Abstract

Pomegranate peel is the main waste fraction of pomegranate fruits, which is an excellent source of phenolic compounds. In this study, microwave-assisted extraction was employed to extract the phenolic compounds from pomegranate peel with water. By using response surface methodology, the effects of microwave output power, extraction time, and solid-liquid ratio on total phenolic yield were investigated and the optimal conditions were determined as follows: microwave output power 600 w, extraction time 60 s, and solid-liquid ratio 20. The average experimental phenolic yield under the optimum conditions was found to be 210.36 ± 2.85 mg GAE/g, which agree with the predicted value of 214.46 mg GAE/g. Different antioxidant assays were utilized to evaluate antioxidant activity of the obtained extract. It was found the extract was an effective scavenger in quenching 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals with IC₅₀ of 14.53 μg/ml. A linear correlation between concentration of the extract and reducing power was observed with a coefficient of r²=0.9992. In Rancimat test, the antioxidant performance of the extract was inferior to that of tertiary butylhydroquinone, which could be attributed to its poor solubility in oil.

Key words: Pomegranate peel, microwave-assisted extraction, response surface methodology, antioxidant