Effect of extraction methods and temperature preservation on total anthocyanins compounds of Peristrophe bivalvis L. Merr leaf

This paper proposes anthocyanins extraction from Peristrophe bivalvis L. Merr. (“lá cẩm”) and preservation. Experiments were performed in water as a solvent using two different extraction methods [conventional extraction (CE) and microwave-assisted extraction (MAE)], including different solvent-to-raw material ratios, temperatures/microwave power, and times of extraction. The total anthocyanin in the extract was analyzed by UV-Vis. Multiple regression analysis was applied to analyze the influence of factors and select the optimal parameters for each extraction process. The influence of storage conditions on the quality of extracts from “lá cẩm” leaves was controlled. It was observed that the ratio of solvent and fresh leaf used, temperature/ microwave power, and extraction time all affected the anthocyanin content recovered from the extract when using different extraction techniques. The MAE technique gave superior results compared to the CE method. The solvent used was slightly higher and the extraction time was 6.2 times shorter than that of the CE method. The optimal parameters of each extraction technique are selected. With the CE method, the solvent-to-fresh leaf ratio was 11.22:1; the optimum temperature and time were 88°C and 27.21 minutes resulting in the anthocyanin content in the extract being 25.61 mg/g dry weight basic (db). Meanwhile, with the MAE method, the solventto-fresh leaf ratio used was 10.83:1 (v/w), the microwave power and the optimal extraction time were 600 W and 4.39 minutes, and the obtained extract had an anthocyanin content of 30.97 mg/g db. In addition, the extract was best preserved in the dark and the storage temperature was −9°C. The remaining anthocyanin content after 30 days of storage was 92.35%. The anthocyanin degradation kinetics was also analyzed. Changes in total anthocyanin followed a zero-order reaction kinetic model. The potential of the half-life of anthocyanin was 221, 114, and 19 days at −9°C, 4°C, and 28°C, respectively.