Evaluation of antioxidant activity of olive leaf extract obtained by ultrasound‐assisted extraction and their antimicrobial activity against bacterial pathogens from food

Abstract

SummaryThe aim of the present study was to evaluate and compare the phenolic content and antioxidant and antimicrobial properties of olive leaf extracts obtained by ultrasound‐assisted extraction (UAE) and conventional extraction (CSE). UAE of olive leaf extracts yielded a higher total phenolic content (TPC) and total flavonoid content (TFC) of 14.31% and 19.50%, respectively. Higher antioxidant activities were found from the extracts prepared with UAE (for 18.5%, 12.5%, 10.9% and 17.6% higher determined by DPPH, ABTS, FRAP and CUPRAC methods, respectively). Good antibacterial inhibitory activity (as MIC and MBC) was observed against both Y. enterocolitica and S. aureus (1.40 ± 0.40 mg mL−1 and 4.00 ± 1.60 mg mL−1, respectively) with the extract prepared with UAE. In conclusion, olive leaf extracts prepared with UAE exhibited higher antioxidant and antimicrobial activities against common food‐borne pathogens than CSE extracts and thus could be beneficial in ensuring food quality and food safety.