摘要
To study the antioxidant constituents from the stems of Dendrobium nobile, and to discuss theft structure-activity relationship. Compounds were isolated from a 60% ethanolic extract by various chromatographic techniques and were identified by spectral analysis. The antioxidant activities of compounds were evaluated by DPPH free radical scavenging assay. Five phenanthrenes and four lignans were obtained from the active fractions ofD. nobile. Their structures were identified as fimbriatone （1）, confusarin （2）, flavanthrinin （3）, 2,5-dihydroxy-4,9-dimethoxyphenanthrene （4）, 3,7-dihydroxy-2,4-dimethoxyphenanthrene （5）, syringaresinol （6）, pinoresinol （7）, medioresinol （8） and lirioresinol-A （9）, respectively. Compounds 2 and 6 exhibited more potent DPPH scavenging activities than vitamin C. All the above compounds were reported from this plant for the first time, and compounds 3, 4 and 9 were reported for the first time from the genus of Dendrobiurn. For all phenanthrenes and lignans, an electron-donating methoxyl group in the ortho position to the phenolic hydroxyl group exhibits enhanced antioxidant activities.
研究金钗石斛茎中的抗氧化活性成分,并探讨它们的构效关系。综合运用现代色谱学和光谱学方法对金钗石斛60%乙醇提取物中的化学成分进行分离鉴定,采用DPPH自由基清除法评价化合物的抗氧化活性。从金钗石斛的活性部位中分离得到5个菲类化合物和4个木脂素类化合物,它们的结构鉴定为流苏菲(1),毛兰菲(2),4-甲氧基菲-2,7-二醇(3),2,5-二羟基-4,9-二甲氧基菲(4),3,7-二羟皋-2,4-二甲氧基菲(5),丁香脂素(6),松脂素(7),5′-甲氧基松脂素(8),鹅掌揪树脂醇-A(9)。化合物2和6对DPPH自由基清除活性强于Vc;化合物3,4,5,7,8和9的活性弱于Vc,但强于BHT。所有化合物均为首次报道从金钗石斛中分离得到,化合物3,4和9为首次报道从石斛属植物中分离得到。在DPPH自由基清除法中,酚羟基的邻位存在具有供电作用的甲氧基时对菲类和木脂素类化合物的抗氧化活性具有积极的作用。
