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

Synthesis and biological evaluation of nectriatide derivatives, potentiators of amphotericin B activity

Nectriatide 1a, a naturally occurring cyclic tetrapeptide, has been reported to a potentiator of amphotericin B (AmB) activity. In order to elucidate its structure-activity relationships, we synthesized nectriatide derivatives with different amino acids in solution-phase synthesis and evaluated AmB-potentiating activity against Candida albicans. Among them, C-and N-terminal protected linear peptides were found to show the most potent AmB-potentiating activity.

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.

Recent developments on the anti-Candida effect of amphotericin B combined with a second drug - a mini-review

Invasive Candida infections threaten human health due to the increasing incidence of resistance to the currently available antifungal agents. Amphotericin B (AMB) is the gold standard therapy to treat these infections. Nevertheless, the use of such substance in the clinic is aggravated by its toxicity. Since AMB binds to membrane sterols, it forms pores on human plasma membranes, mainly in kidney cells, leading to nephrotoxicity. The combination of this drug to a second substance could allow for the use of smaller concentrations of AMB, consequently lowering the probability of adverse effects. This mini-review summarizes information regarding an array of substances that enhance AMB antifungal activity. It may be noticed that several of these compounds target plasma membrane. Interestingly, substances approved for human use also presented combinatory anti-Candida activity with AMB. These data reinforce the potential of associating AMB to another drug as a promising therapeutical alternative to treat Candida infections. Further studies, regarding mechanism of action, pharmacokinetics and toxicity parameters must be conducted to confirm the role of these substances as adjuvant agents in candidiasis therapy.

[Comprehensive Studies on the Synthetic Organic Chemistry of Unique Bioactive Natural Products; Total Synthesis, Drug Discovery, and Development of New Reactions]

Research on natural product chemistry via organic chemistry ranges from isolation and structural elucidation to total synthesis, drug discovery, and chemical biology. Discoveries in organic chemistry, such as novel reactions and synthetic strategies, are enabled by the studies of total synthesis. Thus, organic (synthetic) chemistry and natural product chemistry are correlated. We conducted comprehensive studies, including structure-activity relationship, drug discovery, and total synthesis studies, on the synthetic organic chemistry of natural products with unique biological activities and the development of novel reactions discovered through these products. This review describes the total synthesis of simpotentin, a novel potentiator of amphotericin B, and the development of the novel lactonization reactions of homopropargyl alcohols via intramolecular ketene trapping.

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.

An efficient Agrobacterium tumefaciens-mediated transformation method for Simplicillium subtropicum (Hypocreales: Cordycipitaceae)

Filamentous fungi are the organisms of choice for most industrial biotechnology. Some species can produce a variety of secondary metabolites and enzymes of commercial interest, and the production of valuable molecules has been enhanced through different molecular tools. Methods for genetic manipulation and transformation have been essential for the optimization of these organisms. The genus Simplicillium has attracted increased attention given several potential biotechnological applications. The Simplicillium genus harbors several entomopathogenic species and some isolates have been explored for bioremediation of heavy metal contaminants. Furthermore, the myriad of secondary metabolites isolated from Simplicillium spp. render these organisms as ideal targets for deep exploration and further biotechnological mining possibilities. However, the lack of molecular tools hampered the exploration of this genus. Thus, an Agrobacterium tumefaciens-mediated transformation method was established for Simplicillium subtropicum, employing the far-red fluorescent protein TURBOFP635/Katushka, as a visual marker, and the selection marker SUR gene, that confers resistance to chlorimuron ethyl. Notably, one round of transformation using the established method yielded almost 400 chlorimuron resistant isolates. Furthermore, these transformants displayed mitotic stability for, at least, five generations. We anticipate that this method can be useful for deep molecular exploration and improvement of strains in the Simplicillium genus.

Taxonomic and phylogenetic characterizations reveal four new species of Simplicillium (Cordycipitaceae, Hypocreales) from Guizhou, China

Simplicillium species are commonly found from soil, seawater, rock surface, decayed wood, air and as symbiotic, endophytic, entomopathogenic and mycoparasitic fungi. Minority insect-associated species was reported. Simplicillium coccinellidae, S. hymenopterorum, S. neolepidopterorum and S. scarabaeoidea were introduced as the newly insect-associated species. The phylogenetic analyses of two combined datasets (LSU + RPB1 + TEF and SSU + ITS + LSU) revealed that S. coccinellidae and S. hymenopterorum were both nested in an independent clade. S. neolepidopterorum and S. scarabaeoidea have a close relationship with S. formicidae and S. lepidopterorum, respectively. S. neolepidopterorum can be easily distinguished from S. formicidae by ellipsoidal to cylindrical, solitary conidia which occasionally gather in short imbricate chains. S. scarabaeoidea could be easily distinguished from S. lepodopterorum by having longer phialides and larger conidia. Based on the morphological and phylogenetic conclusion, we determine the four newly generated isolates as new species of Simplicillium and a new combination is proposed in the genus Leptobacillium.

Asymmetric Palladium-Catalyzed Oxycarbonylation of Terminal Alkenes: Efficient Access to β-Hydroxy Alkylcarboxylic Acids

A novel Pd^II -catalyzed enantioselective oxycarbonylation of alkenes has been established. The ligand with an ethyl group at the C-6 position of Pyox plays a significant role in the intermolecular oxypalladation process, leading to high reactivity and excellent enantioselective control. Compared to the conventional methods, the reaction itself features alkenes as easily prepared starting materials, mild and operationally simple reaction conditions, and insensitivities to air and water. Moreover, this method allows for broad alkene substrate scope, excellent regio- and enantioselectivities, scalabilities and a wide array of applications, and provides a useful route for the convenient and straightforward synthesis of chiral β-hydroxy alkylcarboxylic acids/esters.

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.

Simplicilones A and B Isolated from the Endophytic Fungus Simplicillium subtropicum SPC3

Two new tetracyclic polyketides with a spirocenter, simplicilones A (1) and B (2) were isolated from the broth-culture of the endophytic fungus Simplicilliumsubtropicum (SPC3) in the course of our screening for new bioactive secondary metabolites. This endophytoic fungus is naturally harboured in the fresh bark of the Cameroonian medicinal plant Duguetia staudtii (Engl. and Diels) Chatrou. The planar structures of the simplicilones were elucidated by MS and 1D as well as 2D NMR spectroscopic techniques. The relative configuration was assigned by NOESY experiments in conjunction with coupling constants; subsequently, the absolute configurations were assigned by the modified Mosher’s method. The compounds showed weak cytotoxic effects against the cell line KB3.1 (in vitro cytotoxicity (IC₅₀) = 25 µg/mL for 1, 29 µg/mL for 2), but were inactive against the tested Gram-positive and Gram-negative bacteria as well as fungi.

Draft Genome Sequence of Simplicillium aogashimaense 72-15.1, a Putative Endophyte of Brachiaria brizantha

Here, we report a 29-Mb draft genome sequence of strain 72-15.1 of Simplicillium aogashimaense (Cordycipitaceae, Hypocreales). Strain 72-15.1 was a unique fungal isolate obtained from asymptomatic tillers of the tropical grass Brachiaria brizantha.

Here, we report a 29-Mb draft genome sequence of strain 72-15.1 of Simplicillium aogashimaense (Cordycipitaceae, Hypocreales). Strain 72-15.1 was a unique fungal isolate obtained from asymptomatic tillers of the tropical grass Brachiaria brizantha.

Three novel insect-associated species of Simplicillium (Cordycipitaceae, Hypocreales) from Southwest China

In this paper, we introduce three new species of Simplicillium, viz. S. cicadellidae, S. formicidae and S. lepidopterorum, which were isolated from an infected leafhopper, ant and carpenterworm, respectively. Morphological comparisons and phylogenetic analyses based on multigene datasets (LSU+RPB1+RPB2+TEF and ITS+LSU) support the establishment of the three new species. Simplicillium cicadellidae was distinguished from other species in morphological characteristics by having smaller phialides and ellipsoidal conidia, and lacking octahedral crystals. The reverse of colonies were yellowish (#FFBF00), especially in the middle, and radially sulcate. Simplicillium formicidae was morphologically distinguished from other by having longer phialides and filiform to fusoid conidia, and by lacking octahedral crystals. Simplicillium lepidopterorum was morphologically distinguished from other species by having smaller, ellipsoidal to fusiform conidia, and by lacking octahedral crystals. The reverse of the colony was pale white. The three new species are likely to be nourished by plant to animal (especially insect) nutrients based on the evolutionary pattern of the Hypocreales, and they are described herein as being clearly distinct from other species in Simplicillium.

Synergistic antifungal interactions of amphotericin B with 4-(5-methyl-1,3,4-thiadiazole-2-yl) benzene-1,3-diol

Amphotericin B (AmB) is a very potent antifungal drug with very rare resistance among clinical isolates. Treatment with the AmB formulations available currently is associated with severe side effects. A promising strategy to minimize the toxicity of AmB is reducing its dose by combination therapy with other antifungals, showing synergistic interactions. Therefore, substances that display synergistic interactions with AmB are still being searched for. Screening tests carried out on several dozen of synthetic 1,3,4-thiadiazole derivatives allowed selection of a compound called 4-(5-methyl-1,3,4-thiadiazole-2-yl) benzene-1,3-diol (abbreviated as C1), which shows strong synergistic interaction with AmB and low toxicity towards human cells. The aim of the present study was to investigate the type of in vitro antifungal interactions of the C1 compound with AmB against fungal clinical isolates differing in susceptibility. The results presented in the present paper indicate that the C1 derivative shows strong synergistic interaction with AmB, which allows the use of a dozen to several dozen times lower AmB concentration necessary for 100% inhibition of the growth of pathogenic fungi in vitro. Synergistic interactions were noted for all tested strains, including strains with reduced sensitivity to AmB and azole-resistant isolates. These observations give hope for the possibility of application of the AmB - C1 combinatory therapy in the treatment of fungal infections.

Total Synthesis and Absolute Configuration of Simpotentin, a Potentiator of Amphotericin B Activity

The total synthesis of simpotentin (1), a new potentiator of amphotericin B activity against Candida albicans, was achieved. Our research results enabled the access of all stereoisomers of 1 and the elucidation of the unknown absolute configuration of 1. Furthermore, one of the stereoisomers is a better amphotericin B potentiator than 1 and is an excellent lead compound for the development of a novel amphotericin B potentiator.