山苦茶多糖结构表征及抗氧化活性研究

Structural Characteristics and Antioxidant Activity of Polysaccharides from Mallotus oblongifolius

本文从山苦茶中提取得到两个多糖组分水溶性多糖(MOWP)和碱溶性多糖(MOAP),得率分别为6.00%和3.07%。采用高效凝胶渗透色谱法(GPC)分别测定了MOWP和MOAP的分子量分布;采用PMP柱前衍生-高效液相色谱法(HPLC)分别测定了MOWP和MOAP的单糖组成;采用甲基化-气相色谱质谱法(GC/MS)研究了MOWP和MOAP的糖苷键连接方式。此外,采用DPPH·清除法、还原力法以及氧自由基吸收(ORAC)法,评价了MOWP和MOAP的体外抗氧化活性。结果表明:MOWP分子量分别为906 k Da和49 k Da,MOAP的分子量为95 k Da。木糖、半乳糖及葡萄糖构成了酸性多糖MOWP的骨架结构,而酸性多糖MOAP由甘露糖、木糖及半乳糖构成骨架。MOWP和MOAP中→3)-Xylf-(1→、→3)-Galp-(1→以及→3)-Glcp-(1→残基含量均较高。MOWP和MOAP均有一定的抗氧化能力,MOWP清除DPPH·的能力较强,MOAP具有较强的还原能力和氧自由基吸收能力。

A water-soluble polysaccharide(MOWP) and an alkali-soluble polysaccharide(MOAP) were isolated from Mallotus oblongifolius. The MOWP and MOAP yields were 6.00% and 3.07%, respectively. The molecular weights of the MOWP and MOAP were determined by a high performance gel permeation chromatography assay. The molecular weights of the MOWPs were 906 k Da and 49 k Da, and the molecular weight of the MOAP was 95 k Da. The monosaccharide composition was determined by a pre-column derivatization assay. Based on the monosaccharide composition analysis, the MOWP was mainly comprised of glucose, galactose, and xylose. MOAP was mainly comprised of mannose, galactose, and xylose. The glycosidic bonds of MOWPs and MOAPs were determined by a methylation assay. The branched MOWPs and MOAPs were composed mainly of →3)-Xylf-(1→, →3)-Galp-(1→ and →3)-Glcp-(1→ in different ratios. MOWPs and MOAPs exhibited moderate antioxidant capacities. MOWPs showed better DPPH scavenging activity than did MOAPs. MOAPs showed better reducing power and oxygen radical absorbance capacity than did MOWPs.