Cytotoxicity and lipid peroxidation-inhibiting activity of flavonoids

Thirty-five flavonoids of seven different types, namely isoflavonoids, chal cones, dihydroflavonols, flavanols, flavanones, flavones, and flavonols wer e investigated for their ability to inhibit ascorbate-induced microsomal li pid peroxidation and their cytotoxicity. For each activity a structure-acti vity relationship was established. Subsequently, an antioxidant selectivity index, i.e., the maximal non-toxic dose divided by the IC50 value for lipi d peroxidation, was introduced. Kaempferol showed the highest antioxidant s electivity index of all flavonoids tested.