CHAPTER 6: Melatonin

In this work, melatonin (MEL), an indoleamine identified in plants, was studied as a natural powerful antioxidant also present in legumes. The formation of MEL and its isomers seems to be complex in plants, additional in vivo assays being necessary to characterize the biosynthetic pathway genes. Melatonin plays multiple roles in plants, including as a regulator and modulator of growth and reproductive development. Moreover, the presence of melatonin has been described in several seeds, processed food and fermented beverages, with reports of increments in physiological blood levels of melatonin after consumption of foods containing this molecule. Despite the low melatonin levels detected in legumes, the different adverse situations and processes that might increase the final seed melatonin concentration have been studied. The main environmental stresses are drought, light (UV-B radiation), presence of heavy metals, low temperatures and salinity–alkalinity stress, with germination standing out as the process that causes the greatest increase in MEL levels. The possible enhancement of MEL in plant foods, such as legumes, could improve its health-promoting benefits by increasing the MEL blood levels in humans thereby improving antioxidative defense mechanisms.