Synergistic action of amphotericin B and antioxidants against certain opportunistic yeast pathogens

Results of earlier turbidimetric growth experiments showed that certain antioxidants prolonged the antifungal activity of amphotericin B (AB) against Candida albicans, presumably by retarding autoxidative destruction of the drug. Viability studies were designed to examine this in more detail. Subinhibitory concentrations of either butylated hydroxyanisole, n-propyl gallate, or nordihydroguaiaretic acid in combination with fungistatic levels of AB exerted synergistic fungicidal activity against two strains of C. albicans and one of C. parapsilosis. Although synergism was not seen in tests with a strain of Torulopsis glabrata, antioxidants prolonged the inhibitory action of AB against this organism. On the basis of these findings and other considerations that are discussed, it is suggested that stabilization of AB and the ability to act synergistically with AB represent two distinctly different effects of the antioxidants.