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This study is aimed to synergistically intensify the extraction of bioactive compounds (phenolics and flavonoids) from fruit waste pomegranate peel using microwave-assisted extraction (MAE), ultrasonication-assisted extraction (UAE), and their combination (UMAE). Various process parameters such as microwave power (200–800 W), ultrasonication power (200–800 W), solvent compositions, ethanol in water (20–80%), liquid-to-solid ratio, LSR (10–60), and time (5–30 min) are varied, and optimum parameters are determined for maximum extraction of bioactive compounds. The highest extraction yields are found as follows: (i) 56.67% with MAE at 600 W, 60% ethanol, 40 LSR, and time 15 min; (ii) 53.98% with UAE at 400 W, 70% ethanol, 40 LSR, and time 25 min; and (iii) 56.19% with UMAE at 200 + 200 W, 60% ethanol, 40 LSR, and time 15 min. In the extraction yield, "total phenolic content and total flavonoid content" are also examined by using a UV–visible spectrophotometer. The antioxidant property of peel extract is recorded as 85.27%, and microbial inhibition against Escherichia coli is achieved as 15.25 mm at a 10 mg/mL concentration. The kinetic study has been carried out for the extraction rate, and the second-order kinetic model (R2 = 0.99) best fits the experimental data. Fourier transform infrared spectroscopy and high-performance liquid chromatography are used for qualitative and quantitative analysis of polyphenols, such as "punicalagin, gallic acid, and ellagic acid". The result shows the richness of phytochemical content within pomegranate peels, which demonstrates their high antioxidant property and antimicrobial nature, conferring them as efficient byproducts.
Singh et al. (Fri,) studied this question.