New mycotoxins from the scale insect fungus Aschersonia coffeae Henn. BCC 28712

The Biosynthesis, Structure Diversity and Bioactivity of Sterigmatocystins and Aflatoxins: A Review

Sterigmatocystins and aflatoxins are a group of mycotoxins mainly isolated from fungi of the genera Aspergillus. Since the discovery of sterigmatocystins in 1954 and aflatoxins in 1961, many scholars have conducted a series of studies on their structural identification, synthesis and biological activities. Studies have shown that sterigmatocystins and aflatoxins have a wide range of biological activities such as antitumour, antibacterial, anti-inflammatory, antiplasmodial, etc. The sterigmatocystins and aflatoxins had been shown to be hepatotoxic and nephrotoxic in animals. This review attempts to give a comprehensive summary of progress on the chemical structural features, synthesis, and bioactivity of sterigmatocystins and aflatoxins reported from 1954 to April 2024. A total of 72 sterigmatocystins and 20 aflatoxins are presented in this review. This paper reviews the chemical diversity and potential activity and toxicity of sterigmatocystins and aflatoxins, enhances the understanding of sterigmatocystins and aflatoxins that adversely affect humans and animals, and provides ideas for their prevention, research and development.

Enantioselective Synthesis of 2,3,3a,8a-Tetrahydrofuro[2,3-b]benzofuran Scaffolds Enabled by Cu(II)/SPDO-Catalyzed [3+2] Cycloaddition of 2,3-Dihydrofuran and Quinone Esters

An asymmetric [3+2] cycloaddition of quinone esters with 2,3-dihydrofuran has been realized via a newly developed Cu(II)/SPDO complex. It provides straightforward access to 2,3,3a,8a-tetrahydrofuro[2,3-b]benzofurans (TFB) with high enantioselectivity (up to 97.5:2.5 er) and diastereoselectivity (all >20:1 dr). The resulting adducts contain two adjacent stereocenters and a continuously functionalized benzene ring. Additionally, this transformation could be easily performed on a gram scale, allowing for expedient synthesis of natural dihydroaflatoxin D2 and aflatoxin B2.

Diverse host-associated fungal systems as a dynamic source of novel bioactive anthraquinones in drug discovery: Current status and future perspectives

BACKGROUND

Despite, a large number of bioactive anthraquinones (AQs) isolated from host-living fungi, only plant-derived AQs were introduced in the global consumer markets. Host-living fungi represents renewable and extendible resources of diversified metabolites to be exploited for bioactives production. Unique classes of AQs from fungi include halogenated and steroidal AQs, and absent from planta are of potential to explore for biological activity against urging diseases such as cancer and multidrug-resistant pathogens. The structural diversity of fungal AQs, monomers, dimers, trimers, halogenated, etc… results in a vast range of pharmacological activities.

AIM OF REVIEW

The current study capitalizes on uncovering the diversity and distribution of host-living fungal systems producing AQs in different terrestrial ecosystems ranging from plant endophytes, lichens, animals and insects. Furthermore, the potential bioactivities of fungal derived AQs i.e., antibacterial, antifungal, antiviral (anti-HIV), anticancer, antioxidant, diuretic and laxative activities are assembled in relation to their structure activity relationship (SAR). Analyzing for structure-activity relationship among fungal AQs may facilitate bioengineering of more potential analogues. Withal, elucidation of AQs biosynthetic pathways in fungi is discussed from different fungal hosts to open up new possibilities for potential biotechnological applications. Such comprehensive review unravels terrestrial host-living fungal systems as a treasure trove in drug discovery, in addition to future perspectives and trends for their exploitation in pharmaceutical industries.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Such comprehensive review unravels terrestrialhost-living fungal systems as a treasure trove in drug discovery, in addition to future perspectives and trends for their exploitation in pharmaceutical industries.

Two New Austocystin Analogs from the Marine-Derived Fungus Aspergillus sp. WHUF05236

Two new austocystin analogs, austocystin P (1) and austocystin Q (2), along with fourteen known compounds (3-16) were isolated from the fermentation extract of Aspergillus sp. WHUF05236. The planar structures of 1 and 2 were elucidated through 1D, 2D NMR and MS analyses. Their absolute configurations were determined by the time-dependent density functional (TDDFT)-ECD calculation. Compounds 3, 11, and 12 exhibited antimicrobial activities against Helicobacter pylori with MIC values ranging from 20.00 to 43.47 μM. Compounds 3, 6, and 7 showed cytotoxicities against the human colon cancer cell lines Hct-116 with IC₅₀ values of 101.79, 65.46, and 36.72 μM, respectively.

Next-generation microbial drugs developed from microbiome's natural products

Scientists working in natural products chemistry have been enticed by the current advancements being made in the discovery of novel "magic bullets" from microbes homed to all conceivable environments. Even though researchers continue to face challenges funneling the novel bioactive compounds in the global therapeutic industries, it seems most likely that the discovery of some "hit molecules" with significant biomedical applications is not that far. We applaud novel natural products for their ability to combat the spread of superbugs and aid in the prevention of currently observed antibiotic resistance. This in-depth investigation covers a wide range of microbiomes with a proclivity for synthesizing novel compounds to combat the spread of superbugs. Furthermore, we use this opportunity to explore various groups of secondary metabolites and their biosynthetic pathways in various microbiota found in mammals, insects, and humans. This systematic study, when taken as a whole, offers detail understanding on the biomedical fate of various groups of compounds originated from diverse microbiomes. For gathering all information that has been uncovered and released so far, we have also presented the huge diversity of microbes that are associated with humans and their metabolic products. To conclude, this concrete review suggests novel ideas that will prove immensely helpful in reducing the danger posed by superbugs while also improving the efficacy of antibiotics.

Fungal quinones: diversity, producers, and applications of quinones from Aspergillus, Penicillium, Talaromyces, Fusarium, and Arthrinium

Quinones represent an important group of highly structurally diverse, mainly polyketide-derived secondary metabolites widely distributed among filamentous fungi. Many quinones have been reported to have important biological functions such as inhibition of bacteria or repression of the immune response in insects. Other quinones, such as ubiquinones are known to be essential molecules in cellular respiration, and many quinones are known to protect their producing organisms from exposure to sunlight. Most recently, quinones have also attracted a lot of industrial interest since their electron-donating and -accepting properties make them good candidates as electrolytes in redox flow batteries, like their often highly conjugated double bond systems make them attractive as pigments. On an industrial level, quinones are mainly synthesized from raw components in coal tar. However, the possibility of producing quinones by fungal cultivation has great prospects since fungi can often be grown in industrially scaled bioreactors, producing valuable metabolites on cheap substrates. In order to give a better overview of the secondary metabolite quinones produced by and shared between various fungi, mainly belonging to the genera Aspergillus, Penicillium, Talaromyces, Fusarium, and Arthrinium, this review categorizes quinones into families such as emodins, fumigatins, sorbicillinoids, yanuthones, and xanthomegnins, depending on structural similarities and information about the biosynthetic pathway from which they are derived, whenever applicable. The production of these quinone families is compared between the different genera, based on recently revised taxonomy. KEY POINTS: • Quinones represent an important group of secondary metabolites widely distributed in important fungal genera such as Aspergillus, Penicillium, Talaromyces, Fusarium, and Arthrinium. • Quinones are of industrial interest and can be used in pharmacology, as colorants and pigments, and as electrolytes in redox flow batteries. • Quinones are grouped into families and compared between genera according to the revised taxonomy.

Generation of Stilbene Glycoside with Promising Cell Rejuvenation Activity through Biotransformation by the Entomopathogenic Fungus Beauveria bassiana

A stilbene glycoside (resvebassianol A) (1) with a unique sugar unit, 4-O-methyl-D-glucopyranose, was identified through biotransformation of resveratrol (RSV) by the entomopathogenic fungus Beauveria bassiana to obtain a superior RSV metabolite with enhanced safety. Its structure, including its absolute configurations, was determined using spectroscopic data, HRESIMS, and chemical reactions. Microarray analysis showed that the expression levels of filaggrin, HAS2-AS1, and CERS3 were higher, while those of IL23A, IL1A, and CXCL8 were lower in the resvebassianol A-treated group than in the RSV-treated group, as confirmed by qRT-PCR. Compound 1 exhibited the same regenerative and anti-inflammatory effects as RSV with no cytotoxicity in skin keratinocytes and TNF-α/IFN-γ-stimulated HIEC-6 cells, suggesting that compound 1 is a safe and stable methylglycosylated RSV. Our findings suggest that our biotransformation method can be an efficient biosynthetic platform for producing a broad range of natural glycosides with enhanced safety.

Bioactive Dimeric Tetrahydroxanthones with 2,2'- and 4,4'-Axial Linkages from the Entomopathogenic Fungus Aschersonia confluens

Thirteen tetrahydroxanthone dimers, atrop-ascherxanthone A (1), ascherxanthones C-G (2-6), and confluxanthones A-G (7-13), were isolated from the entomopathogenic fungus Aschersonia confluens BCC53152. The chemical structures were determined based on analysis of NMR spectroscopic and mass spectrometric data. The absolute configurations of compounds 1 and 7 were confirmed by single-crystal X-ray diffraction experiments, while the configurations of other compounds were assigned based upon evidence from NOESY and NOEDIFF experiments, modified Mosher's method, and ECD spectroscopic data together with biogenetic considerations. Compounds 1, 3-5, 7-11, and 13 showed antimalarial activity against Plasmodium falciparum (K1, multidrug-resistant strain) (IC₅₀ 0.6-6.1 μM), antitubercular activity against Mycobacterium tuberculosis H37Ra (MIC 6.3-25.0 μg/mL), and cytotoxicity against NCI-H187 (IC₅₀ 0.5-3.5 μM) and Vero (IC₅₀ 0.9-6.1 μM) cells. All tested compounds except for compound 9 exhibited cytotoxicity against KB cells (IC₅₀ 1.3-9.7 μM).

Xanthones and anthraquinones from the soil fungus Penicillium sp. DWS10-P-6

Two new xanthones, oxisterigmatocystins J and K (1-2), and two new anthraquinones, versicolorins D and E (3-4), were isolated from solid cultures of the fungus Penicillium sp. DWS10-P-6, together with twelve known compounds (5-16). Their structures, including their absolute configurations, were characterized on the basis of extensive 1D NMR, 2D NMR, MS and CD spectral data. The cytotoxic activities of compounds 1-12 against HL-60, MDA-MB-231 and PC-3 cells were also evaluated. Compounds 4 and 5 showed significant cytotoxic activity against the HL-60 cell line with IC₅₀ values of 1.65 μM and 1.05 μM, respectively.

Mycotoxins as inhibitors of protein tyrosine phosphatases from the deep-sea-derived fungus Aspergillus puniceus SCSIO z021

Nine new xanthone-type and anthraquinone-type mycotoxins including austocystins J-N (1-5), 7-chloro versicolorin A (6), 3'-hydroxy-8-O-methyl versicolorin B (7), 8-O-methyl versiconol (8) and 2',3'-dihydroxy versiconol (9), together with 17 known analogues (10-26) were isolated from an extract of the deep-sea-derived fungus Aspergillus puniceus SCSIO z021. Their structures were elucidated by detailed analysis of spectroscopic data, and their absolute configurations were further determined by quantum chemical calculations of ECD spectra or comparison of the experimental ECD spectra. Eleven hydrogenated austocystins were synthesized from 1-2, 10-15 and 17 by catalytic hydrogenation for bioactivities evaluation. Totally, 18 of the all 37 compounds showed strong toxicity against brine shrimps or Vero cell, and the toxicity of 8-O-methyldemethylsterigmatocystin (18) (LC₅₀ = 0.020 µM) against brine shrimps was higher than those of three positive controls. In addition, 22 of the isolated compounds also exhibited significant inhibitory activity against seven different protein tyrosine phosphatases (PTPs), among them austocystin H (15) and methyl-averantin (24) were the most potent inhibitors with IC₅₀ values of 0.20-3.0 µM. Their structure-bioactivity relationship was also discussed.

Environment Changes, Aflatoxins, and Health Issues, a Review

Crops contaminated by aflatoxins (AFs), the toxic and carcinogenic mycotoxins produced namely by Aspergillus flavus and Aspergillus parasiticus, have severe impacts on human health. Changes in temperature and water availability related to actual climate changes (increased temperature, heavy rainfalls, and droughts) are modulating factors of mould growth and production of mycotoxins. To protect human and animal health from the harmful effects caused by AFs, the development of a safe and effective multifaceted approach in combating food and feed contamination with AFs is necessary. This review aims to collect and analyze the available information regarding AF presence in food and feed to reinforce AF management and to prevent health issues related to the AF exposure in the light of actual climate changes.

Secondary metabolites from hypocrealean entomopathogenic fungi: novel bioactive compounds

Covering: 2014 up to the third quarter of 2019 Entomopathogens constitute a unique, specialized trophic subgroup of fungi, most of whose members belong to the order Hypocreales (class Sordariomycetes, phylum Ascomycota). These Hypocrealean Entomopathogenic Fungi (HEF) produce a large variety of secondary metabolites (SMs) and their genomes rank highly for the number of predicted, unique SM biosynthetic gene clusters. SMs from HEF have diverse roles in insect pathogenicity as virulence factors by modulating various interactions between the producer fungus and its insect host. In addition, these SMs also defend the carcass of the prey against opportunistic microbial invaders, mediate intra- and interspecies communication, and mitigate abiotic and biotic stresses. Thus, these SMs contribute to the role of HEF as commercial biopesticides in the context of integrated pest management systems, and provide lead compounds for the development of chemical pesticides for crop protection. These bioactive SMs also underpin the widespread use of certain HEF as nutraceuticals and traditional remedies, and allowed the modern pharmaceutical industry to repurpose some of these molecules as life-saving human medications. Herein, we survey the structures and biological activities of SMs described from HEF, and summarize new information on the roles of these metabolites in fungal virulence.

A new antimicrobial indoloditerpene from a marine-sourced fungus aspergillus versicolor ZZ761

A new indoloditerpene (1) and fifteen known compounds (2-16) were isolated from a marine-derived fungus Aspergillus versicolor ZZ761. Structure of the new compound was elucidated as (3 R,9S,12R,13S,17S,18S)-2-carbonyl-3-hydroxylemeniveol based on its HRESIMS data, NMR spectroscopic analyses, the Mosher's method, and ECD calculation. This new indoloditerpene (1) showed antimicrobial activities with MIC values of 20.6 μM against Escherichia coli and 22.8 μM against Candida albicans. Diorcinol (2) and versicolorin B (6) had activities in inhibiting the proliferation of human glioma U87MG and U251 cells with IC₅₀ values of 4.4 and 6.2 μM and 11.3 and 30.5 μM, respectively.

Akanthopyrones A-D, α-Pyrones Bearing a 4-O-Methyl-β-d-glucopyranose Moiety from the Spider-Associated Ascomycete Akanthomyces novoguineensis

Hypocrealean fungi have proved to be prolific bioactive metabolite producers; they have caught the attention of mycologists throughout the world. However, only a few studies on the insect and spider parasitic genus Akanthomyces have so far been carried out. In this study, we report the isolation, structural elucidation and biological activities of four unprecedented glycosylated α-pyrone derivatives, akanthopyrones A–D (1–4), from a culture of Akanthomyces novoguineensis collected in Thailand. The chemical structures of the akanthopyrones were determined by extensive 1D- and 2D-NMR, and HRMS spectroscopic analysis. Their absolute configurations were determined. Akanthopyrone A (1) exhibited weak antimicrobial activity against Bacillus subtilis DSM10 and cytotoxicity against the HeLa cell line KB-3-1, while akanthopyrone D (4) showed weak activity against Candida tenuis MUCL 29892.

Five Unprecedented Secondary Metabolites from the Spider Parasitic Fungus Akanthomyces novoguineensis

Five new compounds including the glycosylated β-naphthol (1, akanthol), a glycosylated pyrazine (2, akanthozine), and three amide derivatives including a hydroxamic acid derivative (3–5) were isolated from the spider-associated fungus Akanthomyces novoguineensis (Cordycipitaceae, Ascomycota). Their structures were elucidated by using high resolution mass spectrometry (HRMS) and NMR spectroscopy. In this study, the antimicrobial, cytotoxic, anti-biofilm, and nematicidal activities of the new compounds were evaluated. The distribution pattern of secondary metabolites in the species was also revealed in which more isolates of A. novoguineensis were encountered and their secondary metabolite profiles were examined using analytical HPLC with diode array and mass spectrometric detection (HPLC-DAD/MS). Remarkably, all isolated compounds are specifically produced by A. novoguineensis.

Mycotoxins from the Fungus Botryotrichum piluliferum

Two new sterigmatocystin derivatives, oxisterigmatocystins E and F (1 and 2, respectively), along with nine known compounds, oxisterigmatocystins G and H (3 and 4, respectively), sterigmatocystin (5), N-0532B (6), O-methylsterigmatocystin (7), N-0532A (8), 6-O-methylversicolorin A (9), 6,8-O-dimethylversicolorin A (10), and 8-O-methylaverufin (11), were isolated from the fungus Botryotrichum piluliferum. The structures of these mycotoxins were elucidated by spectroscopic evidence. Among these, compounds 3, 4, and 9 were discovered as natural products for the first time. Compounds 1, 3, and 4 displayed antimalarial activity toward Plasmodium falciparum (IC₅₀ = 7.9-23.9 μM). In addition, compounds 1-6 and 8-11 exhibited cytotoxicity against KB, MCF-7, and NCI-H187 cell lines (IC₅₀ = 0.38-78.6 μM). However, compounds 1-9 showed cytotoxic effects against the Vero cell line (IC₅₀ = 0.65-12.3 μM). This finding should promote awareness of the contamination of B. piluliferum in the food chain and agricultural soil.

Biologically Active Secondary Metabolites from the Fungi

Many Fungi have a well-developed secondary metabolism. The diversity of fungal species and the diversification of biosynthetic gene clusters underscores a nearly limitless potential for metabolic variation and an untapped resource for drug discovery and synthetic biology. Much of the ecological success of the filamentous fungi in colonizing the planet is owed to their ability to deploy their secondary metabolites in concert with their penetrative and absorptive mode of life. Fungal secondary metabolites exhibit biological activities that have been developed into life-saving medicines and agrochemicals. Toxic metabolites, known as mycotoxins, contaminate human and livestock food and indoor environments. Secondary metabolites are determinants of fungal diseases of humans, animals, and plants. Secondary metabolites exhibit a staggering variation in chemical structures and biological activities, yet their biosynthetic pathways share a number of key characteristics. The genes encoding cooperative steps of a biosynthetic pathway tend to be located contiguously on the chromosome in coregulated gene clusters. Advances in genome sequencing, computational tools, and analytical chemistry are enabling the rapid connection of gene clusters with their metabolic products. At least three fungal drug precursors, penicillin K and V, mycophenolic acid, and pleuromutilin, have been produced by synthetic reconstruction and expression of respective gene clusters in heterologous hosts. This review summarizes general aspects of fungal secondary metabolism and recent developments in our understanding of how and why fungi make secondary metabolites, how these molecules are produced, and how their biosynthetic genes are distributed across the Fungi. The breadth of fungal secondary metabolite diversity is highlighted by recent information on the biosynthesis of important fungus-derived metabolites that have contributed to human health and agriculture and that have negatively impacted crops, food distribution, and human environments.

A New Xanthone Glycoside from the Endolichenic Fungus Sporormiella irregularis

A new xanthone glycoside, sporormielloside (1), was isolated from an EtOAc extract of an endolichenic fungal strain Sporormiella irregularis (No. 71-11-4-1), along with two known xanthones (2, 3). Their structures were determined by detailed spectroscopic analysis (IR, MS, and 1D- and 2D-NMR), a chemical method, and a comparison of NMR data with closely related compounds previously reported. According to the structures of isolated compounds, their plausible biosynthetic pathway was deduced.

Quinofuracins A-E, produced by the fungus Staphylotrichum boninense PF1444, show p53-dependent growth suppression

Quinofuracins A-E, novel anthraquinone derivatives containing β-D-galactofuranose that were isolated from the fungus Staphylotrichum boninense PF1444, induced p53-dependent cell death in human tumor cells. The structures of quinofuracins A-E, including absolute configurations, were elucidated by extensive spectroscopic analysis and chemical transformation studies. Quinofuracins were classified into three groups according to the aglycone moieties. 5'-Oxoaverantin was present in quinofuracins A-C, whereas averantin and versicolorin B were identified in quinofuracins D and E, respectively. These quinofuracins induced p53-dependent growth suppression in human glioblastoma LNZTA3 cells.

Taxonomy, chemodiversity, and chemoconsistency of Aspergillus, Penicillium, and Talaromyces species

Aspergillus, Penicillium, and Talaromyces are among the most chemically inventive of all fungi, producing a wide array of secondary metabolites (exometabolites). The three genera are holophyletic in a cladistic sense and polythetic classes in an anagenetic or functional sense, and contain 344, 354, and 88 species, respectively. New developments in classification, cladification, and nomenclature have meant that the species, series, and sections suggested are natural groups that share many extrolites, including exometabolites, exoproteins, exocarbohydrates, and exolipids in addition to morphological features. The number of exometabolites reported from these species is very large, and genome sequencing projects have shown that a large number of additional exometabolites may be expressed, given the right conditions (“cryptic” gene clusters for exometabolites). The exometabolites are biosynthesized via shikimic acid, tricarboxylic acid cycle members, nucleotides, carbohydrates or as polyketides, non-ribosomal peptides, terpenes, or mixtures of those. The gene clusters coding for these compounds contain genes for the biosynthetic building blocks, the linking of these building blocks, tailoring enzymes, resistance for own products, and exporters. Species within a series or section in Aspergillus, Penicillium, and Talaromyces have many exometabolites in common, seemingly acquired by cladogenesis, but some the gene clusters for autapomorphic exometabolites may have been acquired by horizontal gene transfer. Despite genome sequencing efforts, and the many breakthroughs these will give, it is obvious that epigenetic factors play a large role in evolution and function of chemodiversity, and better methods for characterizing the epigenome are needed. Most of the individual species of the three genera produce a consistent and characteristic profile of exometabolites, but growth medium variations, stimulation by exometabolites from other species, and variations in abiotic intrinsic and extrinsic environmental factors such as pH, temperature, redox potential, and water activity will add significantly to the number of biosynthetic families expressed in anyone species. An example of the shared exometabolites in a natural group such as Aspergillus section Circumdati series Circumdati is that most, but not all species produce penicillic acids, aspyrones, neoaspergillic acids, xanthomegnins, melleins, aspergamides, circumdatins, and ochratoxins, in different combinations.