ANTHOCYANIN PROFILE IS AFFECTED BY MICROWAVE-ASSISTED EXTRACTION CONDITIONS

Jabuticaba and red cabbage are anthocyanin-rich plant commonly consumed in the Brazilian's diet. Anthocyanins are hydrophilic pigments from fruits and vegetables which have gained interest due to their intense color and bioactivity. Solid-liquid extraction is the most common method applied for anthocyanin extraction; however, it is a time and solvent consuming method. During the last years, there is an increased interest in new environmental-friendly extraction techniques. Among them, microwave-assisted extraction (MAE) can be highlighted. MAE relies on the fast heating generated by the microwaves to facilitate the migration of the interest compounds from the matrix to the extraction solution, showing as advantages a reduced extraction time and the use of low solvent volume. The effect of MAE on the anthocyanin profile is still poorly explored. To study the influence of MAE conditions for anthocyanin extraction, a 23 factorial experimental design (DCFC) was applied with samples possessing anthocyanins with different degrees of complexity: non-acylated anthocyanins (jabuticaba) and anthocyanins acylated with cinnamic acids (red cabbage). The independent variables were HCl concentration (0.3 – 0.7%), temperature (90 – 110°C) and volume of acidified methanol (28 - 42 mL). For the jabuticaba peel anthocyanins, the response variables were the concentrations of the cyanidin 3-glucoside, delphinidin 3-glucoside, cyanidin 3-(succinyl)glucoside and total anthocyanins. The response variables for the red cabbage anthocyanins were the concentrations of the anthocyanins caffeoyl-coumaryl -derivatives, caffeoyl-sinapyl-derivatives, caffeoyl-feruloyl-derivatives, non-acylated anthocyanins and total anthocyanins. The profile of anthocyanins obtained by MAE and traditional extraction methods, determined by HPLC-DAD-MS/MS were compared. The total extraction of anthocyanins from jabuticaba peel by MAE was not more efficient than that obtained by the traditional methods. None of the independent variables presented significant effect on the concentration of total anthocyanins, delphinidin 3-glucoside and cyanidin 3-glucoside from jabuticaba peel. On the other hand, cyanidin 3-(succinyl)glucoside concentration was positively affected by the acid concentration contained in the extraction solution and by the temperature of extraction in the studied range. Concerning red cabbage, the total extraction of anthocyanins was more efficient by MAE than by the traditional methods. Additionally, the independent variables affected the anthocyanin profiles in the levels evaluated in the factorial experimental design DCFC. The highest acid concentration resulted in high contents of both non-acylated anthocyanins and caffeoyl-feruloyl-derivatives; however, in low concentration of caffeoyl-coumaryl-anthocyanin derivatives. High temperature also significantly increased the concentrations of both non-acylated anthocyanins and caffeoyl-feruloyl-derivatives. Anthocyanins from jabuticaba and red cabbage were not degraded to low molecular weight compounds during MAE under the tested conditions.
Financial Support: CNPq, FAPESP (grant 2013/07914-8) and CAPES.