A new glucitol from an endophytic fungus Fusarium equiseti Salicorn 8

Endophytic Alternaria and Fusarium species associated to potato plants (Solanum tuberosum L.) in Iran and their capability to produce regulated and emerging mycotoxins

Endophytic fungi live inside virtually every plant species, without causing any apparent disease or damage to the host. Nevertheless, under particular conditions, mutualistic lifestyle of endophytes may change to pathogenic. In this study, the biodiversity of Alternaria and Fusarium species, the two most abundant endophytic fungi isolated from healthy potato plants in two climatically different regions of Iran, Ardebil in the north-west and Kerman in the south-east, was investigated. Seventy-five Fusarium strains and 83 Alternaria strains were molecularly characterized by multi-locus gene sequencing. Alternaria strains were characterized by the sequences of gpd and caM gene fragments and the phylogenetic tree was resolved in 3 well-separated clades. Seventy-three strains were included in the clade A, referred as Alternaria section, 6 strains were included in clade B, referred as Ulocladioides section, and 4 strains were included in clade C, referred as Infectoriae section. Fusarium strains, identified by sequencing the translation elongation factor 1α (tef1), β-tubulin (tub2) and internal transcribed spacer (ITS) genomic regions, were assigned to 13 species, viz. F. brachygibosum, F. clavum, F. equiseti, F. flocciferum, F. incarnatum, F. nirenbergiae, F. nygamai, F. oxysporum, F. proliferatum, F. redolens, F. sambucinum, F. solani and F. thapsinum. Twenty-six selected strains, representative of F. equiseti, F. nirenbergiae, F. oxysporum, F. nygamai, F. proliferatum, and F. sambucinum, were also tested for production of the mycotoxins deoxynivalenol (DON), nivalenol (NIV), diacetoxyscirpenol (DAS), T-2 toxin (T-2), beauvericin (BEA), enniatins (ENNs), fumonisins (FBs), fusaric acid (FA) and moniliformin (MON). None of the tested strains produced trichothecene toxins (DON, NIV, DAS and T-2). Two out of 2 F. equiseti isolates, 1/6 F. oxysporum, 1/3 F. proliferatum, and 1/9 F. nygamai did not produce any of the tested toxins; the rest of strains produced one or more BEA, ENNs, FBs, FA and MON toxins. The most toxigenic strain, F. nygamai ITEM-19012, produced the highest quantities of FBs (7946, 4693 and 4333 μg/g of B1, B2, and B3 respectively), along with the highest quantities of both BEA (4190 μg/g) and MON (538 μg/g). These findings suggest that contamination of potato tubers with mycotoxins in the field or at post-harvest, due to a change in lifestyle of endophytic microflora, should be carefully considered and furtherly investigated.

Ochrolines A-C, three new indole diketopiperazines from cultures of endophytic fungi Bionectria ochroleuca SLJB-2

Three new indole diketopiperazines, ochrolines A-C (1-3), along with three known compounds (4-6), were isolated and identified from the EtOAc extract of the solid fermentation of Bionectria ochroleuca SLJB-2. Notably, compound 1 featured a natural rarely-occurring caged skeleton with a 6/5/6/7 heterotetracyclic bridged ring system. The structures including absolute configurations of 1-3 were fully accomplished by extensive spectroscopic analyses, DFT GIAO 13C NMR and electronic circular dichroism (ECD) calculations. The plausible biogenetic pathways of these new indole diketopiperazines were also proposed. Moreover, the cytotoxic activity screening revealed that compound 2 exhibited moderate inhibitory effect against A549 with inhibition rate of 57.44% at the concentration of 50 μM and compound 1 exhibited mild inhibitory activities against A549, Hela and MCF-7.

Tapping into Tapajos: antibacterial potential of fungal strains isolated from decaying wood in the Brazilian Amazon

The emergence of bacterial resistance to antimicrobials poses a significant health threat. To address this issue, exploring the fungal diversity in freshwater environments in the Amazon Forest has potential in the search for new antimicrobials. This study aimed to investigate the production of antibacterial metabolites by aquatic fungi from Amazon lakes, specifically Lake Juá and Lake Maicá (Brazil-PA). The fungal isolates were obtained from wood fragments submerged in these lakes, and the ethyl acetate extracts were evaluated for antibacterial activity against Staphylococcus aureus ATCC 25923, S. aureus (MRSA), ATCC 43300, Escherichia coli ATCC 25922, and E. coli (ESBL) NCTC 13353. Additionally, toxicity of the extracts (EtOAc with antimicrobial activity) against human fibroblasts MRC-5 was investigated. The study identified 40 fungal strains with antimicrobial screening, and the ethyl acetate extracts of Fluviatispora C34, Helicascus C18, Monodictys C15, and Fusarium solani LM6281 exhibited antibacterial activity. F. solani LM6281 showed the lowest minimum inhibitory concentration (MIC) of 50 µg/mL against S. aureus strains and MIC of 100 µg/mL against E. coli strains including ESBL. The cytotoxicity (IC50) of the extract (EtOAc) of F. solani LM6281 was 34.5 µg/mL. Preliminary studies of the TLC culture and RNM-H from the extract (EtOAc) of F. solani suggested the presence of substances from the class of terpenes, quinones, phenolics, and flavonoids. This study highlights the potential of submerged wood fungi in the Amazon region to produce antibacterial substances, thus identifying them as sources of novel bioactive compounds with potential use in the pharmaceutical industry and regional bioeconomy.

Steroid Components of Marine-Derived Fungal Strain Penicillium levitum N33.2 and Their Biological Activities

Genus Penicillium comprising the most important and extensively studied fungi has been well-known as a rich source of secondary metabolites. Our study aimed to analyze and investigate biological activities, including in vitro anti-cancer, anti-inflammatory and anti-diabetic properties, of metabolites from a marine-derived fungus belonging to P. levitum. The chemical compounds in the culture broth of P. levitum strain N33.2 were extracted with ethyl acetate. Followingly, chemical analysis of the extract leaded to the isolation of three ergostane-type steroid components, namely cerevisterol (1), ergosterol peroxide (2), and (3β,5α,22E)-ergosta-6,8(14),22-triene-3,5-diol (3). Among these, (3) was the most potent cytotoxic against human cancer cell lines Hep-G2, A549 and MCF-7 with IC50 values of 2.89, 18.51, and 16.47 µg/mL, respectively, while the compound (1) showed no significant effect against tested cancer cells. Anti-inflammatory properties of purified compounds were evaluated based on NO-production in LPS-induced murine RAW264.7 macrophages. As a result, tested compounds performed diverse inhibitory effects on NO production by the macrophages, with the most significant inhibition rate of 81.37 ± 1.35% at 25 µg/mL by the compound (2). Interestingly, compounds (2) and (3) exhibited inhibitory activities against pancreatic lipase and α-glucosidase enzymes in vitro assays. Our study brought out new data concerning the chemical properties and biological activities of isolated steroids from a P. levitum fungus.

Secondary Metabolites from the Cultures of Medicinal Mushroom Vanderbylia robiniophila and Their Tyrosinase Inhibitory Activities

Vanderbylia robiniophila (Huaier in Chinese) has been used as a traditional herbal medicine in China for over 1600 years. However, the secondary metabolites of V. robiniophila have not been systematically examined. Corresponding chemical investigation in this study led to the discovery of two new compounds, (22E, 24R)-6β, 7α-dimethoxyergosta-8(14), 22-diene-3β, 5α-diol (1) and vanderbyliolide A (8), along with eight known ones (2-7, 9-10). Their structures were determined by extensive spectroscopic analyses and electronic circular dichroism (ECD) calculations. The tyrosinase inhibitory activity of all isolated compounds was evaluated, and compound 10 showed a potential tyrosinase inhibitory effect with an IC₅₀ value of 60.47 ± 2.63 μM. Kinetic studies of the inhibition reactions suggested that 10 provides the inhibitory ability on tyrosinase in an uncompetitive way.

The endophytic Fusarium strains: a treasure trove of natural products

The complexity and structural diversity of the secondary metabolites produced by endophytes make them an attractive source of natural products with novel structures that can help in treating life-changing diseases. The genus Fusarium is one of the most abundant endophytic fungal genera, comprising about 70 species characterized by extraordinary discrepancy in terms of genetics and ability to grow on a wide range of substrates, affecting not only their biology and interaction with their surrounding organisms, but also their secondary metabolism. Members of the genus Fusarium are a source of secondary metabolites with structural and chemical diversity and reported to exhibit diverse pharmacological activities. This comprehensive review focuses on the secondary metabolites isolated from different endophytic Fusarium species along with their various biological activities, reported in the period from April 1999 to April 2022.

Structure and Biological Activity of Ergostane-Type Steroids from Fungi

Mushrooms are known not only for their taste but also for beneficial effects on health attributed to plethora of constituents. All mushrooms belong to the kingdom of fungi, which also includes yeasts and molds. Each year, hundreds of new metabolites of the main fungal sterol, ergosterol, are isolated from fungal sources. As a rule, further testing is carried out for their biological effects, and many of the isolated compounds exhibit one or another activity. This study aims to review recent literature (mainly over the past 10 years, selected older works are discussed for consistency purposes) on the structures and bioactivities of fungal metabolites of ergosterol. The review is not exhaustive in its coverage of structures found in fungi. Rather, it focuses solely on discussing compounds that have shown some biological activity with potential pharmacological utility.

Assembly and annotation of whole-genome sequence of Fusarium equiseti

Fusarium equiseti is a plant pathogen with a wide range of hosts and diverse effects, including probiotic effects. However, the molecular mechanisms underlying these effects remain unclear, hindering its effective utilization. The final assembly included 16 scaffolds of contiguous sequence without gaps. The total sequence length was 40,776,005 bp, and the GC content of 48.01%. In total, we annotated the putative function of 13,134 genes, accounting for 94.97% of the candidate genes. We identified two and 23 candidate genes that are likely involved in the production of mycotoxins zearalenone and trichothecene, respectively. A comparative genomic analysis supported the high quality of the F. equiseti assembly. Our comprehensive analysis of whole-genome sequence will serve as a valuable resource for future studies of expression, regulation, function and evolution of the genes of F. equiseti as well as studies into disease prevention and control.

Bioprospecting endophytic fungi from Fusarium genus as sources of bioactive metabolites

Endophytic fungi became an attractive source for the discovery of new leads, because of the complexity and the structural diversity of their secondary metabolites. The genus Fusarium comprising about 70 species is extremely variable in terms of genetics, biology, ecology, and consequently, secondary metabolism and have been isolated from countless plants genera from diverse habitats. These endophytic microbes may provide protection and survival strategies in their host plants with production of a repertoire of chemically diverse and structurally unprecedented secondary metabolites reported to exhibit an incredible array of biological activities including antimicrobial, anticancer, antiviral, antioxidants, antiparasitics, immunosuppressants, immunomodulatory, antithrombotic, and biocontrol ability against plants pathogens and nematodes. This review comprehensively highlights over the period 1981-2019, the bioactive potential of metabolites produced by endophytes from Fusarium genus. Abbreviations: AIDS: Acquired immune deficiency syndrome; BAPT: C-13 phenylpropanoid side chain-CoA acyltransferase; CaBr2: Calcium bromide; DBAT: 10-deacetylbaccatin III-10-O-acetyl transferase; DNA: Deoxyribonucleic acid; EI-MS: Electron ionization mass spectrometer; EN: Enniatin; ERK: Extracellular regulated protein kinase; EtOAc: Ethyl acetate; FDA: Food and Drug Administration; GAE/g: Gallic acid equivalent per gram; GC-MS: Gas chromatography-mass spectrometry; HA: Hyperactivation; HCV: Hepatitis C Virus; HCVPR: Hepatitis C Virus protease; HeLa: Human cervical cancer cell line; HIV: Human immunodeficiency viruses; HPLC: High Performance Liquid Chromatography; IAA: Indole-3-acetic acid; IARC: International Agency for Research on Cancer; IC50: Half maximal inhibitory concentration; LC50: Concentration of the compound that is lethal for 50% of exposed population; LC-MS: Liquid chromatography-mass spectrometry; MCF-7: Human breast cancer cell line; MDR: Multidrug-resistant; MDRSA: Multidrug-resistant S. aureus; MFC: Minimum fungicidal concentration; MIC: Minimum inhibitory concentration; MRSA: Multidrug-resistant S. aureus; MTCC: Microbial type culture collection; PBMCs: Peripheral blood mononuclear cells; PCR: Polymerase chain reaction; TB: Tuberculosis; TLC: Thin layer chromatography; TNF: Tumor necrosis factor; WHO: World Health Organization http://www.zoobank.org/urn:lsid:zoobank.org:pub:D0A7B2D8-5952-436D-85C8-C79EAAD1013C.

Novel natural compounds from endophytic fungi with anticancer activity

Plant endophytes are microorganisms that live in healthy plant tissues in part or all of their life history without causing obvious symptoms of infection in the host plants. Endophytes, a new type of microbial resource that can produce a variety of biological constituents, have great values for research and broad prospects for development. This article reviewed the research and development progress of endophytic fungi with cytotoxic activity between 2014 and 2017, including endophytic fungi sources, microbial taxonomy, compound classification and cytotoxic activity. The results showed that the 109 strains of endophytic fungi belong to 3 phyla, 7 classes and 50 genera. The secondary metabolites mainly contained alkaloids, terpenes, steroids, polyketides, quinones, isocoumarins, esters etc. The results of this study provide references for the development of new antitumor drugs and endophytes resources.

Endophytic Fungi-Alternative Sources of Cytotoxic Compounds: A Review

Cancer is a major cause of death worldwide, with an increasing number of cases being reported annually. The elevated rate of mortality necessitates a global challenge to explore newer sources of anticancer drugs. Recent advancements in cancer treatment involve the discovery and development of new and improved chemotherapeutics derived from natural or synthetic sources. Natural sources offer the potential of finding new structural classes with unique bioactivities for cancer therapy. Endophytic fungi represent a rich source of bioactive metabolites that can be manipulated to produce desirable novel analogs for chemotherapy. This review offers a current and integrative account of clinically used anticancer drugs such as taxol, podophyllotoxin, camptothecin, and vinca alkaloids in terms of their mechanism of action, isolation from endophytic fungi and their characterization, yield obtained, and fungal strain improvement strategies. It also covers recent literature on endophytic fungal metabolites from terrestrial, mangrove, and marine sources as potential anticancer agents and emphasizes the findings for cytotoxic bioactive compounds tested against specific cancer cell lines.

Antibacterial secondary metabolites from an endophytic fungus, Fusarium solani JK10

Extensive chemical investigation of the endophytic fungus, Fusarium solani JK10, harbored in the root of the Ghanaian medicinal plant Chlorophora regia, using the OSMAC (One Strain Many Compounds) approach resulted in the isolation of seven new 7-desmethyl fusarin C derivatives (1-7), together with five known compounds (8-12). The structures of the new compounds were elucidated by analysis of their spectroscopic data including 1D, 2D NMR, HRESI-MSⁿ and IR data. The relative configuration of compounds 1/2 was deduced by comparison of their experimental electronic circular dichroism (ECD) and optical rotation data with those reported in literature. The absolute configuration of solaniol (10), a known compound with undefined absolute stereochemistry, was established for the first time by X-ray diffraction analysis of a single-crystal structure using Cu-Kα radiation. The antibacterial activities of the crude fungal extract and the compounds isolated from the fungus were evaluated against some clinically important bacterial strains such as Staphylococcus aureus and Bacillus subtilis, as well as an environmental strain of Escherichia coli and the soil bacterium Acinetobacter sp. BD4. Compounds 3/4 and 6 exhibited antibacterial efficacies against the soil bacterium Acinetobacter sp., comparable to the reference standard streptomycin. All the tested compounds (1-9) demonstrated antibacterial activity against the environmental strain of E. coli, whereas no antibacterial activity was observed against S. aureus and B. subtilis. The antibacterial activity of the isolated compounds typically against E. coli and Acinetobacter sp. provides further insight into the possible involvement of root-borne endophytes in chemical defense of their host plants in selected ecological niches.