ABSTRACT
Objective:To evaluate inhibitory potential of sevenKorean thistles against the advanced glycation endproducts(AGE) formation as well as to identify responsible compounds from the most active species.Methods:We used anin vitroAGE inhibition assay to evaluate the anti-diabetic complication potential of the methanol extracts of the selectedKorean thistles.Results:Among the sevenKorean thistles, the leaves ofCirsium maackii(C. maackii) exhibited the most significant inhibitory activity againstAGE formation.By means of bioassay-directed fractionation, a lignan, chlorogenic acid and14 flavonoids were isolated from the active ethyl acetate soluble fraction of a methanol extract fromC. maackii leaves.Luteolin and its5-O-glucoside have been previously isolated; however, a lignan and13 known compounds were isolated for the first time fromC. maackiileaves in this study.Most of the isolated compounds exhibited inhibitory activities against potentialAGE formation.Among them, cernuoside was shown to be the most potentAGE inhibitor with anIC50 value of21.21 μmol/L.Most importantly, two major flavonoids, luteolin and its5-O-glucoside, also significantly inhibitedAGE formation, withIC50 values of 36.33 and37.47 μmol/L, respectively.Structure activity relationship revealed that the presence of free3' and4' dihydroxyl group in flavonoids skeleton played an important role inAGE inhibition. Conclusions:These results indicate thatC. maackii andC. maackii-derived flavonoids might be explored further to develop therapeutic agents for the prevention of diabetic complications due to their significant inhibitory activity againstAGE formation.