Phenolic fingerprint of 16 different grape varieties by HPLC/DAD/ESI/MS

Introduction: Epidemiological studies have shown the role of phenolic compounds in modulating different metabolic patterns responsible for beneficial effects in human health [1]. Grapes is one of the most important sources of phenolic compounds of the Mediterranean diet. The antioxidant activity of grapes has been previously correlated with the corresponding phytochemical profile [2]. Methods: The aim of this study was the characterization of the phenolic profile of 16 different varieties of table and wine grapes using the High-Performance Liquid Chromatography coupled with electrospray ionization mass spectrometry. The UV spectral data, fragmentation patterns and chromatographic behaviors were compared with data from the scientific literature or the available on-line databases. Results: From the analysis, 59 phenolic compounds were identified: 25 anthocyanins, 18 flavonols and 16 flavan-3-ols; among them, epicatechin, procyanidin B2, malvidin-3-glucoside and quercetin were the most abundant. Among anthocyanins, the glucosides of malvidin, cyanidin, petunidin, peonidin, were the most representative; other derivatives, such as acetyl, coumaroyl and caffeoyl esters were also abundant. Among flavonols, the galactoside, glucoside, glucuronide and rutinoside derivatives of quercetin and kaempferol were the most abundant; other flavonols (e.g. trihydroxyflavone-hexoside and trihydroxyflavone-riboside) were distributed in all grape varieties. Four different proanthocyanidin dimers were observed, but the identification with purified standard was only possible for procyanidin B2. Surprisingly, epigallocatechin and epigallocatechin gallate were not detected in any sample. Conclusions: The results of this study show that the table grapes and, consequently, their unfermented derivatives (e.g. juice), are rich in anti-oxidant compounds. Moreover, the phenolic profile of some grape varieties seems particularly interesting and could represent a significant dietetic tool in promoting human health. References 1. Valls-Pedret C., Lamuela-Raventós R.M., Medina-Remón A., Quintana M., Corella D., Pintó X., Martínez-González M.Á., Estruch R., Ros E., J Alzheimers Dis, 29,773-782 (2012). 2. Aubert C., Chalot G., Food Chem, 1,524-533 (2018).