Modes of antifungal action of (2E)-Alkenals against Saccharomyces cerevisiae

A series of aliphatic (2E)-alkenals from C-5 to C-14 were tested for their antifungal activity against Saccharomyces cerevisiae ATCC 7754. (2E)-Undecenal (C-11) was found to be the most effective with the minimum fungicidal concentration (MFC) of 6.25 mug/mL, followed by (2E)-decenal (C-10) with an MFC of 12.5 mug/mL. The time-kill curve study showed that (2E)-undecenal was fungicidal against S. cerevisiae at any growth stage, and this activity was not influenced by pH values. The (2E)-alkenals inhibited glucose-induced acidification by inhibiting the plasma membrane H+-ATPase. The primary antifungal action of medium-chain (C-9-C-12) (2E)-alkenals against S. cerevisiae comes from their ability to function as nonionic surface-active agents (surfactants), disrupting the native membrane-associated function nonspecifically. Hence, the antifungal activity of (2E)-alkenals is mediated by biophysical processes, and the maximum activity can be obtained when the balance between the hydrophilic and hydrophobic portions becomes the most appropriate.