LC-MS based methods for phytosterols determination in oenological matrices. Targeted metabolomic study of Rioja grape varieties

Abstract

For years, grape berries and red wine have been a subject of investigation with respect to their chemical composition. Several active components from grape skin and seeds were shown to exhibit anti-inflammatory, antioxidant and anti-cancer properties. Likewise, regular and moderate wine consumption, particularly red wine, has been associated with health benefits.Plant sterols, also called phytosterols (PS), are a family of interest among grapevine and grape-derived products. PS are bioactive compounds that exist in all food items of plant origin with positive effects on human health. The nutritional role of these compounds to reduce circulating cholesterol levels in humans has been extensively studied.Gas chromatography (GC) has been the most frequently analytical technique for PS determination in plant-based food and vegetable oils, coupled to different detectors. However, this methodology usually requires a previous derivatization step and does not allow PS conjugates determination. Thus, high performance liquid chromatography (HPLC) coupled to mass spectrometry (MS) has replaced the cited GC techniques.In order to improve the knowledge of chemical composition of grape and wine, the research work described in this thesis aims to study the distribution of PS family in oenological matrices.The first part of this work deals with the optimization of extraction techniques, separation and subsequent detection conditions through LC-MS. To achieve this objective, two analytical methods have been developed. Firstly, an LC-APCI-IT MS method is used for the PS determination in monovarietal red wine cv. Tempranillo. Secondly, an LC-APCI-QTOF MS methodology is applied so as to the PS determination in the different parts of grape berries (pulp, peel and seeds), used to elaborate above mentioned wines.In the second part of this thesis, a metabolomic study has been carried out, as a targeted approach, focusing on phytosterols family in six different varieties of Rioja grapes (Tempanillo, Graciano, Cabernet Sauvignon, Garnacha, White Garnacha and Viura). In order to find significant differences between varieties, Mass Profiler Professional (MPP) software is a powerful informatics tool which helps data analysis and interpretation, applying multivariate statistics (MVA) such as Principal component analysis (PCA) and Partial least square discrimination analysis (PLS-DA).