Microwave assisted extraction of bioactive saponins from the starfish Echinaster sepositus: Optimization by response surface methodology and comparison with ultrasound and conventional solvent extraction

Abstract Microwave assisted extraction (MAE) was investigated for the extraction of total saponins compounds from the starfish Echinaster sepositus. In order to achieve optimization of microwave extraction and to determine the influence of each operational variable (the solvent concentration (X1), irradiation time (X2), microwave power (X3), and liquid solid ratio (X4)) on the extraction of saponins, response surface methodology (RSM) coupled with a Box–Behnken design (BBD) was applied. The optimized experimental conditions were 58.7% aqueous methanol as solvent, 177 W as microwave power for 3 min irradiation time at 43.6 mL g-1 of liquid/solid ratio. The extraction yield under these conditions was 60.3 ± 0.6 mg g-1. The optimized MAE was compared with other methods (ultrasound assisted extraction, UAE) and with conventional solvent extraction (CSE). It was demonstrated that microwave produced saponins extraction 7.8 times as more as that produced by CSE and 3.3 as more as UAE has produced. From the in vitro hemolytic tests and electro-generated O2•− quenching tests, we have noted that the microwave saponins extract was the most active one comparing with both UAE and CSE extracts.