Optimization of extraction of prodelphinidins from bayberry (Myrica rubra Sieb. et Zucc.) leaves.

The antioxidant activity of bayberry leaf extract determined by DPPH• and FRAP assay was comparable with ascorbic acid. Prodelphinidins in the extract had significant positive correlation with the antioxidant activities of bayberry leaf extract. The correlation coefficients (R) were 0.963 and 0.970 for DPPH• and FRAP assay, respectively. In order to develop a new natural antioxidant, a central composite design was employed and the yield of prodelphinidins was selected as the response value to investigate the extraction. The best possible combination of acetone concentration, time, solid-liquid ratio and temperature was obtained for the maximum extraction of prodelphinidins by using response surface methodology (RSM). The extraction yield of prodelphinidins was affected significantly by process variables. The optimal conditions obtained by RSM include 56.93 % acetone, 31.98 min time, 1: 44.52 solid-liquid ratio, and 50.00 °C temperature. Under the optimum condition, the experimental yield of prodelphinidins was 117.3 ± 5.1 mg/g, which was not different from the predicted value significantly.