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      Tryptophan-Ethylester, the False (Unveiled) Melatonin Isomer in Red Wine

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          Abstract

          Among the food plants, the presence of melatonin in grapes ( Vitis vinifera L.) deserves particular attention because of the production of wine, an alcoholic beverage of economic relevance and with putative healthy effects. Furthermore, melatonin isomers have been detected in wine too. Recently, one of these isomers has been identified as tryptophan-ethylester, a compound with the same molecular weight of melatonin. In this Commentary, we briefly comment the source(s) of tryptophan-ethylester in wine and the putative nutritional role(s).

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          Most cited references35

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          Melatonin, melatonin isomers and stilbenes in Italian traditional grape products and their antiradical capacity.

          Although polyphenols represent the paradigm of the health-promoting effects ascribed to grape products, recently, attention has been paid to dietary melatonin, significantly present in Mediterranean foods. In this work, we measured melatonin, its isomers, stilbenes (trans- and cis-resveratrol and their glucosides, piceids) and total polyphenols in some different grape products (red, white and dessert wines, grape juices and Modena balsamic vinegars) of distinct Italian areas. We also evaluated their antiradical activity by DPPH(·) and ABTS(·+) assays. For indoleamine analysis, the separation was carried out on a 1.7-μm C18 BEH column and the detection performed by means of mass spectrometry with electrospray ionization in positive ion mode with multiple reaction monitoring. The confirmation of the peak identity was accomplished by injection into the high-resolution system (Orbitrap) using accurate mass measurements (error below 1.0 ppm). Mass spectrometry analyses revealed, for the first time, the presence of melatonin in dessert wines and balsamic vinegars, as well as the occurrence of three different melatonin isomers in grape products. © 2012 John Wiley & Sons A/S. Published by Blackwell Publishing Ltd.
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            Content of melatonin and other antioxidants in grape-related foodstuffs: measurement using a MEPS-HPLC-F method.

            The strong antioxidant activity of melatonin is well known and it is important to investigate its presence and levels in different foodstuffs, for the purpose of evaluating their nutraceutical properties. As a contribution towards this goal, an original analytical method has been developed for the simultaneous determination of melatonin and other indolic and phenolic antioxidants (including trans- and cis-resveratrol, ferulic acid, tryptophan, serotonin and 5-hydroxyindoleacetic acid) in grape-related foodstuffs and beverages: namely grape, grape juice, must, wine and grappa (Italian pomace brandy). These foodstuffs represent an important part of the diet, both traditionally and in recent times, especially in Mediterranean countries and could be (at least in part) responsible for the beneficial effects involved in the 'French paradox'. The analytical method is based on high-performance liquid chromatography coupled to fluorescence detection, exploiting the native fluorescence of the analytes. A C8 column was used as the stationary phase, while the mobile phase was composed of acidic phosphate buffer and acetonitrile; fluorescence intensity was monitored at λ=386nm while exciting at λ=298nm. The sample pretreatment was carried out by a fast and reliable microextraction by packed sorbent (MEPS) procedure. After validation, the method was applied to the analysis of melatonin and other antioxidants in food and beverages derived from grape, with very good results being obtained. Thus, this methodology may represent a promising tool for the evaluation of the antioxidant properties of nutraceuticals and functional foods. © 2011 John Wiley & Sons A/S.
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              Determination of melatonin and its isomer in foods by liquid chromatography tandem mass spectrometry.

              This study aimed to develop a reliable analytical method for the determination of melatonin and its isomers in various food products. The method entails ethanol extraction of solid samples (or dilution of liquid samples) prior to liquid chromatography coupled to triple quadruple mass spectrometry (LC-MS/MS) analysis of target analytes. The method was in-house validated and successfully applied to various food matrices. Recovery of melatonin from different matrices were found to be 86.0 ± 3.6%, 76.9 ± 5.4%, 98.6 ± 6.4%, and 67.0 ± 4.5% for beer, walnut, tomato and sour cherry samples, respectively. No melatonin could be detected in black and green tea, sour cherry, sour cherry concentrate, kefir (a fermented milk drink) and red wine while the highest amount of melatonin (341.7 ± 29.3 pg/g) was detected in crumb. The highest amounts of melatonin isomer were detected in yeast-fermented foods such as 170.7 ± 29.9 ng/ml in red wine, 14.3 ± 0.48 ng/ml in beer, and 15.7 ± 1.4 ng/g in bread crumb. Copyright © 2013 Elsevier Ltd. All rights reserved.
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                Author and article information

                Journal
                Int J Tryptophan Res
                Int J Tryptophan Res
                International Journal of Tryptophan Research
                International Journal of Tryptophan Research : IJTR
                Libertas Academica
                1178-6469
                2015
                30 March 2015
                : 8
                : 27-29
                Affiliations
                [1 ]Dipartimento di Scienze Agrarie e Ambientali, Università degli Studi di Milano, Milano, Italy.
                [2 ]Dipartimento di Scienze per gli Alimenti, la Nutrizione e l’Ambiente, Università degli Studi di Milano, Milano, Italy.
                Author notes
                Article
                ijtr-8-2015-027
                10.4137/IJTR.S22450
                4381840
                266bf623-09a4-46d8-b6d2-89e1e3065328
                © 2015 the author(s), publisher and licensee Libertas Academica Ltd.

                This is an open-access article distributed under the terms of the Creative Commons CC-BY-NC 3.0 License.

                History
                : 03 December 2014
                : 15 February 2015
                : 28 February 2015
                Categories
                Short Commentary

                Biochemistry
                tryptophan,melatonin,melatonin isomers,tryptophan-ethylester,red wine,grapes
                Biochemistry
                tryptophan, melatonin, melatonin isomers, tryptophan-ethylester, red wine, grapes

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