N-CONTAINING SUGARS FROM MORUS-ALBA AND THEIR GLYCOSIDASE INHIBITORY ACTIVITIES

The reexamination of N-containing sugars from the roots of Morus alba by improved purification procedures led to the isolation of eighteen N -containing sugars, including seven that were isolated from the leaves of Morus bombycis. These N-containing sugars are 1-deoxynojirimycin ( 1), N-methyl-1-deoxynojirimycin (2), fagomine (3), 3-epi-fagomine (4), 1,4-dideoxy-1,4-imino-D-arabinitol (5), 1,4-dideoxy-1,4-imino-D-ribit ol (6), calystegin B-2 (1 alpha,2 beta,3 alpha,4 beta-tetrahydroxy-nor -tropane, 7), calystegin C-1 (1 alpha,2 beta,3 alpha,4 beta,6 alpha-pe ntahydroxy-nor-tropane, 8), 1,4-imino-(2-O-beta-D-glucopyranosyl)-D-ar abinitol (9), and nine glycosides of 1. These glycosides consist of 2- O- and 6-O-alpha-D-galactopyranosyl-1-deoxynojirimycins (10 and 11, re spectively), 2-O-, 3-O- and 4-O-alpha-D-glucopyranosyl-1-deoxynojirimy cins (12, 13, and 14, respectively), and 2-O-, 3-O-, 4-O- and 6-O-beta -D-glucopyranosyl-1-deoxynojirimycins (15, 16, 17, and 18, respectivel y). Compound 4 is a new member of polyhydroxylated piperidine alkaloid s, and the isolation of 6 is the first report of its natural occurrenc e. It has recently been found that the polyhydroxy-nor-tropane alkaloi ds possess potent glycosidase inhibitory activities. Calystegin A(3) i s the trihydroxy-nor-tropane, and calystegins B-1 and B-2 are the tetr ahydroxy-nor-tropane. Calystegin C-1, a new member of calystegins, is the first naturally occurring pentahydroxy-nor-tropane alkaloid. The i nhibitory activities of these compounds were investigated against rat digestive glycosidases and various commercially available glycosidases .