桉叶中2种没食子单宁结构鉴定及其抗氧化研究

对桉叶多酚中主要抗氧化活性成分进行分离纯化时,得到2种具有互变异构结构的没食子单宁,其中一种为首次在桉叶中分离得到.以清除DPPH.、ABTS自由基能力和氧自由基吸收能力(ORAC)法作为抗氧化活性评价方法,采用Diaion HP-20(Tsk)大孔树脂和Toyopearl HW-40(C)凝胶柱色谱分离桉叶多酚,然后采用制备液相色谱仪进行纯化,得到2种具有强抗氧化活性的单体.ORAC实验结果显示,两者的ORAC指标分别为2.25±0.18和1.99±0.63,是标准抗氧化剂Trolox(1.00±0.00)的2倍左右.通过1 H-NMR和13C-NMR鉴定,确定2种物质分别为3-galloyl-4,6-HHDP-D-glucose(Gemin D)和2,3,4,6-二-HHDP-D-glucose(Pedunculagin),且两者葡萄糖环上的1-OH均具有α,β互变的特点,确定为α,β互变异构型没食子单宁,其中3-galloyl-4,6-HHDP-D-glucose(geminD)为首次从桉叶中分离得到.

Two Tautomerizing Gallotannins from Eucalyptus Leaves:Purification,Structure Characterization and Their Antioxidant Activity

The aqueous ethanolic extract of Eucalyptus leaves were used as the antioxidant in food additives,but it was not all clear of antioxidative components.In this paper,two tautomerizing gallotannins with strong antioxidant activity were isolated from the eucalyptus leaves extract.The antioxidant activities of the two components were more than two times that of the standant antioxidant Trolox(ORAC index).The chemical structures were determined by HPLC,1H-NMR and 13C-NMR.The results have shown that one is 3-galloyl-4,6-HHDP-D-glucose(Gemin D),and the other is 2,3,4,6-two-HHDP-D-glucose(Pedunculagin),and the former component is the first to be isolated from this plant.