Depsidones and an α-pyrone derivative from Simplicillium sp. PSU-H41, an endophytic fungus from Hevea brasiliensis leaf [corrected]

Variability of microbiomes in winter rye, wheat, and triticale affected by snow mold: predicting promising microorganisms for the disease control

BACKGROUND

Snow mold caused by different psychrophilic phytopathogenic fungi is a devastating disease of winter cereals. The variability of the snow mold pathocomplex (the quantitative composition of snow mold fungi) has not been evaluated across different crops or different agrocenoses, and no microbial taxa have been predicted at the whole-microbiome level as potential effective snow mold control agents. Our study aimed to assess the variability of the snow mold pathocomplex in different winter cereal crops (rye, wheat, and triticale) in different agrocenoses following the peak disease progression and to arrange a hierarchical list of microbial taxa predicted to be the main candidates to prevent or, conversely, stimulate the development of snow mold pathogens.

RESULTS

The variability of microbiomes between different crops within a particular agrocenosis was largely determined by fungal communities, whereas the variability of microbiomes of a particular crop in different agrocenoses was largely determined by bacterial communities. The snow mold pathocomplex was the most "constant" in rye, with the lowest level of between-replicate variability and between-agrocenoses variability and (similar to the triticale snow mold pathocomplex) strong dominance of Microdochium over other snow mold fungi. The wheat snow mold pathocomplex was represented by different snow mold fungi, including poorly investigated Phoma sclerotioides. To predict snow mold-control microorganisms, a conveyor of statistical methods was formed and applied; this conveyor enables considering not only the correlation between the abundance of target taxa and a phytopathogen but also the stability and fitness of taxa within plant-associated communities and the reproducibility of the predicted effect of taxa under different conditions. This conveyor can be widely used to search for biological agents against various plant infectious diseases.

CONCLUSIONS

The top indicator microbial taxa for winter wheat and rye following the winter period were Ph. sclerotioides and Microdochium, respectively, both of which are causal agents of snow mold disease. Bacteria from the Cellulomonas, Lechevalieria, and Pseudoxanthomonas genera and fungi from the Cladosporium, Entimomentora, Pseudogymnoascus, and Cistella genera are prime candidates for testing their plant-protective properties against Microdochium-induced snow mold disease and for further use in agricultural practice.

Terpestacin and Its Derivatives: Bioactivities and Syntheses

Terpestacin (1), fusaproliferin (2), and their derivatives are a class of sesterterpenes featured by a trans-fused 5/15-membered ring skeleton. There are 45 natural products (1, 2, 4-27, 65-83) isolated from various wild fungi (Fusarium sp., Bipolaris sorokiniana, Arthrinium sp., etc.) or from genetic mutants via biosynthetic gene clusters mining, and 37 derivatives (28-64) produced by semi-synthetic modifications. These compounds show a diverse range of important bioactivities such as antivirus, antimicrobial, cytotoxic, phytotoxic, anti-flammatory, and brine shrimp lethal activities. To date, two racemic and five enantioselective chemical total syntheses of 1 (including 2 and their isomers) have been developed. Over the past decade, a number of biosynthetic gene clusters or their mutants, along with their encoding enzymes responsible for producing sesterterpenes such as terpestacin and its derivatives, have also been identified. This review covers the literature from the year 1993, when 1 was firstly discovered, to May 2024, focusing on the bioactivities and syntheses of 1 and its derivatives or isomers.

Antarctic fungi produce pigment with antimicrobial and antiparasitic activities

Natural pigments have received special attention from the market and industry as they could overcome the harm to health and the environmental issues caused by synthetic pigments. These pigments are commonly extracted from a wide range of organisms, and when added to products they can alter/add new physical-chemical or biological properties to them. Fungi from extreme environments showed to be a promising source in the search for biomolecules with antimicrobial and antiparasitic potential. This study aimed to isolate fungi from Antarctic soils and screen them for pigment production with antimicrobial and antiparasitic potential, together with other previously isolated strains A total of 52 fungi were isolated from soils in front of the Collins Glacier (Southeast border). Also, 106 filamentous fungi previously isolated from the Collins Glacier (West border) were screened for extracellular pigment production. Five strains were able to produce extracellular pigments and were identified by ITS sequencing as Talaromyces cnidii, Pseudogymnoascus shaanxiensis and Pseudogymnoascus sp. All Pseudogymnoascus spp. (SC04.P3, SC3.P3, SC122.P3 and ACF093) extracts were able to inhibit S. aureus ATCC6538 and two (SC12.P3, SC32.P3) presented activity against Leishmania (L.) infantum, Leishmania amazonensis and Trypanossoma cruzii. Extracts compounds characterization by UPLC-ESI-QToF analysis confirmed the presence of molecules with biological activity such as: Asterric acid, Violaceol, Mollicellin, Psegynamide A, Diorcinol, Thailandolide A. In conclusion, this work showed the potential of Antartic fungal strains from Collins Glacier for bioactive molecules production with activity against Gram positive bacteria and parasitic protozoas.

The limitless endophytes: their role as antifungal agents against top priority pathogens

Multi resistant fungi are on the rise, and our arsenal compounds are limited to few choices in the market such as polyenes, pyrimidine analogs, azoles, allylamines, and echinocandins. Although each of these drugs featured a unique mechanism, antifungal resistant strains did emerge and continued to arise against them worldwide. Moreover, the genetic variation between fungi and their host humans is small, which leads to significant challenges in new antifungal drug discovery. Endophytes are still an underexplored source of bioactive secondary metabolites. Many studies were conducted to isolate and screen endophytic pure compounds with efficacy against resistant yeasts and fungi; especially, Candida albicans, C. auris, Cryptococcus neoformans and Aspergillus fumigatus, which encouraged writing this review to critically analyze the chemical nature, potency, and fungal source of the isolated endophytic compounds as well as their novelty features and SAR when possible. Herein, we report a comprehensive list of around 320 assayed antifungal compounds against Candida albicans, C. auris, Cryptococcus neoformans and Aspergillus fumigatus in the period 1980-2024, the majority of which were isolated from fungi of orders Eurotiales and Hypocreales associated with terrestrial plants, probably due to the ease of laboratory cultivation of these strains. 46% of the reviewed compounds were active against C. albicans, 23% against C. neoformans, 29% against A. fumigatus and only 2% against C. auris. Coculturing was proved to be an effective technique to induce cryptic metabolites absent in other axenic cultures or host extract cultures, with Irperide as the most promising compounds MIC value 1 μg/mL. C. auris was susceptible to only persephacin and rubiginosin C. The latter showed potent inhibition against this recalcitrant strain in a non-fungicide way, which unveils the potential of fungal biofilm inhibition. Further development of culturing techniques and activation of silent metabolic pathways would be favorable to inspire the search for novel bioactive antifungals.

Identification of natural marine compounds as potential inhibitors of CDK2 using molecular docking and molecular dynamics simulation approach

The multifunctional enzyme cyclin-dependent kinase 2 (CDK2) protein is essential for cell proliferation, transcription and modulation of the cell cycle. There is a dysfunction that is connected to various diseases, such as cancer, making it an important treatment target in oncology and beyond. The goal of this study is to identify novel CDK2 ATP binding site inhibitors using in silico drug designing. To find competitive inhibitors for the ATP site, molecular docking, molecular dynamics (MD) simulation and free-binding energy calculations were used. Natural compounds retrieved from marine sources (fungi and algae) were docked against protein, and the best-binding compounds were further evaluated using MD simulations. LIG1, LIG2 and LIG3 (ΔGPB = -19.98, -15.82 and -12.98 kcal/mol, respectively) were placed in the top positions based on their overall binding energy calculated using MMPBSA approach. Stability of the complexes was confirmed by carefully analyzing the rmsd and rmsf patterns retrieved from the MD trajectories. Several residues and areas (Leu124, Val123, Phe80, Leu83, Glu81, Arg 126, Asn132, Leu134, Gln131, Lys88 and Glu195) appear to be critical for inhibitor retention across the active pocket, according to RMSD and RMSF. The dynamics of the ligands inside the active pocket were mapped using principle component analysis. It has been observed that LIG1-3 appear to be the best possible inhibitors due to their high binding energies, interaction pattern and retention inside the active pocket.Communicated by Ramaswamy H. Sarma.

Four Undescribed Pyranones from the Scutellaria formosana-Derived Endophytic Fungi Ascomycota sp. FAE17

Four undescribed pyranone derivatives, named ascomycopyrones A-D (1-4), as well as one known analogue simplicilopyrone (5) (this is the first study to report the absolute configuration), were isolated from the endophytic fungus Ascomycota sp. FAE17 derived from the flowers of Scutellaria formosa. The structures of these pyranones were identified by comprehensive spectroscopic and MS analyses, and the absolute configurations were determined by their experimental and quantum chemical electronic circular dichroism (ECD) calculations. All isolated compounds were tested for various bioactivities, including antibacterial, cytotoxic activity, and NO inhibitory activity. Unfortunately, none of the compounds showed significant bioactivities.

High hydrostatic pressure harnesses the biosynthesis of secondary metabolites via the regulation of polyketide synthesis genes of hadal sediment-derived fungi

Deep-sea fungi have evolved extreme environmental adaptation and possess huge biosynthetic potential of bioactive compounds. However, not much is known about the biosynthesis and regulation of secondary metabolites of deep-sea fungi under extreme environments. Here, we presented the isolation of 15 individual fungal strains from the sediments of the Mariana Trench, which were identified by internal transcribed spacer (ITS) sequence analysis as belonging to 8 different fungal species. High hydrostatic pressure (HHP) assays were performed to identify the piezo-tolerance of the hadal fungi. Among these fungi, Aspergillus sydowii SYX6 was selected as the representative due to the excellent tolerance of HHP and biosynthetic potential of antimicrobial compounds. Vegetative growth and sporulation of A. sydowii SYX6 were affected by HHP. Natural product analysis with different pressure conditions was also performed. Based on bioactivity-guided fractionation, diorcinol was purified and characterized as the bioactive compound, showing significant antimicrobial and antitumor activity. The core functional gene associated with the biosynthetic gene cluster (BGC) of diorcinol was identified in A. sydowii SYX6, named as AspksD. The expression of AspksD was apparently regulated by the HHP treatment, correlated with the regulation of diorcinol production. Based on the effect of the HHP tested here, high pressure affected the fungal development and metabolite production, as well as the expression level of biosynthetic genes which revealed the adaptive relationship between the metabolic pathway and the high-pressure environment at the molecular level.

Isolation of new compounds related to xyloketals biosynthesis implies an alternative pathway for furan-fused-chromene formation

In fungi, there is a rare group of natural products harboring the 2,3,3a,9a-tetrahydro-4H-furo[2,3-b]chromene skeleton, represented by xyloketal B, which display a wide range of biological activities and have drawn significant attention. In this work, four new analogues simpliketals A-D (1-4), as well as two other new compounds simplilactones A and B (5 and 6), were isolated from Simplicillium sp. AHK071-01. Their structures were elucidated by extensive NMR spectroscopic methods, ¹³C NMR calculation, single-crystal X-ray diffraction, and ECD calculation. In addition, five known compounds (7-11) including alboatrin (7) were also obtained. Based on the structural similarity of the above compounds, we inferred that compounds 5, 6, and 8-11 might be biosynthetically related with 1-4 and 7, which allowed us to propose an alternative biosynthetic route to generate the furan-fused chromene skeleton of this class of compounds, instead of a previously presumed polyketide-terpenoid hybrid pathway. Finally, cytotoxicity assays showed that 1-4 exhibited weak inhibitory activity on PANC-1 cells and that 2 and 3 possessed moderate activity against SH-SY5Y cells.

Fungal endophytic community associated with Hevea spp.: diversity, enzymatic activity, and biocontrol potential

Plants of the genus Hevea present a great diversity of endophytic fungal species, which can provide bioactive compounds and enzymes for biotechnological use, and antagonist agents for plant disease biological control. The diversity of endophytic fungi associated with leaves of Hevea spp. clones in western Amazonia was explored using cultivation-based techniques, combined with the sequencing of the ITS rRNA-region. A total of 269 isolates were obtained, and phylogenetic analysis showed that they belong to 47 putative species, of which 24 species were unambiguous. The phylum Ascomycota was the most abundant (95.4%), with predominance of the genera Colletotrichum and Diaporthe, followed by the phylum Basidiomycota (4.6%), with abundance of the genera Trametes and Phanerochaete. Endophytic composition was influenced by the clones, with few species shared among them, and the greatest diversity was found in clone C44 (richness: 26, Shannon: 14,15, Simpson: 9.11). The potential for biocontrol and enzymatic production of endophytes has been investigated. In dual culture tests, 95% of the isolates showed inhibitory activity against C. gloeosporioides, and 84% against C. cassiicola. Efficient inhibition was obtained with isolates HEV158C and HEV255M (Cophinforma atrovirens and Polyporales sp. 2) for C. gloeosporioides, and HEV1A and HEV8B (Phanerochaete sp. 3 and Diaporthe sp. 4) for C. cassiicola. The endophytic isolates were positive for lipase (69.6%), amylase (67.6%), cellulase (33.3%), and protease (20.6%). The enzyme index ≥ 2 was found for amylase and lipase. The isolates obtained from rubber trees showed good antimicrobial and enzymatic potential, which can be tested in the future for use in the industry, and in the control of plant pathogens.

Fungal Endophytes: A Potential Source of Antibacterial Compounds

Antibiotic resistance is becoming a burning issue due to the frequent use of antibiotics for curing common bacterial infections, indicating that we are running out of effective antibiotics. This has been more obvious during recent corona pandemics. Similarly, enhancement of antimicrobial resistance (AMR) is strengthening the pathogenicity and virulence of infectious microbes. Endophytes have shown expression of various new many bioactive compounds with significant biological activities. Specifically, in endophytic fungi, bioactive metabolites with unique skeletons have been identified which could be helpful in the prevention of increasing antimicrobial resistance. The major classes of metabolites reported include anthraquinone, sesquiterpenoid, chromone, xanthone, phenols, quinones, quinolone, piperazine, coumarins and cyclic peptides. In the present review, we reported 451 bioactive metabolites isolated from various groups of endophytic fungi from January 2015 to April 2021 along with their antibacterial profiling, chemical structures and mode of action. In addition, we also discussed various methods including epigenetic modifications, co-culture, and OSMAC to induce silent gene clusters for the production of noble bioactive compounds in endophytic fungi.

Diversity, Chemical Constituents, and Biological Activities of Endophytic Fungi Isolated From Ligusticum chuanxiong Hort

The objective of this study was to evaluate the diversity of endophytic fungi of different parts of Ligusticum chuanxiong Hort (CX) and further characterize their biological activities and identify chemical compounds produced by these endophytic fungi. A total of 21 endophytic fungi were isolated and identified from CX. Penicillium oxalicum, Simplicillium sp., and Colletotrichum sp. were identified as promising strains by the color reaction. Comparing different organic extracts of the three strains, it was observed that the ethyl acetate extract of Penicillium oxalicum and Simplicillium sp. and the n-butanol extract of Colletotrichum sp. showed significant antioxidant and antibacterial activities. The ethyl acetate extracts of Penicillium oxalicum had outstanding antioxidant and antibacterial effects, and its radical scavenging rates for ABTS and DPPH were 98.43 ± 0.006% and 90.11 ± 0.032%, respectively. At the same time, their IC₅₀ values were only 0.18 ± 0.02 mg/mL and 0.04 ± 0.003 mg/mL. The ethyl acetate extract of Penicillium oxalicum showed MIC value of only 0.5 mg/mL against Escherichia coli and Staphylococcus aureus. By liquid chromatography-mass spectrometry (LC-MS), we found that Penicillium oxalicum could produce many high-value polyphenols, such as hesperidin (36.06 μmol/g), ferulic acid (1.17 μmol/g), and alternariol (12.64 μmol/g), which can be a potential resource for the pharmaceutical industry. In conclusion, these results increase the diversity of CX endophytic fungi and the antioxidant and antibacterial activities of their secondary metabolites.

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.

Cytotoxicity and Nitric Oxide Production Inhibitory Activities of Compounds Isolated from the Plant Pathogenic Fungus Curvularia sp

Chemical investigation of the mycelia of the pathogenic fungus Curvularia sp. which was isolated from a leaf of Dactyloctenium aegyptium (crowfoot grass), resulted in the isolation of a new compound, curvulariahawadride (5), along with five known compounds (1-4, and 6). Their structures were determined on the basis of spectroscopic data, including 1D and 2D NMR and HRESIMS. The absolute configuration of 5 was established from experimental and calculated electronic circular dichroism (ECD). Compounds 1, 3, and 5 showed nitric oxide (NO) production inhibitory activity with IC₅₀ values of 53.7, 32.8, and 12.8 µM, respectively. Compounds 2 and 4 showed significant cytotoxicity against lung cancer A549, colorectal cancer SW480, and leukemic K562 cells with an IC₅₀ ranging value of 11.73 to 17.59 µM.

Mollicellins S-U, three new depsidones from Chaetomium brasiliense SD-596 with anti-MRSA activities

Fungi are important resources for drug development, as they have a diversity of genes, that can produce novel secondary metabolites with effective bioactivities. Here, five depsidone-based analogs were isolated from the rice media of Chaetomium brasiliense SD-596. Their structures were elucidated using NMR and mass spectrometry analysis. Five compounds, including three new depsidone analogs, mollicellin S (1), mollicellin T (2), and mollicellin U (3), and two known compounds, mollicellin D (4) and mollicellin H (5), exhibited significant inhibition against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA), with MIC values ranging from 6.25 to 12.5 μg ml^-1. Herein, we identified the predicted plausible biosynthetic cluster of the compounds and discussed the structure-activity relationship. Finally, we found that the introduction of aldehyde and methoxyl groups provide marked improvement for the inhibition against MRSA.

Biological Activities of Some New Secondary Metabolites Isolated from Endophytic Fungi: A Review Study

Secondary metabolites isolated from plant endophytic fungi have been getting more and more attention. Some secondary metabolites exhibit high biological activities, hence, they have potential to be used for promising lead compounds in drug discovery. In this review, a total of 134 journal articles (from 2017 to 2019) were reviewed and the chemical structures of 449 new metabolites, including polyketides, terpenoids, steroids and so on, were summarized. Besides, various biological activities and structure-activity relationship of some compounds were aslo described.

Chemical Constituents from Endophytic Fungus Annulohypoxylon cf. stygium in Leaves of Anoectochilus roxburghii

The chemical investigation on endophytic fungus Annulohypoxylon cf. stygium in leaves of Anoectochilus roxburghii (Wall.) Lindl. has been performed. Sixteen compounds were isolated and their structures were identified as (-)-notoamide A, (-)-notoamide B, (+)-versicolamide B, notoamide C, notoamide D, stephacidin A, sterigmatocystin, dihydrosterigmatocystin, secosterigmatocystin, versiconol, averufanin, kipukasin D, kipukasin E, diorcinal, palmarumycin CP2 and (-)-(3R)-mellein methyl ether, respectively, by spectroscopic analysis and comparison with literature data. All the compounds were isolated from Annulohypoxylon genus for the first time. Sterigmatocystin and palmarumycin CP2 showed selective cytotoxic activities against HepG2, HeLa, MCF-7 and HT-29.

Structural deformation in pathogenic bacteria cells caused by marine fungal metabolites: An in vitro investigation

Over the past 50 years, fungal natural products have revolutionized medicine, yielding drugs which have enormous therapeutic potential. The aim of this study was to investigate the probable effect of marine fungal natural products on various skin pathogens. Initially, seventy natural extracts obtained from 35 different marine fungal strains were analysed by the agar well diffusion and broth micro dilution assay for their antibacterial action against six human skin pathogens. The minimum inhibitory effects of all active fungal methanolic extracts on targeted pathogens were observed between 90 and 99% at the concentration of 1 mg/mL. The highest activity was recorded by fungal strains belonging to genera Penicillium, Emericellopsis and Simplicillium. Thereafter, possible effects on target bacterial cells were studied by scanning electron microscopy which show significant destruction and structural deformation in the bacterial cell wall. The results of the present study provided good evidence that the studied marine fungi can be a potential source of natural antibacterial agents against skin bacterial pathogens.

Depsidones and a dihydroxanthenone from the endophytic fungi Simplicillium lanosoniveum (J.F.H. Beyma) Zare & W. Gams PSU-H168 and PSU-H261

Three new compounds including two depsidones (simplicildones J and K) and one dihydroxanthenone (globosuxanthone E) together with nine known compounds were obtained from the crude extracts of two endophytic fungi Simplicillium lanosoniveum (J.F.H. Beyma) Zare & W. Gams PSU-H168 and PSU-H261 which were isolated from the leaves of Hevea brasiliensis. The structures were elucidated by spectroscopic evidence. The absolute configuration of globosuxanthone E was established by means of experimental and calculated TDDFT ECD data. Simplicildone K exhibited antibacterial activity against Staphylococcus aureus and methicillin-resistant S. aureus with equal MIC values of 128 μg/mL. Simplicildone K and globosuxanthone E displayed antifungal activity against Cryptococcus neoformans ATCC90113 with the same MIC values of 32 μg/mL. In addition, known botryohordine C and simplicildone A showed phosphodiesterase 5 inhibitory activity with the IC₅₀ values of 5.69 and 9.96 μM, respectively, and were noncytotoxic toward noncancerous Vero cells.

Curdepsidones B⁻G, Six Depsidones with Anti-Inflammatory Activities from the Marine-Derived Fungus Curvularia sp. IFB-Z10

Six new depsidones, curdepsidones B-G (1-6), were obtained from the marine-derived fungus Curvularia sp. IFB-Z10. Their planar structures were determined by comprehensive analysis of HRESIMS and 1D/2D-NMR data. The absolute configuration of curdepsidones B-C (1-2) were established by synergistic use of DFT/NMR (density functional theory/nuclear magnetic resonance) and TDDFT/ECD (time-dependent density functional theory/electronic circular dichroism) calculations. Partial isolated compounds were tested for their anti-inflammatory activities in Propionibacterium acnes-induced THP-1 cells. Curdepsidone C (2) displayed significant anti-inflammatory properties with an IC50 value of 7.47 ± 0.35 μM, and reduced the P. acnes-induced phosphorylation levels of JNK and ERK in a dose-dependent mechanism. The possible anti-inflammatory mechanism of 2 was also investigated by molecular docking.

Biologically active fungal depsidones: Chemistry, biosynthesis, structural characterization, and bioactivities

Fungi produce a wide range of structurally unique metabolites. Depsidones represent one of the most interesting classes of metabolites, consisting of two 2,4-dihydroxybenzoic acid rings linked together by both ether and ester bonds. Naturally occurring depsidones are produced by lichen, fungi, and plants. They possessed a wide array of bioactivities, including antioxidant, antiproliferative, antimalarial, cytotoxic, antibacterial, radical scavenging, antihypertensive, anti-inflammatory, antifungal, and aromatase and protein kinase inhibitory. In order to point out the potential of this class of compounds, the present review focuses only on the depsidones that have been isolated from fungal source and published from 1978 to 2018. This review outlined the research on the biosynthesis, source, isolation, spectral and physical data, and bioactivities of the naturally occurring fungal depsidones. On the basis of 88 references, > 80 compounds have been described.