Inhibition of selenium dependent glutathione peroxidase and superoxide dismutase in rats by diethyldithiocarbamate: effect of pre-administration of alpha-tocopherol.

Rats pre-administered with alpha-tocopherol (10 mgs/day) for 7 days afforded a significant protection at the tissue level against the lowering of superoxide dismutase and glutathione peroxidase, especially the selenium-dependent glutathione peroxidase. The protective action of alpha-tocopherol in the diethyldithiocarbamate treated rats may be attributed to its antioxidant/free radical scavenging action. It is concluded that selenium-dependent glutathione peroxidase and alpha-tocopherol act in a complementary fashion to block free radical formation.

Lipid peroxidation of fish oils.

Fish and fish oils are the richest sources of ω-3 fatty acids. However, they are susceptible to lipid peroxidation due to their high degree of unsaturation. In the present study, the level of thiobarbituric acid reactive material in various fish oils available in the market with and without added Vitamin E was determined. The peroxide levels in fish oil heated to food frying temperature of 180°C and the effect of addition of vitamin E has also been studied. The results indicate that the peroxide levels in almost all the products available in the market were abnormally high irrespective of their Vitamin E content. This might be due to the inefficient methods used for processing and storage of fish oils. Addition of vitamin E was found to have a significant effect in lowering the rate of peroxidation of fish oil during thermal stress, showing that association of antioxidants with ω-3 fatty acids lowers the rate of lipid peroxidation.

In vitro inhibition of lipid peroxidation in fish by turmeric (Curcuma longa).

The beneficial effects of ∈-3 fatty acids on human health have been well documented. Fish and fish oils are the richest sources of ∈-3 fatty acids. However, due to their high degree of unsaturation, they are highly susceptible to lipid peroxidation. Regular consumption of peroxidised oils may represent a risk factor for the induction and development of atherosclerosis. In view of the above reports, it was considered necessary to study the effects of tumeric on fish lipid peroxidation during standard cooking practices and on time-dependent changes in the peroxidation of fish homogenate. The antioxidant effect of α-tocopherol was also studied to confirm the relevance of the study. The results suggest that turmeric may be considered as a safe, cheap and readily usable antioxidant for food preparations.

In vivo inhibition of selenium dependent glutathione peroxidase and superoxide dismutase in rats by diethyldithiocarbamate.

Intraperitoneal injection of rats with diethyldithiocarbamate (1.2 g/kg body wt) led to maximum diminution of superoxide dismutase activity at 1 hr by 86 and 84% in liver and red blood cell respectively with a gradual return to the normal level at 48 hr after administration of injection. Significant inhibition of selenium-dependent glutathione peroxidase was also observed, which returned to normal at 48 hr after administration of injection. However, maximum decline in its activity was at 12 hr by 52 and 73% in liver and red blood cells respectively. No significant difference in tissue level of selenium-independent glutathione peroxidase was observed during time course study after diethyldithiocarbamate administration. It is possible that inhibition of superoxide dismutase by diethyldithiocarbamate leads to accumulation of superoxide anion which in turn inactivates selenium-dependent glutathione peroxidase by its reaction with selenium at the active site of the enzyme.