Constituents of the flowers of Erigeron annuus with inhibitory activity on the formation of advanced glycation end products (AGEs) and aldose reductase

Seven phenolic compounds, caffeic acid (1), 4-hydroxybenzoic acid (2), 4-methoxybenzoic acid (3), protocatechuic acid (4), eugenol O-beta-D-glucopyranoside (5), 3,6-di-O-feruloylsucrose (6), and 3,5-di-O-caffeoylquinic acid methyl ester (7), were isolated from an EtOAc-soluble partition of the flowers of Erigeron annuus. The structures of 1-7 were determined by spectroscopic data interpretation, particularly 1 D and 2D NMR studies, and by comparison of their data with those published in the literature. All the isolates were subjected to in vitro bioassays to evaluate their inhibitory activities against the formation of advanced glycation end products (AGEs) and rat lens aldose reductase (RLAR). Of the compounds, 1, 6, and 7 exhibited potent inhibitory activities against the formation of AGEs. In the RLAR assay, compound 7 showed the most potent inhibitory activity.