Antioxidative effect and liver protective action of Adzuki polyphenol

Abstract

The antioxidizing effect of Adzuki polyphenol (APP) was studied in in vivo and in vitro experiments. Serum specimens and homogenates of the liver and kidney obtained from the mice which had been given a drink (20 ml/d) containing 0.05% (w/v) APP for one week were less susceptible to oxidizing agents than those obtained from control mice. In particular, liver homogenates obtained from APP treated rats were significantly resistant to oxidizing agents. Increases in the serum GOT activity and production of lipid peroxides in the liver induced in response to an intraperitoneal injection of galactosamine and lipopolysaccharides were significantly suppressed in the mice which had been previously given 0.05% (w/v) APP for one week. The amounts of glutathione and GPx activity in the liver of the APP treated mice were significantly higher than those in the control mice. In view of these results, APP may have the following possible effects: it removes free radicals and reactive oxygen species produced during inflammation, it keeps both the glutathione level and the GPx activity in the body high and thereby suppresses production of lipid peroxides, and as a consequence, it suppresses aggravation of inflammation in the liver. IC 50 of APP for removal of DPPH radicals was 64.2 μ mol/l (converted as a catechin quantity), which was about half of the value of catechin and vitamin C available in the market. Moreover, 2.5 ml solution of human LDL (protein concentration, 70 μ g/ml) containing 80 μ l of 0.05% APP was resistant to the oxidation-promoting action of 200 μ mol/l copper sulfate: Oxidation of LDL started approximately one hour later in the presence of APP than in its absence. These results suggest that APP has both an antioxidative effect and a liver protective action. It was also found in this study that the main monomer type polyphenol in Adzuki was catechin-7β-glucoside.