Antifungal properties of 2-alkynoic acids and their methyl esters

Abstract

Thirteen 2-alkynoic acids and their methyl esters (C3–C12, C14, C16, and C18) were tested against Aspergillus niger, Trichoderma viride, and Myrothecium verrucaria in Sabouraud dextrose agar at pH 4.0 and 5.6. Toxicity to Candida albicans, Trichophyton mentagrophytes, and Mucor mucedo was determined in the same medium at pH 5.6 and 7.0 in the absence and presence of 10% beef serum. The fungitoxicity of the acids was influenced by chain length, pH of the medium, and absence or presence of adsorbents. The toxicity of the esters was influenced primarily by chain length and to a lesser extent by the pH of the medium and the presence of beef serum. The order of activity of the 2-alkynoic acids is C10 = C11 = C12 > C14 = C16 > C9 > C8 > C7.When compared with other fatty acid analogs, the order of fungitoxicity on a weight basis is 2-alkynoic acids > 2-alkenoic acids > alkanoic acids > 2-bromoalkanoic acids > 2-fluoroalkanoic acids. There is an inverse relationship between chain length and pKa of the acids, suggesting that partition behavior is a fundamental determinant of fungitoxicity along with the effect of adsorbents.