Phenylvaleric acid and flavonoid glycosides from Polygonum salicifolium

(3R)-O-beta-D-Glucopyranosyloxy-5-phenylvaleric acid (1), (3R)-O-beta-D-glucopyranosyloxy-5-phenylvaleric acid n-butyl ester (2), and a new dihydrochalcone diglycoside 4'-O-[beta-D-glucopyranosyl-(1-->6)-glucopyranosyl]oxy-2'-hydroxy-3', 6'-dimethoxydihydrochalcone (3), together with six known flavonoid glycosides [kaempferol-3-O-beta-D-glucopyranoside (= astragalin) (4), kaempferol-3-O-beta-D-galactopyranoside (5), quercetin-3-O-beta-D-glucopyranoside (= isoquercitrin) (6), quercetin-3-O-beta-D-galactopyranoside (= hyperoside) (7), quercetin-3-O-(2''-O-galloyl)-beta-D-glucopyranoside (8), and quercetin-3-O-beta-D-glucuronopyranoside (9)] were isolated from the aerial parts of Polygonum salicifolium. The structure elucidation of the isolated compounds was performed by spectroscopic (UV, IR, ESI-MS, 1D- and 2D-NMR), chemical (methylation, enzymatic hydrolysis, partial synthesis), and chromatographic methods (HPLC, Chiralcel OD). The flavonoid glycosides (4-9) demonstrated scavenging properties toward the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical in TLC autographic assays.