Chemistry and bioactivities of secondary metabolites from the genus Fusarium

Alkaloids isolated from the endophytic fungus Fusarium concentricum

Endophytic fungi are an important resource for bioactive natural products. In this study, a new tryptophan derivative fusaconate A (1) and three pyridone alkaloids, including one new pyridone derivative 1'-methoxy-6'-epi-oxysporidinone (2) and two known ones (3-4), were identified from the endophytic fungus Fusarium concentricum which was isolated from the medicinal plant Anoectochilus roxburghii. Their structures were elucidated through extensive spectroscopic analysis, including HR-ESI-MS, 1 D and 2 D NMR. Compound 4 exhibited moderate cytotoxicities against HT29 and PC3 cells with IC50 values of 7.60 and 4.99 μM, respectively.

Irpetones A and B, Anti-Osteoclastic Heptaketides from a Marine Mesophotic Zone Ircinia Sponge-Associated Fungus Irpex sp. NBUF088

Chemical investigation of Irpex sp. NBUF088, associated with an Ircinia sp. sponge located at an 84 m deep mesophotic zone, led to the discovery of two new heptaketides, named irpetones A (1) and B (2). Their structures were identified by analysis of spectroscopic data and quantum-chemical calculations. Compound 1 exhibited inhibition against the receptor activator of NF-κB ligand-induced osteoclastogenesis in bone marrow monocytes with an IC50 of 6.3 ± 0.2 μM, causing no notable cytotoxicity. It was also determined that 1 inhibited the phosphorylation of ERK1/2-JNK1/2-p38 MAPKs and the nuclear translocation of NF-κB, consequently suppressing the activation of MAPK and NF-κB signaling pathways induced by the NF-κB ligand.

Virulence factors of the genus Fusarium with targets in plants

Fusarium spp. comprise various species of filamentous fungi that cause severe diseases in plant crops of both agricultural and forestry interest. These plant pathogens produce a wide range of molecules with diverse chemical structures and biological activities. Genetic functional analyses of some of these compounds have shown their role as virulence factors (VF). However, their mode of action and contributions to the infection process for many of these molecules are still unknown. This review aims to analyze the state of the art in Fusarium VF, emphasizing their biological targets on the plant hosts. It also addresses the current experimental approaches to improve our understanding of their role in virulence and suggests relevant research questions that remain to be answered with a greater focus on species of agroeconomic importance. In this review, a total of 37 confirmed VF are described, including 22 proteinaceous and 15 non-proteinaceous molecules, mainly from Fusarium oxysporum and Fusarium graminearum and, to a lesser extent, in Fusarium verticillioides and Fusarium solani.

The antifungal metabolites isolated from maize endophytic fungus Fusarium sp. induced by OSMAC strategy

Six new sesquiterpenes, fusarchlamols A-F (1, 2, 4-7); one new natural product of sesquiterpenoid, methyltricinonoate (3); and ten known compounds were found from Fusarium sp. cultured in two different media by the one strain many compounds strategy. The compounds (1, 2, and 4-11) were isolated from Fusarium sp. in PDB medium, and compounds (3-5, 8, and 10-17) were discovered from Fusarium sp. in coffee medium. Additionally, the configuration of 8 was first reported in the research by Mosher's method. The structures were established by 1D, 2D NMR, mass spectrometry, calculated ECD spectra, and Mosher's method. Compounds 1, 2, 6/7, 12, and 16 indicated significant antifungal activities against the phytopathogen Alternaria alternata isolated from Coffea arabica with MICs of 1 μg/mL. The investigation on the anti-phytopathogen activity of metabolites can provide lead compounds for agrochemicals.

Three new metabolites from the endophyte Fusarium proliferatum T2-10

One new cyclopeptide, cyclo-(L-Trp-L-Phe-L-Phe) (1), one new 2-pyridone derivative, fusarone A (3), and one new natural indole derivative, ethyl 3-indoleacetate (4), along with six known compounds were isolated from the endophytic fungus Fusarium proliferatum T2-10. The planar structures of three new compounds were identified by spectral methods including 1D and 2D NMR techniques, and the absolute configuration of compound 1 was elucidated by Marfey-MS method. In addition, all compounds were evaluated for their cytotoxic and antibacterial activities in vitro. Compound 2 showed remarkable cytotoxic activities against two human hepatoma cell lines SMMC7721 and HepG2 with IC50 values of 5.89 ± 0.74 and 6.16 ± 0.52 μM, and showed moderate antibacterial activities against Staphylococcus aureus and Enterococcus faecalis with MIC values of 7.81 and 15.62 μg/mL, respectively.

Antibacterial Polyketides Isolated from the Marine-Derived Fungus Fusarium solani 8388

Seven new polyketides named fusarisolins F-K (1-6) and fusarin I (7) were isolated from the marine-derived fungus Fusarium solani 8388, together with the known anhydrojavanicin (8), 5-deoxybostry coidin (9), and scytalol A (10). Their structures were established by comprehensive spectroscopic data analyses, and by comparison of the 1H and 13C NMR data with those reported in literature. Fusarisolin F (1) contained both a dichlorobenzene group and an ethylene oxide unit, which was rare in nature. In the bioassays, fusarisolin I (4), fusarisolin J (5), and 5-deoxybostry coidin (9) exhibited obvious antibacterial activities against methicillin-resistant Staphylococcus aureus n315 with MIC values of 3, 3, and 6 μg/mL, respectively. Fusarisolin H (3) and fusarisolin J (5) showed inhibitory effects against methicillin-resistant Staphylococcus aureus NCTC 10442 with the same MIC value of 6 μg/mL. With the exception of 5, all other compounds did not show or showed weak cytotoxicities against HeLa, A549, and KB cells; while fusarisolin J (5) demonstrated moderate cytotoxicities against the three human cancer cell lines with CC50 values between 9.21 and 14.02 μM.

Cyclic hexadepsipeptides from the fermentation of Fusarium sp. DCJ-A and their cytotoxic activities

Beauvercin H (1), a new cyclic hexadepsipeptide, and two known ones (2 and 3) were isolated from the EtOH extract of the solid culture of Fusarium sp. Their structures were elucidated by spectroscopic analysis, including extensive 1D and 2D NMR techniques, as well as comparison with literature values. Additionally, compounds 1-3 were tested for their cytotoxic activities. The results showed that all isolated compounds exhibited cytotoxic activities against five human cancer cell lines with IC₅₀ values ranging from 1.379 to 13.12 μM.

β-Carboline Alkaloids from Peganum harmala Inhibit Fusarium oxysporum from Codonopsis radix through Damaging the Cell Membrane and Inducing ROS Accumulation

Fusarium oxysporum is a widely distributed soil-borne pathogenic fungus that can cause medicinal herbs and crops to wither or die, resulting in great losses and threat to public health. Due to the emergence of drug-resistance and the decline of the efficacy of antifungal pesticides, there is an urgent need for safe, environmentally friendly, and effective fungicides to control this fungus. Plant-derived natural products are such potential pesticides. Extracts from seeds of Peganum harmala have shown antifungal effects on F. oxysporum but their antifungal mechanism is unclear. In vitro antifungal experiments showed that the total alkaloids extract and all five β-carboline alkaloids (βCs), harmine, harmaline, harmane, harmalol, and harmol, from P. harmala seeds inhibited the growth of F. oxysporum. Among these βCs, harmane had the best antifungal activity with IC₅₀ of 0.050 mg/mL and MIC of 40 μg/mL. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results revealed that the mycelia and spores of F. oxysporum were morphologically deformed and the integrity of cell membranes was disrupted after exposure to harmane. In addition, fluorescence microscopy results suggested that harmane induced the accumulation of ROS and increased the cell death rate. Transcriptomic analysis showed that the most differentially expressed genes (DEGs) of F. oxysporum treated with harmane were enriched in catalytic activity, integral component of membrane, intrinsic component of membrane, and peroxisome, indicating that harmane inhibits F. oxysporum growth possibly through damaging cell membrane and ROS accumulation via regulating steroid biosynthesis and the peroxisome pathway. The findings provide useful insights into the molecular mechanisms of βCs of P. harmala seeds against F. oxysporum and a reference for understanding the application of βCs against F. oxysporum in medicinal herbs and crops.

Polyketides, diketopiperazines and an isochromanone from the marine-derived fungal strain Fusarium graminearum FM1010 from Hawaii

The fungal strain Fusarium graminearum FM1010 was isolated from a shallow-water volcanic rock known as "live rock" at the Richardson's Beach, Hilo, Hawaii. Eleven specialised metabolites, including two undescribed diketopiperazines, three undescribed polyketides, and one undescribed isochromanone, along with five known fusarielin derivatives were obtained from F. graminearum FM1010. The structures of the six undescribed compounds were elucidated by extensive analysis of NMR spectroscopy, HRESIMS, chemical reactions, and electronic circular dichroism (ECD) data. Kaneoheoic acids G-I showed mild inhibitory activity against S. aureus with the MIC values in the range of 20-40 μg/mL when assayed in combination with chloramphenicol (half of the MIC, 1 μg/mL), an FDA approved antibiotic. Kaneoheoic acid I exhibited both anti-proliferative activity against ovarian cancer cell line A2780 and TNF-α induced NF-κB inhibitory activity with the IC₅₀ values of 18.52 and 15.86 μM, respectively.

Decalintetracids A and B, two pairs of unusual 3-decalinoyltetramic acid derivatives with phytotoxicity from Fusarium equiseti D39

The filamentous fungi Fusarium sp. are well-known for their ability to produce abundant specialised metabolites with attractive chemical structures and bioactivities. In this study, chemical analyses of the endophyte F. equiseti D39 led to the isolation and identification of two pairs of undescribed 3-decalinoyltetramic acids (3DTAs) E/Z diastereomers, decalintetracids A and B. Their structures were elucidated by comprehensive spectroscopic analysis and quantum-chemical calculations. Although 3DTAs were commonly reported from fungi, decalintetracid A possessed an unprecedented tricyclo [7.2.1.0^2,7] dodecane skeleton, which added the diversity of these fungal metabolites. In addition, decalintetracid B was featured by a unique 6/6/5 ring system core. A plausible biosynthetic pathway for decalintetracids A and B was proposed. Both compounds exhibited phytotoxicity toward Amaranthus retroflexus L. and Amaranthus hybrid, indicating their potential as natural herbicides.

Rare isotachin-derived from the Dasymaschalon rostratum fungus Penicillium tanzanicum ZY-5

Four rare isotachin-derived, isotachins E-H (1-4), together with two known biogenetically related isotachin derivatives (5 and 6) were isolated from the solid rice fermentation of a fungus Penicillium tanzanicum ZY-5 obtained from a medicinal plant Dasymaschalon rostratum collected from the Changjiang County, Hainan Province, China. Their structures were elucidated using comprehensive spectroscopic methods. The single-crystal X-ray diffraction of compound 5 was determined. Compounds 1-4 have a trans-3-(methylthio)-acrylic acid fragment, which are rare in nature. The inhibitory activities of all compounds against the nitric oxide (NO) production induced by lipopolysaccharide in mouse macrophage RAW 264.7 cells in vitro were evaluated.

Two new prenylated glycine derivatives from the marine-derived fungus Fusarium sp. TW56-10

Two new prenylated glycine derivatives (2-(4-((3-methylbut-2-en-1-yl)oxy)phenyl)acetyl)glycine (1) and methyl (2-(4-((3-methylbut-2-en-1yl)oxy)phenyl)acetyl)glycinate (2), along with nine known compounds (3-11) were purified from the marine-derived fungus Fusarium sp. TW56-10. Their chemical structures were determined by spectroscopic evidence, including extensive nuclear magnetic resonance (NMR), high-resolution electrospray ionization mass spectroscopy (HRESIMS) data, infrared radiation (IR) and Ultraviolet spectra (UV). Compound 4 (8-O-methyl-fusarubin) exhibited cytotoxic activity with IC50 value of 11.45 μM for A549 cells.

Combination of Pseudo-LC-NMR and HRMS/MS-Based Molecular Networking for the Rapid Identification of Antimicrobial Metabolites From Fusarium petroliphilum

An endophytic fungal strain isolated from a seagrass endemic to the Mediterranean Sea (Posidonia oceanica) was studied in order to identify its antimicrobial constituents and further characterize the composition of its metabolome. It was identified as Fusarium petroliphilum by in-depth phylogenetic analyses. The ethyl acetate extract of that strain exhibited antimicrobial activities and an ability to inhibit quorum sensing of Staphylococcus aureus. To perform this study with a few tens of mg of extract, an innovative one-step generic strategy was devised. On one side, the extract was analyzed by UHPLC-HRMS/MS molecular networking for dereplication. On the other side, semi-preparative HPLC using a similar gradient profile was used for a single-step high-resolution fractionation. All fractions were systematically profiled by ¹H-NMR. The data were assembled into a 2D contour map, which we call “pseudo-LC-NMR,” and combined with those of UHPLC-HRMS/MS. This further highlighted the connection within structurally related compounds, facilitated data interpretation, and provided an unbiased quantitative profiling of the main extract constituents. This innovative strategy led to an unambiguous characterization of all major specialized metabolites of that extract and to the localization of its bioactive compounds. Altogether, this approach identified 22 compounds, 13 of them being new natural products and six being inhibitors of the quorum sensing mechanism of S. aureus and Pseudomonas aeruginosa. Minor analogues were also identified by annotation propagation through the corresponding HRMS/MS molecular network, which enabled a consistent annotation of 27 additional metabolites. This approach was designed to be generic and applicable to natural extracts of the same polarity range.

Antifungal Activity and Biocontrol Mechanism of Fusicolla violacea J-1 against Soft Rot in Kiwifruit Caused by Alternaria alternata

Alternaria alternata is the main pathogenic species of various crops, including kiwifruit (Actinidia cinensis). In this study, an antagonistic fungus, J-1, with high antifungal activity against A. alternata was isolated from A. cinensis “Hongyang.” The strain J-1 was identified as Fusicolla violacea via morphological identification and DNA sequencing. This study aimed to evaluate the antifungal activity and potential mechanism of the strain J-1 against A. alternata. The strain J-1 exhibited antifungal activity against A. alternata, with an inhibition rate of 66.1% in vitro. Aseptic filtrate (AF) produced by the strain J-1 could suppress the mycelial growth and conidia germination of A. alternata at the inhibition rates of 66.8% and 80%, respectively, as well as suppress the spread of Alternaria rot in fresh kiwifruit. We observed that many clusters of spherical protrusions appeared at the mycelial tips of A. alternata after treatment with 200 mL L⁻¹ AF of J-1. Scanning electron microscopy analysis results showed that the mycelial structures were bent and/or malformed and the surfaces were rough and protuberant. Variations in temperature, pH, and storage time had little effect on the antifungal activity of the AF. Moreover, the AF could damage the integrity of cell membranes and cause intracellular content leakage. Meanwhile, the chitinase and β-1,3-glucanase enzyme activities increased significantly, indicating that the function of A. alternata cell wall was seriously injured. Eleven antimicrobial metabolites were identified by gas chromatography–mass spectrometry (GC–MS). The strain J-I and its AF exhibited well broad-spectrum antifungal activity against Diaporthe eres, Epicoccum sorghinum, Fusarium graminearum, Phomopsis sp., and Botryosphaeria dothidea, with inhibition rates ranging from 34.4% to 75.1% and 42.7% to 75.2%, respectively. Fusicolla violacea J-1 is a potential biocontrol agent against A. alternata and other fungal phytopathogens.

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.

Study of enzymatic activity in human neuroblastoma cells SH-SY5Y exposed to zearalenone's derivates and beauvericin

Beauvericin (BEA), α-zearalenol (α-ZEL) and β-zearalenol (β-ZEL), are produced by several Fusarium species that contaminate cereal grains. These mycotoxins can cause cytotoxicity and neurotoxicity in various cell lines and they are also capable of produce oxidative stress at molecular level. However, mammalian cells are equipped with a protective endogenous antioxidant system formed by no-enzymatic antioxidant and enzymatic protective systems such as glutathione peroxidase (GPx), glutathione S-transferase (GST), catalase (CAT) and superoxide dismutase (SOD). The aim of this study was evaluating the effects of α-ZEL, β-ZEL and BEA, on enzymatic GPx, GST, CAT and SOD activity in human neuroblastoma cells using the SH-SY5Y cell line, over 24 h and 48 h with different treatments at the following concentration range: from 1.56 to 12.5 μM for α-ZEL and β-ZEL, from 0.39 to 2.5 μM for BEA, from 1.87 to 25 μM for binary combinations and from 3.43 to 27.5 μM for tertiary combination. SH-SY5Y cells exposed to α-ZEL, β-ZEL and BEA revealed an overall increase in the activity of i) GPx, after 24 h of exposure up to 24-fold in individual treatments and 15-fold in binary combination; ii) GST after 24 h of exposure up to 10-fold (only in combination forms), and iii) SOD up to 3.5- and 5-fold in individual and combined treatment, respectively after 48 h of exposure. On the other hand, CAT activity decreased significantly in all treatments up to 92% after 24 h except for β-ZEL + BEA, which revealed the opposite.