Utilizing Yeast as a Model Organism for Drug Discovery Against Eukaryotic Infections

ABSTRACT

Eukaryotic pathogens are responsible for several serious human diseases, however, most drugs used as treatment regimens are ineffective while others still in use are toxic. This study seeks to identify bioactive molecules from wood decay fungal (WDF) extracts with activity against eukaryotic pathogens (especially Candida albicans and Plasmodium falciparum). The Saccharomyces cerevisiae model organism for eukaryotic cell biology studies is extensively used to screen bioactive molecules because it allows for rapid. Twelve WDF cultures were extracted with ethyl acetate, and the extracts were screened against C. albicans and S. cerevisiae by the disc diffusion method. Phenotypic array assays were also conducted on selected wood decay fungal extracts. The 3 most active extracts were then fractionated via bioactivity guided fractionation using different chromatographic techniques (solvent partition chromatography, size-exclusion chromatography and preparative TLC). The antifungal and antiplasmodial activities of the fractions were confirmed using MTT assay and SYBR Green 1 growth inhibition assays respectively.

The phenotypic array assays performed on the selected wood decay fungal extracts showed different responses to C. albicans and S. cerevisiae, and this led to the selection of top the 3 most-effective extracts as the best candidate for natural product isolation. After an extensive bioactivity-guided fractionation, 49 out of a total of 125 2D Preparative TLC fractions showed antifungal activities in the MTT assay while 47 of the 55 second dimensional preparative TLC fractions showed antiplasmodial activities in the SYBR Green 1 growth inhibition assay. These findings define wood decay fungi as a viable source of antifungal and antiplasmodial compounds, which can be pre-selected using S. cerevisiae over hemolysis problems posed by the total fungal extracts. It will take larger volumes xiv of fungal cultures to finally isolate the many active compounds for structural development and possible clinical development.