Isolation, Identification, and Characterization of New Color-Stable Anthocyanins Occurring in Some Red Wines

TLDR

The structures of the four new anthocyanins were determined using FAB‑MS and NMR. Four novel anthocyanins (vitisin A/B and acetylvitisin A/B) were identified in trace amounts in red wines; they are resistant to sulfur dioxide bleaching, retain color up to pH 7, and form stable quinonoidal bases rather than colorless carbinol forms. Keywords: red wine, anthocyanins, vitisin A, vitisin B, vitisidin A, vitisidin B, NMR, FAB‑MS.

Abstract

Four new anthocyanin pigments were found in red wines in trace amounts and are thought to be formed in wines during maturation. Their structures were established by FAB-MS and NMR. Two pigments were identified as the 3-glucoside (vitisin A) and the 3-acetylglucoside (acetylvitisin A) of malvidin containing a C3H2O2 grouping, linking carbon 4 and the 5-hydroxyl group of its molecule (vitisidin A). The other two anthocyanins were identified as the 3-glucoside (vitisin B) and the 3-acetylglucoside (acetylvitisin B) of malvidin containing a CHCH moiety linking carbon 4 and the 5-hydroxyl group of its molecule (vitisidin B or decarboxyvitisidin A). Unlike other anthocyanins these novel compounds were found to be wholly or partly resistant to bleaching by sulfur dioxide and express more color up to pH 7 than malvidin 3-glucoside. Detailed spectral measurements from 250 to 770 nm up to pH 7, including the use of CIELAB 76 measurements, indicate the formation of stable quinonoidal bases, confirming that there could be little formation of the colorless carbinol base forms. Keywords: Red wine; anthocyanins; vitisin A; vitisin B; vitisidin A; vitisidin B; NMR; FABMS