中文摘要：

本文研究了薤白多糖清除各种自由基及其对小鼠急性肝损伤的保护作用。采用浸提、分步醇沉法提取了三种薤白多糖，利用红外光谱初步分析了其结构组成。结果表明：AMP40在清除羟基自由基（·OH）、超氧阴离子自由基（O2＋）等抗氧化评价体系中比AMP60及AMP80具有更强的清除自由基活性，在实验最大浓度时清除率可分别达到40．96％和49．840／0；在对小鼠急性化学性肝损伤的保护作用研究中，发现通过预先灌胃200、400和800mg／kgBW的薤白多糖AMP40，可以抑制肝损伤小鼠血清中谷丙转氨酶（ALT）和谷草转氨酶（AST）活性的升高，同时能使小鼠肝脏中SOD活性、CAT活性、GSH活性以及T-AOC水平显著增加，而MDA含量显著减少（P〈0．05或P〈0．01），且这种变4e-AMP40呈现一定的剂量依赖关系，表明AMP40具有一定的肝保护作用。研究表明了薤白多糖的抗氧化活性与其分子量大小及糖醛酸含量密切相关。

英文摘要：

The in vitro antioxidant activities of polysaccharides from Allium macrostemon Bunge were evaluated by radical scavenging activity, and three kinds of polysaccharides were extracted from fractional alcohol precipitation. The preliminary structures and compositions were analyzed by infrared spectroscopy. During in vitro antioxidant assay, AMP40 exhibited the strongest scavenging activity than the others in scavenging hydroxyl radical （.OH） and superoxide radical （02-）. The in vivo antioxidant activities of crude AMP were investigated that against CC14-induced acute liver damage in Kunming mice. The results showed that pretreatment with AMP40 could markedly improve the activities of those antioxidant enzymes in CC14-treated mice. The antioxidative system tended to be normalized by the protective action of AMP40, and scavenging activity of AMP40 was in a dose-dependent manner. It also showed that antioxidant properties directly related to the molecular weight and the uronic acid content of polysaccharide.