New Anthocyanin Pigments Formed after Condensation with Flavanols

Abstract

The formation of three major pigments has been detected in model solutions imitating wine containing malvidin 3-monoglucoside (Mv-3-glu) and procyanidin B2 in the presence of acetaldehyde. Two of them were reddish-blue compounds whose visible spectra are bathochromically shifted with regard to that of Mv-3-glu. They were assigned to two enantiomers containing Mv-3-glu and B2 moieties linked across their C-8 by an ethyl bridge. A molecular ion at m / z 1097, consistent with such a structure, has been established by LC/MS for both of them. The third majority pigment was an orange-red product possessing a spectrum with a maximum wavelength in the visible region at 511 nm and a molecular ion at m / z 1093. A possible structure containing two flavylium mesomeric forms, corresponding to malvidin and to pelargonidin, has been suggested for this compound. This pigment proved to be more stable than the first two, as well as more resistant to discoloration by increased pH values and SO 2 . Similar pigments, whose spectra possess maximum wavelengths in the visible region between 490 and 511 nm, have also been found in equivalent solutions containing other flavan-3-ols [(+)-catechin, (−)-epicatechin, or procyanidin B3]. Evidence for the formation in red wine of pigments with similar spectral characteristics is also contributed. Keywords: Malvidin 3-monoglucoside; flavan-3-ols; procyanidins; acetaldehyde; anthocyanin-derived pigments; LC/MS