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In this paper, we describe our discovery of burnettiene A (1) as an antimalarial compound from the culture broth of Lecanicillium primulinum (current name: Flavocillium primulinum) FKI-6715 strain utilizing our original multidrug-sensitive yeast system. This polyene-decalin polyketide natural product was originally isolated as an antifungal active compound from Aspergillus burnettii. However, the antifungal activity of 1 has been revealed in only one fungal species, and the mechanism of action of 1 remains unknown. After the validation of mitochondrial function inhibitory of 1, we envisioned a new antimalarial drug discovery platform based on mitochondrial function inhibitory activity. We evaluated antimalarial activity and 1 showed antimalarial activity against Plasmodium falciparum FCR3 (chloroquine sensitive) and the K1 strain (chloroquine resistant). Our study revealed the utility of our original screening system based on a multidrug-sensitive yeast and mitochondrial function inhibitory activity for the discovery of new antimalarial drug candidates., (© The Author(s) 2024. Published by Oxford University Press on behalf of Japan Society for Bioscience, Biotechnology, and Agrochemistry.)

The mitochondrial machineries presiding over ATP synthesis via oxidative phosphorylation are promising druggable targets. Fusaramin, a 3-acyl tetramic acid isolated from Fusarium concentricum FKI-7550, is an inhibitor of oxidative phosphorylation in Saccharomyces cerevisiae mitochondria, although its target has yet to be identified. Fusaramin significantly interfered with [3H]ADP uptake by yeast mitochondria at the concentration range inhibiting oxidative phosphorylation. A photoreactive fusaramin derivative (pFS-5) specifically labeled voltage-dependent anion channel 1 (VDAC1), which facilitates trafficking of ADP/ATP across the outer mitochondrial membrane. These results strongly suggest that the inhibition of oxidative phosphorylation by fusaramin is predominantly attributable to the impairment of VDAC1 functions. Fusaramin also inhibited FoF1-ATP synthase and ubiquinol-cytochrome c oxidoreductase (complex III) at concentrations higher than those required for the VDAC inhibition. Considering that other tetramic acid derivatives are reported to inhibit FoF1-ATP synthase and complex III, natural tetramic acids were found to elicit multiple inhibitory actions against mitochondrial machineries., (© The Author(s) 2021. Published by Oxford University Press on behalf of Japan Society for Bioscience, Biotechnology, and Agrochemistry.)

A new decalin, decatamariic acid, was isolated from a cultured broth of the fungus Aspergillus tamarii FKI-6817. Its absolute configuration was elucidated by NMR and electronic circular dichroism. Decatamariic acid (10 μM) elicited ~50% inhibition of the ATP production in mitochondria isolated from wild-type Saccharomyces cerevisiae without affecting the activities of respiratory enzymes. The action manner of this compound may be interesting as a possible seed for new pesticides.

Two new tetramic acid derivatives, traminines A (1) and B (2), were isolated from a culture broth of Fusarium concentricum FKI-7550 by bioassay-guided fractionation using multidrug-sensitive Saccharomyces cerevisiae 12geneΔ0HSR-iERG6. The chemical structures of 1 and 2 were elucidated by NMR studies. Compounds 1 and 2 inhibited the growth of the multidrug-sensitive yeast strain on nonfermentable medium containing glycerol, but not on fermentable medium containing glucose. These results strongly suggest that they target mitochondrial machineries presiding over ATP production via oxidative phosphorylation. Throughout the assay monitoring overall ADP-uptake/ATP-release in yeast mitochondria, 1 and 2 were shown to inhibit one or more enzymes involving oxidative phosphorylation. Based on biochemical characterization, we found that the interference with oxidative phosphorylation by 1 is attributable to the dual inhibition of complex III and FoF1-ATPase, whereas that by 2 is solely due to the inhibition of complex III. [ABSTRACT FROM AUTHOR]