To evaluate the protective effect of Zataria multiflora boiss. (Zm) extract against arsenic-induced oxidative damage in rats. Rats were orally treated with various doses of Zm (200, 400, and 600 mg/kg) and sodium arsenite (5.5 mg/ kg), alone or in combination, once daily for 30 consecutive days. Twenty-four hours after the last dose, rats were euthanized, and biochemical studies were conducted on their blood samples. Sub-acute exposure to the sub-lethal dose of arsenic markedly altered the blood levels of several biomarkers associated with oxidative stress. Treatment with Zm significantly inhibited the elevation of lipid peroxidation and protein carbonylation and the depletion in total antioxidant capacity in plasma. In addition, Zm effectively increased the total antioxidant capacity of plasma in a dosedependent manner in control and arsenic-treated groups. The results reveal that Zm as an antioxidative medicinal plant reduces oxidative damages induced by arsenic in the doses much lower than the lethal dose (2-4 gr/kg). Since Zm is a safe herbal
drug routinely used as condiment, it can be used as a good supplement for reducing toxicity of low dose of arsenic in long-term exposure. Further studies on human environmentally exposed to arsenic through drinking water and food are proposed to find out effective dose in human.