First confirmation in red wine of products resulting from direct anthocyanin-tannin reactions.

Analysis of wine fractions before and after thiolysis confirmed the occurrence in red wine of direct reactions between anthocyanins and tannins established earlier in model solutions. Results showed the presence of two types of structures differing in the linkage position of the anthocyanin moiety. On one hand, detection of malvidin-3-glucoside (Mv3g) among thiolysis products revealed the presence of anthocyanin-derived pigments in which Mv3g is linked by its C-6 or C-8 top. On the other hand, LC/MS analysis allowed the detection of two derivatives tentatively identified as flavenes or a bicyclic condensation products yielded by the reaction of a flavanol monomer (C-6 or C-8 top) with malvidin-3-glucoside (C-4 position). The presence of the corresponding benzylthioethers after thiolysis of the polymeric fractions confirmed that procyanidins are similarly involved in the latter reaction. Besides, MS also allowed the detection of new benzylthioethers of catechin derivatives released after thiolysis of the wine fractions, indicating that in addition to the postulated processes other types of reactions take place in wines. © 2000 Society of Chemical Industry.