Eco-friendly microwave-assisted extraction of fruit and vegetable peels demonstrates great biofunctional properties

This study aimed to determine the biofunctional properties, such as antioxidant, antimicrobial, anticancer, and antidiabetic activities, of peel extracts obtained through microwave-assisted extraction (MAE) of red beet, dragon fruit, and prickly pear peels using water as a green solvent. Results indicated that the peel extracts exhibited high total phenolic content (TPC), ranging from 345.93 to 1651.17 mg GAE/L. The DPPH scavenging capacity of the extracts ranged between 7.16 and 34.65 mg/mL, while the ABTS scavenging capacity ranged between 0.93 and 15.27 mg/mL. Dragon fruit peel extract (DFE) and prickly pear peel extract (PPE) showed significant α-glucosidase inhibition effects, with 67.79% and 37.50% inhibitions, respectively. Moreover, significant antibacterial activities were observed against five pathogenic bacterial strains (B. cereus, E. coli, S. aureus, L. monocytogenes, and S. enterica) at various concentrations of extracts. The cytotoxic effect of the extracts on HT-29 and HeLa cancer cells was also observed. The most abundant phenolic compound in DFE was rutin (0.558 mg/g); in PPE, hesperidin was the most abundant (0.596 mg/g); and in red beet peel extract (RBE), hesperidin (0.426 mg/g) was the predominant compound.