Comparison of the gastroprotective effect of a diterpene lactone isolated from Croton cajucara with its synthetic derivatives.

The effect of three new derivatives from dehydrocrotonin (DHC-compound I) on gastric damage in different animal models including gastric ulceration induced by a necrotic agent and hypothermic restrained-stress was studied: compound II (produced by reducing the cyclohexenone moiety of DHC with NaBH(4)); compound III (produced by reducing the carbonyls with LiAlH(4)); and compound IV (produced by transforming the lactone moiety into an amide). Their structures were confirmed on the basis of chemical and physicochemical evidence. When previously administered (p.o.) at a dose of 100mg/kg, compound II significantly (P<0.01) reduced gastric injury induced by HCl/ethanol (78%) and indomethacin (88%) better than did reference compound I (48 and 43%, respectively). But the anti-ulcerogenic activity of compound II was completely abolished by the stress-induced ulcer. Reduction of carbonyls with LiAlH(4) (compound III) caused decreased activity, markedly when no protective effect in any of the models was applied (P>0.05). However, compound IV, in which the lactone moiety was changed into an amide, when administered at the same dose (100mg/kg, p.o.), was more effective. The presence of a lactone moiety or Michael acceptor is probably essential for the anti-ulcerogenic effect of these compounds.