Optimization of microwave, ultra sonic and supercritical carbon dioxide assisted extraction techniques for curcumin from curcuma longa

Separation and Purification Technology 79 (2011) 50–55
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Separation and Purification Technology
journal homepage: www.elsevier.com/locate/seppur
Optimization of microwave, ultra-sonic and supercritical carbon dioxide assisted
extraction techniques for curcumin from Curcuma longa
P.S. Wakte
∗
, B.S. Sachin, A.A. Patil, D.M. Mohato, T.H. Band, D.B. Shinde
Pharmaceutical Technology division, Department of Chemical Technology, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004, India
article info
Article history:
Received 30 August 2010
Received in revised form 27 October 2010
Accepted 19 March 2011
Keywords:
Curcumin
Microwave assisted extraction
Soxhlet assisted extraction
Supercritical carbon dioxide assisted
extraction
Ultra-sonic assisted extraction
abstract
A bio-active phytochemical, curcumin, was isolated from dried rhizomes of Curcuma longa using Soxhlet,
microwave, ultra-sonic and supercritical carbon dioxide assisted extraction techniques. The quantifica-
tion of curcumin in resultant extracts was performed using pre-validated HPLC methodology. The critical
parameters viz. effect of pre-irradiation and soaking solvent on the curcumin yield were studied. The
extraction efficiency of all the above described techniques was established in terms of percent curcumin
yields and extraction rate constants. Prior to extraction, microwave and ultra-sonic irradiation of dry
curcuma powder resulted in 68.57 and 40.00% curcumin yield, respectively, whereas water soaked irradi-
ated curcuma powder yielded 90.47 and 71.42% curcumin recovery respectively, during a total extraction

period of five minutes. The maximum extraction rate constant of 47.49 × 10
−2
min
−1
was observed when
using microwave assisted acetone extract of water soaked curcuma rhizomes. The comparison of Soxhlet,
microwave, ultra-sonic and supercritical carbon dioxide assisted extraction in terms of percent yield and
required extraction period showed that microwave assisted extraction technique was more efficient for
the curcumin extraction from powdered C. longa rhizomes.
© 2011 Elsevier B.V. All rights reserved.
1. Introduction
Phytochemicals are, naturally occurring plant-based substances
are considered as potential therapeutic and prophylactic agents.
Among several examples, Curcumin, 1,7-bis(4-hydroxy 3-methoxy
phenyl)-1,6-heptadione-3,5-dione (Fig. 1) is a dietary phytochem-
ical obtained from the dried rhizomes of the turmeric plant
(Curcuma longa).
Turmeric has been used traditionally in “ayurvedic medicine” as
an antiseptic, wound healing, and anti-inflammatory compounds.
The yellow colour, which is characteristic of the turmeric rhizome,
is due to presence of 3–5% of curcuminoids. The curcuminoids
includes curcumin, demethoxycurcumin, bisdemethoxycurcumin
[1] and cyclocurcumin [2] of which curcumin is the major bio-active
constituent.
Traditionally curcumin has been used as a colouring, as a
flavouring substance and as a food preservative [3]. Because of
its wide spectrum of biological activity, an extensive number of
studies have been focused on curcumin. Recently, curcumin has
also been shown to display anti-oxidant [4], anti-cancer [5–7],
Abbreviations: MAE, microwave assisted extraction; SAE, Soxhlet assisted

extraction; SC CO
2
E, supercritical carbon dioxide extraction; UAE, ultra-sonic
assisted extraction.
∗
Corresponding author. Tel.: +91 240 2403307; fax: +91 240 240013.
E-mail address: (P.S. Wakte).
anti-viral, anti-infectious [8] and anti-amyloidogenic properties
[9].
For isolating curcumin as well as other curcuminoids from C.
longa rhizomes, numerous methods are reported: conventional
solvent extraction [10,11], hot and cold percolation [12], use of
alkaline solution [13] and insoluble salt [14].
Moreover, the extraction of curcuminoids using supercritical
carbon dioxide extraction (SC CO
2
E) [15–19], microwave assisted
extraction (MAE) [20] and ultra-sonic assisted extraction (UAE)
techniques [21] have also been reported. Despite the fact that SC
CO
2
extraction of curcumin has previously been reported, some
ambiguity in the use of modifier percentage remains [16]. More-
over, no single report specifically delineates the curcumin yields.
Finally, the length of the MAE and UAE curcuminoids extraction
cycle was quite long [20,21]. Thus, the objectives of this work were
to establish cost effective and efficient extraction procedures for
curcumin by SC CO
2
E, MAE and UAE, to compare the obtained yields

and to describe the processes using mass transfer and extraction
rate concepts.
2. Experimental procedures
2.1. General
The authenticated dried rhizomes of C. longa were ground to
a powder using a pulveriser (K.C. Engineers, Ambala, HR, India).
To select uniform particle size, rhizomes powder was sifted in a
1383-5866/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.seppur.2011.03.010
P.S. Wakte et al. / Separation and Purification Technology 79 (2011) 50–55 51
Fig. 1. Structure of curcumin.
sieve shaker (CIP Machineries, Ahmedabad, GJ, India) with sieves
of different sizes (12, 24, 45, 85 and 120 mesh, Swastika Electric
and Scientific Works, Ambala, HR, India) for a period of 15 min. The
rhizomes powder passed through 120 mesh sieve was collected
and used for further extraction experiments. The standard cur-
cumin (purity 98% by HPLC) was purchased from Sigma–Aldrich
(St-Louis, MO, USA). All solvents used for the extraction and the
chromatographic purpose were of analytical grade (Finar Chemi-
cals Ltd., Ahmedabad, GJ, India) and HPLC grade (Qualigens Fine
Chemicals, Mumbai, MH, India), respectively.
A commercial microwave oven with extraction assembly
(Model: MicroSYNTH, Max power: 1000 W, M/s Milestone, Shelton,
CT, USA), ultrasonic bath (Model: UCB 40, power: 150 W, M/s Spec-
tralab, Thane, MH, India) and a bench top SC CO
2
E unit (Model:
SFE 2000 series, Jasco International Co. Ltd., Hachioji, Tokyo, Japan)
were used for the extraction purposes. The extracts were prepared
freshly and stored temporarily in desiccators (Riviera Glass Pvt. Ltd.,

Mumbai, MH, India) under vacuum until the analysis.
2.2. HPLC method for curcumin analysis
The HPLC analysis of curcumin was essentially performed as
described earlier with the following modifications [22]. The Jasco
HPLC system was equipped with a PU 2089 quaternary gradient
pump, a UV-2075 plus detector, a LC-NetII/ADC communication
module and a HiQ Sil C-18 W column (4.6 mm × 250 mm, 5 ␮m
particle size, KYA Tech corporation, Tokyo, Japan) was used for
chromatographic purpose. Data analysis was carried out using a
ChromPass version 1.8.6.1 software.
The mobile phase consisted of 40% THF and 60% water contain-
ing 1% citric acid (v/v), adjusted to pH 3.0, with concentrated KOH
solution. It was filtered under vacuum through a 0.45␮m mem-
brane filter before use. The eluent flowed isocratically at a flow
rate of 1ml/min. Sample detection was acquired at 420 nm; and
the injection volumes were 10 ␮l.
The analytical method was validated to meet the acceptance
criteria as per International Conference on Harmonization of Tech-
nical Requirements for registration of Pharmaceuticals for Human
Use (ICH) guidelines.
Stock I (1 mg/ml) of curcumin was prepared by weighing
5 mg curcumin using a pre-calibrated weighing balance (Model:
CPA225D, Sartorius, Goettingen, Lower Saxony, Germany), trans-
ferring to 5 ml volumetric flask (Riviera Glass Pvt. Ltd., Mumbai,
MH, India), dissolving by ultra-sonication and diluting with mobile
phase.
Stock I was diluted serially with the mobile phase to obtain 7
calibration standards (10, 20, 40, 80, 160, 320 and 500 ng/ml), 3
quality control standards (15, 200 and 450 ng/ml) and 1 system
suitability standard (300 ng/ml).

The system suitability test was performed using 9 replicate
injections of system suitability standard before analysis of samples.
The acceptance parameters were less than 0.5 and 1.5% relative
standard deviation (RSD) for retention time and peak area, respec-
tively, along with more than 3500 theoretical plates. The linearity
and range was established using 7 calibration standards of cur-
cumin. The peak area vs. concentration plots were subjected to
linear least square regression analysis. Intra- and inter-day accu-
racy was established from quality control standards by evaluating
nominal and mean measured concentrations of quality control
standards which were compared and expressed as % difference
(Diff%). The Diff% between mean measured and nominal concen-
trations were calculated as follows:
Diff % =
Mean measured concentration − nominal concentration
nominal concentration
× 100 (1)
The intra- and inter-day precision (% RSD) was established by
analyzing 9 replicates each of 3 quality control standards on day 1
and again on each of three consecutive days. The lowest concentra-
tion with acceptable accuracy and precision was reported as limit
of quantification (LOQ) for curcumin.
System suitability test showed that retention time (% RSD < 0.5),
peak area (% RSD< 1.5) and number of theoretical plates (<3500)
for curcumin met the acceptance criteria on all the experimental
days. Analysis of the calibration standards showed good correlation
between concentration and resulting peak area (r
2
> 0.999) for cur-
cumin. The intra- and inter-day accuracy (Diff %) for curcumin was

in the range of −2.81 to +2.53 and −3.11 to +3.61, respectively. The
intra- and inter-day precision (% RSD) for curcumin was in the range
of 1.11 to 2.09 and 2.34 to 3.14, respectively. The LOQ of the method
was determined to be 9 ng/ml. The typical HPLC chromatogram of
standard curcumin, curcumin after Soxhlet, MAE, UAE and SC CO
2
E
is shown in Fig. 2A–E.
2.3. Soxhlet assisted extraction (SAE)
SAE was used for the maximum recovery of curcumin from the C.
longa rhizomes. Twenty grams of powdered rhizomes were placed
in thimble (Borosil, Mumbai, MH, India), which was inserted into a
Soxhlet apparatus and extracted with 100 ml acetone. The extrac-
tion was performed for 8 h. After the extraction period, the sample
was collected, filtered and analyzed for curcumin content by HPLC
as described earlier. The SAE of C. longa rhizomes was performed
in five replicates.
2.4. Microwave assisted extraction (MAE)
The MAE was carried out using two different experimental pro-
cedures. The first condition consisted of placing 20 g of dry C. longa
powder in a glass dish (thickness approximately 0.3 cm) and irradi-
ated for a pre-defined time period (1, 3, 5 or 7 min). The irradiation
was performed at 140 W microwave power.
After irradiation, the powder was suspended in ethanol or
acetone (mass:solvent ratio 1:3 w/v) and poured into an extrac-
tion assembly, which consisted of a mono-block rotor and nine
cylindrical vessels (height 8.5 cm × internal diameter 3.5 cm, SK-10
digestion rotor, M/s Milestone, Shelton, CT, USA). The stirring speed
of 400 rpm was kept constant throughout the extraction period. The
extraction was performed at 90 W (extraction solvent: ethanol) and

60 W (extraction solvent: acetone) microwave power.
After the pre-defined extraction period of 5 min, the samples
were collected from the extraction assembly, filtered and analyzed
for its curcumin content by HPLC.
The second experimental condition consisted of placing 20 g of
the dry powder of C. longa in water or ethanol (mass:solvent ratio
1:2 w/v) for a period of 24 h at 20
◦
C. Before irradiation, the excess
solvent content was removed and the wet powder was irradiated
for a pre-defined time period as described in the first experimen-
tal condition. The water soaked powder was irradiated at 270W
whereas ethanol soaked powder was irradiated at 50 W microwave
power.
52 P.S. Wakte et al. / Separation and Purification Technology 79 (2011) 50–55
Fig. 2. Chromatographic profiles of curcumin: curcumin standard (A) and curcumin obtained after Soxhlet assisted extraction (B), microwave assisted extraction (C), ultra-
sonic assisted extraction (D) and supercritical carbon dioxide assisted extraction (E).
The microwave-irradiated powder was suspended in solvents,
extracted and collected samples were analyzed as described in first
experimental condition.
2.5. Ultra-sonic assisted extraction (UAE)
The UAE was performed at the fixed power of 150 W using iden-
tical experimental conditions as described for MAE. Under the first
condition, dry powder (20 g) was placed in a 500 ml glass beaker
and exposed to ultrasonic waves for pre-defined time periods (1,
3, 5 or 7 min). The irradiated powder was suspended in ethanol
or acetone (mass:solvent ratio 1:3 w/v) and sonicated for 5 min
at 21 ± 2
◦
C. The samples were collected, filtered and analyzed for

curcumin content by HPLC.
In the second experimental condition, the dry powder of C. longa
(20 g) was soaked in water or ethanol (mass:solvent ratio 1:2 w/v)
for a period of 24 h at 20
◦
C. Before irradiation, the excess solvent
was removed and the wet powder was exposed to ultrasonic waves,
suspended in solvents and after extraction, samples were analyzed
as described in the first experimental condition.
2.6. Supercritical carbon dioxide extraction (SC CO
2
E)
A flow diagram of SC CO
2
E system is presented in Fig. 3. The
extractor column was densely packed with 10 g of C. longa powder.
The column was carefully fixed in a column oven. The CO
2
from
the cylinder was passed through chiller unit (∼277 K) via a siphon
tube, delivered and compressed to the desired working pressure
by CO
2
delivery pump (PU 2080-CO
2
Plus, Jasco International Co.
Ltd., Hachioji, Tokyo, Japan) mounted with a pressure regulator
(BP-2080 Plus, Jasco International Co. Ltd., Hachioji, Tokyo, Japan),
respectively. The organic modifier (10% ethanol) was introduced
into system by solvent pump (PU 2080 Plus, Jasco International Co.

Ltd., Hachioji, Tokyo, Japan). The temperature and pressure of CO
2
Fig. 3. Flow diagram of SC CO
2
E system.
P.S. Wakte et al. / Separation and Purification Technology 79 (2011) 50–55 53
Fig. 4. Effect of microwave irradiation on dry rhizomes.() % Extraction of curcumin
using ethanol and (
) % extraction of curcumin using acetone.
was manipulated with a pressure regulator. The SC CO
2
was passed
through an extraction column (150 mm length × 15 mm i.d., 10g
capacity) which was placed in a thermostatically controlled oven
(CO-2060 Plus, Jasco International Co. Ltd., Hachioji, Tokyo, Japan).
After the pressure andthe fluid flow rate reached thedesired values,
the six-port valve was turned on so that SC CO
2
was passed through
the extractor; this was counted as the start of the extraction cycle.
In the first operating mode, sufficient SC CO
2
was introduced for a
60 min static conditioning so that sufficient contact with C. longa
powder was established. The second operating mode was followed
by a steady flow of SC CO
2
under the dynamic extraction condi-
tion for 300 min. The exit fluid from the extractor was expanded to
ambient pressure by a pressure regulator. The extract was collected

in a glass vial and analyzed for curcumin content by HPLC.
2.7. Extraction rate constant
At constant volume, assuming that the curcumin mass transfer
process from solid to liquid boundary could be formally treated
as an irreversible first-order reaction, the equation of curcumin
extraction rate constant is:
k =

1
t

ln
S
0
S
t
(2)
where k is the extraction rateconstant (min
−1
), t the extraction time
(min), S
0
the total yield of curcumin (w/w) and S
t
is the remained
extractible curcumin after extraction time t (w/w) [23].
2.8. Statistical analysis
Each experiment was performed in five replicates and the data
was subjected to calculations of mean ± S.E. The mean values were
used for drawing the graphs.

3. Results and discussion
3.1. Soxhlet assisted extraction (SAE)
The conventional SAE of powdered curcuma rhizomes was car-
ried out to recover the maximum extractable amount of curcumin.
After SAE, 2.1 ± 0.1% curcumin was obtained.
3.2. Microwave assisted extraction (MAE)
3.2.1. Effect of microwave irradiation
Fig. 4 depicts the effect of microwave irradiation on the extrac-
tion of curcumin. The dry powder of curcuma rhizomes was
exposed to microwave irradiation and further extracted with
Fig. 5. Effect of microwave irradiation on pre-soaked rhizomes. () % Extraction of
curcumin using ethanol from ethanol soaked curcuma powder, (
) % extraction of
curcumin using ethanol from water soaked curcuma powder and (
) % extraction
of curcumin using acetone from water soaked curcuma powder.
ethanol or acetone. The extraction solvents were selected on the
basis of pilot experiments [Data not shown] and prior reports of
curcumin extraction [20].
The curcumin percentage in the extract increased proportion-
ally with longer microwave irradiation exposure periods. The 1,
3 and 5 min exposures of microwave irradiation resulted in 9.71,
29.14 and 48.57% curcumin recovery, respectively, while using
ethanol as the extraction solvent. When acetone was used as the
extraction solvent, the curcumin concentration in the extract were
13.71, 41.14 and 68.57% for microwave irradiation periods of 1,
3 and 5 min, respectively. Further increase in microwave irradia-
tion exposure period did not show any increment in % curcumin
extraction.
3.2.2. Effect of soaking solvent

Fig. 5 represents the effect of different soaking solvents on cur-
cumin extraction. On the basis of dipole moment and sensitivity
towards microwave irradiation, water and ethanol were selected
as soaking solvents. The rhizome powder was soaked in ethanol or
water for 24 h at 25
◦
C. The ethanol soaked material was extracted
with ethanol whereas water soaked material was extracted with
ethanol or acetone.
While using ethanol as a soaking and an extraction solvent,
the obtained curcumin content was greater by 15.54–57.14% when
compared to the microwave irradiation treatment with exposure
period of 1–5 min. The water soaked powder, when extracted
with ethanol, showed curcumin content up to 67.01% after 5min
microwave irradiation. The acetone extract of water soaked pow-
der demonstrated an increase in curcumin content with increased
microwave irradiation exposure period. The net curcumin content
in resulted extract was enhanced from 37.49 to 90.69% which was
found to be constant even after 7 min of microwave irradiation
exposure.
Earlier Dandekar and Gaikar have reported the effect of water
soaking of C. longa on the extraction of curcuminoids. The study was
performed using MAE technique wherein the soaked powder was
extracted without any pre-treatment like microwave irradiation.
The maximum yield of curcuminoids was obtained after 24 h of
soaking [20].
The preliminary experiments of the present work showed
the prominent effect of microwave irradiation on the curcumin
extraction so the effect of microwave irradiation was studied in
combination with different soaking solvents. The soaking solvents

viz. water and ethanol wereused as modifier to bring about effective
extraction of curcumin from C. longa.
54 P.S. Wakte et al. / Separation and Purification Technology 79 (2011) 50–55
Fig. 6. Effect of ultra-sonic irradiation on dry rhizomes. () % Extraction of curcumin
using ethanol and (
) % extraction of curcumin using acetone.
3.3. Ultra-sonic assisted extraction (UAE)
3.3.1. Effect of ultra-sonic irradiation
Fig. 6 shows the effect of ultra-sonic irradiation on curcumin
extraction from C. longa rhizome powder. The dry powdered mate-
rial was extracted with ethanol or acetone after exposure to
ultra-sonic irradiation. The ethanol extract showed 6.57–32.85%
curcumin content after the ultra-sonic irradiation exposure period
of 1–5 min. Further increases in the exposure period did not show
any increase in the curcumin content of the extract. The acetone
extract showed an increase in curcumin concentration, from 8 to
40%, after the ultra-sonic irradiation period of 1 to 5 min.
3.3.2. Effect of soaking solvent
The effect of soaking solvents on curcumin extraction is depicted
in Fig. 7. When ethanol was used as the soaking and extrac-
tion solvent, 1–5 min ultra-sonic irradiation exposure resulted in
17.55–61.90% curcumin extraction, which was found to be constant
even after 7 min irradiation period.
After ultra-sonic irradiation over the period of 1–5 min,
water soaked powder was extracted with ethanol and ace-
tone. The ethanol and acetone extract showed 19.70–66.66% and
22.15–71.42% curcumin content, respectively.
Mandal et al. has reported the UAE of curcumin wherein the
maximum curcumin extraction was achieved in 70 min [21]. The
present work demonstrated the maximum curcumin yield by UAE

within 5 min extraction period.
Fig. 7. Effect of ultra-sonic irradiation on pre-soaked rhizomes. () % Extraction of
curcumin using ethanol from ethanol soaked curcuma powder, (
) % extraction of
curcumin using ethanol from water soaked curcuma powder and (
) % extraction
of curcumin using acetone from water soaked curcuma powder.
Fig. 8. Curcumin extraction by supercritical CO
2
.() % Extraction of curcumin from
curcuma powder using supercritical CO
2.
.
3.4. Supercritical carbon dioxide extraction (SC CO
2
E)
The SC CO
2
E of curcumin from C. longa powder was achieved
using following optimal extraction conditions: pressure – 30 Mpa,
temperature – 50
◦
C, CO
2
flow rate – 5 ml/min, modifier – 10%
ethanol, static time – 60 min and dynamic time – 300 min. Fig. 8
presents the extraction period vs. the curcumin concentration of
the extract. After the extraction period of 240 min, the result-
ing extract showed 69.37% curcumin concentration which was
observed to be constant, even after 300 min of extraction.

The HPLC chromatogram of SC CO
2
extract showed presence of
only one peak representing curcumin. It has been demonstrated
by Leal et al. that slight modification in pressure and CO
2
flow
rate in SC CO
2
E changed the composition of C. longa extract [19].
Boumann et al. showed that 10% ethanol when used as SC CO
2
mod-
ifier, yielded 100% curcumin from two commercial finely ground
dry C. longa samples [15]. This is in good agreement with obtained
results of SC CO
2
E.
Although SC CO
2
E of curcumin from C. longa powder has pre-
viously been reported by Chassagnez-Mendez et al., the curcumin
recovery was around only 1% over the extraction period of 100 min
using ethanol as modifier wherein the ethanol content in gaseous
phase was not mentioned [16]. Moreover, the time vs. wt % cur-
cuminoids extraction profile showed the presence of curcumin,
demethoxy curcumin, bis-demethoxy curcumin and total curcum-
inoids.
3.5. Extraction rate constant
The extraction rate constant was calculated on the basis of total

curcumin yield that was obtained. In this study S
0
(0.021 g cur-
cumin/g C. longa) was obtained with a Soxhlet extraction for 8h
with acetone. The extraction rate constant (k) for each irradiation
exposure point (1, 3, 5 and 7 min) was calculated and the values are
presented in Tables 1 and 2.
As depicted in Table 1, the k value was increased with increased
microwave and ultra-sonic irradiation exposure period. The treat-
ment of water and ethanol as soaking solvent further increased the
k value. In the case of microwave and ultra-sonic assisted extrac-
tions, the water soaked powder after irradiation when extracted
with acetone resulted in a higher extraction rate constant.
When the SC CO
2
E technique was used for the extraction of
curcumin, the k value was increased from 0.09 × 10
−2
min
−1
to
0.48 × 10
−2
min
−1
when the extraction period was increased from
60 to 300 min (Table 2).
P.S. Wakte et al. / Separation and Purification Technology 79 (2011) 50–55 55
Table 1
Microwave and Ultra-sonic assisted extraction technique based curcumin extraction rate constants.

Extraction technique Soaking solvent Extraction solvent Extraction rate constant
a
(min
−1
) % Yield
b
1 min 3 min 5 min 7 min
Microwave – Ethanol 2.04 × 10
−2
6.89 × 10
−2
13.29 × 10
−2
13.86 × 10
−2
48.57
– Acetone 2.95 × 10
−2
10.60 × 10
−2
23.14 × 10
−2
25.39 × 10
−2
68.57
Ethanol Ethanol 3.38 × 10
−2
10.14 × 10
−2
16.94 × 10

−2
17.10 × 10
−2
57.14
Water Ethanol 4.39 × 10
−2
13.17 × 10
−2
21.97 × 10
−2
22.18 × 10
−2
66.66
Water Acetone 9.40 × 10
−2
28.20 × 10
−2
47.02 × 10
−2
47.49 × 10
−2
90.47
Ultra-sonic – Ethanol 1.35 × 10
−2
4.39 × 10
−2
7.96 × 10
−2
8.54 × 10
−2

32.85
Acetone 1.66 × 10
−2
5.48 × 10
−2
10.21 × 10
−2
10.69 × 10
−2
40.00
Ethanol Ethanol 3.86 × 10
−2
11.58 × 10
−2
19.30 × 10
−2
19.49 × 10
−2
61.90
Water Ethanol 4.39 × 10
−2
13.17 × 10
−2
21.97 × 10
−2
22.18 × 10
−2
66.66
Water Acetone 5.01 × 10
−2

15.03 × 10
−2
25.05 × 10
−2
25.30 × 10
−2
71.42
a
Extraction rate constant is expressed in min
−1
at 1, 3, 5 and 7 min irradiation exposure period.
b
The % yield of curcumin is calculated after total extraction time of 5 min.
Table 2
Supercritical carbon dioxide assisted extraction technique based curcumin extraction rate constants.
Extraction technique Extraction solvent Extraction rate constant
a
(min
−1
) % Yield
b
60 min 120min 180 min 240 min 300min
SC CO
2
ECO
2
+ ethanol 0.09 × 10
−2
0.32 × 10
−2

0.43 × 10
−2
0.48 × 10
−2
0.48 × 10
−2
69.36
a
Extraction rate constant is expressed in min
−1
at 60, 120, 180, 240 and 30 min extraction period.
b
The % yield of curcumin is calculated after total extraction time of 24 min.
3.6. Comparison of SAE, MAE, UAE and SC CO
2
E on the basis of
curcumin yield and extraction time
The conventional Soxhlet assisted acetone extract of C. longa
powder resulted in a 2.1% curcumin yield after 8 h of extraction.
Using the Soxhlet extraction as the basis, the curcumin yields of
MAE, UAE and SC CO
2
E techniques were calculated. The MAE of C.
longa for 5 min recovered a maximum of 90.47% curcumin, whereas
UAE resulted in 71.42% of curcumin with acetone as the extraction
solvent (Table 1). The SC CO
2
E showed a 69.36% curcumin recovery
after an extraction period of 240 min (Table 2). The comparison of
yield and the time required for the extraction of curcumin demon-

strated that MAE technique is more efficient than SAE, UAE and SC
CO
2
E techniques.
4. Conclusion
Efficient MAE, UAE and SC CO
2
E methods for curcumin from
C. longa has been developed. Compared among each other, high
extraction recovery at minimum extraction time was obtained with
MAE. Water soaking effectively contributed in curcumin extraction.
Extraction rate constant of curcumin has been calculated based on
the experimental results. The value of curcumin extraction rate
constant k increased with use of water as soaking solvent and ace-
tone as extraction solvent.
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