Plant catechols prevent lipid peroxidation in human plasma and erythrocytes

The antioxidant activity of several plant catechol derivatives was tested i n buffer, plasma, and human erythrocytes. In buffer, chlorogenic acid (CGA) , caffeic acid (CA), and dihydrocaffeic acid (DCA) reduced ferric iron equa lly well in the ferric reducing antioxidant power (FRAP) assay. Low concent rations of the polyphenols enhanced the ability of plasma to reduce ferric iron by about 10%. In plasma, lipid hydroperoxide and F-2-isoprostane forma tion induced by a water-soluble free radical initiator were reduced by CGA at concentrations as low as 20 muM. During incubation at 37 degreesC, human erythrocytes took up DCA, but not CGA, and intracellular DCA enhanced the ability of erythrocytes to reduce extracellular ferricyanide. When intact e rythrocytes were exposed to oxidant stress generated by liposomes containin g small amounts of lipid hydroperoxides, extracellular CGA at a concentrati on of 5 muM decreased both lipid peroxidation in the liposomes, and spared alpha -tocopherol in erythrocyte membranes. These results suggest that the catechol structure of these compounds convey the antioxidant effect in plas ma and in erythrocytes.