Antifungal activity of octyl gallate.

Antifungal activities of propyl (C3), octyl (C8) and dodecyl (C12) gallates (3,4,5-trihydroxybenzoate) were tested against Saccharomyces cerevisiae ATCC7754 and Zygosaccharomyces bailii ATCC 60483. Octyl gallate was found to be the only active compound with the minimum fungicidal concentration of 25 microg/ml (89 microM) against S. cerevisiae and of 50 microg/ml (177 microM) against Z. bailii, respectively. The inactivation study showed that octyl gallate was fungicidal against both S. cerevisiae and Z. bailii at any stage of growth. These fungicidal activities were not influenced by pH values. Octyl gallate at 100 microg /ml reduced plasma membrane fluidity to 48% of control. On the other hand, dodecyl gallate at the same concentration reduced it to 76% of control. Only octyl gallate inhibited glucose-induced medium acidification, indicating direct or indirect inhibition of plasma membrane H +-ATPase. The primary fungicidal activity of octyl gallate comes from its ability to act as a nonionic surface-active agent (surfactant), though it can not be inferred that membrane damage, such as a decrease in the membrane fluidity, is the only cause of the lethal effect.