Microwave-assisted extraction, chemical characterization of polysaccharides from Lilium davidii var. unicolor Salisb and its antioxidant activities evaluation

Microwave-assisted extraction (MAE) of polysaccharides from Lilium davidii var. unicolor Salisb (LPMAE) was studied. The four parameters, extraction time, microwave power, extraction temperature, extraction temperature and the ratio of solid to water, were optimized using the Box–Behnken design (BBD) with a quadratic regression model built by using response surface methodology (RSM). The optimal extraction conditions for LPMAE were determined as follows: microwave power 597 W, extraction time 60 min, ratio of raw material to liquid 1:65, extraction temperature 50 °C, where the highest yield of LPMAE 36.55 ± 1.1% was achieved. The resulted LPMAE was characterized by FT-IR. The peaks at 3406 cm−1, 2930 cm−1, 1250 cm−1, 1060, 812 cm−1 indicated that LPMAE possesses typical absorption peak of polysaccharides. Monosaccharide composition was determined by GC–MS method. LPMAE was mainly composed of glucose and mannose with the molar ratio of 5.17:4.82. The weight average molar mass (Mw) determined by SEC-LLS was1.193 × 105. In addition, the antioxidative activity of LPMAE was investigated by measuring its scavenging ability on DPPH, hydroxyl radicals and superoxide radical, Chelating activity on ferrous ion and reducing power in vitro. The results indicated that LPMAE has good antioxidant activity.