The good health of Bacchus: Melatonin in grapes, the unveiled myth

The first detection of melatonin in grapes appeared in 2006 with the questioning title 'Melatonin content in grape: myth or panacea?'. Then, in a Letter to the Editor of Journal of Pineal Research, the lead journal covering all aspects of physiology, pathophysiology and endocrinology of melatonin in vertebrates (and all other species), dated 2009, panacea triumphed on myth (the title was 'Melatonin in grape, not just a myth, maybe a panacea') (Iriti, 2009). This meant that, despite the preliminary and incomplete reports regarding melatonin in grapes, a new tessera was added to the mosaic of the complex grape chemistry, further substantiating the health potential of grape products. Since then, melatonin and its isomers were detected both in red and white wines, and a number of exciting papers elucidated that both endogenous and exogenous factors may influence the biosynthesis and accumulation of these indoleamines in grapevine tissues and organs, namely varietal differences, phenological stages, day-night cycle and agrochemical treatments. Probably and similar to polyphenols and other secondary metabolites, many other environmental parameters may regulate melatonin production in grapevine, including climatic conditions, plant-microbe interactions and agricultural practices. On the other hand, because of the paucity of data on the physiological and pathophysiological roles of melatonin in grapevine, we can only hypothesize: from studies on other plants, we predict melatonin is involved in protection from oxidative and abiotic stresses.