Melatonin in grape, not just a myth, maybe a panacea

To the EditorIn 2006, the detection of melatonin in dierent grapecultivars was published with the questioning title Melato-nin content in grape: myth or panacea? [1]. This discoverywas the result of an ongoing series of studies on the abilityof agrochemicals to elicit the synthesis of phytoalexins inplants. Phytoalexins (from Greek alexein, to ward o) areplant secondary metabolites with a broad spectrum biolog-ical activity, whose biosynthesis represents an active plantdefence response against both biotic and abiotic stresses.However, the physiological and pathophysiological func-tion of melatonin in plants is still unclear, though ahormone-like role has been putatively attributed to mela-tonin in some plant species [2–4]. Anyway, many phyto-alexins, such as resveratrol, are powerful bioactivephytochemical constituents of plant-derived functionalfoods and beverages, also named dietary therapeutics ornutraceuticals. In turn, a functional food or beverage is aproduct consumed as part of a normal diet that mayprovide health benets beyond basic nutritional functions,by virtue of its nutraceutical content [5].Since the publication, an intense media coverage ensued,as documented by the number of newspapers, magazinesand websites reporting the nding. However, after theinitial excitement, from an academic point of view, the maingoal of the scientic community was that of ascertaining ifmelatonin in grape can be extracted during fermentationand retained in wine, as attested by two excellent papersvery recently published on this topic. Marcolini et al. [6]reported an original analytical method for the determina-tion of resveratrol and melatonin in wine based on HPLCcoupled to uorescence detection [6]. Almost contempora-neously, Guerrero et al. [7] investigated the presence ofmelatonin in wine; they showed that, in humans, serummelatonin concentration was signicantly increased afterwine intake (1 hr after a single 100-mL wine administra-tion). In this work, the melatonin concentration detected inSpanish wines ranged from 50 to 80 pg/mL, whereas, inItalian wines, it ranged around 0.4–0.5 ng/mL [6, 7].Noticeably, cultivar, agro-meteorological conditions [8],vintage and wine-making procedures presumably contrib-ute to the above reported dierences. Interestingly, inItalian grape cultivars, melatonin content ranged 0.005–0.96 ng/g or 2.5–428 pg/mL, and open eld treatments,with a functional analogue of the plant hormone salicylicacid, greatly enhanced melatonin biosynthesis in Merlotcultivar, with a twofold rise of melatonin level detected inberry skin tissues [1].In conclusion, despite the preliminary and incompletereports regarding melatonin in grape/wine, the presence ofthis indoleamine in these products adds a new element tothe hypothesis of health benets associated to a moderatewine consumption and, more in general, to a Mediterra-nean dietary style, given the recent discovery of melatoninin virgin olive oil [9]. Last, but not the least, the possibilityof enhancing the pharmaconutritional potential of grape/wine with phytosanitary treatments should be further takeninto account [10].Marcello IritiE-mail: marcello.iriti@unimi.it