ROS and Oxidative stress : Studies in the blood of dropsy patients has revealed that there is extensive ROS production (singlet oxygen and hydrogen peroxide) in the argemone oil intoxication leading to depletion of total antioxidants in the body and especially lipid-soluble antioxidants such as vitamin E and A (tocopherol and retinol). There is an extensive damage to the anti-oxidant defense system (anti-oxidant enzymes and anti-oxidants) of blood. Prior, in vitro studies have shown that reactive oxygen species (ROS) are involved in AO induced toxicity causing peroxidative damage of lipids in various hepatic sub-cellular fractions including microsomes and mitochondria of rats. The damage in hepatic microsomal membrane causes loss of activity of cytochrome P-450 and other membrane bound enzymes responsible for xenobiotic metabolism which leads to delayed bioelimination of sanguinarine and enhances its cumulative toxicity. Several lines of evidence have been shown to explain the mechanism of toxicity of argemone oil/alkaloid. The toxicity of sanguinarine has been shown to be dependent on the reactivity of its iminium bond with nucleophilic sites like thiol groups, present at the active sites of the enzymes and other vital proteins and thus suggesting the electrophilic nature of the alkaloid.