Polysaccharide extraction from Sphallerocarpus gracilis roots by response surface methodology

The extraction process of Sphallerocarpus gracilis root polysaccharides (SGRP) was optimized using response surface methodology with two methods [hot-water extraction (HWE) and ultrasonic-assisted extraction (UAE)]. The antioxidant activities of SGRP were determined, and the structural features of the untreated materials (HWE residue and UAE residue) and the extracted polysaccharides were compared by scanning electron microscopy. Results showed that the optimal UAE conditions were extraction temperature of 81 °C, extraction time of 1.7 h, liquid-solid ratio of 17 ml/g, ultrasonic power of 300 W and three extraction cycles. The optimal HWE conditions were 93 °C extraction temperature, 3.6 h extraction time, 21 ml/g liquid-solid ratio and three extraction cycles. UAE offered a higher extraction yield with a shorter time, lower temperature and a lower solvent consumption compared with HWE, and the extracted polysaccharides possessed a higher antioxidant capacity. Therefore, UAE could be used as an alternative to conventional HWE for SGRP extraction.