Antiproliferative constituents in plants 10.: Flavones from the leaves of Lantana montevidensis BRIQ. and consideration of structure-activity relationship

The flavonoid fraction from the leaves of Lantana montevidensis BRIQ. (Verbenaceae) showed antiproliferative activity against human gastric adenocarcinorna (MK-1, GI(50):12 mug/ml), human uterus carcinoma (HeLa, 5 mug/ml), and murine melanoma (B16F10, 5 mug/ml) cells in vitro. Bioactivity-guided chemical investigation of the fraction has resulted in the isolation of apigenin (10) and ten 5,6,7-oxygenated flavones: cirsilineol (1), eupatorin (2), 5,4'-dihydroxy,-6,7,3',5'-tetramethoxyflavone (3), 5,6-dihydroxy-7,3',4'-trimethoxyflavone (4), 5,6,4'-trihydroxy-7,3',5'-trimethoxyflavone (5), 5,6,3'-trihydroxy-7,4'-dimethoxyflavone (6), 5,3',4'-trihydroxy-6,7,5'-trimethoxyflavone (7), cirsiliol (8), hispidulin (9), and eupafolin (11). Antiproliferative activity of the isolated flavones, some other related flavones (luteolin, baicalein, 6-hydroxyluteolin, pectolinarigenin, jaceosidin, desmethoxycentaureidin, eupatilin, and chrysin) from other plant materials, and synthetic 6- and 7-methoxyflavones was evaluated, and the structure-activity relationships were examined.