Study of hydroxycinnamic acids and malvidin 3-monoglucoside derivatives using capillary zone electrophoresis and ultra-performance liquid chromatography

Model solutions (pH = 3.5, 12% ethanol) of malvidin 3-O-glucoside (Mv3glc), the most common free anthocyanin in grapes and red wines from Vitis vinifera, and three free hydroxycinnamic acids present in wines (caffeic, ferulic and p-coumaric acids) were studied. The stability of the precursors and their derivatives was studied during a storage period of six months at 20 °C. Capillary zone electrophoresis with UV–vis detection (CZE/UV–vis) was used to monitor changes in sample composition. Ultra-performance liquid chromatography coupled to mass detection (UPLC/MS) was used to confirm the presence of the compounds formed. Discussion on the migration times of the new pigments as well as on their UV–vis and mass spectra is reported. Six derivatives were detected in model wine solutions containing Mv3glc and caffeic acid. The six derivatives were identified as three condensation products of caffeic acid, 4-vinylcatechol, 4-vinylsyringol and a compound with a molecular ion at m/z 803, whose structure has been tentatively assigned to a caffeic acid linked to Pinotin A. The derivatives 4-vinylphenol and 4-vinylguaiacol pyranoanthocyanins were detected in solutions containing malvidin 3-O-glucoside together with p-coumaric and ferulic acid, respectively. The malvidin 3-O-glucoside derivative, 4-vinylsyringol was also detected in all solutions containing the anthocyanin regardless of the presence of hydroxycinnamic acid.