Effects of Catechins on Superoxide and Hydroxyl Radical

Abstract

Superoxide (O^-₂·) was reduced by the addition of superoxide dismutase (SOD : O^-₂·scavenger) and catechins. In competitive reactions utilizing different concentrations of spin-trap agent, the IC₅₀ values of each sample were changed. With regard to the Cu²⁺/H₂O₂ and Fe²⁺/H₂O₂ reaction systems, metal chelater, hydroxyl radical (·OH) scavenger and catechins eliminated the levels of·OH. For the Cu²⁺/H₂O₂ reaction systems, the IC₅₀ for·OH scavenger changed, but that for metal chelater and catechins did not. However, for the Fe²⁺/H₂O₂ reaction system, the IC₅₀ for·OH scavenger and catechins changed, whereas that for metal chelater did not. The ESR signal for free Cu²⁺ was changed by addition of metal chelater and catechins. In hte spectrophotometer experiments, it was confirmed that the CuCl₂ spectrum was changed by addition of metal chelater and catechins but not by·OH scavenger. Conversely, the FeSO₄ spectrum was not changed by addition of·OH scavenger or catechins, but was altered by metal chelater. Lipid peroxidation was inhibited by catechins in a concentration-dependent manner.Therefore, it was suggested that the catechins did not scavenge directly the generated·OH from the Cu²⁺/H₂O₂ reaction system, but inhibited the generation of·OH by acting on the Cu²⁺/H₂O₂ reaction system. On the other hand, with respect to the·OH generated from the Fe²⁺/H₂O₂ reaction system, it was suggested that the catechins had a direct scavenging capacity of the·OH, but had little chelating activity of iron.It was confirmed that catechins have the ability to scavenge for O^-₂·as well as·OH and to inhibit the generation of·OH by chelation with metal ions.