Chemical Profile, Antioxidant and Antibacterial Activity of Thyme and Oregano Essential Oils, Thymol and Carvacrol and Their Possible Synergism

In this study, chemical composition, antioxidant and antibacterial activities of thyme and oregano essential oils, thymol and carvacrol, as well as their possible synergism were investigated. For chemical profiling of essential oils, GC-MS analysis was performed. Antioxidant capacity was assessed throughout neutralisation of DPPH and OH radicals. For determination of antibacterial activity against selected gram-positive (Staphylococcus aureus and Bacillus cereus) and gram-negative bacteria (Salmonella Infantis, Escherichia coli O157:H7) broth micro-dilution method was used. Finally, the combination testing for potential synergy of thyme and oregano essential oils, thymol and carvacrol was performed using checkerboard method and evaluated with fractional inhibitory concentration. Thymol and carvacrol were found to be dominant components of investigated essential oils. All studied samples expressed strong antioxidant and antibacterial potential. In synergy testing, both combinations (thyme/oregano essential oils and thymol/carvacrol) were found to have additive effect (FIC=0.75). These results confirm thyme and oregano essential oils, thymol and carvacrol as well as their combinations for possible application as natural additives in different products (food, cosmetics and nutriceuticals).