Investigating the Sensitivity and Resistance of Human Infectious Bacteria Against the Extracts of Thymus Species and Identifying Their Bioactive Compounds

Abstract

This research was conducted with the aim of investigating the antibacterial, and antioxidant activity of Thymus eriocalyx and Thymus daenensis extracts against human pathogenic bacteria and identifies their bioactive compounds. The aerial part of T. eriocalyx and T. daenensis were collected from urmia, iran. The alcoholic extracts by maceration method and the antibacterial activity against gram-positive and gram-negative bacteria were performed by disc diffusion assay. Next, minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) by serial dilution method and free radical scavenging activity by 2,2-diphenyl-1-picrylhydrazyl (DPPH) were determined. In addition, the chemical compounds were analyzed by gas chromatography mass spectrometry (GC.MS). The dominant compounds in the methanol extract of T. eriocalyx were thymol (22.84%) and ρ-cymene (9.11%) and for T. daenensis as thymol (24.28%) and carvacrol (11.66%). However, sixteen (81.16%) and thirteen (76.59%) compounds were identified in the methanol extract of T. eriocalyx and T. daenensis, respectively. The most sensitive bacteria were associated to Micrococcus luteus and Bacillus subtilis, respectively, against the methanol extract of T. Daenensis (24±0.33 mm) and T. eriocalyx (21±0.88 mm) with mic of 0.78 mg ml^-. Finally, the lowest half maximal inhibitory concentration (IC₅₀) was 0.125 mg ml^- for the methanol extract of T. daenensis. In general, the extract of this plant can be introduced as a source for the discovery of antimicrobial drugs and antibiotics to control resistant pathogens.