Response surface methodology was used to analyze the results of experiments designed using the Box–Behnken method to extract three phenolic compounds, gallic acid (GA), corilagin (CG) and ellagic acid (EA), from Jatropha curcas Linn. leaves using supercritical CO2 and methanol as a cosolvent. Experiments were carried out from 10 to 30 MPa, 40 to 80C and 30 to 70% (v/v) aqueous methanol. A 3 × 3 Box–Behnken design was used to design the experiments to determine the effects of pressure, temperature and concentration of methanol (MeOH) as well as their interaction on the extraction yield. Three nonlinear equations and 3‐D plots (one for each product) with 10 terms were developed. Analytical and numerical techniques were used to locate the optimal operating conditions. The highest experimental yields were obtained at 10 MPa, 60C and 30% (v/v) methanol modifier for GA; 20 MPa, 80C and 30% (v/v) methanol modifier for CG; and 30 MPa, 40C and 50% (v/v) methanol modifier for EA. The response surface models predicted that the maximum extraction yields of GA, CG and EA were 1,567.68 mg/kg of GA at 10 MPa, 80C and 30% (v/v) aqueous MeOH; 4,693.60 mg/kg of CG at 30 MPa, 80C and 30% (v/v) aqueous MeOH; and 1,089.02 mg/kg of EA at 10 MPa, 80C and 70% (v/v) aqueous MeOH, respectively. Because the theoretical optimum was on the limit of the range of the experiments, future work should focus on new experiments designed around the predicted optimum. PRACTICAL APPLICATIONS The purpose of this research was to study the extraction of gallic acid (GA), corilagin (CG) and ellagic acid (EA) from Jatrapha curcas Linn. leaves using supercritical carbon dioxide (SCCO2) with a methanol cosolvent. Polar organic cosolvents or modifiers can be used to enhance extraction yield of polar solutes by increasing the CO2 polarity. Because methanol (MeOH) has a high polarity index, it was used to extract the three phenolic compounds (polar compounds) in the SCCO2 process. In addition to extracting GA, CG and EA, this research determined the maximum yield and the effect of operating parameters (pressure, temperature and MeOH concentration) using a response surface quadratic model to determine the location of the optimum operating conditions.

The leaves of Jatropha curcas Linn. contain antioxidant, anticancer and anti‐HIV compounds. This research investigated the extraction of the phenolic compound, gallic acid (GA), from Jatropha curcas Linn. leaves using supercritical carbon dioxide (SCCO2) and methanol co‐solvent. The SCCO2 pilot plant extractor, which was 10 times the capacity of a lab scale unit, was designed and built by our research group using a hydraulic pump instead of high pressure pump. The operating pressure was varied from 20 to 40 MPa; the temperature was varied from 40 to 60C; the particle size was varied from 10 to 40 mesh and the modifier concentration was varied from 0 to 70% (v/v) aqueous methanol. An orthogonal L9 (3)4 experimental design was applied to determine the optimal extracting condition and the effect of the parameters. The largest extraction yield from the experiment was 75.39 mg/kg dry weight of leaves at 40 MPa, 50C and 10–16 mesh particles using a 70% (v/v) methanol modifier. However, from the analysis of L9 (3)4, the optimal operating conditions were at 20 MPa, 50C and 10–16 mesh particles using a 70% (v/v) methanol modifier. It was found that temperature, particle size and modifier concentration had a statistically significant influence (at 85% confidence level) on the GA extraction yield. The fact that pressure was not found to be statistically significant is possibly due to the difficulty in controlling pressure in the pilot plant. PRACTICAL APPLICATIONS A pilot plant scale supercritical fluid extraction unit, which was 10 times the size of typical laboratory units, was designed and built in our lab using a low cost hydraulic pump to replace a high pressure pump. The pilot plant was able to reasonably extract gallic acid from the leaves of Jatropha curcas Linn. Preliminary experiments resulted in an optimal set of operating conditions which can be used as a starting point in future work. The system will eventually be instrumented and controlled to access operating data as well as maintain the operation of the extractor at desired set‐points. The advantage of using SCCO2 for the extraction is to achieve pure quality product. Gallic acid, which is one of the phenolic compounds in physic nut leaves, is characterized by various properties such as anti‐inflammatory, antimutagenic, anticancer, antioxidant and antiviral agent.