THE RELATIONSHIP BETWEEN THE CHEMICAL STRUCTURE OF FATTY ACIDS AND THEIR MYCOBACTERICIDAL ACTIVITY

Abstract

The bactericidal activity of long-chain fatty acids on mycobacteria was examined by exposing the organisms to these acids at 0.04 mM in 0.05 M acetate buffer (pH 5.6) . The lethal effect of saturated fatty acids was related to the chainlength of hydrocarbon, C_{14: 0} being the strongest in the activity and longer and shorter fatty acids being less active. Unsaturation, isomerism and the presence of α-hydroxy group were found to be other factors governing the activity. The lethal effect was greater in the order of C_{18: 3}>C_{18: 2}>C_{18: 1 (cis}) >C_{18: 1 (trans}) >α-OH C_{18: 0}>C_{18: 0}. C_{20: 4}was placed between C_{18: 3}and C_{18: 2}in this respect. Esterification of C_{14: 0}, C_{18: 1}and C_{20: 4}to methyl esters and cholesteryl esters abolished completely the bactericidal activity of these acids, suggesting the requirement of carboxyl group for the activity. The relationship between the fatty acid structure and the lethal effect was discussed in reference to these observations.