ABSTRACT
Objective: To find the genuine structure with anti-acetylcholinesterase(anti-AChE)from the phenolic glycosides abundant in Leonurus japonicus(Lamiaceae).The assay for anti-AChE activity is often used to lead anti-Alzheimer's drugs. Methods: The five phenolic glycosides, tiliroside, leonurusoside C, 2'''-syringoylrutin, rutin, and lavanduliofolioside were isolated from L. japonicus. The activities of the glycosides were relatively low. Seven compounds including p-coumaric acid, caffeic acid, hydroxytyrosol, salidroside, syringic acid, kaempferol, and quercetin, which are produced by the hydrolysis of the five glycosides, were also assayed for anti-AChE activity. Results: Of those seven compounds, the five compounds other than salidroside and syringic acid exhibited potent anti-AChE activities.In particular,the IC50s of caffeic acid and quercetin were (1.05 ± 0.19)and (3.58 ± 0.02)μg/mL, respectively. Rutin was the most abundant flavonoid in the extract(9.18 mg/g as measured by HPLC). Conclusion: The substances with potent anti-AChE were caffeic acid, quercetin, p-coumaric acid, kaempferol, and hydroxytyrosol that can be produced from their glycosides.
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.