Antimycobacterial Potential of Essential Oils Used Traditionally for Cough Remedy

Abstract

Tuberculosis (TB) is currently a major health hazard due to multidrug-resistant forms of bacilli. Global efforts are underway to eradicate TB using new drugs with new modes of action, higher activity, and fewer side effects. Essential oils from some dietary herbal species have been used as sources of medicine and food preservatives for over 4000 years. The objective of this research is to investigate the antimycobacterial activity of the essential oils of Boswellia papyrifera (Del) Hochst olibanum, Nigella sativa seeds and Eucalyptus camaldulensis Dehnh leaves, which are used traditionally in treatment of cough and cold. The essential oils from herbal materials were prepared using hydrodistillation method. The essential oils were analyzed for identification of their chemical composition using GC-MS technique. The essential oils were tested in vitro for their activity against nine clinical isolates and a reference susceptible strain (H37Rv) M. tuberculosis in Lowenstein-Jensen (LJ) medium, at concentrations of 75, 50, 30 and 15 μl/mL. The main constituents identified in the investigated essential oils were p-cymene (45.26%) and thymoquinone (35.35 %) in N. sativa oil; octyl acetate (37.3%) and octyl formate (13.3%) in the B. papyrifera oil; 1,8-cineole (75%) and p-cymene (16.7%) in E. camaldulensis oil. The investigated essential oils exhibited anti-tubercular activity, in LJ medium, up to concentration of 15 μl/ml for each oil, towards all the tested strains, three of which were multi-drug resistant strains (MDR-TB), as they resist rifampicin, a marker drug for MDR-TB. This research findings may be useful in developing future powerful drugs for MDR-TB from essential oils, the bioactive phytochemical natural products.

Keywords

• tuberculosis, essential oils, boswellia papyrifera, nigella sativa, eucalyptus camaldulensis, thymoquinone, 1,8-cineole, octyl acetate