Polyhydroxylated alkaloids isolated from mulberry trees (Morus alba L.) and silkworms (Bombyx mori L.)

New polyhydroxylated alkaloids, (2R,3R,4R)-2-hydroxymethyl-3,4-dihydroxypyr rolidine-N-propionamide from the root bark of Morus alba L., and 4-O-alpha -D-galactopyranosyl-calystegine B-2 and 3 beta ,6 beta -dihydroxynortropane from the fruits, were isolated by column chromatography using a variety of ion-exchange resins. Fifteen other polyhydroxylated alkaloids were also is olated. 1-Deoxynojirimycin, a potent alpha -glucosidase inhibitor, was conc entrated 2.7-fold by silkworms feeding on mulberry leaves. Some alkaloids c ontained in mulberry leaves were potent inhibitors of mammalian digestive g lycosidases but not inhibitors of silkworm midgut glycosidases, suggesting that the silkworm has enzymes specially adapted to enable it to feed on mul berry leaves. The possibility of preventing the onset of diabetes and obesi ty using natural dietary supplements containing 1-deoxynojirimycin and othe r alpha -glucosidase inhibitors in high concentration is of great potential interest.