Ultrasonic-assisted extraction optimized by response surface methodology, chemical composition and antioxidant activity of polysaccharides from Tremella mesenterica

Box–Behnken design was employed to optimize the ratio of water to raw material (X1: 20–40 mL/g), extraction time (X2: 20–40 min) and extraction temperature (X3: 40–60 °C) to obtain a high crude polysaccharides yield from Tremella mesenterica (TMP) by ultrasonic-assisted extraction technique (UAE). The optimum conditions were a ratio of water to raw material of 34 mL/g and extraction time of 30 min at 50 °C. Under these conditions, the experimental yield was 8.26%, well matched with the predicted models with the coefficients of determination (R2) of 0.9918. The crude TMP was purified by Sephadex G-100 chromatography, giving two major fractions (TMPA and TMPB), which were composed of xylose, mannose and glucose in molar ratio of 1.00:4.74:0.91 and 1.00:6.63:2.34, respectively. The evaluation of antioxidant activity suggested that the polysaccharides exhibited significant protection against hydrogen peroxide induced oxidative damage in rat erythrocytes and could be explored as a nutraceutical agent.