Acylated flavonol glycosides from the flower of Inula britannica.

Three new acylated flavonol glycosides, patuletin 7-O-(6' '-isobutyryl)glucoside (1), patuletin 7-O-[6' '-(2-methylbutyryl)]glucoside (2), and patuletin 7-O-(6' '-isovaleryl)glucoside (3), were isolated from the n-BuOH extract of Inula britannica flowers by bioassay-guided fractionation, together with other known flavonoids. The structures were elucidated by 1D and 2D NMR, FABMS, and other spectral analyses. The eight flavonoids, including new compounds (1-3), patulitrin (7), nepitrin (8), axillarin (10), patuletin (11), and luteolin (12), showed profound antioxidant activity in DPPH assay and cytochrome-c reduction assay using HL-60 cell culture system.