Mechanism by Which Hydnocarpic Acid Inhibits Mycobacterial Multiplication

Abstract

Recent work in this laboratory has shown that hydnocarpic acid (HA), a principal constituent of chaulmoogra oil, inhibits multiplication in vitro of a number of mycobacterial species. This activity of HA was not shared by several straight-chain fatty acids and by dihydrochaulmoogric acid. A study of the interaction of HA with biotin has been undertaken, based on a structural analogy between biotin and the cyclopentenyl fatty acid. The multiplication of a strain of Mycobacterium intracellulare susceptible to 2 Mug of HA/ml was measured turbidimetrically in Dubos medium, in the presence and absence of biotin and several other compounds. Biotin and, to a lesser extent, adenine plus guanine, palmitic acid, and linoleic acid antagonized growth inhibition by HA. Desthiobiotin, thioctic acid, and succinic acid did not block inhibition of bacterial multiplication by HA. HA may act by blocking the coenzymatic activity of biotin, or it may inhibit microbial biotin synthesis. Resumption of multiplication of M. intracellulare after a period of inhibition by HA in broth culture was found to be accompanied by reduction of the effective concentration of the drug; this could have resulted from metabolism of HA or production of an antagonist to HA by the organisms. Also, those organisms that multiplied in the presence of HA were found to represent HA-resistant mutants of M. intracellulare. Chaulmoogra oil and its major components, chaulmoogric [chemical name 13-(2-cyclopenten-1-yl)tridecanoic] and hydnocarpic [chemical name 1l-(2-cyclopenten-1-yl)undecanoic] acids, were used in the treatment of leprosy for many years, apparently with some effect. However, the mechanism of action of these substances was never elucidated. Early work focused on the fatty acid character of these compounds and the important lipid content of mycobacteria. This resulted in the speculation that these compounds interfered with bacterial cell wall synthesis or function, by a decrease of surface tension or by the adsorption of a monomolecular film onto the surface of the organisms (5,6,8,11). More recent work has attributed the action of chaulmoogra oil to an effect on host defense mechanisms rather than to a direct effect on the organisms (3, 4).Recent work in this laboratory has shown that hydnocarpic acid inhibits both multiplication of Mycobacterium leprae in the mouse foot pad (unpublished data) and also multiplication of a number of cultivable mycobacterial strains in vitro (P. L. Jacobsen, H. Ng, and L. Levy, Amer. Rev. Resp. Dis., in press). Although an effect on host defense mechanisms cannot be excluded, there can be no doubt that hydnocarpic acid exerts a direct antimicrobial action. Adams and his co-workers (10) demonstrated that saturation of chaulmoogric acid reduced antimicrobial activity measured in vitro; the studies in this laboratory confirmed those of Adams, showing that dihydrochaulmoogric acid in a concentration of 2O0Ag/ml failed to inhibit multiplication of several mycobacterial strains susceptible to 2 ,ug of chaulmoogric acid per ...

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“…Chaulmoogra oil has been used as the main treatment for leprosy in Indian and Chinese traditional medicine and, subsequently, in the West before the era of sulfones and antibiotics (27). Hydnocarpic acid had been identified as the principle active ingredient of the oil and showed antimycobacterial activity, apparently acting as an antagonist of biotin (28). The substance was marketed by Burroughs Wellcome as Alepol.…”

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“…One of its compounds, hydnocarpic acid (C 16 H 28 O 2 ), has an in vitro activity against some mycobacteria species. It is however inactive against M. leprae [53].…”

Unconventional application of the Mitsunobu reaction: Selective flavonolignan dehydration yielding hydnocarpins

“…Hydnocarpin and its derivatives show interesting biological activities such as being efficient inhibitors of the multidrug resistance (MDR) efflux pump (e.g., of Staphylococcus aureus ): this activity had been serendipiously employed in traditional medicine (without knowledge of the mechanism) in the treatment of leprosy with chaulmoogra oil. This oil, which is obtained from fruits (kernels) of H. wightiana , contains besides hydnocarpin mainly cyclopentenoic fatty acids [ 16 ], which show pronounced antibiotic activity and inhibit multiplication of mycobacteria [ 17 ]. Combination of these antibiotics together with hydnocarpin (MDR inhibitor) helped to treat such a persistent disease like leprosy caused by M. leprae .…”