Flavonoids from Thyrsanthera suborbicularis and their NO inhibitory activity

Further phytochemical investigation on the whole plant of Thyrsanthera suborbicularis, collected in Cambodia, led to kaempferol (1), vitexin (2), apigenin-7-O-neohesperidoside (3), chrysoeriol-7-O-β-D-glucopyranoside (4), isorhamnetin 3-O-rutinoside (5), kaempferol-3-O-[α-L-rhamnopyranosyl-(13) -α-L-rhamnopyranosyl-(16)-β-D-galactopyranoside (6), kaempferol-3-O-α-L-rhamnopyranosyl(12)-O-[α-L-rhamnopyranosyl (16)]-β-D-glucopyranoside (7), kaempferol-3-O-[6″-O-(E)-p-coumaroyl]- β-D-glucopyranoside (8), kaempferol-3-O-[6″-O-(E)-p-coumaroyl]- β-D-galactopyranoside (9), and amentoflavone (10). All the structures were confirmed by the interpretation of NMR (1D and 2D) and MS data, and comparison with the published values. Of the isolated compounds 1-10, compounds 8 and 10 displayed the inhibitory activity against NO production in LPS-induced Raw 264.7 cells with IC₅₀ values, 3.56 and 15.73 μM, respectively.