Acetylcholine vasorelaxant effect

The second indication came from studies of vascular regulation. Several molecules, such as acetylcholine, were known to cause relaxation of blood vessels. This effect occurred only when the vessels were prepared so that the luminal endothelial cells covering the smooth muscle of the vessel wall were retained. Subsequent studies showed that endothelial cells respond to these vasorelaxants by releasing a soluble endothelial-derived relaxing factor (EDRF). EDRF acts on vascular muscle to elicit relaxation. These findings prompted an intense search for the identity of EDRF. 

NO in response to endothelium-dependent vasorelaxants such as acetylcholine and bradykinin without influencing the relaxant effect of NO itself. These studies are consistent with the view that enzymatically generated NO may play an important negative-feedback regulatory role on eNOS, and therefore on vascular endothelial cell function. 

The chemopreventive activity of hibiscus extracts has been extensively studied recently. The protective effect was demonstrated against human carcinomas, chemically induced toxicity,and hepatotoxici-jy 11,21-27 Antimutagenic activity has also been demonstrated both in vitro and in vivo The chemopreventive activity is attributed mainly to the antioxidant effect of the anthocyanins present in hibiscus extracts. Roselle decoction or infusion reportedly has hypotensive properties with no side effects. This effect has been investigated in more depth in experimental animals and in humans over the past decade and the results seem to support earlier studies especially in mild to moderate hypertension. Suggested mechanisms of action for the hypotensive activity include inhibition of Ca influx into vascular smooth muscle, NO-cGMP-relaxant pathway, and possible acetylcholine-and histamine-like vasorelaxation. ... 

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