Extraction optimization of total triterpenoids from Jatropha curcas leaves using response surface methodology and evaluations of their antimicrobial and antioxidant capacities

Abstract

Triterpenoids are multifunctional secondary metabolites in plants. But little information is available concerning the actual yield, optimal extraction method and pharmacologic activity with regard to triterpenoids from Jatropha curcas leaves (TJL). Hence, response surface methodology (RSM) was used to optimize the extraction parameters. The effects of three independent variables, namely liquid-to-solid ratio, ethanol concentration and extraction time on TJL yield were investigated. TJL obtained by silica column chromatography was tested against bacterial and fungal species relevant to oral disease and wounds through broth microdilution. Antioxidant activity was assessed using the 2,2-diphenyl-2-picrylhydrazyl and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) assays. A second order polynomial model produced a satisfactory fitting of the experimental data with regard to TJL yield (R2 = 0.983, P < 0.01). The optimum extraction conditions were 16 mL/g (liquid-to-solid ratio), 70% (ethanol concentration) and 50 min (extraction time). Predicted values agreed well with the experimental values. TJL had extraordinarily strong antibacterial and antifungal activities (24.42 μg/mL < MIC < 195.31 μg/mL) against all the tested human pathogens except Bacteroides vulgatus (390.62 μg/mL) and Bacteroides stercoris (781.25 μg/mL). The DPPH and ABTS assays revealed a moderate antioxidant activity of TJL compared with ascorbic acid. These results provided reliable scientific basis for further investigation of triterpenoids from J. curcas.