Ultrasonic-assisted extraction and antioxidant activities of polysaccharides from Camellia oleifera leaves

Polysaccharides from Camellia oleifera leaves were extracted by ultrasonic-assisted extraction and optimized with response surface methodology. The optimal conditions of the extraction of polysaccharides were determined to be the extraction time of 1.6 h, extraction temperature of 88 °C and ratio of liquid to raw material of 20, which contributed to the highest yield of 3.77%. The crude polysaccharide was purified and three fractions (CLP-1, CLP-2 and CLP-3) were obtained. Their physicochemical properties were investigated with chemical method. The results indicated that the uronic acid content of CLP-2 was significantly higher than those of CLP-1 and CLP-3, and CLPs were mainly composed of glucose and galactose residue. In vitro antioxidant assay indicated that three polysaccharide fractions showed remarkable antioxidant activities in a concentration-dependent manner. Compared with CLP-1 and CLP-2, CLP-3 exhibited higher iron chelating activity. CLP-2 possessed significant higher hydroxyl radial and 2,2-diphenyl-1-picrydrazy (DPPH) radical scavenging activities than those of CLP-1 and CLP-3. Overall, the polysaccharides derived from C. oleifera leaves might be explored as potential natural antioxidant.