A re-investigation of the mycolic acids of Mycobacterium avium

Mycolic acid methyl esters were extracted from Mycobacterium avium by a mild saponification protocol, designed to preserve labile components. The resulting mixture of alpha-, keto- and wax ester mycolates was accompanied by some degraded omega-carboxymycolic acid dimethyl esters, whose overall structures were found to support previous studies. Chromatography of the mono-carboxylic mycolates gave an inseparable mixture of keto- and wax ester mycolates and separate alpha-mycolates. Reduction of the ketomycolate components allowed isolation and characterisation of intact wax ester mycolates for the first time. Minor alpha- and omega-carboxymycolates were detected in which methyl branches were located on either the proximal or distal sides of trans-alkene groups.