Scavenging of hydroxyl radicals by chlorophyllin

Abstract

Chlorophyllin, a sodium copper salt of chlorophyll, has been known as an anti-mutagen and also as an anti-carcinogen. To understand the mechanism of anti-mutagenic activity of chlorophyllin, which has been known to form a complex with mutagens, the oxygen free radical scavenging effect of chlorophyllin was investigated. It was observed that chlorophyllin removed hydroxyl radicals in vitro. Fenton reaction was used to generate hydroxyl radicals in this experiment because this reaction have been thought to be the main source of hydroxyl radicals in vivo. Chlorophyllin effectively reduced cell death, lipid peroxidation and DNA damage induced by Fenton reaction. It was confirmed that chlorophyllin did not block the Fenton reaction itself. Alternate possibility is that chlorophyllin removed hydroxyl radicals in vitro. However, selenite, another antioxidant, oxidized Fe(II) to Fe(III) and therefore inhibited the Fenton reaction. In contrast to the selenite effect, ascorbate reduced Fe(III) to enhance the Fenton reaction. Glutathione and selenate had no prominent effect on redox state of iron and Fenton reaction. The second order rate constant of the reaction between chlorophyllin and hydroxyl radical was extremely high, compared with other reactions involving hydroxyl radical scavengers such as mannitol, ethanol or dimethyl sulfoxide.