Fusaramin, an antimitochondrial compound produced by Fusarium sp., discovered using multidrug-sensitive Saccharomyces cerevisiae

Rhodium-Catalyzed Difunctionalization of Alkenes Using Cyclic 1,3-Dicarbonyl-Derived Iodonium Ylides

Herein, we introduce an iodonium ylide strategy to achieve novel α-alkylation of cyclic 1,3-dicarbonyls through harnessing C(sp3)-Rh species generated from 5-exo-trig cyclization to provide rapid access to molecular hybridization of medically important isoindolin-1-ones and cyclic 1,3-dicarbonyls from readily available substrates. This approach features mild conditions, good yield, excellent functional group tolerance, and the simultaneous formation of two new chemical bonds and one stereogenic center. Moreover, the hydroxyl group of resulting product provides a good handle for downstream transformations. Importantly, we also demonstrate this strategy can be achieved in a one-pot manner. A C(sp3)-Rh complex was prepared and proved to be the key intermediate.

Total Synthesis of Fusaramin, Enabling Stereochemical Elucidation, Structure-Activity Relationship, and Uncovering the Hidden Antimicrobial Activity against Plant Pathogenic Fungi

Fusaramin (1) was isolated as a mitochondrial inhibitor. However, the fungal producer stops producing 1, which necessitates us to supply 1 by total synthesis. We proposed the complete stereochemical structure based on the biosynthetic pathway of sambutoxin. We have established concise and robust total synthesis of 1, enabling us to determine the complete stereochemical structure and to elucidate the structure-activity relationship, and uncover the hidden antiplant pathogenic fungal activity.

Fusarium-Derived Secondary Metabolites with Antimicrobial Effects

Fungal microbes are important in the creation of new drugs, given their unique genetic and metabolic diversity. As one of the most commonly found fungi in nature, Fusarium spp. has been well regarded as a prolific source of secondary metabolites (SMs) with diverse chemical structures and a broad spectrum of biological properties. However, little information is available concerning their derived SMs with antimicrobial effects. By extensive literature search and data analysis, as many as 185 antimicrobial natural products as SMs had been discovered from Fusarium strains by the end of 2022. This review first provides a comprehensive analysis of these substances in terms of various antimicrobial effects, including antibacterial, antifungal, antiviral, and antiparasitic. Future prospects for the efficient discovery of new bioactive SMs from Fusarium strains are also proposed.

A Combination Strategy of Multidrug-Sensitive Budding Yeast and Chemical Modifications Enabling to Find a New Overlooked Antifungal Compound, Sakurafusariene, from In-House Fractionated Library

In this report, we disclose our discovery of a new antifungal natural product, sakurafusariene (1), from an in-house fractionated library of the culture broth of Fusarium sp. FKI-7550 strain by using a combination strategy of multidrug-sensitive yeast and chemical modification. Throughout our investigation, we encountered challenges in the isolation of natural product 1. A chemical modification strategy via alkylation of 1 allowed for removal of the impurities enabling us to elucidate the structure of 1. Furthermore, we synthesized ester derivatives using a method inspired by the isolation study of 1, which gave us valuable information to understand a preliminary structure-activity relationship against Pyricularia oryzae growth inhibitory activity.

Natural tetramic acids elicit multiple inhibitory actions against mitochondrial machineries presiding over oxidative phosphorylation

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.

Biosynthesis of the Fusarium Mycotoxin (-)-Sambutoxin

4-Hydroxy-2-pyridone alkaloids have attracted attention for synthetic and biosynthetic studies due to their broad biological activities and structural diversity. Here, we elucidated the pathway and chemical logic of (-)-sambutoxin (1) biosynthesis. In particular, we uncovered the enzymatic origin of the tetrahydropyran moiety and showed that the p-hydroxyphenyl group is installed via a late-stage, P450-catalyzed oxidation of the phenylalanine-derived side chain rather than via a direct incorporation of tyrosine.

Traminines A and B, produced by Fusarium concentricum, inhibit oxidative phosphorylation in Saccharomyces cerevisiae mitochondria

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 F_oF₁-ATPase, whereas that by 2 is solely due to the inhibition of complex III.

Harzianic Acid from Trichoderma afroharzianum Is a Natural Product Inhibitor of Acetohydroxyacid Synthase

Acetohydroxyacid synthase (AHAS) is the first enzyme in the branched-chain amino acid biosynthetic pathway and is a validated target for herbicide and fungicide development. Here we report harzianic acid (HA, 1) produced by the biocontrol fungus Trichoderma afroharzianum t-22 (Tht22) as a natural product inhibitor of AHAS. The biosynthetic pathway of HA was elucidated with heterologous reconstitution. Guided by a putative self-resistance enzyme in the genome, HA was biochemically demonstrated to be a selective inhibitor of fungal AHAS, including those from phytopathogenic fungi. In addition, HA can inhibit a common resistant variant of AHAS in which the active site proline is mutated. Structural analysis of AHAS complexed with HA revealed the molecular basis of competitive inhibition, which differs from all known commercial AHAS inhibitors. The alternative binding mode also rationalizes the selectivity of HA, as well as effectiveness toward resistant mutants. A proposed role of HA biosynthesis by Tht22 in the rhizosphere is discussed based on the data.

Fusapyrone A, a γ-pyrone derived from a desert Fusarium sp

In this work, we isolated and characterized fusapyrone A (1), a new γ-pyrone derivative, along with six previously described compounds from the rice fermentation of Fusarium sp. CPCC 401218, a fungus collected from the desert. The structure of 1 was characterized using various spectroscopic analyses, such as MS, IR, 1D, and 2D NMR. The absolute configuration of 1 was determined through the use of ¹³C NMR chemical shifts, electronic circular dichroism (ECD) and optical rotation (OR) calculations. Compound 1 was found to have weak antiproliferative activity for Hela cells, with an IC₅₀ of 50.6 μM.[Formula: see text].

Catalytic Reactions and Energy Conservation in the Cytochrome bc1 and b6f Complexes of Energy-Transducing Membranes

This review focuses on key components of respiratory and photosynthetic energy-transduction systems: the cytochrome bc1 and b6f (Cytbc1/b6f) membranous multisubunit homodimeric complexes. These remarkable molecular machines catalyze electron transfer from membranous quinones to water-soluble electron carriers (such as cytochromes c or plastocyanin), coupling electron flow to proton translocation across the energy-transducing membrane and contributing to the generation of a transmembrane electrochemical potential gradient, which powers cellular metabolism in the majority of living organisms. Cytsbc1/b6f share many similarities but also have significant differences. While decades of research have provided extensive knowledge on these enzymes, several important aspects of their molecular mechanisms remain to be elucidated. We summarize a broad range of structural, mechanistic, and physiological aspects required for function of Cytbc1/b6f, combining textbook fundamentals with new intriguing concepts that have emerged from more recent studies. The discussion covers but is not limited to (i) mechanisms of energy-conserving bifurcation of electron pathway and energy-wasting superoxide generation at the quinol oxidation site, (ii) the mechanism by which semiquinone is stabilized at the quinone reduction site, (iii) interactions with substrates and specific inhibitors, (iv) intermonomer electron transfer and the role of a dimeric complex, and (v) higher levels of organization and regulation that involve Cytsbc1/b6f. In addressing these topics, we point out existing uncertainties and controversies, which, as suggested, will drive further research in this field.

Fusarium: a treasure trove of bioactive secondary metabolites

Covering up to December 2019Fusarium, one of the most common fungal genera, has received considerable attention because of its biosynthetic exuberance, the result of many unique gene clusters involved in the production of secondary metabolites. This review provides the first comprehensive analysis of the secondary metabolites unique to the genus Fusarium, describing their occurrence, bioactivity, and genome features.