Additional antiprotozoal flavonol glycosides of the aerial parts of Helianthemum glomeratum

Bioassay-guided fractionation of the methanol extract of aerial parts from Helianthemum glomeratum afforded five antiprotozoal flavonol glycosides: tiliroside, kaempferol-3-O-(3",6"di-O-E-p-coumaroyl)-beta-glucopyranoside, astragalin, quercitrin and isoquercitrin. The in vitro antiprotozoal assay showed that tiliroside was the most potent antiamoebic and antigiardial compound with IC50 values of 17.5 mu g/mL for Entamoeba histolytica and 17.4 mu g/mL for G. lamblia. Isoquercitrin showed selectivity against E. histolytica (IC50 14.7 mu g/mL) and quercitrin toward G. lamblia (IC50 24.3 mu g/mL). All isolated compounds were less active than metronidazole and emetine, two antiprotozoal drugs used as positive controls. Copyright (c) 2006 John Wiley & Sons, Ltd.