Studies on antihypertensive and antispasmodic activities of Andropogon muricatus Retz.This article is one of a selection of papers published in this special issue (part 1 of 2) on the Safety and Efficacy of Natural Health Products.

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The aqueous-methanolic crude extract of Andropogon muricatus (Am.Cr) was investigated pharmacologically to determine some of its medicinal uses in cardiovascular and gastrointestinal disorders. A series of in vivo and in vitro studies were conducted to evaluate dose-dependent effects of Am.Cr on mean arterial pressure (MAP), cardiac and vascular contractions, and to further investigate the potential mechanism of action. Intravenous administration of Am.Cr (10-50 mg/kg) caused a fall (18%-56%) in MAP in normotensive rats under anesthesia. When tested in isolated guinea pig atria, Am.Cr (0.03-5.0 mg/mL) exhibited a cardiodepressant effect on the rate and force of spontaneous contractions. In isolated rabbit aorta, Am.Cr caused inhibition of K+ (80 mmol/L)-induced contractions at a lower concentration than of phenylephrine. In isolated rabbit jejunum preparations, Am.Cr (0.01-0.10 mg/mL) caused relaxation of spontaneous and high K+ (80 mmol/L)-induced contractions, suggesting that the spasmolytic effect is mediated possibly through calcium channel blockade (CCB). The CCB activity was confirmed when pretreatment of the tissue with Am.Cr (0.03-0.1 mg/mL) shifted the Ca2+ dose-response curves to the right, similar to that caused by verapamil. These data indicate that the blood pressure-lowering and spasmolytic effects of Am.Cr are mediated possibly through a calcium channel blocking activity. Phytochemical screening of Am.Cr revealed the presence of phenols, saponins, tannins, and terpenes, which may be responsible for the observed vasodilator, cardiodepressant, and antispasmodic activities. This study shows potential with respect to its medicinal use in cardiovascular and gut disorders.