Subcritical water extraction of bioactive compounds from Radix Puerariae and optimization study using response surface methodology

Subcritical water extraction (SWE) of bioactive extracts from Radix Puerariae (RP) was firstly optimized by response surface methodology (RSM) and its extraction efficiency was compared with two traditional volatile isolation methods including hot water extraction (HWE) and ethanol reflux extraction (ERE). The optimal SWE parameters were as follows: extraction temperature of 141 °C, extraction time of 58 min, and liquid-solid ratio l of 23:1 mL/g. Under these conditions, yield of bioactive extracts was 28.9 ± 0.2%, which was slightly higher than that obtained by ERE, and more than two-fold the value obtained by HWE respectively. Isoflavones and polysaccharide content in SWE was significantly higher than that of HWE and slight lower than that of ERE. The results indicated that SWE could be a productive and environmental friendly technique for extracting bioactive extracts from RP.