INHIBITION IN-VITRO LINOLEIC-ACID PEROXIDATION AND HEMOLYSIS BY CAFFEOYLTRYPTOPHAN

Antioxidant activities of caffeoyltryptophan were investigated by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging system, the su peroxide anion generation system and the superoxide anion-mediated lin oleic acid peroxidation system. At 10 mu M, caffeoyltryptophan showed greater scavenging activity on DPPH than dl-alpha-tocopherol or ascorb ic acid. DPPH radical scavenging activity of caffeoyltryptophan increa sed dose-dependently at concentrations ranging from 1 to 50 mu M; 1 mo l of caffeoyltryptophan reacted with ca 4 mel of radical. Caffeoyltryp tophan caused 80% inhibition of superoxide anion generation at 50 mu M . The inhibitory activity of caffeoyltryptophan was as strong as that of 5-caffeoylquinic acid. Caffeoyltryptophan inhibited the formation o f conjugated diene from linoleic acid. The inhibitory activity increas ed in the order caffeic acid < 5-caffeoylquinic acid < caffeoyltryptop han < dl-alpha-tocopherol. Effects on the in vitro haemolysis and pero xidation cf mouse erythrocytes induced by H2O2 were also examined. Caf feoyltryptophan exhibited strong inhibitory activities; Tryptophan was ineffective in these systems. These data suggest that caffeoyltryptop han may be a natural antioxidant in the human diet and, as such, may i ntervene in toxicological processes that are mediated by radical mecha nisms. (C) 1998 Elsevier Science Ltd. All rights reserved.