Evaluation of antimicrobial activity of olive leaf extracts by ELISA method

The aim of the study was to investigate the effect of extraction through two methods of maceration and microwave-assisted extraction on phenolic compounds of olive leaves (Mishen cultivar) with solvents of water, 80% methanol and acetone. The highest total phenolic content (211.385±0.13 mg tannic acid/g extract) was related to the methanol extract produced by microwave-assisted extraction but acetone extracts gave the lowest amount for both methods. Comparing the extraction methods showed that MAE had higher extraction efficiency in all three tested solvents. Regarding antimicrobial activity of olive leaf extracts, we evaluated the bactericidal effects of different solvent extracts on Staphilococcus aureus, Salmonella typhi and Escherishia coli. In terms of S. aureus, the lowest minimum inhibitory concentration (MIC= 315 µg/ml) and. minimum bactericidal concentration (MBC= 2500 µg/ml) were observed with acetone extract in MAE and methanol extracts in both methods, respectively. As for E.coli the lowest MIC was 625 µg/ml and the lowest MBC (5000 µg/ml) was associated with water and methanol extracts in microwave-assisted extraction. In terms of S. typhi, the lowest MIC and MBC were 315 and 10000 µg/ml, respectively. To conclude, it was found that S. typhi was the most resistant bacteria against the extracts; in most cases MAE-produced extracts showed more antimicrobial activity compared to traditional-produced extracts.