ABSTRACT Procyanidine was isolated and identified from fruit of Crataegus azarolus (Iraqi endogenous). In vitro and in vivo pharmacological actions of procyanidine were studied. Toxicological and histopathological studies of procyanidne on the mice indicated its safety. The LD 50 of procyanidine estimated to be about 100mg/kg. No antibacterial and antiinflammatory effects were seen with procyanidine. The antagonistic effect of procyanidine on the adenosine receptor was observed on the isolated jejunum of the rabbit. Procyanidine produced quite clear positive inotropic effect on the isolated, stimulated left atrium and papillary muscle of the rabbit, without any significant effects on the heart rate and blood pressure of experimental rats. Also procyanidine produced marked diuretic and natriuretic effects without any significant actions on the potassium excretion in the rat (16mg/kg I:V) and volunteers healthy subjects (50mg orally). The positive inotropic and diuretic actions of procynidine, most probably, are related to its antagonistic effects on the adenosine (Al) receptors. These dual (positive inotropic and diuretic) effects of procyanidine make it a good drug for the treatment of congestive heart failure
