Cardiovascular action of Piper longum
Cardiovascular actions of various plants from Piperaceae family were reported, but little is known about action of long pepper (Piper longum) [1,2,3]. Therefore, we aimed to investigate effects of long pepper ethanolic extract on rat blood pressure (BP) i.e. systolic (Ps), diastolic (Pd), mean arterial pressure (MAP), heart rate (HR) and isolated aorta. Intravenous administration of extract (1, 5, 10mg/Kg BW) significantly decreased Ps, Pd, MAP and HR in anaesthetized rat. Administration of extract (1mg/kg BW) produced the most pronounced hypotensive effect. The higher the doses of the extract used, the lower the %decreases of blood pressure were observed. At all doses studies, %decreases in Pd were significantly greater than that in Ps (P<0.05). HR was significantly decreased at all doses, but the changes appeared to be dose independent. The extract (0.005–0.5mg/ml) induced relaxation in endothelium intact and denuded aorta pre-contracted with either 1µM PE or 80 mM K+. Relaxation of endothelium intact artery was more pronounced than that of endothelium denuded artery (P<0.05). Pretreatment of aorta with 100µM N G-nitro-L-arginine methyl ester or 10µM indomethacin significantly reduced relaxation induced by the extract (P<0.05). In Ca++- free medium, pre-incubation of aorta with the extract (0.5mg/ml) significantly decreased contractile response induced by CaCl2 (1 to 5x mM). In conclusion, the results indicated that long pepper possessed hypotensive and vasodilator action in rat. Mechanism of vasodilation involved both nitric oxide and prostacyclin pathways as well as inhibition of extracelluar calcium entrance into arterial smooth muscle cells.
Acknowledgements: This research was funded by National Research Council of Thailand.
References: 1. Martin, H.B. et. al. (2002) Planta. Med. 68:784–789. 2. Raimundo, J.M. et. al. (2004)J. Pharm. Pharmacol. 56:1457–1462. 3. Runnie, I. et. al. (2004)J. Ethnopharmacol. 92:311–316.