Optimization of extraction of phenolic compounds and antioxidants from passion fruit and rambutan seeds using response surface methodology

Abstract

Passion fruit seed (PS) and rambutan seed (RS) contain sizable amounts of phenolic compounds (PCs) with bioactive compounds including antioxidant activity (AOA). The aim of this study was to optimize the extraction of PCs from PS and RS using response surface methodology (RSM). Preliminary results indicated that the solid to liquid (S-L) ratio of 1:40 (w/v) showed the highest yield (EY) for PS and RS, with values of 11.59 ± 0.08 and 14.55 ± 1.67 g/100 g samples, respectively. The S-L ratio of 1:30 (w/v) was selected as an economic logistic. The predicted response compared to experimental data for EY, EPC, DPPH, ABTS and FRAP of the extracts were 12.41 % (12.68 %), 715 (707), 85 (81), 539 (522) and 107 (160) mg GAE/100 g dry weight for RS and 13.68 % (14.41 %), 3141 (3235), 1327 (1434), 5793 (5564) and 1567 (1509) mg GAE/100 g dry weight for PS, respectively. The experimental data, including EY, EPC, and AOA, were fitted using a 2nd order polynomial equation. The statistical analysis revealed that ethanol concentration and extraction temperature significantly influenced PS (p < 0.001), whereas ethanol concentration primarily affected RS on the EY and EPC. The multiple regression analysis suggested that AOA of PS was significantly affected by linear, quadratic, and interaction of ethanol concentration, extraction time and temperature. Nonetheless, the AOA of RS was only affected by ethanol concentration. The best possible combinations for PS and RS were ethanol concentration 67 and 54 %, extraction temperature 94 and 63 °C, and extraction time 186 and 221 min, respectively, to obtain the maximum EY, extractable phenolic compounds (EPC) and AOA. The composite desirability values for the optimal conditions of PS and RS were 0.74 and 0.68, respectively. Optimal aqueous phenolic extracts from PS and RS could serve as sustainable food-grade ingredients and nutraceutical products.