CHEMICAL COMPOSITION, ANTIMICROBIAL, AND ANTIOXIDANT ACTIVITIES OF TWO MOROCCAN THYMUS ESSENTIAL OILS

Abstract

Objective: The aim of the present study is to investigate chemical constituents of Thymus riatarum and Thymus blecherianus essential oils (EOs) as well as to evaluate, for the first time, their antioxidant effect and antibacterial activity against six bacterial strains responsible for nosocomial infections.Methods: The chemical composition of EOs was analyzed using gas chromatography (GC) and GC-mass spectrometry, the antibacterial capacity of the two thymus species was evaluated against six bacteria species: Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia, Staphylococcus aureus, Acinetobacter baumannii, and Citrobacter sp. using disk diffusion method and microdilution assay. Finally, the antioxidant activity was measured by four different test systems of assay, namely free radical scavenging activities, ferric reducing/antioxidant power assays, total phenolic, and flavonoid contents.Results: A total of 15 compounds representing 99.6% of T. riatarum oil were identified with thymol (28.8%), borneol (20.0%), and α-phellandrene (13.0%) as the main constituents. Eleven components of T. blecherianus were identified representing 98.2% of the total oil composition; the most abundant constituents were as follows: Carvacrol (45.9%), bornyl acetate (20.1%), and borneol (15.7%). Strong antibacterial activity of the two EOs was identified against all bacterial strains tested. Concerning the antioxidant results, T. riatarum EO exhibited higher antioxidant activity than T. blecherianus in the three assays with an IC50 value equal to 5.75±0.06 mg/ml, which was probably due to its high content of polyphenols (28.95±0.13 mg GAE/g DW). Total flavonoid content was found equal for the two EOs.Conclusion: EO of T. riatarum and T. blecherianus from Morocco can be exploited as a natural antibacterial and antioxidant new potential sources.