Extracting, evaluating biological activities of phenolic compounds from yellow onion peels (Allium cepa L.) and their applicability for fish preservation

Abstract

The research aimed to evaluate total phenolic content extracted from onion (Allium cepa L.) peels and some of the extract biological activities. The potential of the extract for preserving fish was also investigated. Onion peel extracted with EtOH 60% at 60°C (60 minutes, solid/liquid ratio 1g/20ml) yielded highest polyphenol content 168.49 ± 0.02 GAE/g DW and flavonoid content (216.43 ± 0.06 mg QE/g DW). The extract showed potent antioxidant property in DPPH radical scavenging assay with IC50 value of 12.48 ± 0.45 μ/mL and good antibacterial activity against Bacillus subtilis, Escherichia coli, Staphylococcus aureus, Salmonella, Pseudomonas aeruginosa with MIC values of 175; 175: 200; 200: 150 (μ/mL) respectively. The extract also displayed alpha-glucosidase inhibition activity with IC50 value of 142.53 μg/mL and negligible tyrosinase inhibition activity. Measurement of the PV, TBARS values of basa catfish fillets coated with the extract solution at different concentrations, it was observed that fish samples treated with 3% extract solution could greatly reduce the lipid oxidation under 4°C and -18°C storage conditions compared with untreated samples. The PV, TBARS values after 4 weeks were comparable to 200ppm BHT treated samples.