Synergistic and potentiating effects of ranitidine and two new anti-ulcer compounds from Enantia chlorantha and Voacanga africana in experimental animal models.

TN, an alkaloid from the fruit of Voacanga africana and a protoberberine-type alkaloid (7,8-dihydro-8-hydroxypalmatine) (1), obtained from the bark of Enantia chlorantha were tested for ulcer preventive and antisecretory activity in combination with ranitidine. When tested alone (50 and 100 mg/kg, p.o.), TN and 1 achieved their anti-ulcer actions through reduced gastric secretion and improved mucus production. 1:1 combinations of 1 and the antisecretory agents (25/25 and 50/50 mg/kg) resulted in significant reduction of ulceration under highly acidic conditions (50-70 mEq/l), suggesting potentiating effects. A combination of TN and ranitidine led to synergistic antisecretory effects.