Mycolic Acids

Literature References: High mol wt a-branched, b-hydroxy fatty acids, components of the cell envelopes of all Mycobacteria. All known mycolic acids have the basic structure R2CH(OH)CHR1COOH where R1 is a C20 to C24 linear alkane and R2 is a more complex structure of 30 to 60 carbon atoms that may contain various numbers of carbon-carbon double bonds and/or cyclopropane rings, methyl branches or oxygen functions such as C=O, CH3OCH=, COOH. The structure of mycolic acids varies by families and species. Three principal categories are known: (1) corynomycolic acids ranging from C28 to C40 found mostly in Corynebacteria; (2) nocardic acids, also called nocardomycolic acids, ranging from C40 to C60, produced by strains of Nocardia; and (3) mycobacterial mycolic acids ranging from C60 to C90. First obtained from a human strain of Mycobacterium tuberculosis and studied in an impure form called "unsaponifiable wax": R. J. Anderson, J. Biol. Chem. 85, 351 (1929). Isoln of the first representative of this group of acids from the human tubercle bacillus and derivation of the name "mycolic acids": F. H. Stodola et al., ibid. 126, 505 (1938). Historical reviews: R. J. Anderson, Fortschr. Chem. Org. Naturst. 3, 145-202 (1939); J. Asselineau, E. Lederer, ibid. 10, 170-273 (1953); J. Asselineau, The Bacterial Lipids (Hermann-Holden Day, Paris-New York, 1962) pp 82-148; E. Lederer, Pure Appl. Chem. 25, 135 (1971). Major mycolic acids of Mycobacterium smegmatis: M. Y. H. Wong et al., J. Biol. Chem. 254, 5734 (1979); M. Y. H. Wong, G. R. Gray, ibid. 5741. Total synthesis of mycolic acids from M. smegmatis: H. C. Huang et al., J. Org. Chem. 47, 4018 (1982). Evaluation as immunotherapeutic agents in the treatment of cancer in animal models: M. V. Pimm et al., Int. J. Cancer 24, 780 (1979). Clinical evaluation in humans: G. J. Vosika, Cancer 44, 495 (1979). Mycolic acids are acid fast. They are always isolated in the form of more or less complex mixtures. They occur in nature esterified with carbohydrates: with arabinose in the cell wall, with trehalose in cord factor, q.q.v.