Study on antimicrobial effects of Olea europaea (Olive) and olive leaf extracts on pathogenic bacteria using Taguchi methodology

Antibacterial activity has recently been demonstrated in Olea europaea products. This was correlated with the presence of different substances such as oleuropein. In this study antibacterial activity of different olive products was examined and their oleuropein content were determined. Also, the effect of different factors on antimicrobial activity was assayed by Taguchi methodology. Three varieties of fruit, leaves, and unrefined olive oil were purchased from Roodbar in Guilan province and ethanolic extract was examined. Antimicrobial activity of olive leaf extracts was performed by disk and well diffusion methods, and pour plate method. Also, effect of different factors such as incubation time, bacterial suspension concentration, type of bacteria, and type of extracts on antibacterial activity was evaluated using Taguchi methodology. HPLC was also performed to measure the oleuropein content. Data analysis was done by using Minitab software. Leaves, fruits, and oil olive extract had significant impact on Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginoa. The results showed that exposure time and type of extracts had a significant antimicrobial effect on pathogenic bacteria. Also, fruit extract had greater antimicrobial activity than olive oil and S. aureus was more (susceptible) than E. coli and P. aeruginosa to olive extracts. In current study, HPLC confirmed oleuropein as main antimicrobial ingredient of mari leaf extracts at 2.63ppm. Different examined extracts of olive have potential for preparation herbal medicines.