A treasure hunt: melatonin in grapes and related foodstuffs

Melatonin is an ubiquitous hormone in the animal kingdom, but is also present in several plants, probably having the role of regulating growth and rest cycles. However, it is also known to have a strong antioxidant and radical-scavenging activity, based on a suicide mechanism basically different form that of phenolic antioxidants and liposoluble vitamins. The presence of melatonin in grapes and wine has been recently reported; the present work deals with the development of an original HPLC-F method for the quantification of melatonin in other grape-derived foodstuffs: grapes, grape juice, must and grappa (Italian pomace brandy), as well as wine. The chromatographic system includes a C18 reversed phase column as the stationary phase and an acidic buffer / acetonitrile mixture as the mobile phase; under these conditions, an analytical run lasts less than 10 minutes. The analyte is natively fluorescent, thus no complicated and time-consuming sample derivatisation is needed; the sample pre-treament is based on a very simple and fast solid phase extraction (SPE) procedure. The results obtained until now are very encouraging in terms of sensitivity and selectivity.