Chemical constituents and aldose reductase inhibitory activities of Betula alba bark and leaves.

Systematic phytochemical investigation of the bark and leaves of Betula alba was independently conducted. A new cyclic diarylheptanoid glucoside (1), five diarylheptanoids (2-6), a phenylethanoid (7), a methyl salicylate glycoside (8), a dihydrobenzofuran glucoside (9), an arylbutanoid glycoside (10), two lignan glycosides (11 and 12), a flavanone glucoside (13), and a triterpene (14) were isolated from the bark of B. alba. On the other hand, two cyclic diarylheptanoids (15 and 16), five flavonoids (17-21), a phenylpropanoid (22), a phenylbutanoid glucoside (23), and a monoterpene glucoside (24) were obtained from the leaves of B. alba. The structures of the isolated compounds (1-24) were identified on the basis of one- and two-dimensional NMR spectroscopic data. Compounds 1-24 were subsequently examined for aldose reductase (AR) inhibitory activity. Compounds 14 and 17-20 moderately inhibited AR activity with IC50 values ranging from 6.6 to 34 µM.