Antimicrobial and antioxidant activity of the extracts from Origanum vulgare L. growing wild in Bosnia and Herzegovina

Antifungal, antimicrobial, insecticidal and antioxidant activities of Origanum vulgare L. provide the basis for suggesting that oregano plant extracts may be useful for prevention and treatment of many infection. The main goal of this study was to determine antimicrobial and antioxidant activities of methanolic and aqueous extracts from the leaves and flowers of Origanum vulgare. Antimicrobial testing of plant extracts was done using well diffusion method. Activity of extracts were tested against Gram positive bacteria: Staphylococcus aureus ATCC 25923, methicillin-resistant Staphylococcus aureus (MRSA) ATCC 33591, Bacillus subtilis ATCC 6633, Enterococcus faecalis ATCC 29212 and five Gram-negative bacteria: Salmonella abony ATCC 6017, Salmonella enterica serovar Enteritidis ATCC 31194, Pseudomonas aeruginosa ATCC 9027, Escherichia coli ATCC 25922, extended-spectrum β-lactamase (ESBL) producing Escherichia coli ATCC 35218 and fungi Candida albicans ATCC 1023. Antibiotics ampicillin, streptomycin and antimycotic nystatin were used as positive controle. The antioxidant activity was determined by using the DPPH (1,1-diphenyl-2-picrylhydrazyl) method. The highest values for inhibition zone for methanolic and aqueous extracts were recorded for Gram positive Bacillus subtilis, Staphylococcus aureus and MRSA. Methanolic extracts exhibited antibacterial activity against tested Gram negative bacteria in variable degree while the growth of these bacteria was not inhibited by aqueous extracts. Tested fungi Candida albicans was not susceptible to investigated oregano extracts. All the extracts showed moderate to potent antioxidant activity, among which the methanolic flower extract demonstrated the strongest antioxidant activity with the IC50 value of 0.205 mg/mL. Therefore it can be concluded that flower and leaf oregano extracts have great antibacterial and antioxidant potential.