Department of Physiology, Faculty of Science, Prince of Songkla University, Hat-Yai, 90112, Thailand.
Eur J Pharmacol. 2010 Dec 15;649(1-3):301-13. doi: 10.1016/j.ejphar.2010.09.038. Epub 2010 Sep 21.
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.
我们旨在研究 Phyllanthus acidus（PA 提取物）叶的正丁醇提取物的降压作用、鉴定其活性物质并阐明其作用机制。PA 提取物可降低麻醉大鼠的血压，而阿托品或普萘洛尔对此无影响。PA 提取物可使预先用苯肾上腺素或氯化钾收缩的胸主动脉环持续扩张，LNA 或去除血管内皮并不改变这些作用。对于预先用苯肾上腺素收缩的主动脉环，PA 提取物的扩张活性不受阿托品、普萘洛尔或吲哚美辛的影响。TEA、glybenclamide 或 ODQ 可显著抑制去内皮的主动脉环中 PA 提取物的扩张活性。硝苯地平或无钙培养基可抑制血管对苯肾上腺素的收缩反应，而 PA 提取物可进一步增强这种反应。从 PA 提取物中分离出腺苷、4-羟基苯甲酸、咖啡酸、没食子酸和山奈酚。它们都可降低血压并扩张主动脉环。LNA 或去除内皮会降低这种活性。ODQ 和 TEA 可减弱腺苷的血管扩张活性，而 glybenclamide 和 ODQ 可减弱没食子酸的作用。这些结果表明，PA 提取物的降压作用可能是由于这五种化合物通过刺激血管内皮释放一氧化氮，部分通过刺激可溶性鸟苷酸环化酶，以及开放血管平滑肌中的 K(ATP)和 K(Ca)通道，直接作用于血管而产生的。
