Parboiled germinated brown rice (PGBR) of Khao Dawk Mali 105 variety was produced by steaming germinated paddy rice, which is well-known for its nutrients and bioactive compounds. In this study we determined the in vivo antioxidant and hepatoprotective effects of PGBR in carbon tetrachloride (CCl(4))-induced oxidative stress in rats. Male Sprague-Dawley rats, (weight 200-250 g) were randomly divided into (1) control, (2) CCl(4), (3) white rice (WR)+CCl(4), (4) brown rice (BR)+CCl(4), and (5) PGBR+CCl(4) groups. PGBR, BR, and WR diets were produced by replacing corn starch in the AIN76A diet with cooked PGBR, BR, and WR powders, respectively. All rats except the control group were gavaged with 50% CCl4 in olive oil (v/v, 1 mL/kg) twice a week for 8 weeks. CCl(4)-treated rats exhibited significant liver injury, lipid peroxidation, protein oxidation, and DNA damage, as well as obvious changes to liver histopathology compared to control. In addition, CCl(4) treatment decreased the activities of CYP2E1 and antioxidant enzymes: glutathione S-transferase, glutathione peroxidase, superoxide dismutase and catalase, and glutathione (GSH) content. However, the PGBR+CCl(4) group exhibited less liver injury, lipid peroxidation, protein oxidation, and DNA damage, as well as better antioxidant enzyme activities and GSH content. Furthermore, PGBR inhibited degradation of CYP2E1 in CCl(4)-induced decrease of CYP2E1 activity. These data suggest that PGBR may prevent CCl(4)-induced liver oxidative stress and injury through enhancement of the antioxidant capacities, which may be due to complex actions of various bioactive compounds, including phenolic acids, γ-oryzanol, tocotrienol, and GABA.
Keywords: antioxidant; carbon tetrachloride; liver injury; oxidative stress; parboiled germinated brown rice.