Materials and Reagents.
Dried and powdered curry powder was purchased from E-mart (Chunchon, Korea) and used for supercritical fluid extraction. Carbon dioxide (99.99 wt % pure) was provided by Bakryoung Special Gas (Chun-chon, Korea). All solvents were HPLC grade from Fisher Scientific Korea Ltd.
Supercritical fluid extractions of curcumin were performed using a JASCO (Tokyo, Japan) LC-900 SFE system. The schematic diagram of the system is shown in
. This system consisted of three sections: fluid delivery, extraction, and collection. The fluid delivery section included a high pressure pump, which delivered supercritical fluid CO
. In the extraction section, supercritical fluid extractions were performed with supercritical fluid CO
. The collection section included a back pressure regulator, which kept the pressure of an extraction vessel at the desired value. The effluent flowing through the back pressure regulator reduced its pressure to atmospheric and thereby solutes in the effluent reduced their solubility to virtually zero. In this way, the solutes were deposited and collected in a collection vessel. Since we used pure CO
as a extracting solvent, the extracts were collected without solvent in the collection vessel.
Schemetic flow diagram of SFE modular system.
Supercritical fluid extracts of curry powder were analyzed by high performance liquid chromatography (HPLC). The HPLC system consisted of a JASCO PU-980 pump, an UV-2075 UV detector and a Waters Spherisorb S5 ODS2 (4.6 × 150 mm, 5 μm particle size) column. An aliquot of 10 μL was injected into the HPLC system. The mobile phase was a mixture of 30% of methanol and 70% of water. The flow rate was 0.8 mL/min, and UV detector operating at 424 nm. A typical HPLC chromatogram is shown in
HPLC chromatograms of curcumins ((a) typical SFE extract from a curry powder, (b): standard curcumin, (c): standard DMC, (d): standard BDMC).
Results and Discussion
SFE conditions for the optimization of the extraction of curcumins from a curry powder were evaluated. The amounts of extracted curcumins were quantitatively measured by HPLC analysis described in the earlier section.
Effect of Pressure on Extraction Efficiency.
It is important to find the optimum SFE operating conditions which would result in the most efficient extraction of curcumins from a curry powder. In particular, the pressure and temperature of supercritical fluid, which are the most important parameters to be optimized, for the efficient SFE experiment. Extraction efficiency of curcumins was investigated as a function of extraction pressure (
). Extraction pressures of 200, 225, 250 and 275 atm were chosen. The pressure of the supercritical fluid plays an important role in the SFE of curcumins from a curry powder. An increase in pressure causes an increase in the fluid density, and thus it results in the increase in the solvating power of the supercritical fluid. As shown in
, the extraction efficiency increases with increasing pressure of extracting fluid until the pressure reaches 250 atm.
Supercritical fluid extraction of curcumins using various pressures
Experimental condition: 120 min extraction at 40 ℃, CO2 flow 3.0 mL/min. RSDs based on triplicate extractions under each condition.
At higher pressure than 250 atm, the extraction efficiency decreases because extraction of curcumins can be competed with extraction of other compounds in the sample matrix. Therefore, the optimized pressure was chosen as 250 atm for the extraction of curcumins from a curry powder.
Effect of Temperature on Extraction Efficiency.
To find the optimum extraction temperature, the temperature of the extraction vessel was varied from 40 ℃ to 70 ℃, under the pressure of 250 atm (
). As shown in
, the best extraction efficiency was obtained at the temperature of 60 ℃. From 40 ℃ to 60 ℃. increased temperature resulted in increased extraction efficiency of curcumins. At higher temperature, curcumins become more volatile and can be easily separated from the matrix. However, at the fairly high temperature (70 ℃), the extraction efficiency of curcumins was decreased due to the decreased density of supercritical fluid.
Supercritical fluid extraction of curcumins using various temperatures
Experimental condition: 120 min extraction at 250 atm, CO2 flow 3.0 mL/min. RSDs based on triplicate extractions under each condition.
Effect of Modifier on Extraction Efficiency.
The effect of modifier on the extraction efficiency of curcumins is shown in in
. The modifier used in this study was ethanol which is known as the most effective modifier for the SFE of curcumins.
As can be seen in
, the poor extraction result (4.53 mg/g) with neat supercritical CO
was obtained. This result is probably caused by the fact that curcumins consisit of polar fuctional groups,
. phenol and ketone. The use of modifier can have a profound effect on increasing the solubility levels of polar solutes in supercritical fluids. When the flow rate of modifier was increased from 0.1 mL/min to 0.3 mL/min, the extraction yield of curcumins increased from 14.29 mg/g to 31.07 mg/g. But at higher flow rate of modifier (0.4 mL/min), the extraction yield of curcumins was decreased. The decreased extraction of curcumins with 0.4 mL/min flow rate of modifier may be attributed to some solute-modifier interactions that can weaken the solute-supercritical CO
interactions. Similar results were obtained for other samples and matrices using modified CO
Supercritical fluid extraction of curcumins using different flow rates of ethanol as a modifier
Experimental condition: 120 min extraction at 60 ℃ and 250 atm, CO2 flow 3.0 mL/min. RSDs based on triplicate extractions under each condition.
Effect of Extraction Time.
In order to determine the optimal extraction time, the extraction time was varied from 90 min to 150 min by the interval of 30 min (
). As can be seen in
, when the extraction time was increased from 90 min to 120 min, the extraction yield of curcumins increased from 26.45 mg/g to 31.07 mg/g. However, no significant increase between 120 min and 150 min was made. Therefore, to have a rapid extraction of curcumins from a curry powder, we selected a shorter extraction time (120 min) as the optimum extraction time.
Supercritical fluid extraction of curcumins using various extraction times
Experimental condition: Supercritical fluid extraction with a ethanol modified CO2 fluid (3.0 mL/min CO2 + 0.3 mL/min ethanol) at 60 ℃ and 250 atm. RSDs based on triplicate extractions under each condition.
Comparison with Solvent Extraction.
For the comparison, curcumins were extracted using the conventional solvent extraction method. The solvent used was methanol since methanol was reported as the most efficient solvent for the extraction of curcumins.
The extraction procedure was the same as that described in the literature.
The amounts of extracted curcumins were 17.82 mg/g curcumin, 4.09 mg/g DMC and 2.82 mg/g BDMC. The total amounts of extracted curcumins were 24.73 mg/g.
In conclusion, curcumins were successfully extracted with a ethanol modified supercritical CO
fluid (3.0 mL/min CO
+ 0.3 mL/min ethanol) at 60 ℃ and 250 atm. Under these conditions, the extracted amount of curcumins was 31.07 mg from 1 g of curry powder. In the case of using solvent extraction, only 24.73 mg of curcumins was extracted from 1 g of curry powder. The CO
-ethanol fluid system gave a higher extraction efficiency than a solvent extraction system for the extraction of curcumins from a curry powder. By use of SFE, sample handling steps are minimized, thus reducing the possible losses of curcumins and saving analysis time. No clean-up steps are employed since the SFE with ethanol modified CO
gives clean extracts which can be easily analyzed with HPLC.
This study was supported by 2013 Research Grant from Kangwon National University (No. 120131229).
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