栝楼雄株茎叶黄酮类化合物的分离及其清除DPPH能力研究

Separation of flavonoids from stems and leaves of male plants in Trichosanthes kirilowii and study on their activity of scavenging DPPH free radical

目的分离纯化栝楼Trichosanthes kirilowii雄株茎叶中黄酮类化合物,并探究其清除1,1-二苯基-2-苦基肼(DPPH)自由基能力的构效关系。方法利用聚酰胺树脂柱、高速逆流色谱及高效液相色谱等手段对栝楼雄株茎叶黄酮类成分进行分离纯化,根据化合物光谱数据鉴定其结构;采用DPPH法测定7个黄酮单体的体外抗氧化活性。结果从栝楼雄株茎叶中分离得到7种黄酮类化合物,分别鉴定为木犀草素(1)、金圣草黄素(2)、木犀草素-7-O-β-D-葡萄糖苷(3)、柯伊利素-7-O-β-D-葡萄糖苷(4)、芹菜素-7-O-β-D-葡萄糖苷(5)、香叶木素-7-O-β-D-葡萄糖苷(6)、槲皮素-3-O-β-D-葡萄糖苷(7)。7种黄酮类化合物清除DPPH自由基能力(IC50)依次为1>3>7>2>4>6>5。结论化合物1、2、6和7为首次从栝楼茎叶中分离得到。7种黄酮类化合物均能有效清除DPPH自由基,化合物1、3、7的DPPH自由基清除能力明显强于其他4种黄酮,比较其结构发现,前3者均存在B环3′,4′邻二羟基;化合物4和6的DPPH清除活性明显弱于化合物3,而在结构上前两者较化合物3存在3′位或4′位羟基甲基化;化合物3清除DPPH自由基能力弱于化合物1,但在结构上仅在A环7位存在糖基取代,考虑糖基化增加了前者的化学位阻。

Objective To study the flavonoids of the stems and leaves of male Trichosanthes kirilowii and to make a primary research on the structure activity relationship between flavonoids and their DPPH-scavenging capacity.Methods Flavonoids from the stems and leaves of male T.kirilowii were separated by chromatographic techniques,such as polyamide resin,high-speed countercurrent chromatography and high performance liquid chromatography.According to the chemical properties and spectral analysis,the chemical structures of the compounds were identified.And we determined the antioxidant ability in vitro of seven flavonoids by DPPH methods.Results Seven flavonoids were isolated from the stems and leaves of male T.kirilowii.They were luteolin （1）,chrysoeriol （2）,luteolin-7-O-β-D-glucoside （3）,chrysoeriol-7-O-β-D-glucoside （4）,apigenin-7-O-β-D-glucoside （5）,diosmetin-7-O-β-D-glucoside （6）,and quercetin-3-O-β-glucoside （7）.Under the present experimental condition,the order of their DPPH-scavenging capacities was 1 〉3 〉7 〉2 〉4 〉6 〉5.Conclusion Compounds 1,2,6,and 7 are isolated from this part of male T.kirilowii for the first time.DPPH-scavenging capacities of the compounds 1,3,and 7 are much stronger than others,but they all have 3＇,4＇ two adjacent hydroxide groups in B ring on the view of structure.DPPH-scavenging capacities of compounds 4 and 6 are much weaker than compound 3,but the former have 3＇ or 4＇ hydroxyl methylation in the structure.DPPH-scavenging capacity will also decrease if there is a 7 hydroxyl glycosylation in ring A by comparing compound 1 and 3.We speculate that it is caused by the increase of the steric hindrance.