Optimization of ionic liquid-based microwave assisted extraction of a diterpenoid lactone-andrographolide from Andrographis paniculata by response surface methodology

Abstract

Abstract An ionic liquid-based microwave assisted extraction (IL-MAE) method was developed for a diterpenoid lactone-andrographolide from Andrographis paniculata by response surface methodology using ionic liquid, 1-butyl-3-methyl-imidazolium chloride ([bmim]Cl). Variable microwave-assisted extraction parameters were selected as concentration of [bmim]Cl, extraction time and microwave power while solid-liquid ratio and extraction temperature were kept constant. Response surface methodology was employed to develop the predictive model for optimization and simulation of the extraction process. A multivariate quadratic regression equation was obtained by central composite design. The 3 D response surface curve and contour plots were obtained by variance of analysis (ANOVA). High performance thin layer chromatography (HPTLC) was performed for quantitative analysis of andrographolide and for comparison of IL-MAE extraction with conventional methods. The optimum extraction conditions were 2.84 mol/L, microwave power 600 W, extraction time 6 min, extraction temperature 70 °C, solid-liquid ratio 1:10. With this novel IL-MAE method, the yield of andrographolide was increased from 1.5% w/w in 7 days (maceration) and 1.8% w/w in 3 h (soxhlation) to 4.71% w/w in 6 min (IL-MAE). At the same time there was reduction in the environmental pollution by using the green solvents/ionic liquids (ILs).