Evaluation of biological activities of Thyme extracts and their use as a naturalalternative to antibiotics for the reduction of pharmaceutical waste

Abstract

Excessive and improper use of chemical antibiotics is dangerous to human health and animals and causes an unhealthy environment. Hence, medicinal plants are expected to be the future alternative source of new antimicrobial products. The present study aimsto determine the chemical composition of Thymus fontanesiiBoiss. & Reut.essential oil (EO) then to isolate andcharacteriseitsmain constituent,thymol,and to evaluatetheir antibacterial and antioxidant activities. The oil was obtained by hydro-distillation from the aerial parts of T. fontanesii at yield of 3.4±0.2% and 06 main compounds were identified using GC/MS technique representing more than 99% of the oil composition. The major constituents were thymol (77.72%) and carvacrol (13.27%). The antimicrobial activity of our extracts was investigated in comparison with four synthetic antibiotics, using the disc diffusion and broth macro-dilution methods against 13 pathogenic bacteria. The antimicrobial evaluation showed that EO and thymol isolate exhibited high antibacterial activity against all the strains tested compared with the synthetic antibiotics, they were capable of inhibiting the growth of bacterial organisms tested with inhibition zones in the range of 10–58.53 mm. The EOwas the most active with MIC and MBC values of (0.035 mg/mL to 0.565 mg/mL). The antioxidant activity of our extracts was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH)radical scavenging method.The antioxidant activity revealed that the EO and thymol isolate demonstrated a very important anti-radical activity compared to the standards (ascorbic acid and BHT). T. fontanesii essential oil showed the strongest (p < 0.05) radical scavenging effect, with 50% inhibitory concentration (IC50) of 15.85 ± 0.23μg/mL. The results showed that the essential oil of T. fontanesii and thymol, its major compound, are an excellent alternative to synthetic antibiotics. They are of great interest because of their availability, non-toxicity and their friendship with the environment, and therefore can be useful for the food and pharmaceutical industries.