Optimization of microwave-assisted extraction conditions for preparing lignan-rich extract from Saraca asoca bark...

Lyoniside is the major constituent of Saraca asoca Linn. (Caesalpiniaceae) bark. There is an immediate need to develop an efficient method to isolate its chemical constituents, since it is a therapeutically important plant.

A rapid extraction method for lyoniside based on microwave-assisted extraction of S. asoca bark was developed and optimized using response surface methodology (RSM).

Lyoniside was analyzed and quantified by high-performance liquid chromatography coupled with ultraviolet detection (HPLC-UV). The extraction solvent ratio (%), material solvent ratio (g/ml) and extraction time (min) were optimized using Box-Behnken design (BBD) to obtain the highest extraction efficiency. The optimal conditions were the use of 1:30 material solvent ratio with 70:30 mixture of methanol:water for 10 min duration.

The optimized microwave-assisted extraction yielded 9.4 mg/g of lyoniside content in comparison to reflux extraction under identical conditions which yielded 4.2 mg/g of lyoniside content. Under optimum conditions, the experimental values agreed closely with the predicted values. The analysis of variance (ANOVA) indicated a high goodness-of-fit model and the success of the RSM method for optimizing lyoniside extraction from the bark of S. asoca.

All the three variables significantly affected the lyoniside content. Increased polarity of solvent medium enhances the lyoniside yield.

The present study shows the applicability of microwave-assisted extraction in extraction of lyoniside from S. asoca bark.