Effect of sustained dietary application of thyme oil on antioxidant parameters and thymol content in plasma and tissues of broilers

Antioxidants are usually understood as chemicals which could eliminate oxidative stress by removing intracellular reactive oxygen species but high doses may block their beneficial effect and moreover, could be toxic. Understanding exact mechanism of action of plant components in animal organism help to propose dose, method and duration of their application.Thymol with strong antioxidant properties is the main component of thyme oil. After absorption from the intestine, thymol enters the bloodstream and is transported to the tissues. We found significant correlation between thymol levels in plasma and feed and duodenal wall, which points to the efficient thymol absorption from the digestive tract into circulation. Erythrocytes play a crucial role in the distribution of circulating polyphenols due to binding to their surface and being able to act like depots. That is why the real thymol concentration in blood could be higher than it was found in plasma. Thyme oil (0.1%, thymol 460 µg/g DM feed) significantly increased superoxide dismutase activity, had tendency to increase glutathione peroxidase activity and significantly decreased malondialdehyde as a product of lipid peroxidation in plasma which points to modulation of antioxidant enzymes activity and improvement of the oxidative stability. Obtained the lowest thymol concentrations in muscle (139 ng/g DM) in comparison with plasma (854 ng/mL), liver (568 ng/g DM) and kidney (5541 ng/g DM) could be due to low thymol penetration or high activity of efflux transporters, hence insufficient to affect antioxidant defence system. In conclusion, thymol effectiveness depends on its systemic availability for the targeted organ.