Determination of antimicrobial and antiquorum sensing activities of olive leaf extracted by different methods

The aim of this study was to obtain an extract rich in total phenolic content from olive leaves using different extraction methods, and to determine the antioxidant capacities, antimicrobial activities, and antiquorum sensing properties of olive leaf extracts. In this context, olive leaves were extracted using classical solvent extraction, ultrasound-assisted extraction, and microwave-assisted extraction methods, and the antimicrobial activities and quorum sensing inhibition effects of the obtained extracts were evaluated. The total phenolic content of olive leaf extracts obtained by using different solvents and extraction methods was determined using the Folin-Ciocalteu method. The antioxidant activity values of olive leaves were assessed using the DPPH radical scavenging activity method and Trolox equivalent antioxidant capacity determination (TEAC) method using the ABTS radical cation. The antimicrobial activities of the extracts obtained using different solvents and extraction methods against the foodborne pathogenic bacteria Staphylococcus aureus ATCC 29213, Escherichia coli ATCC 25922, Bacillus subtilis ATCC 11774, and Klebsiella pneumoniae ATCC 13883 were investigated. In addition, Chromobacterium (C.) violaceum CV026, C. violaceum ATCC 12472 and Pseudomonas aeruginosa PAO1 were used as model microorganisms to evaluate the inhibition effect of quorum sensing. The total phenolic content, antioxidant capacity, and antimicrobial activity of the extract obtained by the microwave-assisted extraction of olive leaves with water were found to be higher. When evaluated in terms of antiquorum-sensing activity, water and methanol-water extracts obtained by the microwave-assisted extraction method showed higher activity against C. violaceum CV026 and ATCC12472 strains.