title: Hypotensive activity of an n-butanol extract and their purified compounds from leaves of Phyllanthus acidus (L.) Skeels in rats.
abstract: We aimed to investigate the effects, identify the active substances and establish the mechanisms involved in the hypotensive activity of an n-butanol extract from leaves of Phyllanthus acidus (PA extract). PA extract caused a decrease in blood pressure of anesthetized rats that was not modified by atropine or propranolol. PA extract caused a persistent dilatation of thoracic aortic rings preconstricted with either phenylephrine or KCl, and these effects were not modified by LNA or removal of the vascular endothelium. For phenylephrine-preconstricted aortic rings, the dilatory activity of the PA extract was not modified by atropine, propranolol or indomethacin. TEA, glybenclamide or ODQ significantly inhibited the dilatory activity of the PA extract on endothelium-denuded aortic rings. Nifedipine or a Ca(2+)-free medium depressed the aortic rings constrictor response to phenylephrine, and that was further augmented by the PA extract. Adenosine, 4-hydroxybenzoic acid, caffeic acid, hypogallic acid, and kaempferol were isolated from the PA extract. Each caused a decrease in blood pressure and dilatation of the aortic rings. LNA or removal of the endothelium reduced this activity. ODQ and TEA attenuated the vasodilatory activity of adenosine whereas glybenclamide and ODQ attenuated the effect of hypogallic acid. These results suggest that the hypotensive activities of the PA extract is likely the result of the direct action of these five compounds on the blood vessels by stimulating release of nitric oxide from the vascular endothelium, in part through stimulation of soluble guanylate cyclase, and opening of K(ATP) and K(Ca) channels in the vascular smooth muscle.
authors.affiliation: Department of Physiology, Faculty of Science, Prince of Songkla University, Hat-Yai, 90112, Thailand.
authors.forename: Yuttapong
authors.initials: Y
authors.lastname: Leeya
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Mulvany
authors.forename: Emerson F
authors.initials: EF
authors.lastname: Queiroz
authors.forename: Andrew
authors.initials: A
authors.lastname: Marston
authors.forename: Kurt
authors.initials: K
authors.lastname: Hostettmann
authors.forename: Chaweewan
authors.initials: C
authors.lastname: Jansakul
mesh_terms: D020001:1-Butanol / Q000737:chemistry; D000818:Animals; D000959:Antihypertensive Agents / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D001013:Aorta, Thoracic / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D055808:Drug Discovery; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006973:Hypertension / Q000188:drug therapy; D066298:In Vitro Techniques; D008518:Medicine, East Asian Traditional; D029803:Phyllanthus / Q000737:chemistry*; D008517:Phytotherapy; D010936:Plant Extracts / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000494:pharmacology*; D018515:Plant Leaves / Q000737:chemistry*; D051381:Rats; D017208:Rats, Wistar; D013785:Thailand; D014664:Vasodilation / Q000187:drug effects
chemical_list: D000959:Antihypertensive Agents; D010936:Plant Extracts; D020001:1-Butanol