Monitoring melatonin and its isomer in Vitis vinifera cv. Malbec by UHPLC-MS/MS from grape to bottle.

Several studies have shown the presence of melatonin and related compounds in grapes and wines. The latter provides evidence of the possibility to enhance the nutraceutical properties of premium wines. However, there are many external factors that can influence the levels of this indolamine in grape and wines. In this study, the monitoring of melatonin and its tentatively identified isomer was carried out during the entire winemaking process in Vitis vinifera cv. Malbec by ultra high-performance liquid chromatography-tandem mass spectrometry. Laboratory and pilot studies were carried out to elucidate the role of grape, yeasts, and tryptophan in the evolution of the indolamines during the fermentation process. Melatonin was detected in grape extract within the range 120-160 ng/g while its isomer was found in musts and finished wines. Our results demonstrate that Saccaromyces cervisiae plays a decisive role in contributing to the content of melatonin and its isomer in wine.