Toshio Morikawa

Aim Bombycis Feces (BF) and Bombyx Batryticatus (BB) are traditional medicines derived from silkworm. We investigated the suppressive effects of BF and BB extracts on elevated blood glucose levels in disaccharide‐loaded rats. Methods Effects of BF and BB extracts on serum glucose levels in sugar‐loaded rats and streptozotocin (STZ)‐induced diabetic mice were recorded, and several glucosidase inhibitory activities were determined in vitro by comparing with those of the natural medicines obtained from the mulberry plant (e.g. , Mori Folium , Mori Cortex , and Mori Fructus ). Results BF and BB methanol extracts were found to suppress the elevated blood glucose level in sucrose‐loaded mice, whereas they did not exhibit any activity in the glucose‐loaded model and in the STZ‐induced model. Through the bioassay‐guided separation of the BF methanol extract using sucrase and maltase inhibitory activities, several pseudo‐sugars, including 1‐deoxynojirimycin ( 1 ), fagomine ( 2 ), and cis ‐5‐hydroxy‐L‐pipecolic acid ( 3 ) were isolated as the active constituents. Oral administration (10 mg/kg) of constituent 1 simultaneous to sucrose loading in rats was found to significantly suppress elevation of the serum glucose level. Conclusion BF and BB extracts were found to inhibit the elevated blood glucose level in disaccharides‐loaded rats due to their α‐glucosidase inhibitory activities. The suppressive effects of BF and BB extracts as well as of the active constituent 1 on the increase in blood glucose were estimated to dwindle at a limited time after administration. Therefore, it is suggested that BF and BB extracts might exert their effective antidiabetic effects when taken with meals.