Antimycobacterial Sterols from Aromatic Stem Sap of Commiphora eminii Engl.

Abstract

The phytochemical analysis on aromatic stem sap of Commiphora eminii afforded two cholesten sterols namely, 4-methyl-cholest-7-en-3-ol (1) and cholest-7-en-3-ol (2). Their chemical structures were deduced using NMR and MS spectral data and with comparison with data available in literatures. The sterols were screened for antimycobacterial activity against Mycobacterium madagascariense (MM) and Mycobacterium indicus pranii (MIP). Only sterol 2 exhibited antimycobacterial activity with MIC values of 1.6 mg/ml against both mycobacteria strains used. In the combination assay, sterols potentiated activity of isoniazid (INH) against test organisms, which are known to be resistant to isoniazid even at higher concentration. Sterol 1 had a fractional minimum inhibition concentration (FMIC) of 0.2 mg/ml while sterol 2 had FMIC values of 0.1 against both MM and MIP. The combination of two sterols alone lacked efficacy. The fact that, sterol 1 lacked efficacy in the normal antimycobacterial assay, and that during the combination assay, it potentiated activity of INH at a low concentration indicates that, sterols may be considered as activity enhancers for antibiotics such as isoniazid, especially when testing against drug resistant Mycobacterium strains.