5-Methylflavasperone and rhamnetin from Guiera senegalensis and their antioxidative and 5-lipoxygenase inhibitory activity

From the methylene chloride extract of the leaves of Guiera senegalensis a novel naphthopyran, 5-methylflavasperone (5,8,10-trimethoxy-2-methyl-4-H-na phtho[1,2-b]pyran-4-one), as well as rhamnetin were isolated. Rhamnetin sho wed a strong inhibitory activity on 5-lipoxygenase from porcine leucocytes with an IC50 value of 0.7 mu M whereas 5-methylflavasperone revealed only a weak inhibitory activity (IC50 > 200 mu M). In the deoxyribose assay both compounds exerted similar antiradicalar effects (IC50 15.8 and 16.7 mu M, r espectively). In another assay only rhamnetin inhibited peroxidation of pho spholipid liposomes (IC50 = 2.4 mu M). For 5-methylflavasperone no dose dep endent inhibition could be observed.