Total phenolic content, antioxidant capacity, and antimicrobial activity of Origanum heracleoticum L., extracted with different solvents

This research was based on the examination of the total phenolic content, antioxidant and antimicrobial activities of hexane, diethyl ether, ethyl acetate, and methanol extracts of Origanum heracleoticum L. grown in Serbia. The antimicrobial activity was determined against five bacteria and two fungi using the disk diffusion method. The total phenolic content of O. heracleoticum solvent extracts was determined and five different tests were used for screening of the antioxidant capacity. The highest total phenolic content was found in ethyl acetate extract (848.48 μg GAE/mg dry extract) and methanol extract (733.43 μg GAE/mg dry extract). The examination of antioxidant activity showed that methanol and ethyl acetate extracts had the strongest activity. The highest correlation was found between DPPH and FRAP (R2 = 0.99), as well as DPPH and CUPRAC (R2= 0.96) assays. The ABTS test was highly correlated with the FRAP test (R2 = 0.95). The antimicrobial assay proved that each extract had an effect against all bacteria and fungi, except against the bacterium Pseudomonas aeruginosa. The highest antibacterial activities were found for methanol extract and ethyl acetate extract against Staphylococcus aureus. The highest antifungal activity was observed for the ethyl acetate extract against both Candida albicans and Aspergillus brasiliensis.