A new flavonoid glucoside from Rhododendron seniavinii.

The leaves of Rhododendron seniavinii Maxim with little phytochemical information are used as folk remedies for the treatment of acute and chronic bronchitis in China. In our pursuing for the biologically active chemical constituents in the leaves, a new flavonoid glycoside 5,7,3'-trimethoxy-quercetin-3-O-β-D-glucopyranoside (1) was isolated from the water extract of its leaves, together with two known compounds 5,7,3'-trimethoxy-quercetin (2) and ovafolinin B-9'-O-β-D-glucopyranoside (3). The structures of the new flavonoid glucoside as well as two known compounds were elucidated by spectroscopic and chemical methods.