Hemisynthesis and structural and chromatic characterization of delphinidin 3-O-glucoside-vescalagin hybrid pigments.

During red wine maturation in the presence of oak wood, reactions involving anthocyanins and ellagitannins might affect wine organoleptic properties such as color and astringency. In this work, the condensation reaction between myrtillin (delphinidin 3-O-glucoside) and vescalagin has been performed to determine the behavior of this anthocyanin in this kind of reaction and to assess the possible impact of such a reaction in wine color modulation. Two different hybrid pigments have been hemisynthetized and characterized by HPLC-DAD-MS and NMR spectroscopy. These pigments have been identified as 1-deoxyvescalagin-(1β→8)-myrtillin (major) and 1-deoxyvescalagin-(1β→6)-myrtillin (minor). The minor pigment could be formed both by the condensation reaction and by a regioisomerization process from the major pigment. Moreover, the chromatic properties of these pigments have been studied and compared to those of myrtillin. The hybrid pigments showed an important bathochromic shift (ca. 20 nm) in the maximum absorbance wavelength and lower molar absorption coefficients.