title: Vasodilatory actions of xanthones isolated from a Tibetan herb, Halenia elliptica.
abstract: In this study, six major xanthones, isolated and identified from Halenia elliptica were investigated for their vasodilatory actions in isolated rat coronary artery. The xanthones, including 1-hydroxy-2,3,5-trimethoxy-xanthone (HM-1), 1-hydroxy-2,3,4,7-tetramethoxy-xanthone (HM-2), 1-hydroxy-2,3,4,5-tetramethoxy-xanthone (HM-3), 1,7-dihydroxy-2,3,4,5-tetramethoxy-xanthone (HM-4), 1,5-dihydroxy-2,3-dimethoxy-xanthone (HM-5) and 1,7-dihydroxy-2,3-dimethoxy-xanthone (HM-7) caused vasodilation in the coronary artery pre-contracted with 1 microM 5-hydroxytryptamine (5-HT), with EC(50) values ranging from 1.4+/-0.1 microM (HM-1) to 6.6+/-1.4 microM (HM-2). The EC(50) values of the other xanthones were between those of HM-1 and HM-2. Removal of endothelium of the coronary artery led to decreases in the vasorelaxant effects of HM-1, HM-7 but not HM-2, HM-3, HM-4 and HM-5. Our results showed that xanthones isolated from Halenia elliptica are vasoactive substances which exhibit either endothelium-dependent or endothelium-independent mechanisms in rat coronary artery. The potency and mechanism(s) of the vasorelaxant effects of these xanthones may be relevant to the structure-activity differences in the level and the position of the substituent groups with the primary xanthone structure.
authors.affiliation: School of Chinese Medicine, The Chinese University of Hong Kong, Hong Kong, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.forename: Jian-Gong
authors.initials: JG
authors.lastname: Shi
authors.forename: Mu-Zou
authors.initials: MZ
authors.lastname: Wang
authors.forename: Chun-Tao
authors.initials: CT
authors.lastname: Che
authors.forename: John H K
authors.initials: JH
authors.lastname: Yeung
mesh_terms: D000818:Animals; D003331:Coronary Vessels / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects*; D029965:Gentianaceae / Q000737:chemistry*; D008297:Male; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin; D018490:Serotonin Agents; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000302:isolation & purification / Q000494:pharmacology; D044004:Xanthones / Q000302:isolation & purification / Q000494:pharmacology*
chemical_list: D010936:Plant Extracts; D018490:Serotonin Agents; D014665:Vasodilator Agents; D044004:Xanthones; D012701:Serotonin