PHARMACOLOGY OF PIPER-MARGINATUM JACQ A FOLK MEDICINAL PLANT USED AS AN ANALGESIC, ANTIINFLAMMATORY AND HEMOSTATIC

The pharmacological activities of the water extract of Piper marginatu m Jacq. (Piperaceae), a plant reputed in the Brazilian folk medicine f or its analgesic/antiinflammatory, hemostatic and skin wound-healing p roperties, were assessed. Intraperitoneal injection (i.p.) of the extr act (0.1 to 1 g/kg) in mice and rats caused piloerection, sialorrhea, lacrimation, muscle relaxation and dyspnea. At doses above 1 g/kg the extract caused respiratory arrest and death. Intravenous injection of the extract (0.1 to 0.5 mg/kg) into anesthetized rats caused a dose-re lated hypertension (by 27 to 48 %) that was blocked by prazosin (1 mg/ kg) and yohimbine (2 mg/kg). Pithing, reserpine treatment and ganglion ic blockade with hexamethonium (5 mg/kg) enhanced the effect. Oral tre atment of unanesthetized rats and intragastric administration to anest hetized animals also produced hypertension. The sympathomimetic activi ty of the extract in isolated vas deferens, left atria and mesenteric arterial bed preparations paralleled that of noradrenaline, and was bl ocked to the same extent as noradrenaline by alpha-blockers. The plant extract (0.5 and 1 g/kg, p.o.) also reduced carrageenin-induced paw e dema in rats by 80 to 90 % of the control, but it had less effect on t he volume of exudate and leucocyte migration in carrageenin-induced pl eurisy. Likewise, the extract had a small analgesic effect on the acet ic acid-induced writhing test in mice. It is concluded that the antied ema effect of the plant extract is mainly related to its vasoconstrict or constituent(s). This sympathomimetic activity may explain the plant 's reputed hemostatic properties when applied topically to bleeding sk in wounds. The predominant vasoconstrictor component of P. marginatum detected in HPLC analysis was noradrenaline, whose activity is apparen tly preserved in the crude extract and produces vasoconstriction after oral administration.