Melatonin in plants

Once thought to be exclusively a molecule of the animal kingdom, melatonin has now been found to exist in plants as well. Among a number of actions, m elatonin is a direct free radical scavenger and an indirect antioxidant. Me latonin directly detoxifies the hydroxyl radical (circle OH), hydrogen pero xide, nitric oxide, peroxynitrite anion, peroxynitrous acid, and hypochloro us acid. The products from each of these reactions have been identified in pure chemical systems and in at least one case in vivo; the interaction pro duct of melatonin with the circle OH, i.e., cyclic 3-hydroxymelatonin, is f ound in the urine of humans and rats. Some of the products that are produce d when melatonin detoxifies reactive species are also highly efficient scav engers. As a result, a cascade of scavenging reactions may enhance the anti oxidant capacity of melatonin. Additionally, melatonin increases the activi ty of several antioxidative enzymes, thereby improving its ability to prote ct macromolecules from oxidative stress. Melatonin is endogenously produced and is also consumed in edible plants. In animal experiments, feeding mela tonin-containing foods raised blood levels of the indole. Because physiolog ic concentrations of melatonin in the blood are known to correlate with the total antioxidant capacity of the serum, consuming foodstuffs containing m elatonin may be helpful in lowering oxidative stress.