Antioxidant, Antimicrobial Activities, and Characterization of Phenolic Compounds of Thyme (Thymus vulgaris L.), Sage (Salvia officinalis L.), and Thyme–Sage Mixture Extracts

Abstract

The antioxidant properties of sage (Salvia officinalis L.) and thyme (Thymus vulgaris L.), and their mixtures were examined using the 2,2-Diphenyl-1-picrylhydrazyl (DPPH•) scavenging activity and ferric-reducing activity of plasma (FRAP) methods. The antimicrobial activity of the plant extracts against four bacterial strains (Escherichia coli, Staphylococcus aureus, Bacillus cereus, and Salmonella typhomorium) was determined using the agar well diffusion method. Results showed the highest overall rate of increase in total phenolic (13.67 mg·GAE/g·DW), and flavonoid (6.75 mg·QUE/g·DW) contents in the thyme–sage mixture extract compared with the thyme and sage extracts. As found by GC-MS analysis of methanolic extracts, thymol, apigenin, rosmarinic acid, and carvacrol were the most abundant phenolic compounds in the thyme–sage extract. The lowest EC50 (DPPH•, 55.51 μg·ml−1) and the highest FRAP value (95.51 mM Fe (II) mg−1 extract) were recorded in the extract of the thyme–sage mixture compared with sage and thyme extracts, and butylated hydroxytoluene solution (BHT). The highest antimicrobial activity against E. coli, S. aureus, B. cereus, and S. typhomorium was observed in the thyme–sage mixture with the inhibition zone diameters of 22.13, 28.67, 31.25, and 23.65 mm, respectively. It is concluded that the extract obtained from the thyme–sage mixture has more potential to be used in the pharmaceutical and food industry as a natural antibacterial and antioxidant agent.