Five new flavone 5-O-glycosides from Lethedon tannaensis: Lethedosides andlethediosides

Five new 7-methoxy-flavone 5-O-glycosides were isolated from a cytotoxic Me OH extract of Lethedon tannaensis, and the structures were elucidated by 2D NMR spectral analysis and by chemical methods. Lethedosides A (1), B (2), and C (3) were 5-O-glucosides of 7,3 ',4 '-tri-O-methylluteolin, 7,3 ',4 ', 5 '-tetra-O-methyltricetin, and 7,3 ',4 '-tri-O-methytricetin, respectively ; lethediosides A (4) and B (5) and a known compound 6 were 5-O-xylosylgluc osides of 7,3 ',4 '-tri-O-methylluteolin, 7,3 ',4 ',5 '-tetra-O-methyltrice tin, and 7,4 '-di-O-methylapigenin, respectively. These flavonoids were eit her inactive or weakly active against KB tumor cells, in contrast to previo usly isolated flavones from the same plant.