Castanospermine-glucosides are potent, selective, long-acting sucrase inhibitors

Castanospermine-glucosides (CS-glcs) are new compounds which have been evaluated as glycohydrolase inhibitors in rats. 7-O-alpha-D-Glucopyranosyl-CS (7 alpha-glc-CS) and 8 alpha-glc-CS were potent sucrase inhibitors with IC50s of 40 and 30 nM, respectively. Their sucrase inhibition was poorly reversible. They were much weaker liver lysosomal alpha-glucosidase inhibitors with IC50s of 40,000 nM. 1 alpha-glc-CS and 8 beta-glc-CS were both weaker and less selective sucrase inhibitors. In vivo, 7 alpha-glc-CS and 8 alpha-glc-CS effectively reduced the glycemic response to an oral 2 g/kg sucrose load at doses less than or equal to 1 mg/kg. 8 alpha-glc-CS was effective when administered up to 4 hr before sucrose. The known glucohydrolase inhibitors 1-deoxynojirimycin and N-hydroxyethyl-1-deoxy-nojirimycin were also potent sucrase inhibitors (IC50s = 200 and 400 nM, respectively) but their sucrase inhibition was readily reversible in vitro and their in vivo duration of action was much shorter than for the CS-glcs. Among the glucohydrolase inhibitors tested, the prolonged in vivo duration of action could be predicted by poor reversibility from sucrase. These CS-glcs provide a new generation of sucrase inhibitors which may be useful in the treatment of diabetes mellitus.