176

Chapter 6

Ultrasound Assisted Extraction

of Curcumin from Curcuma

Amada

177

Chapter 6

ULTRASOUND ASSISTED EXTRACTION OF CURCUMIN

FROM CURCUMA AMADA

The present work investigates and elucidates the extraction of the natural product by

ultrasound assisted method and its comparison with conventional extraction methods.

The objectives of this research are to study the ultrasonic extraction of curcumin from

Curcuma amada and comparison with conventional extraction processes. Further it is

planned to study the effect of various operating parameters on the extraction.

6.1 Introduction

Natural plants contain range of bioactive constituents such as lipids, phytochemicals,

pharmaceutics, flavors, fragrances and pigments. The plant extracts are widely used in

cosmetics, pharmaceutical and food industries. Traditional mechanical and chemical

processes have been regularly used to extract costly natural compounds from plants

for commercial purpose [1]. Different processes which are used for the extraction of

products from plant materials include solvent extraction [2], steam distillation [3],

high hydrostatic pressure extraction [4], pulse electric field process [5], high pressure

process [6] etc. Traditional techniques are often associated with high temperature

operations, longer extraction times and poor extraction efficiency [7-12]. Mechanical

processes are associated with lower extraction yields and in case of chemical

extraction methods organic solvents are used which are harmful to environment and

human beings [10-11,13]. Moreover, many natural products are thermally unstable

and may be degraded during thermal extraction [8-11]. High energy consumption is

also one of prominent disadvantage of conventional extraction processes [14].

Stringent rules related to the use of organic solvents have encouraged researchers to

develop clean extraction technologies [15].

There is growing demand for new extraction techniques with shortened extraction

time, reduced organic solvent consumption and increased pollution prevention [1].

Novel extraction methods such as ultrasound-assisted extraction [11], microwave-

assisted extraction [16], supercritical fluid extraction [17-18] and accelerated solvent

extraction [19-20] are fast and efficient for extracting chemicals from plant sources.

178

Recently, the application of ultrasound in solvent extraction has been the topic of

many investigations. Ultrasound can be effectively used to improve the extraction rate

by increasing the mass transfer rates and possible rupture of cell wall due to formation

of microcavities leading to higher product yields with shorter extraction time and

lesser solvent consumption [21]. The formation and collapse of microscopic bubbles

during ultrasonic irradiations releases huge amount of energy as heat, pressure and

mechanical shear [22]. The mechanical and thermal effects of ultrasound result in

disruption of cell walls, particle size reduction and enhanced mass transfer across cell

membranes [23-24]. The collapse of cavitation bubbles generates micro-turbulence,

high-velocity inter-particle collisions and perturbation in micro-porous particles of the

plant materials leading to acceleration of eddy diffusion and internal diffusion [21,

23-25].

Curcuma longa commonly known as turmeric belonging to the family Zingiberaceae

has been used traditionally in “ayurvedic medicine” as an antiseptic, wound healing,

and anti-inflammatory compounds. Curcuma amada, (C. amada) is a closely related

species of C. longa commonly known as “Mango ginger” due to its characteristic raw-

mango aroma. The rhizome of Curcuma amada is rich in essential oils and more than

130 chemical constituents with biomedical significance have been isolated from it

[26]. Curcumin, 1,7-bis(4-hydroxy 3-methoxyphenyl)-1,6-heptadione-3,5-dione is a

dietary phytochemical found in the dried rhizomes of curcuma species. Curcumin

provides about 75 % of the total curcuminoids, while demethoxycurcumin provides

10-20 % and bisdemethoxycurcumin generally provides < 5 %. The most important

use of curcumin is in the prevention of cancer and treatment of infection with human

immunodeficiency virus (HIV) [27-28].

For isolating curcuminoids from rhizomes of Curcuma species several methods are

reported such as steam distillation [29], conventional solvent extraction [30-33], use

of alkaline solution [34] and hot and cold percolation [35] etc. Further, the modified

methods such as microwave assisted extraction (MAE) [36-37], supercritical carbon

dioxide [36,38] and ultrasound assisted extraction (UAE) [27, 39] are also reported.

In this work Curcumin was selected as the model plant constituentto study the

comparative effect of ultrasound assisted extraction with conventional Soxhlet

179

extraction as curcumin has got many valuable applications. The key objectives of this

work are to perform a laboratory scale study investigating

1) Ultrasound assisted extraction process for curcumin from C. amada and its

comparison with the conventional extraction processes.

2) The effect of parameters affecting the extraction process such as type of

solvent, extraction time, solid to solvent ratio, temperature, ultrasonic

frequency and ultrasonic power.

3) Optimization of sonication conditions for maximum recovery of curcumin.

4) Extraction kinetics of ultrasound assisted extraction of curcumin.

6.2 Experimental Method

6.2.1 Materials

The authenticated dried rhizomes of C. amada were bought from the local traditional

medicine shop Green Pharmacy, Pune, India. These rhizomes of C. amada were

washed, shade dried and ground to a powder using a pulverizer. After that the powder

was screened through different screens for 20 min for getting different particle sizes.

The range of particle sizes was from 0.09 to 0.85 mm. Curcumin standard of

analytical reagent grade was provided by LobaChemie Pvt. Ltd., India. Different

solvents used for the extraction and the chromatographic purpose were of analytical

grade and HPLC grade. Acetonitrile and methanol were used as solvent for High

Pressure Liquid Chromatography. HPLC grade and other solvents were procured from

Merck Specialities Private Limited, India.

6.2.2 Soxhlet extraction

Conventional Soxhlet apparatus which consists of distillation flask, thimble holder

and the condenser was used for extraction. The arrangement in the extractor is such

that the vapors of the solvent are generated from the solvent reservoir which passes

through the thimble before going to the condenser where they are condensed. The

condensed fresh solvent comes in contact with C. amada powder in the thimble where

extraction occurs. When the liquid reaches the overflow level in the thimble, the

liquid moves through the siphon back into the reservoir carrying extracted solutes into

the bulk liquid. During the actual experiment 10 g of C. amada powder was placed in

thimble and 250 mL of solvent was taken in solvent reservoir. The Soxhlet extraction

180

was performed for 8 h at 78oC. Samples were withdrawn at regular intervals and

filtered for HPLC analysis. To compare the efficiency of different extraction

procedures the yield obtained with Soxhlet extraction was considered as maximum

yield (considered as 100% yield) [36] which corresponds to 12.75 mg of curcumin

extarcted per g of C. amada powder. All other experimental results are compared with

this value.

6.2.3 Batch extraction

The measured quantity of the C. amada powder (6 g) was taken in a glass reactor and

150 mL ethanol corresponding to soild: solvent ratio of 1:25 was taken in a glass

reactor equipped with a propeller agitator for agitation. The agitation was provided to

ensure that the raw material particles remained in suspension during the total run time.

The experiment was carried out at room temperature (30oC) for 8 h. Samples were

withdrawn at regular intervals and filtered prior to HPLC analysis.

6.2.4 Ultrasound assisted extraction (UAE)

Ultrasound assisted extraction operation was done with 6 g of C. amada powder

mixed with 150 mL of solvent. The experimental unit consists of a glass vessel,

ultrasound probe with 250 W rated output power, 22 kHz frequency and Probe tip

diameter 20 mm (Dakshin, Mumbai India). The sonication probe was placed directly

into the solvent containing the C. amada powder and the mixture was irradiated for

1h. Extraction vessel was placed inside a constant temperature water bath to ensure

that the temperature of the solvent reservoir did not increase drastically. Ultrasonic

horn was operated in pulsed mode (5 s on followed by 5 s off). Samples were

withdrawn at regular intervals and then filtered to get clear extract which was then

diluted and analyzed using HPLC. A stirrer was used to obtain good solvent/plant

material contact.

Extraction experiments were carried out to study the effect of parameters which affect

the extraction yield such extraction time, solvent, solid to solvent ratio, particle size,

extraction temperature, ultrasound power and ultrasonic frequency. Five different

solvents ethanol, methanol, acetone, ethyl acetate and water were employed to select

the most suitable solvent for extraction operation. Solid to solvent ratio was varied

from 1:15 to 1:55, keeping all other parameters constant. The effect of raw material

particle size was studied using four different sizes, 0.09, 0.10, 0.21 and 0.85 mm. To

181

study the effect of temperature on extraction, the temperature of the extraction flask

was varied from 25 to 55oC in the intervals of 10

oC. To study the effect of ultrasound

frequency, another probe with 40 kHz frequency having similar specification as the

22 kHz probe was used [Dakshin, Mumbai, India, Probe tip diameter 20 mm and 250

W rated output power]. The effect of ultrasound power has been studied by varying

rated power from 130 to 250 W at frequency of 22 kHz and keeping other

experimental parameters constant.

A common problem with the ultrasound is that the actual power supplied inside the

vessel is lower than that provided by the output controller. Calorimetric studies were

performed to study the energy efficiency of the ultrasonic probe. Actual power

dissipated in the bulk of liquid was calculated by measuring the rise in temperature of

a fixed quantity of water for a given time as per the method suggested in the literature

[40]. Calorimetric studies indicated the energy efficiency of the probe to be around

5.6 %.

A Jeol JSM-6360A analytical scanning electron microscope (SEM) was used to check

surface structure of C. amada powder before and after ultrasonic irradiation.

6.2.5 Kinetic modelling

Mathematical modelling can be used in the design, optimization and control of the

extraction processes, as well as provides useful information for scaling up the

equipment. Modelling and optimization can help in increasing the extract yield [41].

Combination of mathematical principles and experimental investigations can be used

for predicting the extraction yield and influence of various operating parameters.

Several theoretical, empirical and semi-empirical models simulating the solid–liquid

extraction of bioactive substances from natural materials are reported [42]. However it

should be noted that the variations in the type of models and even in the same model

can be ascribed to the differences in target analytes, structure of raw material source

and the method of extraction [43]. Mathematical models to describe ultrasound-

assisted extraction of natural products from plant constituents are also reported in the

literature. Kinetics of ultrasound assisted extraction of resinoid was described by

phenomenological model. The model successfully described the two-step extraction

process consisting of washing followed by diffusion of extractable substances and

showed that ultrasound influenced only the first step [41]. The mechanism of mass

182

transfer of phenolics in wine under ultrasound environment was described in terms of

the release kinetics of total phenolics by a second-order kinetic model and a diffusion

model [44]. The kinetics of UAE of phenolic compounds from grape marc was

explained by the two site kinetic model and the effective diffusion coefficient was

determined by the diffusion model based on the Fick’s second law [42]. Similarly

ultrasonically mediated extraction of phenolic compounds from grape pomace was

represented by Weibull model [45]. A mathematical model based on Fick’s first law

was used for obtaining optimal parameters in the ultrasound-assisted extraction of

capsaicin from red peppers. The prediction tendency of the mathematical model was

in very good agreement with the experimental data and the error was in the allowable

range [46]. Peleg’s model was used by Jokic et al. [47], Karacabey et al. [43] and

Vetal et al. [48] to explain the extraction of different natural compounds.

In the present work Peleg’s model has been used to estimate extraction rate constant,

initial extraction rate and equilibrium concentration. The influence of operating

parameters on the kinetic parameters was also analyzed.

6.2.6 Analytical method

The analysis of curcumin was performed using high performance liquid

chromatography (Bischoff, Column: C18, 250 L x4.6 mm, 5 µm). HPLC column was

cleaned by elution, filtration, and degasion. Elution runs for 1 hour, then the column

was washed using acetonitrile for 1 h. After the washing step, the column was

conditioned by eluting mobile phase for 30 minutes and at the same time it was run

for baseline. The mobile phase consisted of 2% acetic acid and acetonitrile (45:55)

which was filtered under vacuum through a 0.45µm membrane filter before use. The

eluent flowed isocratically at a flow rate of 1mL/min. The detector was adjusted at

425 nm and 35oC with the injection volume of 10 µL. Calibration curve was prepared

for five concentrations of curcumin standard solution (10, 20, 30, 50, and 100 ppm).

Before use each solution was filtered by syringe filter 0.45 μm. The solutions were

injected into injector and the area under curve was recorded. The calibration curve

was plotted by using peak area of curcumin as ordinate (y) and concentration of

curcumin as abscissa (x) and subjected to linear least square regression analysis. The

equation of linear regression of the calibration curve was calculated as:

y = 1174.6 x (1)

183

Analysis of the calibration standards showed good correlation between concentration

and resulting peak area for curcumin with R2> 0.996. The calibration curve is shown

in figure 6.1 and Chromatographic profile of curcumin obtained after Soxhlet

extraction in shown in figure 6.2.

Figure 6.1: Calibration curve for Curcumin

Figure 6.2: Chromatographic profile of curcumin obtained after Soxhlet extraction

y = 1174.6 x

0

20000

40000

60000

80000

100000

120000

140000

0 20 40 60 80 100 120

Are

a

Curcumin concentration (ppm)

0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0

-50,000

100,000

200,000

300,000

450,000CURCUMIN #7 2 hr 22-11-2013 UV_VIS_1µ AU

min

1 - 3.0532 - 5.0423 - 6.3704 - 7.457 5 - 10.7946 - 17.210

7 - 19.324

8 - curcumin - 21.789

WVL:425 nm

184

6.3 Results and Discussion

6.3.1 Kinetic model

In the literature, different models have been used for the description of extraction

process and the assessment of effects of operating parameters on the extraction

efficiency and product quality. Peleg introduced the following well-known

semiempirical kinetic model (Equation 2) to describe the sorption isotherms of food

materials [49].

tKK

tCCt

21

0

(2)

Further, this model was used for describing the extraction kinetics of natural products

because the shape of extraction curves (concentration vs. time) and the sorption

curves (moisture content vs. time) is alike [47]. Hence the experimental data were

fitted with Peleg’s model (Equation 2) to explain the solid–liquid extraction of

curcumin from C. amada. In equation (2), Ct is the concentration of curcumin at time

t (mg curcumin/g C. amada powder), K1 is Peleg’s rate constant (min.g/mg) and K2 is

Peleg’s capacity constant (g/mg) and Co is the initial concentration of target solute

(curcumin). Initially fresh solvent is used therefore Co is zero and this term can be

omitted from Peleg’s equation. The modified Peleg’s equation representing the

concentration of target solute (curcumin) in extraction solvent against time can be

written as:

tKK

tCt

21 (3)

Peleg’s rate constant K1 andPeleg’s capacity constant K2 can be calculated from the

slope and intercept of the graph of 1/Ct vs. 1/t. Once these constants are calculated

then Ct at different times can be calculated by using equation (3).

6.3.2 Kinetics of ultrasound assisted extraction

The aim of this study was to examine the influence of different solvents (ethanol,

methanol, acetone, ethyl acetate and water), extraction temperatures (25, 35, 45 and

55 ◦C), solid to solvent ratio (1:15, 1:25, 1:35, 1:45 and 1:55), particle size (0.09,

0.106,0.21 and 0.85 mm), rated power (130, 160, 190, 220 and 250 W) and frequency

(22 and 40 kHz) on the extraction of curcumin from C. amada. The experimental

185

results are compared with the modelled values obtained with equation (3) for various

process parameters.

Deciding the irradiation time is a critical decision in ultrasound assisted extraction

processes. The sonication time has to be carefully optimized, since exposure to

ultrasonic irradiations may damage the quality of the solute in some cases of heat

sensitive materials [50]. The yield of extraction increases with time till the

equilibrium between the objective constituents in the plant cells and in the solvent, but

once the equilibrium is established it does not increase with time [51].

The amount of curcumin extracted per g of C. amada with time is shown in figure 6.3

for different solvents.

Figure 6.3: Effect of different solvents on extraction of curcumin using Ultrasound

assisted extraction (Solid to solvent ratio- 1:25, Particle size- 0.09 mm, Temperature-

35oC, Ultrasound frequency- 22 kHz, Ultrasound power- 250 W)

As seen in figure 6.3 the extraction yield was significantly time-dependant and

increased with irradiation time. However, the extraction yield of curcumin increased

very fast during the first 15 min. This can be attributed to the curcumin concentration

difference between the plant material and the solvent and the easy availability of

curcumin in the outer part of particles in the initial period. Once the curcumin from

the outer part was extracted the yield of curcumin increased slowly with the extraction

time till 1 h because of the lower concentration gradient and the difficulty in

extracting the remaining curcumin located in the interior part of the plant cell. Thus

0

2

4

6

8

10

0 10 20 30 40 50 60

Con

cen

trati

on

(m

g

Cu

rcu

min

/g)

Time (min)

Ethanol

Methanol

Acetone

Ethyl acetae

Pelegs Model

186

the results indicated that the efficient extraction period for achieving maximum yield

of curcumin was about 1 h. Therefore all the experiments were carried out for 1 h

ultrasound irradiation time.

6.3.3 Optimization of process parameters and validation of model

6.3.3.1 Effect of extraction solvent

The first step in any extraction method is the selection of the most suitable solvent for

extracting the objective constituents from the matrix of the sample. The interaction

between natural products and the solvent system is quite unpredictable due to

complex structure of natural products and chemical characteristics of the solvents.

Selection of solvent is done according to the purpose of extraction, polarity of the

interested components, polarity of undesirable components, overall cost and safety

[52]. Among the various properties of solvents, the polarity of solvent is the most

important property because the solubility of different natural products depends on the

polarity of solvents. Polar solute is soluble in polar solvents like ethanol, methanol,

dimethyl formamide (DMF), etc; while nonpolar solutes dissolve in non-polar

solvents like benzene, hexane, cyclohexane, toluene, etc. [21]. Polarity increases the

permeability of the cell wall and thus helps in increasing the extraction yield [48].

Also the ability of the solvent for absorbing and transmitting the energy of the

ultrasound is an important consideration in ultrasound assisted extraction processes.

For selection of the solvent, choice was made between five different solvents ethanol,

methanol, acetone, ethyl acetate and water. The extraction conditions were solid to

solvent ratio of 1:25, raw material particle size 0.09 mm, ultrasound power 250 W and

frequency 22 kHz and the results are reported in figure 6.3. In figure 6.3 the results

are not reported for water as a solvent because less than 2% curcumin was extracted

with water. Though water is a very polar solvent it has been observed that water has a

poor capacity of extraction of curcumin due to low solubility of curcumin in water.

In figure 6.3, it can be seen that use of methanol and acetone resulted in 62.6 and

60.9% curcumin extraction respectively and maximum 72% curcumin extraction

(9.18 mg/g) was achieved with ethanol. There is marginal difference in the recoveries

obtained with methanol and acetone. Moreover as compared to ethanol, methanol and

acetone, use of ethyl acetate resulted in lesser extraction of curcumin (50.6%) because

of its non polar nature.

187

The highest extraction was achieved with ethanol due to its physical properties such

as higher polarity, vapour pressure, lower viscosity and surface tension. The solvent’s

vapour pressure is a vital factor amongst these physical properties and the vapour

pressure is proportional to the boiling point. As compared to other solvents used in

this study ethanol has the highest the boiling point except that of water. Thus, the

relatively high boiling point and its molecular affinity towards curcumin results in

ethanol being a better solvent than others [53-54]. Hence ethanol, which is generally

recognized as a safe (GRAS) solvent, was selected as the most appropriate solvent for

extraction of curcumin.

The experimental data were fitted with Peleg’s model and the extraction curves

constructed by using Peleg’s model and their comparison with the experimental data

are shown in figure 6.3. The prediction tendency of the mathematical model shown in

figure 6.3 reasonably matches the experimental data. The obtained parameters of

Peleg’s model (constants K1 and K2), and the root mean squared deviation (RMSD)

values are shown in Table 6.1.

Table 6.1:Effect of different solvents on the kinetic parameters: Values of Peleg’s

constants and comparison between experimental values and model values for

curcumin yield

Solvent Experimental

Ceq

(mg

Curcumin/g)

K1

(min.g/mg)

K2

(g/mg)

Calculated

Ceq

(mg

Curcumin/g)

RMSD

(mg/g)

Ethanol 9.18 0.33 0.10 8.88 0.36

Methanol 7.98 0.74 0.11 7.90 0.10

Acetone 7.76 0.19 0.12 7.62 0.12

Ethyl

acetate 6.45 0.17 0.15 6.33 0.14

6.3.3.2 Effect of extraction temperature

Temperature affects many physical properties such as viscosity, diffusivity, solubility,

vapor pressure and surface tension [53, 55]. The effect of temperature on extraction of

188

curcumin was investigated for temperatures ranging from 25 to 55oC. The other

operating parameters were as follows: solvent ethanol, solid to solvent ratio of 1:25,

raw material particle size 0.09 mm, ultrasound power 250 W and frequency 22 kHz

for an extraction period of 60 min. The results are depicted in figure 6.4.

The temperature affects solute diffusivity and solute solubility. With rise in

temperature solute diffusivity increases, thus the extraction improves. Generally, the

higher extracting temperature is favorable for extraction due to the increased

solubility [18, 52, 56]. In the present work, extraction of curcumin increased with an

increase of temperature from 25 to 55oC as demonstrated in figure 6.4. A significant

increase in curcumin extraction was observed over the extraction temperature range

(25-55oC). At 25

oC, 66% curcumin (8.41mg/g) was extracted whereas higher

temperature of 55oC resulted in 93.4% curcumin extraction (11.90 mg/g) as compared

to Soxhlet extraction. The diffusion of curcumin from the inner parts of plant material

was accelerated when the temperature increased with simultaneous increment in the

extraction yield.

With higher temperature intermolecular interactions within the solvent are decreased

which gives rise to higher molecular motion consequently causing the solubility to

increase [53]. Additionally the solvent viscosity decreases and the diffusivity

increases, thus the efficiency of extraction increases. Increase in temperature may also

cause opening of cell matrix, and as a result, curcumin availability for extraction

increases. Thus the higher temperature was found beneficial for higher curcumin

recovery. On the other hand, performing the extraction at higher temperature may

cause increased vaporization of solvent andhigher energy cost [56-58]. Additionally

some degradation processes can also occur at high temperature resulting in lower

recoveries [53]. Therefore while deciding the optimum temperature for further

experiments, in spite of getting highest extraction at 55oC it was not used for further

experiments. Comparing the results for 35and 45oC it is observed that at 35

oC 72%

curcumin is extracted while at 45oC 74.8% extraction is achieved. As there is not a

significant difference in the results at 35and 45oC, all other experiments were carried

out at optimum temperature of 35 oC.

The experimental values were modelled and fitted in the Peleg’s kinetic model as

shown in figure 6.4. From figure 6.4 it can be seen that there is a reasonable

agreement between the modelled values and experimental values for all temperatures

189

except for 55oC. At this temperature there is a large deviation in the experimental data

and the values predicted by Peleg’s model during the last 30 min. This can be

attributed to the synergistic effect of cavitation and higher temperature which may

have resulted in opening of cell matrix resulting in availability of more amount of

curcumin from the interior parts of the cell material for extraction. As a result higher

value of RMSD is seen for the higher temperature (Table 6.2). The obtained

parameters of Peleg’s model (constants K1 and K2), and the root mean squared

deviation (RMSD) for different temperatures are shown in Table 6.2.

Figure 6.4: Effect of extraction temperature on extraction of curcumin using

Ultrasound assisted extraction (Solvent- Ethanol, Solid: Solvent ratio - 1:25, Particle

size- 0.09 mm, Ultrasound frequency- 22 kHz, Ultrasound power- 250 W)

Table 6.2:Effect of temperature on the kinetic parameters: Values of Peleg’s

constants and comparison between experimental values and model values for

curcumin yield

Temperature

(oC)

Experimental

Ceq

(mg

Curcumin/g)

K1

(min.g/mg)

K2

(g/mg)

Calculated

Ceq

(mg

Curcumin/g)

RMSD

(mg/g)

25 8.41 0.30 0.13 7.34 0.59

35 9.18 0.33 0.10 8.88 0.36

45 9.54 0.48 0.11 8.12 0.77

55 20.95 0.69 0.05 14.57 3.09

0

4

8

12

16

20

0 10 20 30 40 50 60

Con

cen

trati

on

(m

g C

urc

um

in/g

)

Time (min)

25

35

45

55

Pelegs Model

190

6.3.3.3 Effect of solid to solvent ratio

The mass/volume ratio of solid/solvent is a factor that must be studied to increase the

efficacy of ultrasound-assisted extraction. For the conventional techniques of solid-

liquid extraction, the intention is to reduce the ratio of solid/solvent and in many cases

this increases the extraction volume obtained [57].

The effect of solid to solvent ratio on curcumin extraction was studied for different

ratios starting from 1:15 to 1:55. During this investigation the other operating

parameters were as follows- extraction solvent: ethanol, temperature 35oC, raw

material particle size 0.09 mm, ultrasound power 250 W and frequency 22 kHz,

extraction time: 60 min. The results are reported in figure 6.5. It can be observed that

as the solid to solvent ratio increased from 1:15 to 1:25, the % extraction of curcumin

increased from 46% (5.86 mg/g) to 72% (9.18 mg/g) and then weakened as this ratio

was further increased.

In general, a larger solvent volume can dissolve plant constituents more efficiently

leading to an enhancement of the extraction yield. The larger solid to solvent ratio

means a larger concentration gradient between the solid and the bulk of the liquid

favouring the mass transfer. However, if the solution is very dilute, an extra quantity

of solvent would not lead to a sufficient increase in the concentration difference and

there would be limited enhancement in extraction yield. Since the limitation to mass

transfer is more confined to the interior part of solid matrix, larger amount of solvent

would not change the driving force [59]. Similar results of decreased extraction with

increased quantity of solvent are reported by Zhao et al. [60]. At the same time using

a large amount of solvent was not considered to be cost-effective due to the high

operating cost of solvents and energy consumption. Thus for the present case the ratio

of 1:25 of the dry weight of C. amada powder to ethanol seems to be appropriate.

The experimental values of curcumin concentration corresponding to different times

and the values predicted by the kinetic model are plotted in figure 6.5. The calculated

values and Peleg’s constants are given in Table 6.3 showing a satisfactory agreement

with experimental values.

191

Figure 6.5: Effect of solid to solvent ratio on extraction of curcumin using

Ultrasound assisted extraction (Solvent- Ethanol, Temperature- 35oC, Particle size-

0.09 mm, Ultrasound frequency- 22 kHz, Ultrasound power- 250 W)

Table 6.3:Effect of solid to solvent ratio on the kinetic parameters: Values of Peleg’s

constants and comparison between experimental values and model values for

curcumin yield

Solid to

solvent

ratio

Experimental

Ceq

(mg

Curcumin/g)

K1

(min.g/mg)

K2

(g/mg)

Calculated

Ceq

(mg

Curcumin/g)

RMSD

(mg/g)

1:15 3.60 0.67 0.28 3.33 0.15

1:25 9.18 0.33 0.10 8.88 0.36

1:35 7.57 0.11 0.13 7.35 0.15

1:45 8.12 0.13 0.12 7.79 0.21

1:55 7.53 0.18 0.13 7.45 0.17

6.3.3.4 Effect of particle size

The influence of particle size on the extraction was studied for four different particle

sizes of 0.09, 0.106, 0.21 and 0.85 mm. The following extraction conditions were

employed. Extraction solvent: ethanol, temperature 35oC, solid to solvent ratio of

1:25, ultrasound power 250 W and frequency 22 kHz, extraction time: 60 min and the

0

2

4

6

8

10

0 10 20 30 40 50 60

Con

cen

trati

on

(m

g C

urc

um

in/g

)

Time (min)

1:15

1:25

1:35

1:45

192

results are reported in figure 6.6. The smaller is the particle size of the raw material,

the more is its contact surface area; hence a smaller size is always advantageous

during extraction operations. The results depicted in figure 6.6 indicate that the

extraction of curcumin increased with decrease in particle size. This can be attributed

to expanded contact area and shorter diffusion paths associated with smaller particle

size. In fact, increasing the contact area enhances the solute mass transfer [50, 60].

Due to reduction in the size of raw material particles, the number of cells directly

exposed to extraction by solvent is increased and thus exposed to cavitation effects

induced by ultrasound leading to enhanced extraction [11]. Also, ultrasound can

enhance the extracting power of the solvent by driving solvent into the matrix to

extract the targeted components.

Figure 6.6: Effect of raw material particle size on extraction of curcumin using

Ultrasound assisted extraction (Solvent- Ethanol, Temperature-35oC, Solid: Solvent

ratio-1:25, Ultrasound frequency- 22 kHz, Ultrasound power- 250 W)

Figure 6.6 shows the extraction curves constructed on the basis of Peleg’s model

constants and their comparison with the experimental data. The figure demonstrates a

good agreement of the experimental data with the approximation data using Peleg’s

model for ultrasound assisted extraction of curcumin from C. amada. Thus these

results proved that the kinetic model was valid for the present system. The obtained

0

2

4

6

8

10

0 10 20 30 40 50 60

Con

cen

trati

on

(m

g C

urc

um

in/g

)

Time (min)

0.09 mm

0.106 mm

0.21 mm

0.85 mm

Pelegs Model

193

parameters of Peleg’s model (constants K1 and K2), and Ceq for curcumin

corresponding to different particle sizes are shown in Table 6.4.

Table 6.4:Effect of raw material particle size on the kinetic parameters: Values of

Peleg’s constants and comparison between experimental values and model values for

curcumin yield

Particle

size

(mm)

Experimental

Ceq

(mg

Curcumin/g)

K1

(min.g/mg)

K2

(g/mg)

Calculated

Ceq

(mg

Curcumin/g)

RMSD

(mg/g)

0.09 9.18 0.33 0.10 8.88 0.36

0.106 6.35 0.43 0.15 6.23 0.24

0.21 7.85 0.70 0.13 6.90 0.51

0.85 7.01 0.60 0.14 6.32 0.42

6.3.3.5 Effect of input power

The influence of ultrasound power on curcumin extraction was investigated with

following extraction conditions: solvent- ethanol, temperature 35oC, solid: solvent

ratio of 1:25, particle size 0.09 mm, and ultrasound frequency of 22 kHz. The input

power was varied from 100 to 250 W and the results are shown in figure 6.7.

Figure 6.7: Effect of ultrasound power on extraction of curcumin using Ultrasound

assisted extraction (Solvent- Ethanol, Temperature-35oC, Solid:Solvent ratio-1:25,

Particle size- 0.09 mm, Ultrasound frequency-22 kHz)

0

2

4

6

8

10

0 10 20 30 40 50 60

Con

cen

trati

on

(m

g C

urc

um

in/g

)

Time (min)

130 W

160 W

190 W

220 W

250 W

Pelegs Model

194

As expected the % extraction of curcumin increased with increase in ultrasound

power. When the ultrasound power was raised from 130 to 250 W, the curcumin yield

increased from 5.99 to 9.18 mg/g. Obviously, ultrasound power was critical in

improving the curcumin yield. From the microscopic point of view, with the increase

of ultrasound power, destruction of cell wall was more pronounced by the ultrasound

energy [58]. The maximum ultrasound power of available ultrasound device was 250

W hence it was selected as the optimal value. Also if the experiments are performed at

higher power then controlling the temperature of the system may be difficult at such

high power levels [17].

For a given medium and a fixed radiation area ultrasonic vibrations are in direct

proportion with the ultrasonic power. The higher the ultrasound power is, the stronger

are the vibrations and the cavity collapse is more violent hence the curcumin

extraction will increase [18,61]. The physical effects associated with ultrasonic

vibrations such as strengthened osmosis, cracked or damaged cell walls, increased

solute diffusion, interfacial turbulence and spot energy may be responsible for the

increased extraction with higher ultrasonic power [58, 62].

Figure 6.7 shows the comparison of curcumin concentration predicted by the model

and experimental values. The estimated values of the kinetic model parameters for

different ultrasound power are represented in Table 6.5. The predicted and

experimental values of the curcumin yield are in good agreement with each other.

Table 6.5:Effect of ultrasound power on the kinetic parameters: Values of Peleg’s

constants and comparison between experimental values and model values for

curcumin yield

Power

(W)

Experimental

Ceq

(mg

Curcumin/g)

K1

(min.g/mg)

K2

(g/mg)

Calculated

Ceq

(mg

Curcumin/g)

RMSD

(mg/g)

130 5.99 1.02 0.16 5.46 0.34

160 7.21 0.16 0.16 6.06 0.78

190 8.56 0.28 0.12 7.88 0.48

220 8.27 0.33 0.12 7.48 0.42

250 9.18 0.33 0.10 8.88 0.36

195

6.3.3.6 Effect of ultrasound frequency

The effect of ultrasound frequency was studied at two different frequencies of 22 and

40 kHz under the optimal extraction parameters obtained from the previous

experiments. The experimental results are reported in figure 6.8. From the figure it

can be seen that the percentage extraction of curcumin at 40 kHz is 50.2% whereas at

22 kHz frequency it is 72% for the similar operating conditions. Sound intensity is

proportional to the square of the product of frequency and amplitude, therefore for a

constant intensity, higher magnitudes value is obtained at lower frequency. As a

result, better cavitation effect is achieved at 22 kHz in comparison to that at 40 kHz

resulting in higher extraction of curcumin [63-64]. At high frequency a decrease in the

amount and intensity of cavitation in liquids has been reported [65].

Figure 6.8: Effect of ultrasound frequency on extraction of curcumin using

Ultrasound assisted extraction (Solvent–Ethanol, Temperature-35oC, Solid: Solvent

ratio- 1:25, Particle size- 0.09 mm, Ultrasound power- 250 W)

Further the scattering and attenuation of sound waves is lesser at lower frequencies

and cavitation is easily possible at lower frequency as compared to higher frequency.

Thus, with the same ultrasonic power, the dissipative energy of 40 kHz was higher

whereas, the energy for enhancing extraction was lower. This could be the possible

reason for higher extraction yield at lower frequency [61-62, 66]. Additionally at

high frequency, the rarefaction (and compression) cycles time for bubbles to grow to

a sufficient size to cause disruption of the cell wall was shorter, hence lesser

0

2

4

6

8

10

0 10 20 30 40 50 60

Con

cen

trati

on

(m

g C

urc

um

in/g

)

Time (min)

22 kHz

40 KHz

Pelegs Model

196

extraction at higher frequency. In earlier reports similar trend of decrease in amount

of extraction with higher frequency has been reported [11, 51, 61, 62, 64]. Owing to

these results all the experiments were performed at 22 kHz.

The experimental values of the concentration of curcumin and the values predicted by

Pelegs model are plotted in figure 6.8. Table 6.6 summarizes the kinetic parameters of

the Pelegs model. It can be concluded that the experimental values are in good

accordance with the model values.

Table 6.6:Effect of ultrasound frequency on the kinetic parameters: Values of Peleg’s

constants and comparison between experimental values and model values for

curcumin yield

Frequency

(kHz)

Experimental

Ceq

(mg

Curcumin/g)

K1

(min.g/mg)

K2

(g/mg)

Calculated

Ceq

(mg

Curcumin/g)

RMSD

(mg/g)

22 9.18 0.33 0.10 8.88 0.36

40 6.40 1.11 0.15 5.79 0.30

6.3.4 Comparison of UAE and conventional extraction under optimum

conditions

Apart from Soxhlet extraction and ultrasound assisted extraction, the batch extraction

was also carried out and the results are compared in figure 6.9. Batch extraction was

carried out at room temperature (30oC) for 8 h by using a stirred batch reactor,

Soxhlet extraction was done at 78oC for 8 h and ultrasound assisted extraction was

done at 35oC for 1h. In all the three experiments the other operating conditions were:

solvent ethanol, solid to solvent ratio of 1:25, raw material particle size 0.09 mm. As

mentioned earlier, for the sake of comparison the amount of curcumin extracted

during Soxhlet extraction was considered as 100% (12.75 mg/g).

Batch extraction resulted in 61.9% curcumin extraction (7.89 mg/g) in 8 h whereas

ultrasound assisted method resulted in 72% curcumin extraction (9.18 mg/g) in 1 h

only. The extraction efficiency has increased significantly due to ultrasound and the

pronounced effect of ultrasound was evident from these results. Though the higher

amount of curcumin extraction is achieved with Soxhlet extraction it is quite an

197

energy intensive process because it is carried out at much higher temperature and for

very long duration of time as against ultrasound assisted extraction. The shear forces

generated due to cavitation, as well shock waves; may have caused physical

disruption of the plant cell walls thus facilitating the release of extractable compound

[11]. Along with plant material swelling and hydration enhancement, ultrasound

contributes to reduction in mass transfer resistance as well as more efficient solvent

penetration into the cell material [24, 67]. Further, enhancement in the extraction is

also due to localized mixing which is occurring due to cavitation [48].

Comparing the results of batch extraction with Soxhlet extraction and UAE, it is seen

that lesser amount of curcumin was extracted after 8 h of experimental run. The

primary reason for this result can be ascribed to the temperature of operation which is

30oC. At such a low temperature there will not be any effect on intermolecular

interactions within the solvent and its solubility will also not increase. Consequently

there will be lesser hydration and swelling of the plant material. At the same time

during UAE the cavity collapse releases large amount of energy at numerous locations

in the solvent which is responsible for increase in the molecular interactions and the

solubility of solvent. Also the intensity of agitation created by the stirrer in batch

reactor setup is inadequate for increasing the mass transfer of solvent into the cell

matrix. Thus the lower temperature operation and reduction in the extraction time are

the major advantages offered by UAE as against the conventional methods.

Figure 6.9: Comparison of Soxhlet extraction (time = 8 h), batch extraction (time = 8

h) and ultrasound assisted extraction (time = 1 h)

8 h

8 h

1 h

0

20

40

60

80

100

% E

xtr

act

ion

of

Cu

rcu

min

198

6.3.5. Surface characterization of C. amada powder using Scanning electron

microscope

The effect of the ultrasound on the microstructure of the C. amada powder was

investigated by using scanning electron microscopy (SEM). Figure 6.10 shows a set

of scanning electron microscopic images of (a) non-irradiated and (b) 1 h ultrasound

irradiated C. amada powder at a magnification factor of 500. The figure shows that

the surface morphology of C. amada powder visibly changed and several

microfractures appeared in the powder after exposure to ultrasonication.

Application of powerful sonication can led to milling of vegetal material reducing the

particle size [11]. Structural breakage was caused by the ultrasonic cavitating energy

resulting in the reduction of the particle size and the contact surface area was

increased which may have resulted in more extraction. Improvement in the extraction

yield was observed because ultrasound can rupture the cell wall of the plant material

and once the cell wall is broken curcumin residing in the interior part can be easily

released from the matrix into the extraction medium [54].

(a) (b)

Figure 6.10: Scanning electron micrographs of (a) non-irradiated and (b) 1 h

ultrasound irradiated C. amada powder

199

6.4 Conclusion

In the present work ultrasound assisted extraction was used as an efficient alternative

to conventional extraction methods for the isolation of curcumin from Curcuma

amada. Comparison of the results of conventional Soxhlet extraction and batch

extraction with ultrasound assisted extraction indicated that ultrasound significantly

improved the curcumin extraction yield. These improvements may be basically

attributed to the mechanical and thermal effects of ultrasound. Furthermore, the whole

procedure that was developed is quite rapid, easy to be carried out and does not

necessitate special equipment.

The different operating parameters influencing the extraction yield such as the type of

solvent, extraction time, solvent to solute ratio, extraction temperature, ultrasound

frequency and ultrasound power are investigated. Ethanol was selected as the best

solvent for the process. The curcumin extraction increased with increasing

temperature, increasing ultarsound input power and decreasing particle size. With

increase in the frequency of ultrasound the curcumin extraction decreased probably

because of faster energy attenuation at higher frequency. The interpretation of the

results showed that the optimal values of the variables affecting the extraction were

extraction time 1 h, temperature 35oC, solid to solvent ratio 1:25, particle size 0.09

mm, ultrasound power 250 W and ultrasound frequency of 22 kHz. The primary

benefit of the ultrasound action is related to shortening of the extraction time and it

can be carried out at lower temperatutre which can avoid the degradation of thermally

unstable ingredients in plant material.

Scanning electron microscopy images of ultrasound irradiated samples showed the

particle breakage leading to increased contact surface area favourable for higher

extraction. Peleg’s model has been used for the prediction of amount of curcumin

extracted at given time for all experimental conditions. The model is validated by

plotting experimental and predicted values of amount of curcumin in extract with

good agreement.

200

References

1. L. Wang, C. L. Weller, Recent advances in extraction of nutraceuticals from

plants, Trends Food Sci. Tech. 17 (2006) 300-312.

2. V. V. Belova, A. A. Voshkin, A. I. Kholkin, A. K. Payrtm, Solvent extraction

of some lanthanides from chloride and nitrate solutions by binary extractants,

Hydrometallurgy 97 (2009) 198-203.

3. E. Reverchon, I. De Marco, Supercritical fluid extraction and fractionation of

natural matter, J. Supercrit. Fluids 38 (2006) 146-166.

4. M. Corrales, A. F. García, P. Butz, B. Tauscher, Extraction of anthocyanins

from grape skins assisted by high hydrostatic pressure, J. Food Eng. 90 (2009)

415-421.

5. V. Loginova, E. Vorobiev, O. Bals, N. I. Lebovka, Pilot study of counter

current cold and mild heat extraction of sugar from sugar beets assisted by

pulsed electric fields, J. Food Eng. 102 (2011) 340-347.

6. X. Jun, Caffeine extraction from green tea leaves assisted by high pressure

processing, J. Food Eng. 94 (2009) 105-109.

7. Z. Lianfu, L. Zelong, Optimization and comparison of ultrasound/microwave

assisted extraction (UMAE) and ultrasonic assisted extraction (UAE) of

lycopene from tomatoes, Ultrason. Sonochem. 15 (2008) 731-737.

8. C. Da Porto, D. Decorti, Ultrasound-assisted extraction coupled with under

vacuum distillation of flavour compounds from spearmint (carvone-rich)

plants: Comparison with conventional hydrodistillation, Ultrason. Sonochem.

16 (2009) 795-799.

9. M. K. Khan, M. A. Vian, A. S. F. Tixier, O. Dangles, F. Chemat, Ultrasound-

assisted extraction of polyphenols (flavanone glycosides) from orange (Citrus

sinensis L.) peel, Food Chem. 119 (2010) 851-858.

10. A. C. Kimbaris, N. G. Siatis, D. J. Daferera, P. A. Tarantilis, C. S. Pappas, M.

G. Polissiou, Comparison of distillation and ultrasound-assisted extraction

methods for the isolation of sensitive aroma compounds from garlic (Allium

sativum), Ultrason. Sonochem. 13 (2006) 54-60.

11. M. Vinatoru, Mass transfer enhancement in supercritical fluids extraction by

means of power ultrasound, Ultrason. Sonochem. 8 (2001) 303-313.

201

12. F. Adje, Y. F. Lozano, P. Lozano, A. Adima, F. Chemat, E. M. Gaydou,

Optimization of anthocyanin, flavonol and phenolic acid extractions from

Delonix regia tree flowers using ultrasound-assisted water extraction, Ind.

Crops Prod. 32 (2010) 439-444.

13. R. M. Pena, J. Barciel, C. Herrero, S. G. Martin, Comparison of ultrasound-

assisted extraction and direct immersion solid-phase microextraction methods

for the analysis of monoterpenoids in wine, Talanta 67 (2005) 129-135.

14. S. R. Shirsath, S. H. Sonawane, P. R. Gogate, Intensification of extraction of

natural products using ultrasonic irradiations- A review of current status,

Chem. Eng. Process. 53(2012) 10-23.

15. E. Reverchon, L. S. Osseo, Comparison of processes for supercritical carbon

dioxide extraction of oil from soybean seeds, J. Am. Oil Chem. Soc. 71 (1994)

1007-1012.

16. C. Leonelli, T. J. Mason, Microwave and ultrasonic processing: Now a

realistic option for industry, Chem. Eng. Process. 49 (2010) 885-900.

17. S. Balachandran, S. E. Kentish, R. Mawson, M. Ashokkumar, Ultrasonic

enhancement of the supercritical extraction from ginger, Ultrason. Sonochem.

13 (2006) 471-479.

18. A. Hu, S. Zhao, H. Liang, T. Qiu, G. Chen, Ultrasound assisted supercritical

fluid extraction of oil and coixenolide from adlay seed, Ultrason. Sonochem.

14 (2007) 219-224.

19. B. Kaufmann, P. Christen, Recent extraction techniques for natural products:

Microwave-assisted extraction and pressurized solvent extraction, Phytochem.

Analysis 13 (2002) 105-113.

20. R. M. Smith, Extractions with superheated water, J. Chromatogr. A 975

(2002) 31-46.

21. D. Jadhav, B. N. Rekha, P. R. Gogate, V. K. Rathod, Extraction of vanillin

from vanilla pods: A comparison study of conventional soxhlet and ultrasound

assisted extraction, J. Food Eng. 93 (2009) 421- 426.

22. A. H. Metherel, A. Y. Taha, H. Izadi, K. D.Stark, The application of

ultrasound energy to increase lipid extraction throughput of solid matrix

samples(flaxseed), Prostaglandins, Leukotrienes. Essent. Fatty Acids 81

(2009) 417-422.

202

23. K. Vilkhu, R. Mawson, L. Simons, D. Bates, Applications and opportunities

for ultrasound assisted extraction in the food industry- A review, Innov. Food

Sci. Em. Technol. 9 (2008) 161-169.

24. M. Toma, M. Vinatoru, L. Paniwnyk, Investigation of the effects of ultrasound

on vegetal tissues during solvent extraction, Ultrason. Sonochem. 8 (2001)

137-142.

25. P. Valachovic, A. Pechova, T. J. Mason, Towards the industrial production of

medicinal tincture by ultrasound assisted extraction, Ultrason. Sonochem. 8

(2001) 111-118.

26. S. A. Jatoi, A. Kikuchi, S. A. Gilani, K. N. Watanabe, Phytochemical,

pharmacological and ethnobotanical studies in mango ginger (Curcuma amada

Roxb.; Zingiberaceae), Phytother. Res. 21 (2007) 507-516.

27. S. Rouhani, N. Alizadeh, S. Salimi, T. H. Ghasemi, Ultrasound assisted

extraction of natural pigments from rhizomes of Curcuma Longa L., Prog.

Color Colorants Coat. 2 (2009) 103-113.

28. P. Anand, S. G. Thomas, A. B. Kunnumakkara, C. Sundaram, K. B.

Harikumar, B. Sung, S. T. Tharakan, K. Misra, I. K. Priyadarsini, K. N.

Rajasekharan, B. B. Aggarwal, Biological activities of curcumin and its

analogues (Congeners) made by man and mother nature, Biochem. Pharmacol.

76 (2008) 1590-1611.

29. D. Shahwar, M. A. Raza, S. Bukhari, G. Bukhari, Ferric reducing antioxidant

power of essential oils extracted from Eucalyptus and Curcuma species, Asian

Pac. J. Trop. Biomed. (2012) S1633-S1636.

30. S. Roy, S. S. Raychoudhuri, In vitro regeneration and estimation of curcumin

content in four species of curcuma, Plant Biotechnol. 21 (2004) 299-302.

31. N. Janaki, J. L. Bose, An improved method for the isolation of curcumin from

turmeric, Curcuma longa L., J. Ind. Chem. Soc. 44 (1967) 985-989.

32. S. Srivastava, M. Srivastava, S. Mehrotra, A. K. S. Rawat, A HPTLC method

for chemotaxonomic evaluation of some Curcuma species and their

commercial samples, J. Sci. Ind. Res. 68 (2009) 876-880.

33. S. Ahmad, M. Ali, S. H. Ansari, F. Ahmed, Phytoconstituents from the

rhizomes of Curcuma aromatic Salisb., J. Saudi Chem. Soc. 15 (2011)287-

290.

203

34. C. E. Stransky, Process for producing water and oil soluble curcumin coloring

agents, US Patent 4, 138, 212 (1979).

35. N. Krishnamurthy, A. G. Mathew, E. S. Nambudiri, S. Shivashankar, Y. S.

Lewis, C.P. Natarajan, Oil and oleoresins of turmeric, Trop. Sci. 18 (1976) 37-

39.

36. P. S. Wakte, B. S. Sachin, A. A. Patil, D. M. Mohato, T. H. Band, D. B.

Shinde, Optimization of microwave, ultra-sonic and supercritical carbon

dioxide assisted extraction techniques for curcumin from Curcuma longa, Sep.

Purif. Technol. 79 (2011) 50-55.

37. D. V. Dandekar, V.G. Gaikar, Microwave assisted extraction of curcuminoids

from Curcuma longa, Sep. Sci. Technol. 37 (2002) 2669-2690.

38. A. L. C. Mendez, N. T. Machado, M. E. Araujo, J. G. Maia, M. A. A.

Meireles, Supercritical CO2 extraction of curcumins and essential oil from the

rhizomes of turmeric (Curcuma longa L.), Ind. Eng. Chem. Res. 39 (2000)

4729 - 4733.

39. V. Mandal, S. Dewanjee, R. Sahu, S. C. Mandal, Design and optimization of

ultrasound assisted extraction of curcumin as an effective alternative for

conventional solid liquid extraction of natural products, Nat. Prod. Commun.

4 (2009) 95-100.

40. P. R. Gogate, I. Z. Shirgaonkar, M. Sivakumar, P. Senthilkumar, N. P.

Vichare, A. B. Pandit, Cavitation reactors: Efficiency analysis using a model

reaction, Amer. Inst. Chem. Engrs. J. 47(2001) 2526-2538.

41. P. S. Milic, K. M. Rajkovic, O. S. Stamenkovic, V. B. Veljkovic, Kinetic

modeling and optimization of maceration and ultrasound-extraction of resinoid

from the aerial parts of white lady’s bedstraw (Galium mollugo L.), Ultrason.

Sonochem. 20 (2013) 525-534.

42. Y. Tao, Z. Zhang, D. W. Sun, Experimental and modeling studies of

ultrasound-assisted release of phenolics from oak chips into model wine,

Ultrason. Sonochem. 21(2014) 1839-1848.

43. E. Karacabey, L. Bayindirli, N. Artik, G. Mazza, Modelling solid-liquid

extraction kinetics of trans-resveratrol and trans-ε-viniferin from grape cane, J.

Food Process Eng. 36 (2013) 103-112.

204

44. Y. Tao, Z. Zhang, D. W. Sun, Kinetic modeling of ultrasound-assisted

extraction of phenolic compounds from grape marc: Influence of acoustic

energy density and temperature, Ultrason. Sonochem. 21 (2014) 1461-1469.

45. M. R. González-Centeno, F. Comas-Serra, A. Femenia, C. Rosselló, S. Simal,

Effect of power ultrasound application on aqueous extraction of phenolic

compounds and antioxidant capacity from grape pomace (Vitis vinifera L.):

Experimental kinetics and modelling, Ultrason. Sonochem. 22 (2015) 506-

514.

46. L. Yue, F. Zhang, Z. Wang, Ultrasound-assisted extraction of capsaicin from

red peppers and mathematical modeling, Separ. Sci. Technol. 47 (2012) 124-

130.

47. S. Jokic, D. Velic, M. Bilic, A. Bucic-Kojic, M. Planinic, S. Tomas,

Modelling of the process of solid-liquid extraction of total polyphenols from

soybeans, Czech J. Food Sci. 28 (2010) 206-212.

48. M. D. Vetal, V. G. Lade, V. K. Rathod, Extraction of ursolic acid from

ocimum sanctum by ultrasound: Process intensification and kinetic studies,

Chem. Eng. Process. 69(2013) 24- 30.

49. M. Peleg, An empirical model for the description of moisture sorption curves,

J. Food Sci. 53 (1988) 1216-1219.

50. M. Romdhane, C. Gourdon, Investigation in solid–liquid extraction: Influence

of ultrasound, Chem. Eng. J. 87 (2002) 11-19.

51. J. Dong, Y. Liu, Z. Liang, W. Wang, Investigation on ultrasound-assisted

extraction of salvianolic acid B from Salvia miltiorrhiza root, Ultrason.

Sonochem. 17 (2010) 61-65.

52. J. Wang , B. Sun, Y. Cao, Y. Tian, X. Li, Optimisation of ultrasound-assisted

extraction of phenolic compounds from wheat bran, Food Chem. 106 (2008)

804- 810.

53. S. Hemwimon, P. Pavasant, A. Shotipruk, Ultrasound-assisted extraction of

anthraquinones from roots of Morinda citrifolia, Ultrason. Sonochem. 54

(2007) 44- 50.

54. Y. Sun, D. Liu, J. Chen, X. Ye, D. Yu, Effects of different factors of

ultrasound treatment on the extraction yield of the all-trans-β-carotene from

citrus peels, Ultrason. Sonochem. 18 (2011) 243-249.

205

55. Y. Yang, F. Zhang, Ultrasound-assisted extraction of rutin and quercetin from

Euonymus alatus (Thunb.) Sieb, Ultrason. Sonochem. 15 (2008) 308-313.

56. Q. A. Zhang, Z. Q. Zhang, X. F. Yue, X. H. Fan, T. Li, S. F. Chen, Response

surface optimization of ultrasound-assisted oil extraction from autoclaved

almond powder, Food Chem. 116 (2009) 513-518.

57. G. F. Barbero, A. Liazid, M. Palma, C. G. Barroso, Ultrasound-assisted

extraction of capsaicinoids from peppers, Talanta 75 (2008) 1332-1337.

58. Y. Zou, C. Xie, G. Fan, Z. Gu, Y. Han, Optimization of ultrasound-assisted

extraction of melanin from Auricularia auricula fruit bodies, Innovative Food

Sci. Emer. Technol. 11 (2010) 611-615.

59. Z. Lou, H. Wang, M. Zhang, Z. Wang, Improved extraction of oil from

chickpea under ultrasound in a dynamic system, J. Food Eng. 98 (2010) 13-18.

60. S. Zhao, K. Kwok, H. Liang, Investigation on ultrasound assisted extraction of

saikosaponins from Radix Bupleuri, Sep. Purif. Technol. 55 (2007) 307-312.

61. V. M. Kulkarni, V. K. Rathod, Mapping of an ultrasonic bath for ultrasound

assisted extraction of mangiferin from Mangifera indica leaves, Ultrason.

Sonochem. 21 (2014) 606-611.

62. Y. Gao, B. Nagy, X. Liu, B. Simándi, Q. Wang, Supercritical CO2 extraction

of lutein esters from marigold (Tagetes erecta L.) enhanced by ultrasound, J.

Supercrit. Fluids 49 (2009) 345-350.

63. K. M. Swamy, K. L. Narayana, Intensification of leaching process by dual-

frequency ultrasound, Ultrason. Sonochem. 8 (2001) 341-346.

64. S. Boonkird, C. Phisalaphong, M. Phisalaphong, Ultrasound-assisted

extraction of capsaicinoids from Capsicum frutescens on a lab- and pilot-plant

scale, Ultrason. Sonochem. 15 (2008) 1075-1079.

65. T. J. Mason, J. P. Lormier, Sonochemistry: Theory application and uses of

ultrasound in chemistry, John Wiley & Sons, New York, 1988.

66. D. Luo, T. Qiu, Q. Lu, Ultrasound-assisted extraction of ginsenosides in

supercritical CO2 reverse Microemulsions, J. Sci. Food. Agric. 87 (2007) 431-

436.

67. T. Jerman, P. Trebše, B. M. Vodopivec, Ultrasound-assisted solid liquid

extraction (USLE) of olive fruit (Olea europaea) phenolic compounds, Food

Chem. 123 (2010) 175-182.