柿子单宁的制备及其抗氧化活性研究

利用含有1％盐酸的无水甲醇提取柿子果肉中的单宁，粗提液经大孔树脂AB-8初步纯化后，再经超滤膜法制得柿子单宁两级分：高分子量单宁(High Molecular Weight Tannin，HMWT)以及小分子量单宁(Small Molecular Weight Tannin，SMWT)。HMWT具有良好的水溶性，凝胶渗透色谱(GPC)分析表明其分子量分布范围为1.16×10⁴～1.54×10⁴。抗氧化试验表明：HMWT对2-脱氧-D-核糖、甲基紫、水杨酸体系产生的羟基自由基均具有很强的清除能力，其最大清除率分别为90.47%、96.46%、87.77%，；HMWT对邻苯三酚自氧化和亚油酸脂质过氧化亦有较强的抑制作用，其最大抑制率分别为56.57%、69.63%。在所有体系中HMWT抗氧化能力呈明显的剂量效应关系，且效果均强于相同浓度的葡萄籽原花青素(OPC)及SMWT，同时表明HMWT是柿子单宁的主要抗氧化活性组分。

Preparation and antioxidant activity of tannin from persimmon pulp

Persimmon tannin was extracted from persimmon pulp with methanol acidified with 1% HCl, then AB-8 macroporous adhesive resin and polysulfone ultrafilter membrane with molecular weight cutoff of 10000 were employed to purify and fractionate the crude extract, and two fractions: Small Molecular Weight Tannin(SMWT) and High Molecular Weight Tannin(HMWT) were obtained. The molecular weight distribution of HMWT was determined to be in the range of 1.16×10⁴ to 1.54×10⁴. Antioxidant properties of HMWT were evaluated in 2-deoxy-D-Ribose system, methyl violet system, salicylic acid system, pyrogallol autoxidation system, and linoleic acid lipid peroxidation system. The maximum scavenging rate of HMWT on hydroxyl radical in 2-deoxy-D-Ribose, methyl violet and salicylic acid system were 90.47%, 96.46% and 87.77%, respectively; the maximum inhibiting effect of HMWT on pyrogallol autoxidation and linoleic acid lipid preoxidation were 56.57% and 69.63%, respectively. HMWT exhibited excellent antioxidant activity in all tested sytems in a dose-dependent manner and the antioxidant activity of HMWT was significantly stronger than those of SMWT and grape seeds proanthocyanidins(OPC). This results suggest that HMWT is the main antioxidant in persimmon pulp.