黄瓜多糖的体外抗氧化活性

摘要

Objective： To determine total carbohydrate content in cucumber,isolate polysaccharides from it and analyze uronic acid content,monosaccharide composition and in vitro antioxidant activity of extracts obtained.Methods： Phenol-sulfuric acid and sulfuric acid-carbazole methods were employed to evaluate total carbohydrate content and uronic acid content,respectively.In addition,high performance liquid chromatography（HPLC） based on pre-column derivatization with 1-phenyl-3-methyl-5-pyrazolone（PMP） was employed to analyze the monosaccharide composition of cucumber polysaccharides.Moreover,the scavenging activity of cucumber polysaccharides against 1,1-diphenyl-2-picrylhydrazyl（DPPH）,superoxide anion（O2-·） and hydroxyl（·OH） free radicals and total reducing power（TRP） of cucumber polysaccharides were evaluated in vitro.Results： The total carbohydrate and uronic acid contents in cucumber polysaccharides were 63.5% and 10.6%,respectively.The monosaccharide composition of cucumber polysaccharides was made up of D-mannose（Man）,L-rhamnose（Rha）,D-glucuronic acid（GlcUA）,D-galacturonic acid（GalUA）,D-glucose（Glc）,D-xylose（Xyl）,D-galactose（Gal）,L-arabinose（Ara） with a molar ratio of 4.08：2.78：1.00：5.82：6.07：2.78：8.48：6.58.Cucumber polysaccharides revealed high antioxidant activity,and the scavenging rates at the concentration of 20 mg/mL against DPPH,superoxide anion and hydroxyl free radicals were 92.31%,83.57% and 77.59%,respectively.Moreover,cucumber polysaccharides also exhibited strong reducing power.Conclusion： Cucumber polysaccharides are typically heteropolysaccharides with stronger antioxidant activity.%目的：测定黄瓜中总糖含量,分离制备黄瓜多糖并测定其糖醛酸含量、单糖组成以及评价其体外抗氧化活性。方法：采用苯酚-硫酸法测定黄瓜提取物中的总糖含量;用硫酸-咔唑法测定黄瓜多糖中的糖醛酸含量;采用1-苯基-3-甲基-5-吡唑啉酮（PMP）柱前衍生化高效液相色谱（HPLC）分析单糖组成;并在体外抗氧化评价体系研究黄瓜多糖对DPPH自由基、超氧阴离子自由基（O-2.）和羟自由基（.OH）的清除活性以及总还原力（TRP）。结果表明：黄瓜多糖的总糖含量为63.5%,糖醛酸含量为10.6%。HPLC分析表明：黄瓜多糖由D-甘露糖、L-鼠李糖、D-葡萄糖醛酸、D-半乳糖醛酸、D-葡萄糖、D-木糖、D-半乳糖、L-阿拉伯糖等8种单糖组成,物质的量比为4.08：2.78：1.00：5.82：6.07：2.78：8.48：6.58。黄瓜多糖有明显的抗氧化活性,在质量浓度为20mg/mL时,对DPPH自由基、O-2.、.OH的清除率分别为92.31%、83.57%和77.59%,并发现其有明显的还原能力。结论：黄瓜多糖是一种典型的杂多糖,具有较强的抗氧化活性。