title: Bioactive bibenzyl derivatives and fluorenones from Dendrobium nobile.
abstract: Bioassay-guided fractionation of the 60% ethanol extract of the stems of Dendrobium nobile using the DPPH assay led to the isolation of two new bibenzyl derivatives, nobilin D (1) and nobilin E (2), and a new fluorenone, nobilone (3), together with seven known compounds (4-10). Their structures were determined on the basis of spectroscopic analyses. Compounds 1, 2, 4, 7, 8, and 10 exhibited significant antioxidant activity higher than or equivalent to vitamin C in the DPPH assay, and compounds 1, 3, 4, and 7-10 displayed higher antioxidant activity than vitamin C in the ORAC assay. Compounds 1, 2, and 10 also exhibited stronger inhibitory effects on NO production than resveratrol.
authors.affiliation: Research Institute of Tsinghua University in Shenzhen, Key Laboratory for New Drugs Research of Traditional Chinese Medicine in Shenzhen, Shenzhen 518057, People's Republic of China.
authors.forename: Xue
authors.initials: X
authors.lastname: Zhang
authors.forename: Jie-Kun
authors.initials: JK
authors.lastname: Xu
authors.forename: Jue
authors.initials: J
authors.lastname: Wang
authors.forename: Nai-Li
authors.initials: NL
authors.lastname: Wang
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kurihara
authors.forename: Sumumu
authors.initials: S
authors.lastname: Kitanaka
authors.forename: Xin-Sheng
authors.initials: XS
authors.lastname: Yao
mesh_terms: D000975:Antioxidants / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D001632:Bibenzyls / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D001713:Biphenyl Compounds; D031667:Dendrobium / Q000737:chemistry*; D004365:Drugs, Chinese Herbal / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D005449:Fluorenes / Q000737:chemistry / Q000302:isolation & purification* / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis / Q000378:metabolism; D010851:Picrates / Q000494:pharmacology; D018547:Plant Stems / Q000737:chemistry; D010946:Plants, Medicinal / Q000737:chemistry*; D000077185:Resveratrol; D045788:Sesquiterpenes, Germacrane; D013267:Stilbenes / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D001632:Bibenzyls; D001713:Biphenyl Compounds; D004365:Drugs, Chinese Herbal; D005449:Fluorenes; D010851:Picrates; D045788:Sesquiterpenes, Germacrane; D013267:Stilbenes; C517578:nobilin D; C517579:nobilin E; C517580:nobilone; D009569:Nitric Oxide; C004931:1,1-diphenyl-2-picrylhydrazyl; D000077185:Resveratrol