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.