UHPLC-Q-Orbitrap /MS2 identification of (+)-Catechin oxidation reaction dimeric products in red wines and grape seed extracts

Abstract

B-type procyanidin dimers and (+)-catechin dimeric oxidation products were analyzed in grape seed extracts and red wines (UHPLC-Q-Orbitrap MS). The different dimers had different fragmentation patterns according to their interflavan linkage position. Oxidation dimeric compounds had a specific fragment ion at m/z 393, missing for B-Type dimers fragmentations. A fragment ion at m/z 291 occurred and was specific for oxidation dimeric compounds with a COC linkage. Higher level oxidation products had abundant specific fragments: m/z 425, 397 and 245. These fragmentations were useful to identify them in complex samples such as grape seed extracts and wines. Three grape varieties and three ripening stages were selected and the corresponding seed extracts were obtained. The analyses revealed an increasing trend for the oxidation markers during grape ripening. The analysis of Syrah wines (2018, 2014, 2010) showed a decreasing trend of these molecules during wine ageing which might be due to further oxidation.

Keywords: Flavanol; Grape seed; Orbitrap; Oxidation; Oxidation markers; UHPLC/MS; Wine.