Medicinal flowers. XXIII. New taraxastane-type triterpene, punicanolic acid, with tumor necrosis factor-alpha inhibitory activity from the flowers of Punica granatum

The methanolic extract from the flowers of Punica granatum L. (Punicaceae) was found to show inhibitory effect on tumor necrosis factor-alpha (TNF-alpha, 1 ng/ml)-induced cytotoxicity in L929 cells. By bioassay-guided separation, a new taraxastane-type triterpene, punicanolic acid (1), was isolated from the active fraction (ethyl acetate-soluble fraction) together with four triterpenes (2--5), two galloyl glucoses (6, 7), two flavones (8, 9), and beta-sitosterol. Among the constituents, 1, oleanolic acid (2), maslinic acid (4), 1,2,6-tri-O-galloyl beta-D-glucopyranoside (6), 1,2-di-O-galloyl-4,6-O-(S)-hexahydroxydiphenoyl beta-D-glucopyranoside (7), and luteolin (8) significantly inhibited TNF-alpha-induced cytotoxicity in L929 cells at 30 microM.