Antioxidant and free radical-scavenging properties of three flavonoids isolated from the leaves of Rhamnus alaternus L. (Rhamnaceae) : A structure-activity relationship study
2009
Ammar, Rebai Ben | Bhouri, Wissem | Sghaier, Mohamed Ben | Boubaker, Jihed | Skandrani, Ines | Neffati, Aicha | Bouhlel, Ines | Kilani, Soumaya | Mariotte, Anne-Marie | Chekir-Ghedira, Leila | Dijoux-Franca, Marie-Geneviève | Ghedira, Kamel
Fractionation of the methanolic and total oligomer flavonoid enriched extracts from Rhamnus alaternus leaves resulted in the isolation of three flavonoids: kaempferol 3-O-isorhamninoside (1), rhamnocitrin-3-O-isorhamninoside (2) and rhamnetin-3-O-isorhamninoside (3), along with apigenin, kaempferol and quercetin. The structures were determined using data obtained from FAB-MS, ¹H and ¹³C NMR spectra, as well as by various correlation experiments (COSY, HMQC and HMBC). The antioxidant activities of the isolated compounds were evaluated by measuring their ability to scavenge the DPPH radical and superoxide anions, to inhibit H₂O₂-induced lipid peroxidation in human K562 cells, and to inhibit xanthine oxidase activity. Compound 3 was a strong scavenger of DPPH and superoxide anion radicals, and a potent inhibitor of H₂O₂-induced lipid peroxidation, with respective IC ₅₀ values of 1.5, 35 and 106μg/ml, whereas compound 1 showed the better activity in the inhibition of xanthine oxidase activity with an IC ₅₀ value of 18μg/ml, showing some structure-activity relationships.
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