Effect of culture conditions on metabolites produced by the crinoid-derived fungus Aspergillus ruber 1017

New Ethylated Derivatives of Sulfur- and Nitrogen-Containing Artifacts from Tenodera sinensis Egg Pod and Their Anti-Renal Fibrosis

Three pairs of enantiomers and one achiral molecule that are new ethylated derivatives of sulfur and nitrogen-containing compounds named mantidisamides E-H (1-4), along with twenty known ones (5-24), were derived from the ethanol extract of Tenodera sinensis Saussure. The structures of these new compounds and their absolute configurations were assigned on the basis of spectroscopic analyses and computational methods. The assessment of activities in NRK-52e cells induced by TGF-β1 demonstrated that the previously undescribed compounds 1 and 2 exhibited a significant capacity to inhibit the expression of proteins (fibronectin, collagen I, and α-SMA). Moreover, the biological activity of these compounds was found to increase with rising concentrations. Notably, compounds 1-4 should be artifacts; however, undescribed compounds 1 and 2, which possessed obvious biological activity, might be attractive for chemists and biologists due to the potential for more detailed exploration of their properties. It is worth mentioning that compounds 1 and 2 remain novel structures even in the absence of the ethoxy group.

The potential of marine-derived piperazine alkaloids: Sources, structures and bioactivities

Marine-derived piperazine alkaloids (MDPAs) constitute a significant group of natural compounds known for their diverse structures and biological activities. Over the past five decades, substantial efforts have been devoted to isolating these alkaloids from marine sources and characterizing their chemical and bioactive profiles. To date, a total of 922 marine-derived piperazine alkaloids have been reported from various marine organisms. These compounds demonstrate a wide range of pharmacological properties, including cytotoxicity, antibacterial, antifungal, antiviral, and various other activities. Notably, among these activities, cytotoxicity emerges as the most prominent characteristic of marine-derived piperazine alkaloids. This review also summarizes the structure-activity relationship (SAR) studies associated with the cytotoxicity of these compounds. In summary, our objective is to provide an overview of the research progress concerning marine-derived piperazine alkaloids, with the aim of fostering their continued development and utilization.

Antibacterial Indole Diketopiperazine Alkaloids from the Deep-Sea Cold Seep-Derived Fungus Aspergillus chevalieri

A large body of fungal secondary metabolites has been discovered to exhibit potent antibacterial activities with distinctive mechanisms and has the potential to be an untapped resource for drug discovery. Here, we describe the isolation and characterization of five new antibacterial indole diketopiperazine alkaloids, namely 24,25-dihydroxyvariecolorin G (1), 25-hydroxyrubrumazine B (2), 22-chloro-25-hydroxyrubrumazine B (3), 25-hydroxyvariecolorin F (4), and 27-epi-aspechinulin D (5), along with the known analogue neoechinulin B (6) from a fungal strain of deep-sea cold seep-derived Aspergillus chevalieri. Among these compounds, 3 and 4 represented a class of infrequently occurring fungal chlorinated natural products. Compounds 1-6 showed inhibitory activities against several pathogenic bacteria with MIC values ranging from 4 to 32 μg/mL. It was revealed that compound 6 could induce structural damage to the Aeromonas hydrophila cells based on the observation by scanning electron microscopy (SEM), which led to the bacteriolysis and death of A. hydrophila, suggesting that neoechinulin B (6) might be a potential alternative to novel antibiotics development.

Coupling Microplate-Based Antibacterial Assay with Liquid Chromatography for High-Resolution Growth Inhibition Profiling of Crude Extracts: Validation and Proof-of-Concept Study with Staphylococcus aureus

With the identification of novel antibiotics from nature being pivotal in the fight against human pathogenic bacteria, there is an urgent need for effective methodologies for expedited screening of crude extracts. Here we report the development and validation of a simple and dye-free antimicrobial assay in 96-well microplate format, for both determination of IC₅₀ values and high-resolution inhibition profiling to allow pin-pointing of bioactive constituents directly from crude extracts. While commonly used antimicrobial assays visualize cell viability using dyes, the developed and validated assay conveniently uses OD₆₀₀ measurements directly on the fermentation broth. The assay was validated with an investigation of the inhibitory activity of DMSO against Staphylococcus aureus, temperature robustness, interference by coloured crude extracts as well as inter-day reproducibility. The potential for high-resolution S. aureus growth inhibition profiling was evaluated on a crude extract of an inactive Alternaria sp., spiked with ciprofloxacin.

Marine-derived fungi as a source of bioactive indole alkaloids with diversified structures

Marine-derived fungi are well known as rich sources of bioactive natural products. Growing evidences indicated that indole alkaloids, isolated from a variety of marine-derived fungi, have attracted considerable attention for their diverse, challenging structural complexity and promising bioactivities, and therefore, indole alkaloids have potential to be pharmaceutical lead compounds. Systemic compilation of the relevant literature. In this review, we demonstrated a comprehensive overview of 431 new indole alkaloids from 21 genera of marine-derived fungi with an emphasis on their structures and bioactivities, covering literatures published during 1982-2019.

An Updated Review on the Secondary Metabolites and Biological Activities of Aspergillus ruber and Aspergillus flavus and Exploring the Cytotoxic Potential of Their Isolated Compounds Using Virtual Screening

The secondary metabolites and biological activities of Aspergillus ruber and Aspergillus flavus were comprehensively reported. About 70 compounds were isolated from both species that belong to different classes using conventional and advanced chromatographic techniques and unambiguously elucidated employing one- and two-dimensional nuclear magnetic resonance (1D and 2D NMR) and high resolution mass spectrometry (HRMS). Some of them displayed promising antiviral, anti-inflammatory, and antioxidant activities. In silico studies were conducted on human cyclin-dependent kinase 2 (CDK-2), human DNA topoisomerase II (TOP-2), and matrix metalloprotinase 13 (MMP-13) in an effort to explore the cytotoxic potential of the diverse compounds obtained from both Aspergillus species. 1,6,8-Trihydroxy-4-benzoyloxy-3-methylanthraquinone (23) revealed the most firm fitting with the active pockets of CDK-2 and MMP-13; meanwhile, variecolorin H alkaloid (14) showed the highest fitting within TOP-2 with ∆G equals to −36.51 kcal/mole. Thus, fungal metabolites could offer new drug entities for combating cancer. Relevant data about both Aspergillus species up to August 2020 were gathered from various databases comprising Scifinder (https://scifinder.cas.org/scifinder/login) for secondary metabolite-related studies; meanwhile, for biology-related articles, data were collected from both PubMed (http://www.ncbi.nlm.nih.gov/pubmed/) and Web of Knowledge (http://www.webofknowledge.com) as well.

An Economical High-Throughput "FP-Tag" Assay for Screening Glycosyltransferase Inhibitors*

O-GlcNAc transferase (OGT) is involved in many cellular processes, and selective OGT inhibitors are valuable tools to investigate O-GlcNAcylation functions, and could potentially lead to therapeutics. However, high-throughput OGT assays that are suitable for large-scale HTS and can identify inhibitors targeting both acceptor, donor sites, and allosteric binding-sites are still lacking. Here, we report the development of a high-throughput "FP-Tag" OGT assay with bovine serum albumin (BSA) as a low-cost and superior "FP-Tag". With this assay, 2-methyleurotinone was identified as a low-micromolar OGT inhibitor. This type of assay with BSA as "FP-Tag" would find more applications with other glycosyltransferases.

Novel piperazine-2,5-dione analogs bearing 1H-indole: Synthesis and biological effects

In this work, a series of novel piperazine-2,5-dione derivatives bearing indole analogs (2a-2q) was designed and synthesized. The synthesized compounds were characterized by IR, ¹H NMR, ¹³C NMR spectroscopy, and ESI-MS. They were then evaluated for their anti-depressant, anti-inflammatory, and analgesic activities in vivo. The experimental results revealed that all the compounds showed clear anti-depressant, anti-inflammatory, and analgesic effects at a dose of 10 mg/kg. Among them, compounds 2e and 2q exhibited the best anti-depressant effects (the percent decreases in the duration of immobility were 70.2% and 71.2%, respectively), which were similar to that of fluoxetine (67.9%) in the forced swim test. Additionally, compounds 2e and 2q also displayed good anti-inflammatory and analgesic activities. Literature reports have highlighted the anti-inflammatory and analgesic effects of anti-depressant drugs, suggesting that they may have a similar mechanism of action. Therefore, further studies to investigate the possible mechanisms of action of compounds 2e and 2q are warranted.

Classification of Aspergillus, Penicillium, Talaromyces and related genera (Eurotiales): An overview of families, genera, subgenera, sections, series and species

The Eurotiales is a relatively large order of Ascomycetes with members frequently having positive and negative impact on human activities. Species within this order gain attention from various research fields such as food, indoor and medical mycology and biotechnology. In this article we give an overview of families and genera present in the Eurotiales and introduce an updated subgeneric, sectional and series classification for Aspergillus and Penicillium. Finally, a comprehensive list of accepted species in the Eurotiales is given. The classification of the Eurotiales at family and genus level is traditionally based on phenotypic characters, and this classification has since been challenged using sequence-based approaches. Here, we re-evaluated the relationships between families and genera of the Eurotiales using a nine-gene sequence dataset. Based on this analysis, the new family Penicillaginaceae is introduced and four known families are accepted: Aspergillaceae, Elaphomycetaceae, Thermoascaceae and Trichocomaceae. The Eurotiales includes 28 genera: 15 genera are accommodated in the Aspergillaceae (Aspergillago, Aspergillus, Evansstolkia, Hamigera, Leiothecium, Monascus, Penicilliopsis, Penicillium, Phialomyces, Pseudohamigera, Pseudopenicillium, Sclerocleista, Warcupiella, Xerochrysium and Xeromyces), eight in the Trichocomaceae (Acidotalaromyces, Ascospirella, Dendrosphaera, Rasamsonia, Sagenomella, Talaromyces, Thermomyces, Trichocoma), two in the Thermoascaceae (Paecilomyces, Thermoascus) and one in the Penicillaginaceae (Penicillago). The classification of the Elaphomycetaceae was not part of this study, but according to literature two genera are present in this family (Elaphomyces and Pseudotulostoma). The use of an infrageneric classification system has a long tradition in Aspergillus and Penicillium. Most recent taxonomic studies focused on the sectional level, resulting in a well-established sectional classification in these genera. In contrast, a series classification in Aspergillus and Penicillium is often outdated or lacking, but is still relevant, e.g., the allocation of a species to a series can be highly predictive in what functional characters the species might have and might be useful when using a phenotype-based identification. The majority of the series in Aspergillus and Penicillium are invalidly described and here we introduce a new series classification. Using a phylogenetic approach, often supported by phenotypic, physiologic and/or extrolite data, Aspergillus is subdivided in six subgenera, 27 sections (five new) and 75 series (73 new, one new combination), and Penicillium in two subgenera, 32 sections (seven new) and 89 series (57 new, six new combinations). Correct identification of species belonging to the Eurotiales is difficult, but crucial, as the species name is the linking pin to information. Lists of accepted species are a helpful aid for researchers to obtain a correct identification using the current taxonomic schemes. In the most recent list from 2014, 339 Aspergillus, 354 Penicillium and 88 Talaromyces species were accepted. These numbers increased significantly, and the current list includes 446 Aspergillus (32 % increase), 483 Penicillium (36 % increase) and 171 Talaromyces (94 % increase) species, showing the large diversity and high interest in these genera. We expanded this list with all genera and species belonging to the Eurotiales (except those belonging to Elaphomycetaceae). The list includes 1 187 species, distributed over 27 genera, and contains MycoBank numbers, collection numbers of type and ex-type cultures, subgenus, section and series classification data, information on the mode of reproduction, and GenBank accession numbers of ITS, beta-tubulin (BenA), calmodulin (CaM) and RNA polymerase II second largest subunit (RPB2) gene sequences.

Secondary Metabolites from Marine-Derived Fungi from China

Marine-derived fungi play an important role in the search for structurally unique secondary metabolites, some of which show promising pharmacological activities that make them useful leads for drug discovery. Marine natural product research in China in general has made enormous progress in the last two decades as described in this chapter on fungal metabolites. This contribution covers 613 new natural products reported from 2001 to 2017 from marine-derived fungi obtained from algae, sponges, corals, and other marine organisms from Chinese waters. The genera Aspergillus (170 new natural products, 28%) and Penicillium (70 new natural products, 11%) were the main fungal producers of new natural products during the time period covered, whereas sponges (184 new natural products, 30%) were the most abundant source of new natural products, followed by corals (154 new natural products, 25%) and algae (130 new natural products, 21%). Close to 40% of all natural products covered in this contribution displayed various bioactivities. The major bioactivities reported were cytotoxicity against different cancer cell lines, antimicrobial (mainly antibacterial) activity, and antiviral activity, which accounted for 13%, 9%, and 3% of all natural products reported. In terms of structural classes, polyketides (188 new natural products, 31%) play a dominant role, and if prenylated polyketides and nitrogen-containing polyketides (included in meroterpenes and alkaloids in this contribution) are taken into account, their total number even exceeds 50%. Nitrogen-containing compounds including peptides (65 new natural products, 10%) and alkaloids (103 new natural products, 17%) are the second largest group.

A new O-cinnamoyl threonine derivative from gene adpA overexpression strain Streptomyces sp. HS-NF-1222A

A new O-cinnamoyl threonine derivative, O-(2-(3-methyloxiranyl) cinnamoyl) threonine (1), was isolated from the gene adpA overexpression strain Streptomyces sp. HS-NF-1222A. The structure of 1 was determined based on HRESIMS and extensive NMR analysis.

Marine natural products

Covering: January to December 2017This review covers the literature published in 2017 for marine natural products (MNPs), with 740 citations (723 for the period January to December 2017) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1490 in 477 papers for 2017), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. Geographic distributions of MNPs at a phylogenetic level are reported.

A Nonheme FeII/2-Oxoglutarate-Dependent Oxygenase Catalyzes a Double Bond Migration within a Dimethylallyl Moiety Accompanied by Hydroxylation

Prenylation of cyclodipeptides contributes largely to the structure diversification and biological activity. The prenylated products can be further metabolized by modifications like hydroxylation with cytochrome P450 enzymes or nonheme Fe^II/2-oxoglutarate-dependent oxygenases. Herein, we cloned and overexpressed NFIA_045530 from Neosartorya fischeri, which shares high sequence similarity with the nonheme Fe^II/2-oxoglutarate-dependent oxygenase FtmOx1_Af from Aspergillus fumigatus on the amino acid level. FtmOx1_Af is a member of the biosynthetic enzymes for fumitremorgin-type mycotoxins and catalyzes the conversion of fumitremorgin B to verruculogen by insertion of an oxygen molecule into the two prenyl moieties. The recombinant protein EAW25734 encoded by NFIA_045530 was purified to apparent homogeneity and then was used for incubation with intermediates of the fumitremorgin biosynthetic pathway. LC-MS analysis revealed no consumption of fumitremorgin B but good conversion with its biosynthetic precursor tryprostatin B in the presence of Fe^II and 2-oxoglutarate. Structure elucidation confirmed 22-hydroxylisotryprostatin B and 14α, 22-dihydroxylisotryprostatin B as the major enzyme products. Further detailed biochemical characterization led to the identification of a novel enzyme, which catalyzes a double bond migration within the dimethylallyl moiety of tryprostatin B with concomitant hydroxylation. Incubation with ¹⁸O₂-enriched atmosphere confirmed O₂ as the major origin of the hydroxyl groups. Solvent exchange was also observed for that at C22. LC-MS analysis confirmed the presence of 22-hydroxylisotryprostatin B in a Neosartorya fischeri extract, highlighting the role of this enzyme in the metabolism of intermediates of the fumitremorgin/verruculogen pathway. A plausible reaction mechanism implementing a radical rearrangement prior to accepting a hydroxyl radical from Fe^III is discussed.

Structural Diversity and Biological Activities of the Cyclodipeptides from Fungi

Cyclodipeptides, called 2,5-diketopiperazines (2,5-DKPs), are obtained by the condensation of two amino acids. Fungi have been considered to be a rich source of novel and bioactive cyclodipeptides. This review highlights the occurrence, structures and biological activities of the fungal cyclodipeptides with the literature covered up to July 2017. A total of 635 fungal cyclodipeptides belonging to the groups of tryptophan-proline, tryptophan-tryptophan, tryptophan-Xaa, proline-Xaa, non-tryptophan-non-proline, and thio-analogs have been discussed and reviewed. They were mainly isolated from the genera of Aspergillus and Penicillium. More and more cyclodipeptides have been isolated from marine-derived and plant endophytic fungi. Some of them were screened to have cytotoxic, phytotoxic, antimicrobial, insecticidal, vasodilator, radical scavenging, antioxidant, brine shrimp lethal, antiviral, nematicidal, antituberculosis, and enzyme-inhibitory activities to show their potential applications in agriculture, medicinal, and food industry.