PHARMACOLOGICAL STUDIES ON HYPOTENSIVE AND SPASMOLYTIC ACTIVITIES OF PURE COMPOUNDS FROM MORINGA-OLEIFERA

Bioassay directed fractionation of an ethanolic extract of Moringa ole ifera (MO) leaves resulted in the isolation of four pure compounds, ni azinin A (1), niazinin B (2), niazimicin (3) and niaziminin A + B (4 5). Intravenous administration of either one of the compounds (1-10 m g/kg) produced hypotensive and bradycardiac effects in anaesthetized r ats. Pretreatment of the animals with atropine (1 mg/kg) completely ab olished the hypotensive and bradycardiac effects of acetylcholine (ACh ), whereas cardiovascular responses to the test compounds remained una ltered, ruling out the possible involvement of muscarinic receptor act ivation. In isolated guinea-pig atria all the compounds (50-150 mug/mL ) produced negative inotropic and chronotropic effects. Each compound inhibited K+-induced contractions in rabbit aorta as well as ileal con tractions induced by ACh or histamine at similar concentrations. Spont aneous contractions of rat uterus were also inhibited equally by all c ompounds. These data indicate that the direct depressant action of the se compounds exhibited on all the isolated preparations tested is prob ably responsible for its hypotensive and bradycardiac effects observed in vivo. Moreover, spasmolytic activity exhibited by the constituents of the plant provides a scientific basis for the traditional uses of the plant in gastrointestinal motility disorders.