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 (X-1: 20-40 mL/g), extraction time (X-2:20-40 min) and extraction temperature (X-3: 40-60 degrees 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 degrees C. Under these conditions, the experimental yield was 8.26%, well matched with the predicted models with the coefficients of determination (R-2) 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. (C) 2010 Elsevier Ltd. All rights reserved.