Optimized method for preparation of methyl pyranoanthocyanins and analyzed by HPLC-MS/MS

Based on the raw material of red pigments extracts of grape skins, the optimized conditions for the synthesis of methyl pyranoanthocyanin by reactions of anthocyanins in acetone solutions were studied by orthogonal experiment design. The factors which had effects on reaction yield of methyl pyranoanthocyanin were investigated in terms of ratio of reactants (grape anthocyanins to acetone) , concentration of extracts of red grape skins, reaction temperature and pH. HPLC was used to monitor the reaction process and the resulting product pigment was analyzed by HPLC-DAD-EI-MS/MS qualitatively and quantitatively. The optimal synthesis conditions were as follows:the ratio of extracts of red grape skins (mg) to acetone (mL) was 15∶1, concentration of grape skin pigments was 2.5mg/mL, reaction temperature was set at 45℃ and pH was 3.0.The main reaction product was confirmed by HPLC-MS/MS to be methyl pyranoMv with the yield of 49.4%after nine days. The characteristic spectral of the purified methyl pyranoMv pigment was at 478 nm, which was distinctly blue-shifted when compared to original anthocyanins. The experimental results provided an effective and economic approach to the high efficient preparation of methyl pyranoMv pigment for further studies of functional and physical-chemical properties.