Flavonoids as antioxidants evaluated by in vitro and in situ liver chemiluminescence

Administration of eriodyctiol and (+)-catechin (10 mg/100 g of body weight) to mice inhibited the enhancement of in situ liver chemiluminescence produced by CCl4 (0.5 ml/100 g) by 32 and 38% respectively. 3,4-Dicaffeoylquinic acid was less effective (13%), and cynarin had no effect. Previously, these compounds and other polyphenols were assayed as in vitro antioxidants by their abilities to inhibit the tert-butyl hydroperoxide (t-BOOH)-initiated chemiluminescence of mouse liver homogenates, and the IC50 (microM) values were as follows: (+)-catechin, 3; eriodyctiol, 9; myricetin and 4,2',4'-trihydroxy-6'-metoxychalcone, 15; 3,4-dicaffeoylquinic acid, 20; isochlorogenic acid, 30; caffeic acid, 5,6,3'-trihydroxy-7,4'-dimethoxyflavone and cynarin, 50; chlorogenic acid and apigenin, 150; quercetin, pedalitin, sylimarin and quercetin-3-methyl ester, 200; 7,4'-dihydroxy-5-methoxyflavonone and kaempferol-3,7-dirhamnoside, 500; quercitrin, 900; and galangin-3-methyl ether, genkwanin, hesperidin, ombuoside, phloridzin, quinic acid, rhoifolin, rutin and sophoricoside, greater than 1 mM. The in vitro and in vivo effects of these flavonoids and polyphenols may be related to their antioxidant abilities, making them promising substances to be investigated as water-soluble protectors against lipid peroxidation and other free radical-mediated cell injury.