Comparative study of eight well-known polyphenolic antioxidants

ABSTRACT Eight antioxidants from five different polyphenolic classes (cinnamic acids, benzoic acids, flavonoids, proanthocyanidins and stilbenes), and the water‐soluble vitamin E derivative trolox were examined for their antioxidant activity in‐vitro. In addition, the compounds were tested for their cytotoxicity on growing fibroblasts and their inhibition of the classical pathway of the complement system. Procyanidin C1 was shown to be a good scavenger of both DPPH* and HO*, and a strong inhibitor of lipid peroxidation and the classical pathway of the complement system. Consequently, procyanidin C1 was classified as the most promising antioxidant in‐vitro of all compounds tested. In contrast, genistein exhibited a very low antioxidant activity in both the lipid peroxidation and the DPPH* scavenging assay, a high cytotoxicity and a low complement‐inhibiting activity.