INHIBITION OF INTESTINAL CHLORIDE SECRETION BY PROANTHOCYANIDINS FROMGUAZUMA-ULMIFOLIA

The antisecretory activity of Guazuma ulmifolia bark was examined in r abbit distal colon mounted in an Ussing chamber. Chloride secretion wa s stimulated by cholera toxin and prostaglandin E(2) (PGE(2)). Guazuma ulmifolia extract (GUE) completely inhibited cholera toxin-induced se cretion if the extract was added to the mucosal bath prior to the toxi n. Adding the extract after administration of the toxin had no effect on secretion. GUE did not inhibit PGE(2)-induced chloride secretion. T hese results indicate an indirect antisecretory mechanism. SDS-PAGE an alysis of cholera toxin treated with GUE confirmed this presumption. G UE specifically interacted with the A subunit of the toxin. Preliminar y phytochemical examinations showed that the most active fraction cont ains procyanidins with a degree of polymerisation higher than 8.