Tumor inhibitors—XXXIII

From a cytotoxic extract of Eupatorium semiserratum DC., five flavones were isolated. Three of the compounds were characterized as the previously-known pectolinarigenin, and two new flavones, eupatorm and eupatilin. Structural studies are described which have led to assignment of the 5,3′-dihydroxy-6,7,4′-trimethoxyflavone structure (1) for eupatorin, and the 5,7-dihydroxy-6,3′,4′-trimethoxyflavone structure (11) for eupatilin. From a cytotoxic extract of Eupatorium cuneifolium (TOURN.) L., two flavones were isolated. The compounds were characterized as the previously-known hispidulin and a new flavone, eupafolin. Structural studies are described which have led to assignment of the 5,7,3′,4′-tetrahydroxy-6-methoxyflavone structure (18) for eupafolin. The earlier assignment of structure 18 for pedalitin is shown to be incorrect, and the alternative 5,6,3′,4′-tetrahydroxy-7-methoxyflavone structure (24) is proposed for pedalitin.