Identification of Thymol as an Antitubercular Agent from Ocimum gratissimum Leaf Essential Oil
Samuel E. Okhale *
Department of Medicinal Plant Research and Traditional Medicine, National Institute for Pharmaceutical Research and Development, Idu Industrial Area, P.M.B. 21 Garki, Abuja, Nigeria
Peters Oladosu
Department of Microbiology and Biotechnology, National Institute for Pharmaceutical Research and Development, Idu Industrial Area, P.M.B. 21 Garki, Abuja, Nigeria
Abayomi T. Orishadipe
Chemistry Advanced Laboratory, Sheda Science and Technology Complex, P. M. B. 186 Garkipo, Sheda, Abuja, Nigeria
Joseph I. Okogun
Department of Medicinal Plant Research and Traditional Medicine, National Institute for Pharmaceutical Research and Development, Idu Industrial Area, P.M.B. 21 Garki, Abuja, Nigeria and Department of Chemistry, University of Ibadan, Nigeria
*Author to whom correspondence should be addressed.
Abstract
Ocimum gratissimum consumed as a vegetable is used to treat cough, tuberculosis and dysentery in Nigeria. Hydro-distillation of the fresh leaves of O. gratissimum yielded a golden yellow essential oil 0.5% v/w which exhibited minimum inhibitory concentration (MIC) of 48 µg/ml against Mycobacterium bovis BCG strain. Activity-guided fractionation of the oil into neutral and acidic portions followed by column chromatography led to the isolation of a crystalline compound with MIC of 9.8 µg/ml while the control drug isoniazid had MIC of 0.07 µg/ml. GC-MS and 1H NMR analyses revealed the bioactive crystalline compound to be thymol.
Keywords: Ocimum gratissimum, essential oil, acidic fraction, thymol, antitubercular activity