Durable Antihyperglycemic Effect of 6-O-Caffeoylsophorose with α-Glucosidase Inhibitory Activity in Rats

To evaluate the duration of antihyperglycemic effects of 6-O-caffeoylsophorose (CS), a newly identified natural α-glucosidase inhibitor from fermented purple-sweet potato, a single oral administration of CS was given to maltose-loaded Sprague-Dawley rats. Administration of CS (200 mg/kg) 30 min or 60 min before maltose administration produced an elevation of blood glucose level by administration of 2 g/kg of maltose in rats that was significantly lower than for no administration (control). In contrast, simultaneous or pro-administration of CS with maltose eliminated the antihyperglycemic effect. CS significantly reduced rat intestinal α-glucosidase activity in all of the small intestinal mucosal regions with a maximal reduction ratio of ca. 40% up to 60 min after CS administration. Thereafter, the intestinal α-glucosidase activity tended to return to basal level. These findings suggest that the antihyperglycemic effect of CS is restricted to pre-administration within 60 min.