Antioxidant activities potential of tea polysaccharide fractions obtained by ultra filtration

Three polysaccharide fractions (TPS1, TPS2 and TPS3) with different molecular weights were obtained using ultra filtration membranes from crude tea polysaccharide (CTPS) extracted from abandoned lower grade tea leaves. Each fraction contained different contents of neutral sugar, uronic acid, protein, and total polyphenols. These differences provided basis for the antioxidant and free radical scavenging activity of these polysaccharide fractions. The molecular weights of TPS1, TPS2, and TPS3 were around 2.40   ×   10 5   Da, 2.14   ×   10 4   Da, and 2.46   ×   10 3   Da, respectively. In general, TPS1 and CTPS had stronger antioxidant activity, TPS2 and TPS3 had lower antioxidant activity. TPS1 had higher activity for DPPH and lipid per oxidation inhibition. But it had lower capacity for reducing power and metal chelating. This might be due to its higher content of hexuronic acid and larger molecular weight. The order of inhibition activity of lipid per oxidation of various polysaccharide fractions was the same as DPPH radical scavenging activity, as well as the order of metal chelating activity of various polysaccharide fractions similar to hydroxyl radical scavenging activity, which demonstrated that hydroxyl radical scavenging activity of polysaccharide relied heavily on the Fe 2+ metal chelating to decrease the generation of hydroxyl radical.