Simplifungin and Valsafungins, Antifungal Antibiotics of Fungal Origin

Modulators for palmitoylation of proteins and small molecules

As an essential form of lipid modification for maintaining vital cellular functions, palmitoylation plays an important role in in the regulation of various physiological processes, serving as a promising therapeutic target for diseases like cancer and neurological disorders. Ongoing research has revealed that palmitoylation can be categorized into three distinct types: N-palmitoylation, O-palmitoylation and S-palmitoylation. Herein this paper provides an overview of the regulatory enzymes involved in palmitoylation, including palmitoyltransferases and depalmitoylases, and discusses the currently available broad-spectrum and selective inhibitors for these enzymes.

Update on fungal lipid biosynthesis inhibitors as antifungal agents

Fungal diseases today represent a world-wide problem. Poor hygiene and decreased immunity are the main reasons behind the manifestation of this disease. After COVID-19, an increase in the rate of fungal infection has been observed in different countries. Different classes of antifungal agents, such as polyenes, azoles, echinocandins, and anti-metabolites, as well as their combinations, are currently employed to treat fungal diseases; these drugs are effective but can cause some side effects and toxicities. Therefore, the identification and development of newer antifungal agents is a current need. The fungal cell comprises many lipids, such as ergosterol, phospholipids, and sphingolipids. Ergosterol is a sterol lipid that is only found in fungal cells. Various pathways synthesize all these lipids, and the activities of multiple enzymes govern these pathways. Inhibiting these enzymes will ultimately impede the lipid synthesis pathway, and this phenomenon could be a potential antifungal therapy. This review will discuss various lipid synthesis pathways and multiple antifungal agents identified as having fungal lipid synthesis inhibition activity. This review will identify novel compounds that can inhibit fungal lipid synthesis, permitting researchers to direct further deep pharmacological investigation and help develop drug delivery systems for such compounds.

New potentiators of amphotericin B activity, shodoamides A to C produced by Pseudophialophora sp. BF-0158

During our screening program for new potentiators of amphotericin B activity against Candida albicans, shodoamides A to C (1-3) were isolated from a culture broth of the fungus Pseudophialophora sp. BF-0158 fermented under shaking conditions. A known congener named shodoamide D (4) in this paper was obtained from a culture broth of the BF-0158 strain fermented under static conditions. The structures of 1-4 were assigned based on spectroscopic analyses, including NMR and MS, and were found to have a common N-(2´,3´,4´-trihydroxybutyl)-6-methyl-2,4-tetradecadienamide structure. Compounds 1-3 exhibited no antifungal activity, but they induced up to 32-fold increases in amphotericin B activity against C. albicans by a microdilution method.

New piericidin rhamnosides as potentiators of amphotericin B activity against Candida albicans produced by actinomycete strain TMPU-A0287

Four new piericidin rhamnosides (2, 4-6) together with three known piericidins (1, 3, 7) were isolated from the culture broth of the unidentified actinomycete strain TMPU-A0287 as potentiators of antifungal amphotericin B (AmB) activity. The structures of piericidins were elucidated by spectroscopic analyses, including NMR and MS. Compounds 2 and 4-6 possessed a ketone at C-10 and one or two methoxy groups on the rhamnose in their structures. Compounds 1-7 did not exhibit antifungal activity against Candida albicans and all potentiated AmB activity. The MIC values of AmB against C. albicans combined with 1-7 (4.0 μg ml-1) decreased from 0.50 to 0.063 or 0.031 μg ml-1, yielding an 8- or 16-fold increase in AmB activity.

Biosynthesis of the Sphingolipid Inhibitors Sphingofungins in Filamentous Fungi Requires Aminomalonate as a Metabolic Precursor

Sphingofungins belong to a group of structurally related sphingolipid inhibitors produced by fungi, which specifically inhibit serine palmitoyl transferases, enzymes catalyzing the initial step during sphingolipid biosynthesis. Sphingolipids are integral parts of the eukaryotic cell membrane, and disturbances in their homeostasis have been linked to various human diseases. It has been suggested that external interventions, via sphingolipid inhibitors, may represent a promising approach for alternative therapies. Here, we identified and elucidated the biosynthetic gene cluster responsible for the biosynthesis of sphingofungins B, C, and D in Aspergillus fumigatus. Moreover, in vitro analyses have shown that sphingofungin biosynthesis starts with the condensation of a C18 polyketide with the uncommon substrate aminomalonate. Furthermore, the investigations on sphingofungin E and F produced by Paecilomyces variotii pointed out that different aminomalonate derivatives are used as substrates for those chemical variants. This research boosts knowledge on the general biosynthesis of sphingolipid inhibitors in fungi.

The genus Simplicillium and Emericellopsis: A review of phytochemistry and pharmacology

The demand for novel and improved medicine from biological sources to cater to the biopharmaceutical sector has increased significantly in recent years. Among the vast and miscellaneous microbial diversity, fungi provide a prolific source of structurally unique and biologically active secondary metabolites. Natural products obtained from fungi have reformed the era of biomedicine, providing effective drugs that have diverse healing potential. In this review, we focus on the isolation, chemical structure, and bioactivity of biomolecules that have been identified and studied for the first time. Further, we also explain in substantial detail that how the vast uninvestigated Emericellopsis and Simplicillium species may serve as a potential treasure trove of chemically diverse compounds.

Podogigants A and B, two new potentiators of amphotericin B activity, from Sordariomycete Podostroma giganteum

Two new compounds, podogigants A (1) and B (2), were isolated from the culture broth of Podostroma giganteum. This is the first report on the identification of secondary metabolites in P. giganteum. The structures of 1 and 2 were elucidated through spectroscopic analysis, including 2D NMR spectroscopy assisted by chemical derivatization, which revealed the presence of farnesyl- and geranyl-hydroquinone structures, respectively. Compounds 1 and 2 exhibited no antifungal activity even at a concentration of 64 μg/mL, whereas they potentiated amphotericin B (AmB) activity against several species of fungi. In particular, 1 potentiated AmB activity against C. albicans and R. oryzae by up to 32-fold (MIC value of AmB decreased from 1.0 to 0.032 µg/mL), while 2 potentiated AmB activity against C. albicans by up to 16-fold.

Antifungal Drug Development: Targeting the Fungal Sphingolipid Pathway

Fungal infections are becoming more prevalent and problematic due to the continual rise of immune deficient patients as well as the progressive development of drug resistance towards currently available antifungal drugs. There has been a significant increase in the development of antifungal compounds with a similar mechanism of action of current drugs. In contrast, there has been very little progress in developing compounds inhibiting totally new fungal targets or/and fungal pathways. This review focuses on novel compounds recently discovered to target the fungal sphingolipids and their metabolizing enzymes.

Nectriatide, a Potentiator of Amphotericin B Activity from Nectriaceae sp. BF-0114

A new compound, designated nectriatide (1), was isolated as a potentiator of amphotericin B (AmB) activity against Candida albicans from the culture broth of Nectriaceae sp. BF-0114. This structure was elucidated based on spectroscopic analyses (1D and 2D NMR data), chemical methods, and total synthesis. Compound 1 was a unique cyclotetrapeptide consisting of l-N-methyltyrosine, anthranilic acid, l-alanine, and l-valine. Compound 1 and several synthetic derivatives, including linear peptides, potentiated AmB activity against C. albicans by up to 16-fold (the MIC value of AmB decreased from 0.5 μg/mL to 0.031 μg/mL in combination with test compound).

Depsidones and a dihydroxanthenone from the endophytic fungi Simplicillium lanosoniveum (J.F.H. Beyma) Zare & W. Gams PSU-H168 and PSU-H261

Three new compounds including two depsidones (simplicildones J and K) and one dihydroxanthenone (globosuxanthone E) together with nine known compounds were obtained from the crude extracts of two endophytic fungi Simplicillium lanosoniveum (J.F.H. Beyma) Zare & W. Gams PSU-H168 and PSU-H261 which were isolated from the leaves of Hevea brasiliensis. The structures were elucidated by spectroscopic evidence. The absolute configuration of globosuxanthone E was established by means of experimental and calculated TDDFT ECD data. Simplicildone K exhibited antibacterial activity against Staphylococcus aureus and methicillin-resistant S. aureus with equal MIC values of 128 μg/mL. Simplicildone K and globosuxanthone E displayed antifungal activity against Cryptococcus neoformans ATCC90113 with the same MIC values of 32 μg/mL. In addition, known botryohordine C and simplicildone A showed phosphodiesterase 5 inhibitory activity with the IC₅₀ values of 5.69 and 9.96 μM, respectively, and were noncytotoxic toward noncancerous Vero cells.

Simpotentin, a new potentiator of amphotericin B activity against Candida albicans, produced by Simplicillium minatense FKI-4981

Simpotentin, a new potentiator of amphotericin B activity against Candida albicans and Cryptococcus neoformans, was isolated from the culture broth of Simplicillium minatense FKI-4981 by Diaion HP-20 column chromatography, centrifugal partition chromatography, and preparative HPLC. The structure of simpotentin was elucidated by spectroscopic analyses including NMR and MS. The compound has a mannose core to which two medium-chain fatty acids are linked. Simpotentin was found to potentiate amphotericin B activity against C. albicans by the microdilution method.

Sphingolipid biosynthesis in man and microbes

A new review covering up to 2018 Sphingolipids are essential molecules that, despite their long history, are still stimulating interest today. The reasons for this are that, as well as playing structural roles within cell membranes, they have also been shown to perform a myriad of cell signalling functions vital to the correct function of eukaryotic and prokaryotic organisms. Indeed, sphingolipid disregulation that alters the tightly-controlled balance of these key lipids has been closely linked to a number of diseases such as diabetes, asthma and various neuropathologies. Sphingolipid biogenesis, metabolism and regulation is mediated by a large number of enzymes, proteins and second messengers. There appears to be a core pathway common to all sphingolipid-producing organisms but recent studies have begun to dissect out important, species-specific differences. Many of these have only recently been discovered and in most cases the molecular and biochemical details are only beginning to emerge. Where there is a direct link from classic biochemistry to clinical symptoms, a number a drug companies have undertaken a medicinal chemistry campaign to try to deliver a therapeutic intervention to alleviate a number of diseases. Where appropriate, we highlight targets where natural products have been exploited as useful tools. Taking all these aspects into account this review covers the structural, mechanistic and regulatory features of sphingolipid biosynthetic and metabolic enzymes.