Cytotoxic Phenolics From Calligonum Polygonoides L. Subsp. Comosum

Calligonum polygonoides L. subsp. comosum family Polygonaceae is a slow-growing small leafless desert shrub. It is used in folk medicine as a stimulant and astringent. Chromatographic separation of the ethyl acetate and n-butanol soluble fractions of the hydroalcoholic extract afforded two new flavonoids; kaempferol-3-O-β-D-(6''-n-butylglucuronide) (1) and kaempferol-3-O-β-D-(6''-methyl glucuronide) (2). Moreover, four phenolic compounds are isolated for the first time from the genus; quercetin-3-O-β-D-(6''-n-butyl glucuronide) (3), astragalin (4), gallic acid (5) and taxifolin (6), in addition to seven known phenolics. Structure elucidation of these compounds was performed through extensive study of their spectroscopic data including MS, ID and 2D NMR spectra. The cytotoxic activity of the isolated compounds was evaluated against liver HePG2 and breast MCF-7 cell lines using sulphorhodamine-B assay. Quercetin showed the highest cytotoxic activity against the two cell lines (IC₅₀ = 4.877 µg/ml and 0.8668 µg/ml respectively).