As part of our screening of antioxidant extracts from spices and food plants, the antioxidant activity of the EtHO extract of the flowers of aerial parts of Sedum praealtum was tested. Since the extract showed significant activity, a bioassay-directed fractionation of it was carried out. This investigation resulted in the isolation of kaempferol and quercetin as the principle responsible for the antioxidant activity. The antioxidant ability was quantified using the Fogliano method, which is known as DMPD. Flavonols which were characterized by NMR. This similar antioxidant effect has been obtained on some fruits studied by different authors using this same method.