EVALUATION OF THE ANTIOXIDANT ACTIONS OF FERULIC ACID AND CATECHINS

We have evaluated the abilities of ferulic acid, (+/-) catechin, (+) c atechin and (-) epicatechin to scavenge the reactive oxygen species hy droxyl radical (OH.), hypochlorous acid (HOCl) and peroxyl radicals (R O2.). Ferulic acid tested at concentrations up to 5 mM inhibited the p eroxidation of phospholipid liposomes. Both (+/-) and (+) catechin and (-) epicatechin were much more effective. All the compounds tested re acted with trichloromethyl peroxyl radical (CCl3O2.) with rate constan ts > 1 x 10(6) M-1 s-1. A mixture of FeCl3-EDTA, hydrogen peroxide (H2 O2) and ascorbic acid at pH 7.4, has often been used to generate hydro xyl radicals (OH.) which are detected by their ability to cause damage to the sugar deoxyribose. Ferulic acid, (+) and (+/-) catechin and (- ) epicatechin inhibited deoxyribose damage by reacting with OH. with r ate constants of 4.5 x 10(9) M-1 s-1, 3.65 x 10(9) M-1 s-1, 2.36 x 10( 9) M-1 s-1 and 2.84 x 10(9) M-1 s-1 respectively. (-) Epicatechin, fer ulic acid and the(+) and (+/-) catechins exerted pro-oxidant action, a ccelerating damage to DNA in the presence of a bleomycin-iron complex. On a molar basis, ferulic acid was less effective in causing damage t o DNA compared with the catechins. A mixture of hypoxanthine and xanth ine oxidase generates O2 radical anion which reduces cytochrome c to f errocytochrome c. (+) Catechin and (-) epicatechin inhibited the reduc tion of cytochrome c in a concentration dependent manner. Ferulic acid and (+/-) catechin had only weak effects. All the compounds tested we re able to scavenge hypochlorous acid at a rate sufficient to protect alpha-1-antiproteinase against inactivation. Our results show that cat echins and ferulic acid possess antioxidant properties. This may becom e important given the current search for ''natural'' replacements for synthetic antioxidant food additives.