Flavonols from Scurrula ferruginea Danser (Loranthaceae).

Three natural flavonols compounds have been isolated from the ethyl acetate fraction of Scurrula ferruginea Danser (Loranthaceae). Besides quercetin and quercitrin, an unusual flavonol glycoside 4"-O-acetylquercitrin was isolated. Structures were determined using spectroscopic methods including UV, NMR and HRMS-EI. The incidence of 4"-O-acetylquercitrin, not previously reported in the Loranthaceae, is discussed. Cytotoxic evaluation on four human cancer cell lines showed quercetin to be the most active with IC50 of 35 microM on U251 (human glioblastoma cells).