Plant-derived tabersonine exert its antifungal activity by repressing the expression of ergosterol biosynthesis and cell wall mannoprotein encoding genes in Saccharomyces cerevisiae.

Plants have various mechanisms to defend themselves against fungal infection. Previous reports have shown that the extract of Voacanga africana seeds exhibits effective antifungal activity, which attracts many attentions to further identify the exact active constituents from the extract for potential antifungal drugs development. Tabersonine, a terpenoid indole alkaloid produced in many plant species, is the most abundant alkaloid accumulated in V. africana seeds. Further investigation shows that yeast growth is inhibited by tabersonine treatment and this growth inhibition is dose-dependent both on agar plates and in liquid medium. Microscopic analysis indicates that yeast cells with DMSO control treatment are growing very well with globose in shape, while some of tabersonine-treated yeast cells show irregular shape during cultivation. Furthermore, transcriptional analysis shows that tabersonine treatment obviously represses the expression of cell wall mannoprotein encoding genes (DAN1, TIR4) and ergosterol biosynthesis genes (ERG1, ERG2, ERG6, and ERG11), which indicates that tabersonine abundantly accumulated in V. africana seeds achieves its antifungal activity by possibly targeting the formation of cell wall and cell membrane in yeast.