In order to comprehensive understanding of the active substances of Allii macrostemonis bulbus (AMB), this study conducted the extraction, purification, structure and antioxidant activity of AMB polysaccharides. The crude polysaccharides were obtained by hot water and ethanol precipitation extraction, and five purified polysaccharide fractions were obtained (AMBP-1, AMBP-2, AMBP-3, AMBP-4 and AMBP-5) with different molecular weights. Structural characterization of five fractions by chromatography, spectroscopy, TGA and Zeta potential analysis. AMBP-1, AMBP-2 and AMBP-3 were primarily composed of mannose, glucose and galacturonic acid. Whereas AMBP-4 and AMBP-5 were primarily composed of mannose, glucuronic acid, galacturonic acid, glucose, galactose, arabinose, xylose. Five fractions possessed differences in characteristic morphology, thermal stability and Zeta potential. Further investigated,the results revealed that five fractions comprised of 1 → 4、1 → 6 linked d-glucopyranose as the main chain with different branch by using methylation with GC-MS and ¹D-NMR. Any one of AMB polysaccharides displayed the ability to scavenge free radicals, chelate iron with a dose-effect relationship. Among which AMBP-5 displayed the strongest antioxidant contribute to its rich uronic acid, monosaccharide composition and large molecular weight. This study has enriched the research on the chemical composition of AMB and provides a theoretical basis for developed as a functional food.

为全面了解蒜头球茎（AMB）的活性物质，本研究对AMB多糖的提取、纯化、结构和抗氧化活性进行了研究。粗多糖通过热水和乙醇沉淀提取得到，得到5种不同分子量的纯化多糖组分（AMBP-1、AMBP-2、AMBP-3、AMBP-4和AMBP-5）。通过色谱、光谱、TGA 和 Zeta 电位分析对五种馏分的结构进行表征。AMBP-1、AMBP-2和AMBP-3主要由甘露糖、葡萄糖和半乳糖醛酸组成。而AMBP-4和AMBP-5主要由甘露糖、葡萄糖醛酸、半乳糖醛酸、葡萄糖、半乳糖、阿拉伯糖、木糖组成。五个馏分在特征形态上有差异，热稳定性和 Zeta 电位。进一步研究，结果表明由1→4、1→6组成的五个部分相连通过GC-MS和1D-NMR进行^{甲基化，以}d-吡喃葡萄糖为主链，具有不同的支链。任何一种AMB多糖都显示出清除自由基、螯合铁的能力，具有剂量-效应关系。其中AMBP-5表现出最强的抗氧化作用，这得益于其丰富的糖醛酸、单糖成分和较大的分子量。本研究丰富了AMB化学成分的研究，为开发作为功能性食品提供了理论依据。