Three new C-alkylated flavonoids from Desmodium oblongum

Three new C-alkylated flavonoids, 4′-hydroxy-8-isobutyryl-7-methoxy-6-methyl-flavone (1), 4′,7-dimethoxy-8-isobutyryl-6-methyl-flavone (2), and 4′,7-dimethoxy-8-isobutyryl-flavone (3), together with three know ones luteolin (4), kaemferol (5), and quercetin (6), were isolated from Desmodium oblongum. Their structures were elucidated by spectroscopic methods, including extensive 1D- and 2D-NMR techniques. Compound 1 showed cytotoxicity against NB4, SHSY5Y, and MCF7 cell lines with IC50 values of 8.5, 6.5, and 7.8 μM; compound 2 showed cytotoxicity against SHSY5Y and PC3 cell lines with IC50 values of 5.0 and 6.8 μM; compound 3 displayed cytotoxicity against SHSY5Y and MCF7 cell lines with IC50 values of 6.4 and 9.4 μM, respectively.