Bacopa monnieri and its constituents is hypotensive in anaesthetized rats and vasodilator in various artery types

Abstract

Ethnopharmacological relevance: Bacopa monnieri (Brahmi) provides traditional cognitive treatments possibly reflecting improved cerebral hemodynamics. Little is known about the cardiovascular actions of Brahmi. We sought to assess its effects on blood pressure and on isolated arteries, thus providing insights to clinical applications.

Materials and methods: Intravenous Brahmi (20-60 mg/kg) was tested on arterial blood pressure and heart rate of anaesthetized rats. In vitro vasorelaxation was assessed in arteries, with and without blockers of nitric oxide synthase (L-NAME), cyclooxygenase (indomethacin), and mechanical de-endothelialisation. The effects of Brahmi on Ca(2+) influx and release from stores were investigated.

Results: Intravenous Brahmi extract (20-60 mg/kg) decreased systolic and diastolic pressures without affecting heart rate. Brahmi evoked relaxation in isolated arteries in order of potency: basilar (IC50=102 ± 16 μg/ml)>mesenteric (171 ± 31)>aortae (213 ± 68)>renal (IC50=375 ± 51)>tail artery (494 ± 93)>femoral arteries (>1,000 μg/ml). Two saponins, bacoside A3 and bacopaside II, had similar vasodilator actions (IC50=8.3 ± 1.7 and 19.5 ± 6.3 μM). In aortae, without endothelium or in L-NAME (10-4M), Brahmi was less potent (IC50=213 ± 68 to 2170 ± 664 and 1192 ± 167 μg/ml, respectively); indomethacin (10-5M) was ineffective. In tail artery, Brahmi inhibited K(+)-depolarization induced Ca(2+) influx and Ca(2+) release from the sarcoplasmic reticulum by phenylephrine (10-5M) or caffeine (20mM).

Conclusions: Brahmi reduces blood pressure partly via releasing nitric oxide from the endothelium, with additional actions on vascular smooth muscle Ca(2+) homeostasis. Some Brahmi ingredients could be efficacious antihypertensives and the vasodilation could account for some medicinal actions.