Studies on Antioxidant Activity of Bibenzyls and Phenolic Components from Dendrobium nobile
ZHANG Xue1,2,3,XU Jie-kun3,WANG Nai-li1,3,HIROSHI Kurihara4,YAO Xin-sheng3,WANG Zhao2(1.Key Laboratory for Research & Development of New Drugs from Traditional Chinese Medicine & Natural Products in Shenzhen Research Institute of Tsinghua University in Shenzhen,Shenzhen 518057,China;2. Medical School,Tsinghua University,Beijing 100084,China;3. College of Traditional Chinese Materia Medica,Shenyang Pharmaceutical University,Shenyang 110016,China;4.Institute of Traditional Chinese Medicine & Natural Products,College of Pharmacy,Jinan University,Guangzhou 510632,China)
OBJECTIVE To study the antioxidant activity of bibenzyls and phenolic components isolated from the 60% EtOH extract of Dendrobium nobile,and discuss the structure-activity relationship.METHODS Compounds were isolated from the 60% EtOH extract of Dendrobium nobile through various chromatographic techniques and identified by spectral data.The antioxidant activity of 16 compounds was evaluated by DPPH free radical scavenging assay and oxygen radical absorbance capacity assay.RESULTS Three new bibenzyls and thirteen phenolic compounds were obtained.Their structures were characterized as nobilin A(1),nobilin B(2),nobilin C(3),syringic acid(4),2-hydroxyphenylpropanol(5),vanillin(6),apocynin(7),coniferyl aldehyde(8),syringaldehyde(9),syringylethanone(10),p-hydroxybenzaldehyde(11),3-hydroxy-4-methoxyphenylethanol(12),α-hydroxysyringylethanone(13),dihydroxyconiferyl alcohol(14),p-hydroxybenzoic acid(15),and p-hydroxyphenylpropionic acid(16),respectively.In the DPPH assay,compound 4 exhibited significant scavenging activity,compared with vitamin C.Compounds 1,2,12 and 14 showed higher activity than BHT and weaker activity than vitamin C.The activity of compounds 3 and 8 was very weak.In the ORAC assay,compound 2～4,7～10,and 15 displayed stronger peroxyl radical scavenging activity than vitamin C,and compound 12,14,16 showed weak activity.CONCLUSION Most of the bibenzyls and phenolic components exhibited antioxidant activity in different levels,and the relationship between structure and activity was found.