic res­
piratory disease (Nordgård & Draget, 2011; Pritchard et al., 2016;
Pritchard et al., 2019; Sletmoen et al., 2012). The OligoG could directly
interact with mucin and reduce its linearization and flexibility, leading
to effective detachment of cystic fibrosis (CF) mucus (Ermund et al.,
2017; Pritchard et al., 2016).
MOS on the other hand, plays important roles in the treatment of
human melanoma and Alzheimer's disease (AD). MOS produced by Mspecific alginate lyase strongly inhibits anchorage-independent colony
formation of human melanoma cells compared to polymannuronate and
GOS (Belik et al., 2020). It is suggested that MOS might be a potential
drug candidate for synergistic tumor therapy. More recently, two groups
demonstrated that MOS (DP2-DP11) could significantly inhibit the ag­
gregation of amyloid-β (Aβ) oligomer and Aβ fibril formation, although
their respective MOS samples were prepared by different methods (Bi
et al., 2021; Wang et al., 2019). Their results suggested the mannuronate
component and proper DP may play pivotal roles in alleviating AD.
In addition, G/M ratio may determine spatial conformation of AOS
and affect their gelation, mechanical properties and biological activity.
As mentioned in 2.1, G block has a tendency to form a helical confor­
mation while M block has a relatively straight chain-like conformation
due to their different linkage at C-1 and C-4 (Mackie et al., 1983; Pla­
zinski, 2011). Alginate with higher M residues was characterized by
higher tensile strength and percent of elongation than alginate with
dominated G bocks (Costa et al., 2018). It is well-known that alginates
containing G-blocks can form strong hydrogels in the presence of diva­
lent cations such as calcium in the so-called egg-box model (Grant et al.,

1973). However, several reports also indicate that such cooperative
ionotropic gelation only occurs when the length of the G blocks involved
in the dimerization exceeds a certain length (Skjåk-Bræk et al., 1986;
Smidsrød & Haug, 1972). For example, 3 and 8 ± 2 contiguous G resi­
dues are required to form stable junction zones for Sr2+- and Ca2+induced gelation respectively (Stokke et al., 1991; Stokke et al., 1993).
Thus, AOS with low G/M ratio and DP might not form stable crosslinking
conformation even in the presence of divalent cations and maintain high
water solubility which is conducive to their delivery in vivo while AOS
with higher DP and GM ratio may maintain gel-forming property similar
to alginate, which makes them have potential application as drug car­
riers. G blocks normally form stiffer, brittle, and mechanically more
stable gels. On the contrary, M blocks form a softer and more elastic gel
(Ashikin et al., 2010). As a potential drug carrier candidate, MOS were
added in an alginate-based drug delivery system, which improved me­
chanical properties and antifungal activity of the whole delivery system
(Szekalska et al., 2019). The flexible conformation of MOS may facilitate
penetration into bacterial cells and makes them show better antimi­
crobial effect than GOS, which usually forms stiff chains (Hu et al.,
2005).

2.4. Structure-function relatioship of AOS
The size, composition and structure of AOS vary due to algal species
(Guo et al., 2016; Li, Jiang, Guan, & Wang, 2011), degradation patterns
(Li et al., 2019; Wang et al., 2019) and modification methods (Bi et al.,
2020; Liu et al., 2015). The structural features of AOS, including degrees
of polymerization, the G/M ratio, residue structure and spatial confor­
mation, are responsible for biological functions of AOS. The following
are some examples that reflect structure-function relationship of AOS.
2.4.1. DP
AOS DP5 (pentamer composed of randomly arranged G and M) ob­

tained by enzymatic digestion rather than AOS DP2, DP3 or DP4,
exhibited significant inhibitory functions on the growth of osteosarcoma
cells in vitro (Chen et al., 2017). Unsaturated guluronate oligomers
(DP3–DP6) significantly enhanced the bacterial phagocytosis of mac­
rophages, especially GOS DP5 (the guluronate pentamer) showed the
maximum enhancement among all oligomers measured (Xu, Bi, et al.,
2014). These studies suggested that AOS with different DP, even derived

2.4.3. Special terminal structure
AOS derived by enzymatic digestion usually have unsaturated
structure at non-reducing end while AOS obtained by oxidative degra­
dation are always ring-opened at reducing end to form carboxyl groups
(Fig. 2). The unsaturated and oxidative terminal structure are key fac­
tors determining biological function of AOS.
4


M. Wang et al.

Carbohydrate Polymers 271 (2021) 118408

(Wang et al., 2019). These studies suggest that the molecular mecha­
nisms of AOS are greatly affected by different terminal structures.
It also suggests that there is a direct relationship between structural
characteristics of AOS and their biological activities. The molecular size,
G/M ratio and terminal structure play important roles in determining
the biological functions and action modes of AOS.
In order to obtain AOS products with stable structure and unique
function, several important aspects need to be considered: 1) The source
of alginate; The G/M ratio, content and order of alginate are always

different due to algal species and their respective environments. Algi­
nate derived from Laminaria japonica with an M/G ratio of 1.86 (Guo
et al., 2016) was degraded by alginate lyase from Pseudomonas sp. HZJ
216 for 6 h at 30 ◦ C, producing AOS with DP 2 to 6. However, when the
alginate source changed to another brown seaweed, Laminaria sp. with
M/G ratio of 2.28, AOS products were mainly oligomers of DP 2 and 3
under exactly the same degradation conditions (Li, Jiang, Guan, &
Wang, 2011). Therefore, the uniform alginate source is a prerequisite for
obtaining stable AOS. 2) Production technology; Production techniques
greatly affect the structural properties and biological functions of AOS
products. For example, the type of alginate lyase is the most essential
factor affecting the final product in enzymatic technique. An alginate
lyase that could specially produce AOS with DP 5 to 7 was reported
(Huang et al., 2013). Recently, two mannuronate-specific alginate lyase
were found in a marine bacterium Formosa algae and the human gut
microbe Bacteroides cellulosilyticus (Belik et al., 2020; Stender et al.,
2019). These alginate lyases can be applied to produce special AOS
products. The development and standardization of efficient and stable
production technology is the key to ensure the quality, yield and variety
of AOS products. 3) Purification and characterization methods; In most
cases, AOS are mixtures of oligomers with varied DP, different G/M
ratios and sequences. Thus, it is very important to develop purification
and analytical methods for qualification and quantification of AOS.
Nowadays, FT-IR and NMR spectroscopy are widely used to obtain

Table 1
Anti-tumor activities of AOS.
Mechanism of anti-tumor

Cancer style and Cell line

Reference

Inhibition of cell growth and
colony formation

Human bone cancer cell MG-63

Chen et al.
(2017)
Belik et al.
(2020)
Han et al.
(2019)
Yang et al.
(2017)
Arlov et al.
(2015)
Zhou et al.
(2018)
Arlov et al.
(2015)

Human melanoma cells SK-MEL-5,
SK-MEL-28, and RPMI-7951
Human prostate cancer cells
DU145 and PC-3
Human aneurysm
Human myeloma RPMI-8226 cells

Induction of cell apoptosis
Reduction of angiogenesis
induced by HGF

Human non-small cell lung cancer
cells A549 and LTEP-a-2
Human myeloma RPMI-8226 cells

The unsaturated mannuronate oligosaccharides (UMOS) predomi­
nantly contains mannuronic acids (M/G ratio = 2.12) and exhibits su­
perior anti-obesity effect via suppressing the accumulation of
triglycerides and improving the intestinal microflora (Kim, 2018). The
unsaturated alginate oligosaccharides (UAOS) also exhibited significant
anti-obesity effect (Li et al., 2019). Moreover, this anti-obesity effect was
only related to the unsaturated structure but independent of the G or M
composition.
MOS derived from enzymatic digestion and oxidative degradation
exhibited a similar inhibition to Aβ oligomer aggregation. However, the
underlying molecular mechanisms of these two kind MOS in the treat­
ment of AD were different, although their DP and G/M ratio were very
similar. The unsaturated MOS enhanced autophagy to promote clear­
ance of amyloid precursor protein (APP) and Aβ in AD cell models (Bi
et al., 2021) while the oxidative MOS reconstituted gut microbiota and
improved anti-neuroinflammation responses to inhibit AD progression

Fig. 3. The proposed mechanism of AOS for suppressing the tumorigenicity of prostate cancer cells.
Adapted according to Han et al. (2019).
5

M. Wang et al.

Carbohydrate Polymers 271 (2021) 118408

precise and key information for AOS structure (Bi et al., 2020; Liu et al.,
2005; Liu et al., 2015; Lundqvist et al., 2012). High performance liquid
chromatography (HPLC), mass spectrometry (MS) and related tech­
niques are used to purify and characterize AOS (Fu et al., 2013; Jona­
than et al., 2013; Zhang et al., 2006).

and chest pain, pulse-less legs, persistent cough and wound infection
were also reduced. The clinical trial demonstrated that AOS with DP 3 to
6 effectively reduced aneurysm recurrence after EVAR. As a bioactive
small molecule, AOS could cause changes of related signal pathway such
as the expression of miR-29b (a small noncoding RNA) and toll-like re­
ceptor signaling. According to their results, the expression levels of miR29b in aortic aneurysm patients were significantly reduced after AOS
treatment. Consequently, it affected the toll-like receptor (TLR)
signaling pathway involving variety of downstream related factors such
as mitogen-activated protein kinase (MAPK), nuclear factor kappa B
(NF-κB), interleukin 1 (IL-1) β, and interleukin 6 (IL-6). They concluded
that AOS can prevent the regeneration of aneurysms by reducing the
level of TLR4, NF-κB, IL-1β, and IL-6 via the inhibition of miR-29b.
Myeloma, also known as plasma cell tumor, is a malignant tumor
originating from the plasma cells in the bone marrow. The major char­
acteristic of myeloma cells is the high expression of the cell surface
heparin sulfate proteoglycan syndecan-1 (Sdc-1) (Gambella et al.,
2015). Human growth factor (HGF) interacts with Sdc-1 and increases
downstream HGF signaling, promoting angiogenesis, cell migration and
tumor growth (Aref et al., 2003). Blocking the interaction between HGF
and Sdc-1 can effectively inhibit the proliferation of tumor cells. Arlov

et al. found that sulfated AOS could directly bind to HGF, preventing
HGF from interacting with Sdc-1 (Arlov et al., 2015). The sulfated AOSbound HGF was released from the surface of myeloma cells when
appropriate sizes of sulfated AOS were used. In contrast, no HGF release
was observed upon treatment with non-sulfated AOS.
A recent study showed that VAOS, a novel modified coordination
compound, have an effective inhibitory effect on NSCLC in both cultured
cells and mouse models with transplanted tumor cells (Zhou et al.,
2018). It was further confirmed that VAOS (12.5, 25, 50 μM) could
induce apoptosis of NSCLC cells by activating protein kinase B (AKT) to
increase intracellular reactive oxygen species (ROS) levels. Phosphorus
colorimetric analysis showed that VAOS significantly inhibited the
dephosphorylation activity of phosphatase and tensin homolog on
chromosome 10 (PTEN), another member of the protein tyrosine phos­
phatases (PTPases)-upstream factor of AKT. In addition, ectopic PTEN
overexpression decreased VAOS-induced apoptosis. In vivo, VAOS
treatment (intraperitoneal injection, 30 mg/kg for 2 weeks) triggered
the hyperactivation of AKT through significant reduction of phosphatase
activity of PTEN, leading to ROS accumulation and apoptosis of NSCLC
cells.

3. Potential applications of AOS for biomedicine
3.1. Cancer therapies
Cancer is a major public health problem worldwide. In the last de­
cades, numerous active substances with anti-cancer effects have been
reported. As a natural product from marine algae, AOS and their de­
rivatives have various anti-cancer effect (Table 1).
Han and colleagues reported on AOS's capacity to inhibit prostate
cancer cell growth via the Hippo (Ste20-like protein kinase, mutations in
this gene lead to tissue overgrowth, or a “hippopotamus”-like pheno­
type) /YAP (Yes-associated protein) pathway (Han et al., 2019). AOS

trigger the activation or suppression of regulatory processes in prostate
cancer cells involving various transcription factors and effectors (Fig. 3).
First, AOS could activate the Hippo signaling pathway, which negatively
regulates YAP activity through a cascade of phosphorylation. Reduced
expression of the oncogene YAP and an increase in phosphorylated YAP
protein were observed in prostate cancer cells in response to AOS
treatment. The recruitment of both the coactivator YAP and c-Jun (a
component of the transcription factor activator protein-1, belongs to the
Jun family containing c-Jun, JunB, and JunD) into the upstream
response region of the sialyltransferase ST6Gal-1 promoter was largely
blocked due to the absence of YAP. As a result, a decrease of ST6Gal-1,
which plays a fundamental role in growth, migration, and invasion of
prostate cancer cells was detected at different levels of transcription,
translation and sialylation both in cultured cells and in a xenograft
mouse model. Finally, proliferation of human prostate cancer cells was
attenuated at a non-cytotoxic concentration of AOS (0.5 mg/ml for cell
lines; 2.5 mg/kg for mouse models) via repression of the Hippo/YAP/cJun pathway and sialylation caused by downregulation of ST6Gal-1
gene expression (Han et al., 2019).
In a clinical trial, AOS could significantly suppress aneurysm recur­
rence caused by endovascular aortic repair (EVAR) (Yang et al., 2017).
Compared with the control, the size of residual aneurysms was signifi­
cantly reduced after 2-year treatment with AOS (oral administration, 10
mg/day). The incidence of EVAR-related adverse effects, such as back

Fig. 4. The proposed mechanism of Se-PM for anti-inflammation effect.
Adapted according to Bi, Lai, Cai, et al., 2018 and Bi, Lai, Han, et al., 2018).
6


M. Wang et al.

Carbohydrate Polymers 271 (2021) 118408

Fig. 5. The proposed mechanism of AOS for anti-oxidation effect.
Adapted according to Jiang et al. (2021) and Zhao, Han, et al. (2020).

3.2. Anti-inflammation

Se-PM, a modified AOS derivate, significantly attenuated the in­
flammatory response in LPS-activated murine macrophage RAW264.7
cells, primary microglia and astrocytes by suppressing the activation of
NF-κB and MAPK signaling pathways (Bi, Lai, Cai, et al., 2018; Bi, Lai,
Han, et al., 2018). The cytotoxicity of Se-PM was measured by CCK-8
assay. It showed that Se-PM did not exert any cytotoxic effects on pri­
mary glial cells when the concentration of Se-PM reached 0.8 mg/ml. As
shown in Fig. 4, Se-PM treatment significantly decreased phosphoryla­
tion of NF-κB inhibitor (IκB-α), Akt p38 kinases (p38), extracellular
signal-regulated kinases (ERK) and c-Jun N-terminal kinases (JNK). It
lead to reduced phosphorylation and nuclear translocation of tran­
scription factors, especially p65. Therefore, the expressions of down­
stream target genes iNOS and COX-2 were dramatically reduced. As a
result, the production of related pro-inflammatory mediators, including
ROS, NO, PGE2 and the secretion of pro-inflammatory cytokines,
including TNF-α, IL-1β and IL-6 also decreased in cells incubated with
Se-PM. Finally, Se-PM inhibited the inflammatory response in different
types of LPS-triggered cells, respectively. Moreover, Se-PM remarkably
suppressed carrageenan-induced pro-inflammatory cytokine production
and LPS-triggered microglial and astrocytic activation in different
mouse models. Se-PM might block the interaction between LPS and re­
ceptors on the surface of LPS-induced in RAW264.7 cells. These studies

might contribute to the comprehensive understanding of the potential
health benefits of Se-PM for alleviating the prolonged and excessive
inflammation induced by human degenerative diseases, including can­
cer, cardiovascular diseases, type 2 diabetes, and arthritis.

Frequent uses of anticancer drugs cause a series of side effects,
especially gastrointestinal inflammation. A variety of agents, such as
probiotics, selenium, volatile oils and prebiotics have been used to
reduce pharmacotherapy-induced intestinal disruption (Araújo et al.,
2015; Justino et al., 2014; Lee et al., 2017; Ting et al., 2017; Yao et al.,
2013. However, little success has been reported in these efforts. Novel
bioactive substances are urgently needed to assist the recovery of
inflammation after cancer therapy.
It has been shown that AOS could effectively alleviate the inflam­
mation caused by busulfan, a drug used for patients with chronic
myeloid leukemia (Zhao, Feng et al., 2020). AOS also enhances integrity
and migration ability of IPEC-J2 cells (porcine small intestinal cell line)
(Xiong et al., 2020). The underlying molecular mechanisms are multi­
faceted and wide-ranging, including the regulation of AOS on cellular
transcriptome, and the subsequent responses of different types of in­
testinal cells. SiRNA trials in IPEC-J2 cells confirmed that AOS per­
formed their function by interacting with mannose receptors on the cell
surface. Consequently, the extensive remodeling of transcriptomes in
different type small intestine cells was observed. The researchers iden­
tified 184 active and differentially expressed genes, including multiple
transcription factors and associated cofactors. Finally, AOS (oral gavage,
10 mg/kg for 2 weeks) rescued the developmental time line of different
types of small intestinal cells (enterocytes, goblet, Paneth, tuft cells)
disrupted by busulfan, and their respective functions involving micro­
villi organization, cell junction, antibacterial humoral response, and

others. In addition, the improved plasma metabolome further verified
that AOS could recover small intestinal function in patients undergoing
anticancer chemotherapy. Moreover, fecal microbiota transplantation
(FMT) from AOS-treated mice was an effective measure for alleviating
small intestine mucositis through reconditioning gut microbiota and
improving blood metabolome on a multi-omics scale (Zhang et al.,
2020). In another study, it showed that AOS alleviated TNF-α-induced
inflammatory injury by decreasing pro-inflammatory cytokine (IL-6 and
TNF-α) concentrations and TNF receptor 1 (TNFR1)-mediated apoptosis
rate in TNF-α-treated IPEC-J2 cells (Wan et al., 2020).

3.3. Anti-microbial activities
Microbial infections represent one of the major causes of human
diseases. The biofilm-forming abilities and the resulting increased drug
resistance of pathogens make them a formidable challenge and remain
difficult to overcome (Ceri et al., 1999; Moskowitz et al., 2004). AOS
have exhibited great potential in the treatment of microbial infections
caused by the most common opportunistic pathogens including Pseu­
domonas aeruginosa, Acinetobacter baumannii, and Candida species
(Pritchard, Jack, Powell, et al., 2017; Pritchard, Powell, Jack, et al.,
7


M. Wang et al.

Carbohydrate Polymers 271 (2021) 118408

Fig. 6. The proposed mechanism of AOS for anti-obesity effect
Adapted according to Li et al. (2019) and Wang et al. (2020).

2017; Stokniene et al., 2020; Tøndervik et al., 2014).
Powell et al. reported that the OligoG CF-5/20 could significantly
reduce the biomass, thickness and density of biofilm of Pseudomonas
aeruginosa during early biofilm formation or even after biofilm estab­
lishment (Powell et al., 2018). They revealed that the OligoG CF-5/20
not only inhibited bacterial biofilm growth but also destroyed the
well-defined structure of established biofilm. They further demonstrated
that OligoG CF-5/20 could rapidly diffuse into the whole biofilm and
make the biofilm collapse from the inside, due to disrupting the struc­
ture of extracellular polysaccharides matrix and DNA-Ca2+-DNA
bridges, both of which are essential for biofilm formation and matura­
tion (Bales et al., 2013; Flemming & Wingender, 2010). In addition, the
synergistic use of OligoG CF-5/20 with antibiotics enhanced the efficacy
of antibiotics. Most recently, Stokniene et al. has reported the artificial
bi-functional compounds of OligoG CF-5/20–polymyxins exhibited
prolonged antimicrobial and antibiofilm activities against multidrugresistant Gram-negative bacterial pathogens compared to parent anti­
biotic whilst reducing antibiotic toxicity to human (Stokniene et al.,
2020).
OligoG CF-5/20 also showed an effective inhibitory effect on in­
fections caused by Candida albicans through reducing the candidal
growth, mycelium formation and invasion (Pritchard, Powell, Khan,
et al., 2017). Moreover, the gene expression and protein production of
key phospholipase as the major virulence factor was significantly
decreased in OligoG pre-treated C. albicans ATCC 90028 cells.

of the development of various degenerative diseases, especially
atherosclerosis.
Studies have shown that AOS treatment can significantly enhance
the activity of antioxidant enzymes and the accumulation of free radical
scavengers, including superoxide dismutase (SOD), catalase (CAT) and

glutathione (GSH) in human umbilical vein endothelial cells (HUVECs)
(Jiang et al., 2021; Zhao, Han, et al., 2020). AOS treatment also reduced
H2O2-induced ROS accumulation, the production of malondialdehyde
(MDA), one of the final products of lipid peroxidation, and the secretion
of endothelin-1 (ET-1), a signaling molecule to stimulate ROS and su­
peroxide generation. In addition, AOS protected HUVECs against
oxidative stress-induced apoptosis by regulating expression of genes
involving in the caspase-mediated apoptosis pathway and integrinα/FAK/PI3K pathway (Fig. 5). These studies suggested that AOS can
protect endothelial cells, due to their effective antioxidant and anti­
apoptotic activities, providing a promising therapeutic strategy for
preventing and treating atherosclerosis.
3.5. Anti-obesity
Obesity is a metabolic disorder characterized by excessive accumu­
lation of body fat, leading to a variety of diseases, such as hypertension,
hyperlipidemia, diabetes and even cancer. It has become a major
problem threatening human health. In addition to general recommen­
dations with regard to proper diet and exercise, several different ap­
proaches to treat obesity have been proposed, such as the use of
functional food supplements that have anti-obesity effects. As a
naturally-derived food additive with various beneficial effects, AOS
might be a candidate for the treatment of obesity (Guo et al., 2016,
2017; Li et al., 2019; Nakazono et al., 2016).
Li et al. investigated the anti-obesity effects of the unsaturated AOS
(UAOS) from the enzymatic degradation of Laminaria japonicais, in a
high-fat diet (HFD) mouse model (Li et al., 2019). They found that UAOS
showed stronger anti-obesity effects than acid hydrolyzed saturated AOS
(SAOS), judged by the greater reduction in body and liver weights,

3.4. Anti-oxidation
Oxidative stress reflects an imbalance between the systemic mani­

festation of ROS and the innate antioxidant defense systems. Distur­
bances in the normal redox state of cells can cause toxic effects through
the production of peroxides and free radicals that damage proteins,
lipids, and DNA. Oxidative stress leads to cell dysfunction and apoptosis
via driving disruptions in normal mechanisms of cellular signaling. In
humans, oxidative stress is thought to be associated with the occurrence
8


M. Wang et al.

Carbohydrate Polymers 271 (2021) 118408

Fig. 7. The proposed mechanism of AOS for AD therapies effect.
Adapted according to Wang et al., 2019).

adipose tissue mass, serum and liver lipid contents. Similar studies have
also shown that the UAOS provides greater biological activity (Guo
et al., 2016, 2017; Nakazono et al., 2016). UAOS causes significant in­
crease on both AMPKα and acetyl-CoA carboxylase (ACC) phosphory­
lation in adipocytes, suggesting that UAOS acts as an anti-obesity agent
through AMPK signaling.
In another study, it is observed that AOS treatment induces reduction
in size of adipocytes and lipid metabolism improvement, such as
decrease of TG and low-density lipoprotein cholesterol (LDL-C) levels
and inhibition of lipogenesis genes expression (Wang et al., 2020). AOS
alleviated HFD-induced metabolic disorders and inflammation via
modulating gut microbial communities, and the consequent release of
microbiota-dependent short-chain fatty acids (SCFAs) and reduction of
endotoxin levels. AOS treatment recovered the HFD-disturbed gut

microbiota by increasing the abundance of specific and beneficial gut
microbiota, including Akkermansia muciniphila, Lactobacillus reuteri and
Lactobacillus gasseri (Fig. 6). These results showed that the inhibitory
effect of AOS on obesity was closely related to their regulation of in­
testinal microorganism.

Recently, several studies have shown that AOS plays an important role
with different action modes in the pathogenesis of AD.
The effects of two different forms of AOS, MOS (derived from
enzymatic digestion) and Se-PM (modified with Se) on the treatment of
AD were evaluated by Bi et al. (2020) and Bi et al. (2021). Both MOS and
Se-PM significantly inhibited the aggregation of Aβ1–42 oligomer, which
is suggested to be the most neurotoxic form, and suppressed Aβ1–42, APP
and BACE1 expression in N2a-sw cells. In addition, ROS production and
oxidative stress levels were decreased by MOS and Se-PM. These results
suggested that the Se and the unsaturated double bonds in the AOS
might be a vital factor in exerting their biological function. Subse­
quently, they found that MOS could activate autophagy via suppressing
mTOR signaling pathway, promoting clearance of intracellular accu­
mulation of APP and Aβ in AD cell models; while Se-PM could attenuate
cell apoptosis and improve cell survival of N2a-sw cells via reducing the
expression of cytochrome c and enhancing the mitochondrial membrane
potential.
Studies revealed that GV-971, a kind of MOS derived from oxidative
degradation, exerts its role in treating AD by targeting the gut-brain axis
(Wang et al., 2019). GV-971 could improve cognitive functions by
remodeling gut microbiota, reducing the production of abnormal me­
tabolites, especially phenylalanine and isoleucine, preventing the inva­
sion of peripheral immune cells to the brain, inhibiting
neuroinflammation, and reducing brain Aβ deposition and tau hyper­

phosphorylation (Fig. 7). A phase 3 clinical trial showed that GV-971
significantly reversed cognitive impairment in patients with mild to
moderate AD. In addition, GV-971 had been demonstrated to cross the
blood-brain barrier, and directly bind to multiple subregions of Aβ to
inhibit the formation of Aβ fibril and destabilize the Aβ aggregates into

3.6. Alzheimer's disease therapies
Alzheimer's disease (AD) is a chronic neurodegenerative disease. AD
is characterized by the deposition of amyloid-β (Aβ) in the brain forming
plaques (plaques); and the hyperphosphorylation of tau protein causing
neurofibrillary tangles (NFTs) and loss of neurons, accompanied by glial
cell proliferation (Jana & Pahan, 2010). The Aβ peptide is generated
from amyloid precursor protein (APP) by β-secretase (BACE) and
γ-secretases cutting orderly (Lazarov & Demars, 2012; Mattson, 2004).
9


M. Wang et al.

Carbohydrate Polymers 271 (2021) 118408

non-toxic monomers. The elaboration of the action mechanism of GV971 undoubtedly provides an important scientific basis for the indepth understanding of targeting gut microbiota as a novel treatment
strategy for AD, and a detailed experimental basis for the research and
development of similar drugs as a novel treatment path for AD. At
present, the GV-971 has already been marketed in China and approved
by the FDA in proceeding international Phase 3 clinical trials.

et al., 2017; Mou & Miao, 2019). AOS were also applied in aquaculture
industry due to their beneficial effects on growth performance, immu­
nity, and disease resistance of tilapia (Oreochromis niloticus) (Van Doan

et al., 2016).
3.9. Safety and commercialization of AOS
Biosafety assessment of AOS is important for their potential appli­
cations in biomedical field. None of AOS (-ED, -AH, and -OD) exhibited
cytotoxic effects on RAW264.7 cells at a concentration of 1 mg/ml in
WST-8 assay (Xu, Wu, et al., 2014). AOS with concentration of 1 mg/ml
did not cause toxicity to endothelial cells, isolated from human aneu­
rysm (Yang et al., 2017). Zhao et al. found that AOS treatment at
different doses (0.05, 0.1, 0.2, 0.4, and 0.8 mg/ml) showed no cyto­
toxicity on HUVECs (Zhao, Han, et al., 2020). No obvious cell toxicity
and mutagenicity of AOS were observed in mice after 31 days of oral
administration at dosage of 600 mg/mouse/day (Ogawa et al., 2001). A
double-blind, randomized, placebo controlled, 3 days, dose-escalation
phase I study (NCT00970346) to test the in vivo safety and tolera­
bility of inhaled OligoG CF-5/20 in healthy volunteers have been
completed, as well as a multicenter, randomized, placebo controlled,
crossover phase II study (NCT01465529) with 28 days treatment periods
to evaluate the safety, tolerability and preliminary efficacy of OligoG CF5/20 in subjects with CF chronically colonized with Pseudomonas aeru­
ginosa. At present, OligoG CF-5/20 is in phase IIb/III clinical trials in CF
patients. In the recently completed phase III trial (NCT02293915), GV971 (900 mg twice a day for 24 weeks) was demonstrated to meet the
primary endpoint, with statistical significance (p < 0.001). No serious
adverse events were observed, with similar incidence rate between GV971 and placebo group (Wang et al., 2019). Nowadays, GV-971, a lowmolecular-weight mannuronic acid oligomer, has been manufactured
into sodium oligomannate capsules and successfully marketed in China.
In general, all these studies demonstrated that the doses of AOS had no
obvious toxicity and side-effects for different cell lines, mouse models
and human patients, which indicated safety of AOS for utilization as
food supplements, drug carriers or pharmaceutical ingredients. How­
ever, the future applications of AOS in biomedical field still require a
large number of perspective efforts on the metabolism and safety of all
AOS products, due to their diverse composition, variable structure and

multiple modification styles.
Commercialization is a good way to realize large-scale application of
AOS products. At present, there are only a few commercially available
AOS-based biomedical products. The GV-971 related products have
been marketed in China after more than 20 years of research and
development. GV-971 is the first new Alzheimer drug to receive regu­
latory approval globally since 2003. This typical and successful case will
provide great inspiration and a wealth of practical experience for the
development of AOS-based drugs in future. In addition, the drug
candidate Oligo G CF-5/20 has proven to be safe. Its serial products are
being developed by a pharmaceutical company named AlgiPharma,
which has successfully completed five clinical trials (NCT00970346;
NCT01465529; NCT01991028; NCT02157922; NCT02453789)
including a drug deposition study in CF patients. Multiple formulations
for inhalation, oral, and topical administration for the treatment of
respiratory diseases and microbial infections are expected to be ready in
the near future.

3.7. Drug carrier
Considering that alginate hydrogels are difficult to degrade in vivo,
Park et al. proposed AOS as a drug matrix in oral sustained release
formulations (Park et al., 2021). They simulated the passage of an oral
drug through the stomach into intestine via controlling pH of the reac­
tion solution in vitro. AOS obtained by enzyme digestion could form
spherical gel containing lysosome through liquid dropping test and
protect the lysosome from degradation or hydrolysis under acidic con­
ditions (pH 1.2). Then, the gel was dissolved and the embedded lyso­
some was released at near-neutral pH (pH 6.8). The morphological
integrity and antimicrobial activity of lysosomes were largely preserved.
Therefore, they suggested that AOS have potential as oral delivery sys­

tem of drugs, proteins, and lysosomes for the treatment of metabolic
diseases. In addition, AOS could alleviate enterotoxigenic E. coli-induced
intestinal mucosal damage in weaned pigs, and improve intestinal
morphology and growth (Wan et al., 2016, 2018). The above studies
indicate that AOS may not only serve as carriers to deliver special drugs,
but also act as stimulators on intestinal microecology.
In another study, AOS with high M content were used as matrices for
drug delivery and enhancing the antifungal activity of posaconazole
(POS) (Szekalska et al., 2019). They used the freeze-thaw technique to
prepare AOS gels. This method involves solvent crystallization during
freezing, which led to the compression of the space of AOS chains,
increased forces between AOS chains, allowing their connection and
formation of the hydrogels after thawing. In this way, the conventional
antifungal drugs were embedded in AOS with appropriate concentra­
tions and proportions in order to obtain optimal mucoadhesive and
prolonged drug release. Finally, it was shown that POS-containing
mucoadhesive films, based on AOS for buccal delivery, possessed
larger zones of inhibition and reduced the growth of all tested Candida
spp.
In general, AOS have improved water solubility and bioavailability
due to their short chain length. Although AOS are different from alginate
in molecular size, they still maintain the properties of forming effective
gel similar to alginate by adjusting the AOS size, proportion and con­
centration and using proper preparation technique. These studies indi­
cated that AOS related gels also had good mucoadhesive and swelling
properties and prolonged drug release effect, all of which are important
and necessary for a drug carrier (Park et al., 2021; Szekalska et al.,
2019). AOS have additional properties such as antimicrobial effect,
enhancing drug efficacy and inducing physiologic and pathophysiologic
stress response (Liu et al., 2019; Stokniene et al., 2020; Tusi et al., 2011).

Therefore, AOS, as a kind of natural and emerging drug carrier with dual
curative effect, have a broad application prospect and are worth further
research and development.
3.8. Other medical effects
In addition to the above multiple pharmacological benefits, AOS
have other medical effects. AOS can alleviate pulmonary hypertension
in mice via restoration of the TGFβ1/p-Smad2 signaling pathway and
restraining the activation of P-selectin/p38MAPK/NF-κB (Feng, Hu,
et al., 2020; Hu et al., 2019). AOS could prevent D-galactose-mediated
cataracts in C57BL/6 J mice through inhibiting oxidative stress and upregulating genes related to antioxidant system (Feng, Yang, et al., 2020).
Two studies showed that AOS exhibited protection effect on senescent
cardiomyocytes and could alleviate myocardial reperfusion injury (Guo

4. Conclusion and perspective
In summary, the physicochemical and biochemical properties of
AOS, such as small molecular size, low viscosity, high water solubility,
and intestinal absorption, make them suitable for preparation in a va­
riety of dosage forms for different administration modes, including
inhalation, intraperitoneal injection (i.p.) and oral gavage (Pritchard
et al., 2016; Wang et al., 2019; Zhou et al., 2018). AOS could perform
their unique biological functions in three modes, as extracellular
10


M. Wang et al.

Carbohydrate Polymers 271 (2021) 118408

Table 2
Summary of different AOS and their action modes.

Source

Method

Extracellular signaling molecules
Alginate sodium
Enzymatic digestion

Size

Ingredient
and doses

Function

Mechanism

Reference

DP
2–10

G, M
0–2.5 mg/
kg
G
1 mg/ml for
cell
2 mg/
mouse

Se-PM
0.8 mg/ml
5 mg/
mouse

Inhibit prostate cancer cell
growth

Activate the Hippo/YAP pathway
block the recruitment of YAP and c-Jun
attenuates α2,6-sialylation modification
Stimulates TLR4/Akt/NF-κB, TLR4/
Akt/mTOR and MAPK signaling
pathways

Han et al. (2019)

Neuroimmunoregulatory
activity
Anti-inflammation
Neuroprotection

Attenuate NF-κB and MAPK Signaling
pathways activation and
proinflammatory mediator production;
inhibit N2a-sw cell apoptosis

Bi, Lai, Cai, et al.
(2018), Bi, Lai, Han,
et al. (2018), Bi et al.

(2019), and Bi et al.
(2020)
Jiang et al. (2021)

Alginate (sigma)

Alginate lyase from
Pseudoalteromonas sp.

DP
2–8

Alginate (sigma)

Acid hydrolysis
sulfation, selenylation

Mr
3000

Alginate
Sinopharm
Chemical
Reagent Co., Ltd
AOS
Qingdao BZ
Oligo Biotech
Co. Ltd
AOS
Qingdao BZ

Oligo Biotech
Co. Ltd
Alginate
Qingdao
Bright Moon
Seaweed Group
Co., Ltd.
Laminaria digitata

Immobilized AlgL17

DP
1–4

G, M
0–1 mg/ml

Antioxidant

Upregulation of ROS scavenging
activities and attenuation of the caspasemediated apoptosis pathway

NMa

DP
2–10

G, M
0–0.8 mg/
ml

Protects endothelial cells
against oxidative stress injury

Zhao, Han, et al.
(2020)

Alginate lyase from
Pseudomonas sp. HZJ
216

Mr
1200
DP
2–6
DP
2–6

M/G, 1/2.6
200 mg/kg

Prevents acute doxorubicin
cardiotoxicity

Regulated integrin-a/FAK/PI3K
pathway
against oxidative stress-induced
apoptosis
Suppressing oxidative stress and
endoplasmic reticulum-mediated

apoptosis

G, M
0.6 mg/ml

Alleviating inflammatory
injury in intestinal epithelial
cells

Reducing TNFR1-dependent apoptosis

Wan et al. (2020)

Enzymatic digestion
acidic hydrolysis
alginate lyase Aly08
from Vibrio sp.

Mr
3500
DP
2,3

G, M

Improve epidermal
homeostasis in aged skin
effective anti-obesity effects

Increases stem cell proliferation and

self-renewal in aged keratinocytes
Activate AMPK signaling via increasing
both AMPK and ACC phosphorylation

Charruyer et al.
(2016)
Li et al., 2019

NM

Mr
2600–3200

Antimicrobial

Inhibition of microbial growth,
disturb biofilm formation and
persistence and reduce resistance to
antibiotic treatment alter the structure
of mucus, modulate mucin assembly,
and reduce the elastic and viscous
properties of sputum from CF patients

Khan et al. (2012),
Pritchard, Powell,
Jack, et al. (2017),
Pritchard, Powell,
Khan, et al. (2017)
Ermund et al., 2017,
Pritchard et al.

(2016),
Pritchard et al.
(2019)

Laminaria
japonicais
Laminaria
hyperborea

Alginate lyase from
Streptomyces
violaceoruber

Potent prebiotic agents
AOS Nanjing
NM
Junlan
Biotechnology
Company
Laminaria
alginate lyase Aly08
japonicais
from Vibrio sp.
Alginate sodium
Oxidative degradation

G, M
0–400 mg/
kg
OligoG

(CF-5/20)
G>85%
0.2, 2, 6 and
10%

Improve innate immunity

Treatment of chronic
respiratory disease

Fang et al. (2017)

Guo et al. (2016)

DP
1–4

G, M
500 mg/kg

Improves lipid metabolism
and inflammation in HFD-fed
mice

Modulate gut microbiota release of
microbiota-dependent SCFAs
decrease of endotoxin

Wang et al. (2020)

Mr
420
DP
2–10

G, M
400 mg/kg
M
(GV-971)
50, 100 mg/
kg

Attenuated obesity-related
metabolic abnormalities
Inhibit AD progression

Modulate gut microbiota

Li et al. (2020)

Remodels gut microbiota and suppresses
gut bacterial amino acids-shaped
neuroinflammation

Geng et al. (2019)
and Wang et al.
(2019)

Drug carrier or wound dressings
AOS Xi'an

Obtained from
Haoxuan
Laminaria japonica
Biotech Co., Ltd.

Mr
2900

Increase the activity of
antifungal drugs

Alginate lyase

NM

(sigma)
Brown seaweed

(sigma)
Enzymolysis

Optimal mucoadhesive and swelling
properties and prolonged drug release
affected the growth reduction of
Candida spp.
Exhibit pH-sensitive characteristics
keep lysozyme antimicrobial activity

Szekalska et al.
(2019)

Alginate sodium

M 48%
G 16%
MG 36%
1, 2% (w/w)
NM
2% (w/v)

NM

NM

Promote wound healing
debridement effect

Provide weak acid wet for wound
healing environment
prevent tissue adhesion and infection
reduce the adverse reactions of antiinflammatory drugs

Miao et al. (2019)

a

In vivo oral drug delivery

NM: Not Mentioned.

11

Park et al., 2016


M. Wang et al.

Carbohydrate Polymers 271 (2021) 118408

signaling molecules to induce host biological reactions; as prebiotics to
stimulate and improve the interactions between symbiotic microbiota
and host metabolism; as drug adjuvant or carrier to enhance the efficacy
of drug itself. As shown in Table 2, different sources of raw materials,
preparation methods and modification styles determinate the structure
and properties of final AOS products, which affect their beneficial
functions and special effects. The doses of AOS vary according to the
applications, such as 0–1 mg/ml for cell line treatments, 2.5–500 mg/
kg/day or 5 mg/mouse for xenograft mouse models treatments, and
0.2–10% as drug carrier or antimicrobials.
The challenges on current AOS research include: 1) Most studies are
limited to the laboratory level. Only a few studies involve in clinical
trials in humans; 2) Production of AOS is far from being industrialized.
As for enzymatic digested AOS, the low yield and hydrolysis efficiency of
current alginate lyases are the key restricting factors for industrial
production; 3) AOS production cost is too high. Consequently, drugs
based on AOS, especially those that are not yet included in the medical
insurance, are expensive and increase the economic burden on patients.
In spite of these challenges, AOS have great research significance,
development value and a broad application prospect due to their strong
structural plasticity, high bioavailability and diverse beneficial effects. It

is worth investing more efforts for their potential applications.
In future studies, researchers should focus on the following aspects:
1) More clinical trials in humans need to be operated to provide detailed
experimental evidences for increasing the reliability and persuasiveness
of AOS products. 2) More efficient manufacturing technology need to be
developed to finally improve the production rate and yield of AOS. One
strategy is to obtain stable and efficient alginate lyase, which requires indepth research on large-scale screening and identification of alginate
lyase-producing microbes (Sawant et al., 2015; Wang et al., 2017),
cloning and expression of alginate lyase-encoding genes (Inoue & Ojima,
2019; Pilgaard et al., 2019; Yang et al., 2019; Yang et al., 2020), puri­
fication and characterization of enzymes with high catalytic activity
(Belik et al., 2020; He et al., 2018; Stender et al., 2019), and optimiza­
tion of enzymatic hydrolysis process (Arntzen et al., 2021; Hu et al.,
2021; Wang et al., 2016; Xu et al., 2021). 3) In addition, the advanced
multidisciplinary techniques need to be developed to modify and char­
acterize AOS, revealing their underlying structure-function relationship.
We believe that the rise and prosperity of AOS-based drugs will be
realized in the near future through the joint efforts of researchers.

Arntzen, M.Ø., Pedersen, B., Klau, L. J., Stokke, R., Oftebro, M., Antonsen, S. G., …
Eijsink, V. G. H. (2021). Alginate degradation: Insights obtained through
characterization of a thermophilic exolytic alginate lyase. Applied and Environmental
Microbiology, 87, e02320–e02399.
Ashikin, W. H. N. S., Wong, T. W., & Law, C. L. (2010). Plasticity of hot air-dried
mannuronate-and guluronate-rich alginate films. Carbohydrate Polymers, 81,
104–113.
Bales, P. M., Renke, E. M., May, S. L., Shen, Y., & Nelson, D. C. (2013). Purification and
characterization of biofilm-associated EPS exopolysaccharides from ESKAPE
organisms and other pathogens. PLoS One, 8, Article e67950.
Bartsch, I. W. C., Bischof, K., Buchholz, C. M., Buck, B. H., Eggert, A., Feuerpfeil, P., …

Wiese, J. (2008). The genus Laminaria sensu lato: Recent insights and developments.
European Journal of Phycology, 43, 1–86.
Belik, A., Silchenko, A., Malyarenko, O., Rasin, A., Kiseleva, M., Kusaykin, M., &
Ermakova, S. (2020). Two new alginate lyases of PL7 and PL6 families from
polysaccharide-degrading bacterium Formosa algae KMM 3553T: structure,
properties, and products analysis. Marine Drugs, 18, 130.
Bi, D., Lai, Q., Cai, N., Li, T., Zhang, Y. Y., Han, Q. G., … Xu, X. (2018). Molecular
mechanisms and in vivo evaluation of the anti-inflammatory effect of selenopolymannuronate derived from alginate. Journal of Agricultural and Food Chemistry,
66, 2083–2091.
Bi, D., Lai, Q., Han, Q., Cai, N., He, H., Fang, W., Yi, J., Li, X., Xu, H., Li, X., Hu, Z.,
Liu, Q., & Xu, X. (2018). Seleno-polymannuronate attenuates neuroinflammation by
suppressing microglial and astrocytic activation. Journal of Functional Foods, 51,
113–120.
Bi, D., Lai, Q., Li, X., Cai, N., Li, T., Fang, W., Han, Q., Yu, B., Li, L., Liu, Q., Xu, H., Hu, Z.,
& Xu, X. (2019). Neuroimmunoregulatory potential of seleno-polymannuronate
derived from alginate in lipopolysaccharide-stimulated BV2 microglia. Food
Hydrocolloids, 87, 925–932.
Bi, D., Li, X., Li, T., Li, X., Lin, Z., Yao, L., Li, H., Xu, H., Hu, Z., Zhang, Z., Liu, Q., & Xu, X.
(2020). Characterization and neuroprotection potential of seleno-polymannuronate.
Frontiers in Pharmacology, 11, 21.
Bi, D., Yao, L., Lin, Z., Chi, L., Li, H., Xu, H., Du, X., Liu, Q., Hu, Z., Lu, J., & Xu, X. (2021).
Unsaturated mannuronate oligosaccharide ameliorates beta-amyloid pathology
through autophagy in Alzheimer's disease cell models. Carbohydrate Polymers, 251,
Article 117124.
Ceri, H., Olson, M., Stremick, C., Read, R., Morck, D., & Buret, A. J. (1999). The Calgary
biofilm device: New technology for rapid determination of antibiotic susceptibilities
of bacterial biofilms. Journal of Clinical Microbiology, 37, 1771–1776.
Charruyer, A., Fong, S., Yue, L., Arron, S. T., & Ghadially, R. (2016). Phycosaccharide AI,
a mixture of alginate polysaccharides, increases stem cell proliferation in aged
keratinocytes. Experimental Dermatology, 25, 738–740.

Chen, J., Hu, Y., Zhang, L., Wang, Y., Wang, S., Zhang, Y., Guo, H., Ji, D., & Wang, Y.
(2017). Alginate oligosaccharide DP5 exhibits antitumor effects in osteosarcoma
patients following surgery. Frontiers in Pharmacology, 8, 623.
Costa, M. J., Marques, A. M., Pastrana, L. M., Teixeira, J. A., Sillankorva, S. M., &
Cerqueira, M. A. (2018). Physicochemical properties of alginate-based films: Effect
of ionic crosslinking and mannuronic and guluronic acid ratio. Food Hydrocolloids,
81, 442–448.
Donati, I., & Paoletti, S. (2009). Material properties of alginates. In B. Rehm (Ed.),
Alginates: Biology and applications (pp. 1–53). Heidelberg: Springer.
Ermund, A., Recktenwald, C. V., Skjak-Braek, G., Meiss, L. N., Onsoyen, E., Rye, P. D., …
Hansson, G. C. (2017). OligoG CF-5/20 normalizes cystic fibrosis mucus by chelating
calcium. Clinical and Experimental Pharmacology & Physiology, 44, 639–647.
Etcheverry, S. B., Williams, P., & Baran, E. J. (1994). The interaction of the vanadyl (IV)
cation with chondroitin sulfate A. Biological Trace Element Research, 42, 43–52.
Etcheverry, S. B., Williams, P., & Baran, E. J. (1997). Synthesis and characterization of
oxovanadium(IV) complexes with saccharides. Carbohydrate Research, 302, 131–138.
Fan, Y., Li, Y., Zhang, J., Ding, X., Cui, J., Wang, G., Wang, Z., & Wang, L. (2019).
Alginate enhances memory properties of antitumor CD8+ T cells by promoting
cellular antioxidation. ACS Biomaterials Science & Engineering, 5, 4717–4725.
Fang, W., Bi, D., Zheng, R., Cai, N., Xu, H., Zhou, R., Lu, J., Wan, M., & Xu, X. (2017).
Identification and activation of TLR4-mediated signalling pathways by alginatederived guluronate oligosaccharide in RAW264.7 macrophages. Scientific Reports, 7,
1663.
Feng, W., Hu, Y., An, N., Feng, Z., Liu, J., Mou, J., Hu, T., Guan, H., Zhang, D., & Mao, Y.
(2020). Alginate oligosaccharide alleviates monocrotaline-induced pulmonary
hypertension via anti-oxidant and anti-inflammation pathways in rats. International
Heart Journal, 61, 160–168.
Feng, W., Yang, X., Feng, M., Pan, H., Liu, J., Hu, Y., Hu, Y., Wang, S., Zhang, D., Ma, F.,
Mao, Y., Pan, H., Liu, J., & Mao, Y. (2020). Alginate oligosaccharide prevents against
D-galactose-mediated cataract in C57BL/6J mice via regulating oxidative stress and
antioxidant system. In Current Eye Research (pp. 1–9).

Flemming, H.-C., & Wingender, J. (2010). The biofilm matrix. Nature Reviews.
Microbiology, 8, 623–633.
Ford, L., Stratakos, A. C., Theodoridou, K., Dick, J. T. A., Sheldrake, G. N., Linton, M., …
Walsh, P. J. (2020). Polyphenols from brown seaweeds as a potential antimicrobial
agent in animal feeds. ACS Omega, 5, 9093–9103.
Fu, Q., Liang, T., Li, Z., Xu, X., Ke, Y., Jin, Y., & Liang, X. (2013). Separation of
carbohydrates using hydrophilic interaction liquid chromatography. Carbohydrate
Research, 379, 13–17.
Gambella, M., Palumbo, A., & Rocci, A. (2015). MET/HGF pathway in multiple myeloma:
From diagnosis to targeted therapy? Expert Review of Molecular Diagnostics, 15,
881–893.
Garcia-Vaquero, M., Rajauria, G., Tiwari, B., Sweeney, T., & O'Doherty, J. (2018).
Extraction and yield optimisation of fucose, glucans and associated antioxidant

Funding
This work was supported by the Young Talents Invitation Program of
Shandong Provincial Colleges and Universities (20190601); Natural
Science Foundation of Shandong Province (ZR2019QB018); and the
Young Scientists Fund of National Natural Science Foundation of China
(41401285).
Declaration of competing interest
The authors declare no conflict of interest.
References
Afonso, N. C., Catarino, M. D., Silva, A. M. S., & Cardoso, S. M. (2019). Brown
macroalgae as valuable food ingredients. Antioxidants (Basel), 8, 365.
Araújo, C. V., Lazzarotto, C. R., Aquino, C. C., Figueiredo, I. L., Costa, T. B., de Oliveira
Alves, L. A., … Oria, R. B. (2015). Alanyl-glutamine attenuates 5-fluorouracilinduced intestinal mucositis in apolipoprotein E-deficient mice. Brazilian Journal of
Medical and Biological Research, 48, 493–501.
Aref, S., Goda, T., & El-Sherbiny, M. J. H. (2003). Syndecan-1 in multiple myeloma:
Relationship to conventional prognostic factors. Hematology, 8, 221–228.

Arioli, T., Mattner, S. W., & Winberg, P. C. (2015). Applications of seaweed extracts in
Australian agriculture: Past, present and future. Journal of Applied Phycology, 27,
2007–2015.
Arlov, O., Aachmann, F. L., Feyzi, E., Sundan, A., & Skjak-Braek, G. (2015). The impact of
chain length and flexibility in the interaction between sulfated alginates and HGF
and FGF-2. Biomacromolecules, 16, 3417–3424.

12


M. Wang et al.

Carbohydrate Polymers 271 (2021) 118408

activities from Laminaria digitata by applying response surface methodology to high
intensity ultrasound-assisted extraction. Marine Drugs, 16, 257.
ˇ
ˇ
Generali´c Mekini´c, I., Skroza, D., Simat,
V., Hamed, I., Cagalj,
M., & Popovi´c Perkovi´c, Z.
(2019). Phenolic content of brown algae (Pheophyceae) species: Extraction,
identification, and quantification. Biomolecules, 9, 244.
Geng, M., Guan, H., Xin, X., Yang, Z., & Sun, G. (2019). Alginate oligosaccharides and the
derivatives thereof as well as the manufacture and the use of the same. Qingdao, CN: U.S.
Patent: Ocean University of China.
Grant, G. T., Morris, E. R., Rees, D. A., Smith, P. J., & Thom, D. (1973). Biological
interactions between polysaccharides and divalent cations: The egg-box model. FEBS
Letters, 32, 195–198.
Grasdalen, H. (1983). High-field, 1H-n.m.r. spectroscopy of alginate: Sequential

structure and linkage conformations. Carbohydrate Research, 118, 255–260.
Gunathilaka, T. L., Samarakoon, K., Ranasinghe, P., & Peiris, L. D. C. (2020). Antidiabetic
potential of marine brown algae-a mini review. Journal of Diabetes Research, 2020,
Article 1230218.
Guo, J. J., Ma, L. L., Shi, H. T., Zhu, J. B., Wu, J., Ding, Z. W., … Ge, J. B. (2016). Alginate
oligosaccharide prevents acute doxorubicin cardiotoxicity by suppressing oxidative
stress and endoplasmic reticulum-mediated apoptosis. Marine Drugs, 14, 231.
Guo, J. J., Xu, F. Q., Li, Y. H., Li, J., Liu, X., Wang, X. F., … An, Y. (2017). Alginate
oligosaccharide alleviates myocardial reperfusion injury by inhibiting nitrative and
oxidative stress and endoplasmic reticulum stress-mediated apoptosis. Drug Design,
Development and Therapy, 11, 2387–2397.
Han, Y., Zhang, L., Yu, X., Wang, S., Xu, C., Yin, H., & Wang, S. (2019). Alginate
oligosaccharide attenuates alpha2,6-sialylation modification to inhibit prostate
cancer cell growth via the hippo/YAP pathway. Cell Death & Disease, 10, 374.
He, M., Guo, M., Zhang, X., Chen, K., Yan, J., & Irbis, C. (2018). Purification and
characterization of alginate lyase from Sphingomonas sp. ZH0. Journal of Bioscience
and Bioengineering, 126, 310–316.
Hu, F., Cao, S., Li, Q., Zhu, B., & Yao, Z. (2021). Construction and biochemical
characterization of a novel hybrid alginate lyase with high activity by module
recombination to prepare alginate oligosaccharides. International Journal of Biological
Macromolecules, 166, 1272–1279.
Hu, X., Jiang, X., Gong, J., Hwang, H., Liu, Y., & Guan, H. (2005). Antibacterial activity
of lyase-depolymerized products of alginate. Journal of Applied Phycology, 17, 57–60.
Hu, Y., Feng, Z., Feng, W., Hu, T., Guan, H., & Mao, Y. (2019). AOS ameliorates
monocrotaline-induced pulmonary hypertension by restraining the activation of Pselectin/p38MAPK/NF-κB pathway in rats. Biomedicine & Pharmacotherapy, 109,
1319–1326.
Huang, L., Zhou, J., Li, X., Peng, Q., Lu, H., & Du, Y. (2013). Characterization of a new
alginate lyase from newly isolated Flavobacterium sp. S20. Journal of Industrial
Microbiology and Biotechnology, 40(1), 113–122.
Inoue, A., & Ojima, T. (2019). Functional identification of alginate lyase from the brown

alga Saccharina japonica. Scientific Reports, 9, 4937.
Iwamoto, M., Kurachi, M., Nakashima, T., Kim, D., Yamaguchi, K., Oda, T., Iwamoto, Y.,
& Muramatsu, T. (2005). Structure-activity relationship of alginate oligosaccharides
in the induction of cytokine production from RAW264.7 cells. FEBS Letters, 579,
4423–4429.
Iwamoto, Y., Xu, X., Tamura, T., Oda, T., & Muramatsu, T. (2003). Enzymatically
depolymerized alginate oligomers that cause cytotoxic cytokine production in
human mononuclear cells. Bioscience Biotechnology and Biochemistry, 67, 258–263.
Jana, A., & Pahan, K. (2010). Fibrillar amyloid-β-activated human astroglia kill primary
human neurons via neutral sphingomyelinase: Implications for Alzheimer’s disease.
Journal of Neuroscience, 30, 12676–12689.
Jiang, Z., Zhang, X., Wu, L., Li, H., Chen, Y., Li, L., Ni, H., Li, Q., & Zhu, Y. (2021).
Exolytic products of alginate by the immobilized alginate lyase confer antioxidant
and antiapoptotic bioactivities in human umbilical vein endothelial cells.
Carbohydrate Polymers, 251.
Jonathan, M. C., Bosch, G., Schols, H. A., & Gruppen, H. (2013). Separation and
identification of individual alginate oligosaccharides in the feces of alginate-fed pigs.
Journal of Agricultural and Food Chemistry, 61, 355–560.
Justino, P. F., Melo, L. F., Nogueira, A. F., Costa, J. V., Silva, L. M., Santos, C. M., …
Soares, P. M. G. (2014). Treatment with Saccharomyces boulardii reduces the
inflammation and dysfunction of the gastrointestinal tract in 5-fluorouracil-induced
intestinal mucositis in mice. British Journal of Nutrition, 111, 1611–1621.
Khan, S., Tondervik, A., Sletta, H., Klinkenberg, G., Emanuel, C., Onsoyen, E., …
Thomas, D. W. (2012). Overcoming drug resistance with alginate oligosaccharides
able to potentiate the action of selected antibiotics. Antimicrobial Agents and
Chemotherapy, 56, 5134–5141.
Kim, D. W. (2018). Non-reducing end unsaturated mannuronic acid oligosaccharides and
compositions containing same as active ingredient. Gwangju, KR: United States: Industry
Foundation of Chonnam National University.
Lavaud, J., & Goss, R. (2014). The peculiar features of non-photochemical fluorescence

quenching in diatoms and Brown algae. In B. Demmig-Adams, G. Garab,
W. Adams, III, & Govindjee (Eds.), Non-photochemical quenching and energy dissipation
in plants, algae and cyanobacteria (pp. 421–443). Dordrecht: Springer.
Lazarov, O., & Demars, M. P. (2012). All in the family: How the APPs regulate
neurogenesis. Frontiers in Neuroscience, 6, 81.
Lee, J. M., Chun, H. J., Choi, H. S., Kim, E. S., Seo, Y. S., Jeen, Y. T., … Sul, D. J. N.
(2017). Selenium administration attenuates 5-flurouracil-induced intestinal
mucositis. Nutrition and Cancer, 69, 616–622.
Lee, K. Y., & Mooney, D. J. (2012). Alginate: Properties and biomedical applications.
Progress in Polymer Science, 37, 106–126.
Li, L. Y., Jiang, X. L., Guan, H. S., & Wang, P. (2011). Preparation, purification and
characterization of alginate oligosaccharides degraded by alginate lyase from
Pseudomonas sp. HZJ 216. Carbohydrate Research, 346(6), 794–800.

Li, S., He, N., & Wang, L. (2019). Efficiently anti-obesity effects of unsaturated alginate
oligosaccharides (UAOS) in high-fat diet (HFD)-fed mice. Marine Drugs, 17, 540.
Li, S., Wang, L., Liu, B., & He, N. (2020). Unsaturated alginate oligosaccharides
attenuated obesity-related metabolic abnormalities by modulating gut microbiota in
high-fat-diet mice. Food & Function, 11, 4773–4784.
Liu, H., Geng, M., Xin, X., Li, F., Zhang, Z., Li, J., & Ding, J. (2005). Multiple and
multivalent interactions of novel anti-AIDS drug candidates, sulfated
polymannuronate (SPMG)-derived oligosaccharides, with gp120 and their anti-HIV
activities. Glycobiology, 15, 501–510.
Liu, J., Yang, S., Li, X., Yan, Q., Reaney, M. J., & Jiang, Z. (2019). Alginate
oligosaccharides: Production, biological activities, and potential applications.
Comprehensive Reviews in Food Science and Food Safety, 18, 1859–1881.
Liu, S., Liu, G., & Yi, Y. (2015). Novel vanadyl complexes of alginate saccharides:
Synthesis, characterization, and biological activities. Carbohydrate Polymers, 121,
86–91.
Lundqvist, L. C. E., Jam, M., Barbeyron, T., Czjzek, M., & Sandstrom, C. (2012). Substrate

specificity of the recombinant alginate lyase from the marine bacteria Pseudomonas
alginovora. Carbohydrate Research, 352, 44–50.
Mackie, W., Perez, S., Rizzo, R., Taravel, F., & Vignon, M. (1983). Aspects of the
conformation of polyguluronate in the solid state and in solution. International
Journal of Biological Macromolecules, 5, 329–341.
Mattson, M. P. (2004). Pathways towards and away from Alzheimer’s disease. Nature,
430, 631–639.
de Mesquita, M. M. F., Crapez, M. A. C., Teixeira, V. L., & Cavalcanti, D. N. (2018).
Potential interactions bacteria-brown algae. Journal of Applied Phycology, 31,
867–883.
Miao, Y., Sun, T., & Sun, G. (2019). Application of alginate oligosaccharides and sodium
alginate in breast abscess incision and drainage. IOP Conference Series: Materials
Science and Engineering, 562, Article 012135.
Moskowitz, S. M., Foster, J. M., Emerson, J., & Burns, J. L. (2004). Clinically feasible
biofilm susceptibility assay for isolates of Pseudomonas aeruginosa from patients with
cystic fibrosis. Journal of Clinical Microbiology, 42, 1915–1922.
Mou, J., & Miao, Y. J. (2019). Protective effect of alginate oligosaccharide on senescent
cardiomyocytes. Chronic Diseases Prevention Review, 9, 28–33.
Nakazono, S., Cho, K., Isaka, S., Abu, R., Yokose, T., Murata, M., Ueno, M., Tachibana, K.,
Hirasaka, K., Kim, D., & Oda, T. (2016). Anti-obesity effects of enzymaticallydigested alginate oligomer in mice model fed a high-fat-diet. Bioactive Carbohydrates
and Dietary Fibre, 7, 1–8.
Nordgård, C. T., & Draget, K. I. (2011). Oligosaccharides as modulators of rheology in
complex mucous systems. Biomacromolecules, 12, 3084–3090.
Ogawa, H., Kajimoto, N., Hiura, N., & Chaki, T. (2001). Effects of sodium alginate
oligosaccharide on serum lipids, serum minerals and urinary minerals in rats. Journal
of Japan Society of Nutrition and Food Sciences, 54, 297–303.
Overland, M., Mydland, L. T., & Skrede, A. (2019). Marine macroalgae as sources of
protein and bioactive compounds in feed for monogastric animals. Journal of the
Science of Food and Agriculture, 99, 13–24.
Park, H. J., Ahn, J. M., Park, R. M., Lee, S. H., Sekhon, S. S., Kim, S. Y., … Min, J. (2016).

Effects of alginate oligosaccharide mixture on the bioavailability of lysozyme as an
antimicrobial agent. Journal of Nanoscience and Nanotechnology, 16, 1445–1449.
Park, R. M., Nguyen, N. H. T., Lee, S. M., Kim, Y. H., & Min, J. (2021). Alginate
oligosaccharides can maintain activities of lysosomes under low pH condition.
Scientific Reports, 11, 11504.
Pilgaard, B., Wilkens, C., Herbst, F. A., Vuillemin, M., Rhein-Knudsen, N., Meyer, A. S., &
Lange, L. (2019). Proteomic enzyme analysis of the marine fungus Paradendryphiella
salina reveals alginate lyase as a minimal adaptation strategy for brown algae
degradation. Scientific Reports, 9, 12338.
Plazinski, W. (2011). Molecular basis of calcium binding by polyguluronate chains.
Revising the egg-box model. Journal of Computational Chemistry, 32, 2988–2995.
Powell, L. C., Pritchard, M. F., Ferguson, E. L., Powell, K. A., Patel, S. U., Rye, P. D., …
Thomas, D. W. (2018). Targeted disruption of the extracellular polymeric network of
Pseudomonas aeruginosa biofilms by alginate oligosaccharides. NPJ Biofilms and
Microbiomes, 4, 13.
Pritchard, M. F., Jack, A. A., Powell, L. C., Sadh, H., Rye, P. D., Hill, K. E., &
Thomas, D. W. (2017). Alginate oligosaccharides modify hyphal infiltration of
Candida albicans in an in vitro model of invasive human candidosis. Journal of
Applied Microbiology, 123, 625–636.
Pritchard, M. F., Oakley, J. L., Brilliant, C. D., Rye, P. D., Forton, J., Doull, I. J. M., …
Lewis, P. D. (2019). Mucin structural interactions with an alginate oligomer
mucolytic in cystic fibrosis sputum. Vibrational Spectroscopy, 103, Article 102932.
Pritchard, M. F., Powell, L. C., Jack, A. A., Powell, K., Beck, K., Florance, H., …
Thomas, D. W. (2017). A low-molecular-weight alginate oligosaccharide disrupts
pseudomonal microcolony formation and enhances antibiotic effectiveness.
Antimicrobial Agents and Chemotherapy, 61 (e00762-17).
Pritchard, M. F., Powell, L. C., Khan, S., Griffiths, P. C., Mansour, O. T., Schweins, R., …
Ferguson, E. L. (2017). The antimicrobial effects of the alginate oligomer OligoG CF5/20 are independent of direct bacterial cell membrane disruption. Scientific Reports,
7, 44731.
Pritchard, M. F., Powell, L. C., Menzies, G. E., Lewis, P. D., Hawkins, K., Wright, C., …

Thomas, D. W. (2016). A new class of safe oligosaccharide polymer therapy to
modify the mucus barrier of chronic respiratory disease. Molecular Pharmaceutics, 13
(3), 863–872.
Rioux, L. E., & Turgeon, S. L. (2015). Seaweed carbohydrates. In B. K. Tiwari, &
D. J. Troy (Eds.), Seaweed sustainability (pp. 141–192). San Diego: Academic Press.
Salehi, B., Sharifi-Rad, J., Seca, A. M. L., Pinto, D., Michalak, I., Trincone, A., …
Martins, N. (2019). Current trends on seaweeds: Looking at chemical composition,
phytopharmacology, and cosmetic applications. Molecules, 24, 4182.

13


M. Wang et al.

Carbohydrate Polymers 271 (2021) 118408

Santelices, B. (2007). The discovery of kelp forests in deep-water habitats of tropical
regions. Proceedings of the National Academy of Sciences, 104, 19163–19164.
Saraswati, G., P., E., Iskandriati, D., Tan, C. P., & Andarwulan, N. (2019). Sargassum
seaweed as a source of anti-inflammatory substances and the potential insight of the
tropical species: A review. Marine Drugs, 17, 590.
Sari-Chmayssem, N., Taha, S., Mawlawi, H., Gu´egan, J.-P., Jefti´c, J., & Benvegnu, T.
(2015). Extracted and depolymerized alginates from brown algae Sargassum vulgare
of Lebanese origin: Chemical, rheological, and antioxidant properties. Journal of
Applied Phycology, 28, 1915–1929.
Sawant, S. S., Salunke, B. K., & Kim, B. S. (2015). A rapid, sensitive, simple plate assay for
detection of microbial alginate lyase activity. Enzyme and Microbial Technology, 77,
8–13.
Skjåk-Bræk, G., Smidsrød, O., & Larsen, B. (1986). Tailoring of alginates by enzymatic
modification in vitro. International Journal of Biological Macromolecules, 8, 330–336.

Sletmoen, M., Maurstad, G., Nordgård, C. T., Draget, K. I., & Stokke, B. T. (2012).
Oligoguluronate induced competitive displacement of mucin–alginate interactions:
Relevance for mucolytic function. Soft Matter, 8, 8413.
Smidsrød, O., & Haug, A. R. N. E. (1972). Dependence upon the gel-sol state of the ionexchange properties of alginates. Acta Chemica Scandinavica, 26, 2063–2074.
Stender, E. G. P., Dybdahl Andersen, C., Fredslund, F., Holck, J., Solberg, A., Teze, D., …
Svensson, B. (2019). Structural and functional aspects of mannuronic acid-specific
PL6 alginate lyase from the human gut microbe Bacteroides cellulosilyticus. Journal
of Biological Chemstry, 294, 17915–17930.
Stokke, B. T., Smidsrød, O., Bruheim, P., & Skjåk-Bræk, G. (1991). Distribution of uronate
residues in alginate chains in relation to alginate gelling properties. Macromolecules,
24, 4637–4645.
Stokke, B. T., Smidsrød, O., Zanetti, F., Strand, W., & Skjåk-Bræk, G. (1993). Distribution
of uronate residues in alginate chains in relation to alginate gelling properties—2:
Enrichment of β-d-mannuronic acid and depletion of α-l-guluronic acid in sol
fraction. Carbohydrate Polymers, 21, 39–46.
Stokniene, J., Powell, L. C., Aarstad, O. A., Aachmann, F. L., Rye, P. D., Hill, K. E., …
Ferguson, E. L. (2020). Bi-functional alginate oligosaccharide-polymyxin conjugates
for improved treatment of multidrug-resistant gram-negative bacterial infections.
Pharmaceutics, 12, 1080.
ˇ
Synytsya, A., Copíkov´
a, J., Kim, W. J., & Park, Y. I. (2015). Cell Wall polysaccharides of
marine algae. In S.-K. Kim (Ed.), Springer handbook of marine biotechnology (pp.
543–590). Heidelberg: Springer.
Szekalska, M., Wroblewska, M., Trofimiuk, M., Basa, A., & Winnicka, K. (2019). Alginate
oligosaccharides affect mechanical properties and antifungal activity of alginate
buccal films with posaconazole. Marine Drugs, 17, 692.
Thanh, T. T., Tran, V. T., Yuguchi, Y., Bui, L. M., & Nguyen, T. T. (2013). Structure of
fucoidan from brown seaweed Turbinaria ornata as studied by electrospray ionization
mass spectrometry (ESIMS) and small angle X-ray scattering (SAXS) techniques.

Marine Drugs, 11, 2431–2443.
Ting, Z., Lu, S. H., Qian, B., Li, L., Wang, Y. F., Yang, X. X., … Yu, J. (2017). Volatile oil
from amomi fructus attenuates 5-fluorouracil-induced intestinal mucositis. Frontiers
in Pharmacology, 8, 786.
Tøndervik, A., Sletta, H., Klinkenberg, G., Emanuel, C., Powell, L. C., Pritchard, M. F., …
Hill, K. E. (2014). Alginate oligosaccharides inhibit fungal cell growth and potentiate
the activity of antifungals against Candida and Aspergillus spp. PLoS One, 9, Article
e112518.
Trincone, A. (2015). Short bioactive marine oligosaccharides: Diving into recent
literature. Current Biotechnology, 4, 212–222.
Tusi, S. K., Khalaj, L., Ashabi, G., Kiaei, M., & Khodagholi, F. (2011). Alginate
oligosaccharide protects against endoplasmic reticulum- and mitochondrialmediated apoptotic cell death and oxidative stress. Biomaterials, 32, 5438–5458.
Van Doan, H., Tapingkae, W., Moonmanee, T., & Seepai, A. (2016). Effects of low
molecular weight sodium alginate on growth performance, immunity, and disease
resistance of tilapia, Oreochromis niloticus. Fish & Shellfish Immunology, 55, 186–194.
Wan, J., Jiang, F., Xu, Q., Chen, D., & He, J. (2016). Alginic acid oligosaccharide
accelerates weaned pig growth through regulating antioxidant capacity, immunity
and intestinal development. RSC Advances, 6, 87026–87035.
Wan, J., Zhang, J., Chen, D., Yu, B., Mao, X., Zheng, P., … He, J. (2018). Alginate
oligosaccharide alleviates enterotoxigenic Escherichia coli-induced intestinal mucosal
disruption in weaned pigs. Food & Function, 9, 6401–6413.
Wan, J., Zhang, J., Yin, H., Chen, D., Yu, B., & He, J. (2020). Ameliorative effects of
alginate oligosaccharide on tumour necrosis factor-alpha-induced intestinal
epithelial cell injury. International Immunopharmacology, 89, Article 107084.

Wang, M., Chen, L., Liu, Z., Zhang, Z., Qin, S., & Yan, P. (2016). Isolation of a novel
alginate lyase-producing Bacillus litoralis strain and its potential to ferment
Sargassum horneri for biofertilizer. Microbiologyopen, 5(6), 1038–1049.
Wang, M., Chen, L., Zhang, Z., Wang, X., Qin, S., & Yan, P. (2017). Screening of alginate
lyase-excreting microorganisms from the surface of brown algae. AMB Express, 7, 74.

Wang, X., Sun, G., Feng, T., Zhang, J., Huang, X., Wang, T., Xie, Z., Chu, X., Yang, J.,
Wang, H., Chang, S., Gong, Y., Ruan, L., Zhang, G., Yan, S., Lian, W., Du, C.,
Yang, D., Zhang, Q., … Geng, M. (2019). Sodium oligomannate therapeutically
remodels gut microbiota and suppresses gut bacterial amino acids-shaped
neuroinflammation to inhibit Alzheimer's disease progression. Cell Research, 29,
787–803.
Wang, Y., Li, L., Ye, C., Yuan, J., & Qin, S. (2020). Alginate oligosaccharide improves
lipid metabolism and inflammation by modulating gut microbiota in high-fat diet fed
mice. Applied Microbiology and Biotechnology, 104, 3541–3554.
Xiong, B., Liu, M., Zhang, C., Hao, Y., Zhang, P., Chen, L., Tang, X., Zhang, H., & Zhao, Y.
(2020). Alginate oligosaccharides enhance small intestine cell integrity and
migration ability. Life Sciences, 258, Article 118085.
Xu, X., Bi, D., Wu, X., Wang, Q., Wei, G., Chi, L., … Wan, M. (2014). Unsaturated
guluronate oligosaccharide enhances the antibacterial activities of macrophages. The
FASEB Journal, 28(6), 2645–2654.
Xu, X., Wu, X., Wang, Q., Cai, N., Zhang, H., Jiang, Z., Wan, M., & Oda, T. (2014).
Immunomodulatory effects of alginate oligosaccharides on murine macrophage
RAW264.7 cells and their structure-activity relationships. Journal of Agricultural and
Food Chemistry, 62, 3168–3176.
Xu, X., Zeng, D., Wu, D., & Lin, J. (2021). Single-point mutation near active center
increases substrate affinity of alginate lyase AlgL-CD. Applied Biochemistry and
Biotechnology. />Yang, M., Li, N., Yang, S., Yu, Y., Han, Z., Li, L., & Mou, H. (2019). Study on expression
and action mode of recombinant alginate lyases based on conserved domains
reconstruction. Applied Microbiology and Biotechnology, 103, 807–817.
Yang, S., Liu, Z., Fu, X., Zhu, C., Kong, Q., Yang, M., & Mou, H. (2020). Expression and
characterization of an alginate lyase and its thermostable mutant in Pichia pastoris.
Marine Drugs, 18, 305.
Yang, Y., Ma, Z., Yang, G., Wan, J., Li, G., Du, L., & Lu, P. (2017). Alginate
oligosaccharide indirectly affects toll-like receptor signaling via the inhibition of
microRNA-29b in aneurysm patients after endovascular aortic repair. Drug Design,

Development and Therapy, 11, 2565–2579.
Yao, Q., Ye, X., Wang, L., Gu, J., & Guo, Y. (2013). Protective effect of curcumin on
chemotherapy-induced intestinal dysfunction. International Journal of Clinical and
Experimental Pathology, 6, 2342–2349.
Zhang, P., Liu, J., Xiong, B., Zhang, C., Kang, B., Gao, Y., Li, Z., Ge, W., Cheng, S.,
Hao, Y., Shen, W., Yu, S., Chen, L., Tang, X., Zhao, Y., & Zhang, H. (2020).
Microbiota from alginate oligosaccharide-dosed mice successfully mitigated small
intestinal mucositis. Microbiome, 8, 112.
Zhang, Z., Yu, G., Zhao, X., Liu, H., Guan, H., Lawson, A. M., & Chai, W. (2006).
Sequence analysis of alginate-derived oligosaccharides by negative-ion electrospray
tandem mass spectrometry. Journal of the American Society for Mass Spectrometry, 17,
621–630.
Zhao, J., Han, Y., Wang, Z., Zhang, R., Wang, G., & Mao, Y. (2020). Alginate
oligosaccharide protects endothelial cells against oxidative stress injury via integrinalpha/FAK/PI3K signaling. Biotechnology Letters, 42, 2749–2758.
Zhao, Y., Feng, Y., Liu, M., Chen, L., Meng, Q., Tang, X., Wang, S., Liu, L., Li, L., Shen, W.,
& Zhang, H. (2020). Single-cell RNA sequencing analysis reveals alginate
oligosaccharides preventing chemotherapy-induced mucositis. Mucosal Immunology,
13, 437–448.
Zhou, L., Yi, Y., Yuan, Q., Zhang, J., Li, Y., Wang, P., Xu, M., & Xie, S. (2018). VAOS, a
novel vanadyl complexes of alginate saccharides, inducing apoptosis via activation
of AKT-dependent ROS production in NSCLC. Free Radical Biology & Medicine, 129,
177–185.
Zhou, R., Shi, X., Gao, Y., Cai, N., Jiang, Z., & Xu, X. (2015). Anti-inflammatory activity
of guluronate oligosaccharides obtained by oxidative degradation from alginate in
lipopolysaccharide-activated murine macrophage RAW 264.7 cells. Journal of
Agricultural and Food Chemistry, 63, 160–168.
Zhu, B., Ni, F., Xiong, Q., & Yao, Z. (2020). Marine oligosaccharides originated from
seaweeds: Source, preparation, structure, physiological activity and applications.
Critial Reviews in Food Science and Nutrition, 61, 60–74.
Zou, P., Lu, X., Zhao, H., Yuan, Y., Meng, L., Zhang, C., & Li, Y. (2019). Polysaccharides

derived from the brown algae Lessonia nigrescens enhance salt stress tolerance to
wheat seedlings by enhancing the antioxidant system and modulating intracellular
ion concentration. Frontiers in Plant Science, 10, 48.

14