CO2 supercritical fluid extraction and characterization of polysaccharide from bamboo (Phyllostachys heterocycla) leaves

CO2 supercritical fluid technique with an ethanol modifier was used to extract bamboo (Phyllostachys heterocycla) leave's polysaccharide (BLPs) regarding various operating conditions. Pressure (30, 40 and 50 MPa), extraction temperature (40, 45 and 50 degrees C), extraction time (2, 3 and 4 h) and modifier dosage (20, 25 and 30 mL) were important operating factors affecting the yield and total antioxidant activity of each BLPs extraction. The optimal parameters for harvesting the BLPs were an extracting time of 2 h plus 40 MPa pressure with 30 mL of ethanol modifier at 50 degrees C. In this case, 2.47% BLPs (in wt) was extracted. The BLPs, after purified by D101 macroporous resin and DEAE-cellulose column, with the average molecular weight of 5.05 x 104 Da are composed of rhamnose, fucose, arabinose, xylose, mannose, glucose, and galactose in the molar ratio of 1.318:2.100:1.189:1.016:1:4.776:1.318, respectively. It showed the best antioxidant activity, and its total antioxidant activity of the BLPs extracted was equivalent to 20.70 mg ascorbic acid [(VcE)/g]. In a word, our technique should be potential for producing the best yield and activity of bamboo (Phyllostachys heterocycla) leave's polysaccharide.