A Review of Biological and Pharmacological Actions of Melatonin: Oxidant and Prooxidant Properties

Melatonin as an indoleamine exists in most of mammals and produced by various organs. It involved in circadian regulation of physiological and neuroendocrine function. Also it modulates diverse physiological functions such as sleep and sexual behavior. During the last decade, melatonin has been shown to possess potent free radical scavenger properties against reactive oxygen species (ROS). Moreover, by induction of the expression of antioxidant enzymes and reduction of the activation of pro-oxidant enzymes, melatonin indirectly could protect cells against a variety of free radical-related diseases. Besides, melatonin has been shown to promote the generation of ROS at pharmacological concentrations in in-vitro studies. Although melatonin could potentially be useful but safety, efficacy remains uncertain. In the present report, we review the studies which document the influence of melatonin on the various oxidative stress associated diseases. We also analyze the possible mechanisms by which melatonin induce ROS formation.