Allergy-preventive phenolic glycosides from Populus sieboldii.

Allergy-preventive activity was demonstrated for an extract of the bark of Populus sieboldii in a continuing search for allergy-preventive substances from natural sources. By bioassay-directed fractionation of this plant bark, two new phenolic glycosides, siebolside A {2-hydroxy-5-[(benzoyloxy)methyl]phenyl (6'-O-acetyl) beta-D-glucopyranoside} (1) and siebolside B {2-hydroxy-5-[(benzoyloxy)methyl]phenyl beta-D-glucopyranoside} (2), were isolated, together with three known compounds, salicin (3), sakuranin (4), and neosakuranin (5). The structures of 1 and 2 were elucidated by spectroscopic methods. Compounds 1-5 all showed allergy-preventive effects.