Fusarimine, a novel polyketide isoquinoline alkaloid, from the endophytic fungus Fusarium sp. LN12, isolated from Melia azedarach

Screening and Genomic Analysis of Alkaloid-Producing Endophytic Fungus Fusarium solani Strain MC503 from Macleaya cordata

The extensive harvesting of Macleaya cordata, as a biomedicinal plant and a wild source of quaternary benzo[c]phenanthridine alkaloids, has led to a rapid decline in its population. An alternative approach to the production of these bioactive compounds, which are known for their diverse pharmacological effects, is needed. Production of these compounds using alkaloid-producing endophytic fungi is a promising potential approach. In this research, we isolated an alkaloid-producing endophytic fungus, strain MC503, from the roots of Macleaya cordata. Genomic analysis was conducted to elucidate its metabolic pathways and identify the potential genes responsible for alkaloid biosynthesis. High-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS) analyses revealed the presence and quantified the content of sanguinarine (536.87 μg/L) and chelerythrine (393.31 μg/L) in the fungal fermentation extract. Based on our analysis of the morphological and micromorphological characteristics and the ITS region of the nuclear ribosomal DNA of the alkaloid-producing endophyte, it was identified as Fusarium solani strain MC503. To the best of our knowledge, there is no existing report on Fusarium solani from Macleaya cordata or other medicinal plants that produce sanguinarine and chelerythrine simultaneously. These findings provide valuable insights into the capability of Fusarium solani to carry out isoquinoline alkaloid biosynthesis and lay the foundation for further exploration of its potential applications in pharmaceuticals.

Unveiling the fungal color palette: pigment analysis of Fusarium solani species complex and Curvularia verruculosa clinical isolates

Fungal species in the Nectriaceae, such as Fusarium spp. (Hypocreales: Nectriaceae), are etiologic agents of hyalohyphomycosis capable of producing violaceous or yellowish pigments under certain conditions, while Curvularia spp. (Pleosporales: Pleosporaceae) are agents of phaeohyphomycosis and typically produce melanin in their cell walls. In nectriaceous and pleosporaceous fungi, these pigments are mainly constituted by polyketides (e.g., azaphilones, naphthoquinones, and hydroxyanthraquinones). Considering the importance of pigments synthesized by these genera, this work focused on the selective extraction of pigments produced by eight Fusarium solani species complex and one Curvularia verruculosa isolate recovered from dermatomycosis specimens, their separation, purification, and posterior chemical analysis. The pigments were characterized through spectral and acid-base analysis, and their maximum production time was determined. Moreover, spectral identification of isolates was carried out to approach the taxonomic specificity of pigment production. Herein we describe the isolation and characterization of three acidic pigments, yellowish and pinkish azaphilones (i.e., coaherin A and sclerotiorin), and a purplish xanthone, reported for the first time in the Nectriaceae and Pleosporaceae, which appear to be synthesized in a species-independent manner, in the case of fusaria.

Amamine, an isoquinoline alkaloid from the Kitasatospora sp. HGTA304

Amamine (1), a new isoquinoline alkaloid, was isolated from the culture extract of an actinomycete Kitasatospora sp. HGTA304. The structure of 1 was determined by NMR and MS analyses in combination with UV data. Compound 1 displayed α-glucosidase inhibitory potential (IC50 value of 56 μM) compared with acarbose (IC50 value of 549 μM) as standard.

A systematic review on endophytic fungi and its role in the commercial applications

MAIN CONCLUSION

EF have been explored for its beneficial impact on environment and for its commercial applications. It has proved its worth in these sectors and showed an impact on biological properties of plants by producing various bioactive molecules and enzymes. Endophytes are plant mutualists that live asymptomatically within plant tissues and exist in almost every plant species. Endophytic fungi benefit from the host plant nutrition, and the host plant gains improved competitive abilities and tolerance against pathogens, herbivores, and various abiotic stresses. Endophytic fungi are one of the most inventive classes which produce secondary metabolites and play a crucial role in human health and other biotic aspects. This review is focused on systematic study on the biodiversity of endophytic fungi in plants, and their role in enhancing various properties of plants such as antimicrobial, antimycobacterial, antioxidant, cytotoxic, anticancer, and biological activity of secondary metabolites produced by various fungal endophytes in host plants reported from 1994 to 2021. This review emphasizes the endophytic fungal population shaped by host genotype, environment, and endophytic fungi genotype affecting host plant. The impact of endophytic fungi has been discussed in detail which influences the commercial properties of plants. Endophytes also have an influence on plant productivity by increasing parameters such as nutrient recycling and phytostimulation. Studies focusing on mechanisms that regulate attenuation of secondary metabolite production in EF would provide much needed impetus on ensuring continued production of bioactive molecules from a indubitable source. If this knowledge is further extensively explored regarding fungal endophytes in plants for production of potential phytochemicals, then it will help in exploring a keen area of interest for pharmacognosy.

Isoquinoline Alkaloids as Protein Tyrosine Phosphatase Inhibitors from a Deep-Sea-Derived Fungus Aspergillus puniceus

Puniceusines A-N (1-14), 14 new isoquinoline alkaloids, were isolated from the extracts of a deep-sea-derived fungus, Aspergillus puniceus SCSIO z021. Their structures were elucidated by spectroscopic analyses. The absolute configuration of 9 was determined by ECD calculations, and the structures of 6 and 12 were further confirmed by a single-crystal X-ray diffraction analysis. Compounds 3-5 and 8-13 unprecedentedly contained an isoquinolinyl, a polysubstituted benzyl or a pyronyl at position C-7 of isoquinoline nucleus. Compounds 3 and 4 showed selective inhibitory activity against protein tyrosine phosphatase CD45 with IC₅₀ values of 8.4 and 5.6 µM, respectively, 4 also had a moderate cytotoxicity towards human lung adenocarcinoma cell line H1975 with an IC₅₀ value of 11.0 µM, and 14, which contained an active center, -C=N⁺, exhibited antibacterial activity. An analysis of the relationship between the structures, enzyme inhibitory activity and cytotoxicity of 1-14 revealed that the substituents at C-7 of the isoquinoline nucleus could greatly affect their bioactivity.

Root Endophytes and Ginkgo biloba Are Likely to Share and Compensate Secondary Metabolic Processes, and Potentially Exchange Genetic Information by LTR-RTs

Ginkgo biloba is a pharmaceutical resource for terpenes and flavonoids. However, few insights discussed endophytes' role in Ginkgo, and whether genetic exchange happens between Ginkgo and endophytes remains unclear. Herein, functional gene profiles and repetitive sequences were analyzed to focus on these issues. A total of 25 endophyte strains were isolated from the Ginkgo root and distributed in 16 genera of 6 phyla. Significant morphological diversities lead to the diversity in the COG functional classification. KEGG mapping revealed that endophytic bacteria and fungi potentially synthesize chalcone, while endophytic fungi might also promote flavonoid derivatization. Both bacteria and fungi may facilitate the lignin synthesis. Aspergillus sp. Gbtc_1 exhibited the feasibility of regulating alcohols to lignans. Although Ginkgo and the endophytes have not observed the critical levopimaradiene synthase in ginkgolides synthesis, the upstream pathways of terpenoid precursors are likely intact. The MVK genes in Ginkgo may have alternative non-homologous copies or be compensated by endophytes in long-term symbiosis. Cellulomonas sp. Gbtc_1 became the only bacteria to harbor both MEP and MVA pathways. Endophytes may perform the mutual transformation of IPP and DMAPP in the root. Ginkgo and bacteria may lead to the synthesis and derivatization of the carotenoid pathway. The isoquinoline alkaloid biosynthesis seemed lost in the Ginkgo root community, but L-dopa is more probably converted into dopamine as an essential signal-transduction substance. So, endophytes may participate in the secondary metabolism of the Ginkgo in a shared or complementary manner. Moreover, a few endophytic sequences predicted as Ty3/Gypsy and Ty1/Copia superfamilies exhibited extremely high similarity to those of Ginkgo. CDSs in such endophytic LTR-RT sequences were also highly homologous to one Ginkgo CDS. Therefore, LTR-RTs may be a rare unit flowing between the Ginkgo host and endophytes to exchange genetic information. Collectively, this research effectively expanded the insight on the symbiotic relationship between the Ginkgo host and the endophytes in the root.

Fusarium: a treasure trove of bioactive secondary metabolites

Covering up to December 2019Fusarium, one of the most common fungal genera, has received considerable attention because of its biosynthetic exuberance, the result of many unique gene clusters involved in the production of secondary metabolites. This review provides the first comprehensive analysis of the secondary metabolites unique to the genus Fusarium, describing their occurrence, bioactivity, and genome features.

Didymellanosine, a new decahydrofluorene analogue, and ascolactone C from Didymella sp. IEA-3B.1, an endophyte of Terminalia catappa

Didymellanosine (1), the first analogue of the decahydrofluorene-class of natural products bearing a 13-membered macrocyclic alkaloid conjugated with adenosine, and a new benzolactone derivative, ascolactone C (4) along with eight known compounds (2, 3, 5–10), were isolated from a solid rice fermentation of the endophytic fungus Didymella sp. IEA-3B.1 derived from the host plant Terminalia catappa. In addition, ascochitamine (11) was obtained when (NH₄)₂SO₄ was added to rice medium and is reported here for the first time as a natural product. Didymellanosine (1) displayed strong activity against the murine lymphoma cell line L5178Y, Burkitt's lymphoma B cells (Ramos) and adult lymphoblastic leukemia T cells (Jurkat J16), with IC₅₀ values of 2.0, 3.3 and 4.4 µM, respectively. When subjected to a NFκB inhibition assay, didymellanosine (1) moderately blocked NFκB activation in the triple-negative breast cancer cell line MDA-MB 231. In an antimicrobial assay, ascomylactam C (3) was the most active compound when tested against a panel of Gram-positive bacteria including drug-resistant strains with MICs of 3.1–6.3 µM, while 1 revealed weaker activity. Interestingly, both compounds were also found active against Gram-negative Acinetobacter baumannii with MICs of 3.1 µM, in the presence of a sublethal concentration (0.1 µM) of colistin.

An unusual decahydrofluorene-class alkaloid from Didymella sp. exhibited NFκB inhibitory and antimicrobial activities.

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.

New β-Lactone with Tea Pathogenic Fungus Inhibitory Effect from Marine-Derived Fungus MCCC3A00957

Fusarium solani H915 (MCCC3A00957), a fungus originating from mangrove sediment, showed potent inhibitory activity against tea pathogenic fungus Pestalotiopsis theae. Successive chromatographic separation on an ethyl acetate (EtOAc) extract of F. solani H915 resulted in the isolation of five new alkenoic diacid derivatives: fusarilactones A-C (1-3), and fusaridioic acids B (4) and C (5), in addition to seven known compounds (6-12). The chemical structures of these metabolites were elucidated on the basis of UV, IR, HR-ESI-MS, and NMR spectroscopic data. The antifungal activity of the isolated compounds was evaluated. Compounds with a β-lactone ring (1, 2, and 7) exhibited potent inhibitory activities, while none of the other compounds show activity. The ED₅₀ values of the compounds 1, 2, and 7 were 38.14 ± 1.67, 42.26 ± 1.96, and 18.35 ± 1.27 μg/mL, respectively. In addition, inhibitory activity of these compounds against 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) synthase gene expression was also detected using real-time RT-PCR. Results indicated that compounds 1, 2, and 7 may inhibit the growth of P. theae by interfering with the biosynthesis of ergosterol by down-regulating the expression of HMG-CoA synthase.

Profiling of the Transcriptomic Responses of Clonostachys rosea Upon Treatment With Fusarium graminearum Secretome

Clonostachys rosea strain ACM941 is a fungal bio-control agent patented against the causative agent of Fusarium Head Blight, Fusarium graminearum. Although the molecular details remain enigmatic, previous studies have suggested that C. rosea may secrete F. graminearum growth inhibitors. Further toward this, experiments described herein show that induction of C. rosea cultures by the addition of an aliquot of F. graminearum(Fg)-spent media (including macroconidia), yield C. rosea (Cr)-spent media that elicited higher anti-F. graminearum activity than either control or deoxynivalenol (DON)-induced Cr-spent media. To gain additional insight into the genetic and metabolic factors modulating this interaction, transcriptomic (RNAseq) profiles of C. rosea in response to DON and Fg-spent media treatment, were developed. This analysis revealed 24,112 C. rosea unigenes, of which 5,605 and 6,285 were differentially regulated by DON and F-spent media, respectively. More than half of these unigenes were up-regulated, with annotations, most notably in the Fg-spent media treatment data, suggesting enhancement of polyketide (PK) and non-ribosomal peptide (NRP) secondary metabolite precursor synthesis, and PK/NRP-like synthases. Four ABC transporters were also up-regulated in response to Fg-spent media. Further analysis showed that the PK and NRP-like synthases belong to three gene clusters that also include ABC transporters, and other genes known to tailor secondary metabolite biosynthesis. The RNAseq data was further validated using quantitative RT-qPCR. Taken together, these results show that C. rosea responds to the presence of Fg-spent media (and to a lesser extent, DON-alone) by up-regulating unique aspects of its secondary metabolism-related genetic repertoire. The identities and roles of C. rosea secondary metabolites produced by the targeted gene clusters are now under investigation.

Structural Diversity and Biological Activities of Novel Secondary Metabolites from Endophytes

Exploration of structurally novel natural products greatly facilitates the discovery of biologically active pharmacophores that are biologically validated starting points for the development of new drugs. Endophytes that colonize the internal tissues of plant species, have been proven to produce a large number of structurally diverse secondary metabolites. These molecules exhibit remarkable biological activities, including antimicrobial, anticancer, anti-inflammatory and antiviral properties, to name but a few. This review surveys the structurally diverse natural products with new carbon skeletons, unusual ring systems, or rare structural moieties that have been isolated from endophytes between 1996 and 2016. It covers their structures and bioactivities. Biosynthesis and/or total syntheses of some important compounds are also highlighted. Some novel secondary metabolites with marked biological activities might deserve more attention from chemists and biologists in further studies.

Bioactive terpenoids from Santalum album derived endophytic fungus Fusarium sp. YD-2

Two new spiromeroterpenoids, namely fusariumin A (1) and B (2), along with four known terpenoids, asperterpenoid A (3), agathic acid (4), guignardone N (5), and trametenolic acid (6), were obtained from the endophytic fungus Fusarium sp. YD-2, derived from the twigs of Santalum album. Their structures were elucidated by a combination of spectroscopic analyses. The absolute configuration of 1 was determined by single-crystal X-ray diffraction using Cu Kα radiation, and that of 2 was elucidated on the basis of experimental and calculated electronic circular dichroism spectra. Compound 2 exhibited moderate anti-inflammatory activity in vitro by inhibiting nitric oxide (NO) production in lipopolysaccharide activated RAW264.7 cells with an IC₅₀ value of 50 μM, and compound 3 showed strong anti-inflammatory activity with an IC₅₀ value of 1.6 μM. In the antibacterial assay, compound 1 displayed significant activities against Staphylococcus aureus and Pseudomonas aeruginosa with an MIC value of 6.3 μg mL⁻¹, and compound 3 showed moderate activities against Salmonella enteritidis and Micrococcus luteus with MIC values of 6.3 and 25.2 μg mL⁻¹, respectively.

Two new spiromeroterpenoids, namely fusariumin A (1) and B (2), along with four known terpenoids, asperterpenoid A (3), agathic acid (4), guignardone N (5), and trametenolic acid (6), were obtained from the endophytic fungus Fusarium sp. YD-2, derived from the twigs of Santalum album.

Cytotoxic Naphthoquinone and Azaanthraquinone Derivatives from an Endophytic Fusarium solani

Bioactivity-guided fractionation of the ethyl acetate extract obtained from the culture of the endophytic fungus Fusarium solani resulted in the isolation of one new naphthoquinone, 9-desmethylherbarine (1), and two azaanthraquinone derivatives, 7-desmethylscorpinone (2) and 7-desmethyl-6-methylbostrycoidin (3), along with four known compounds. Their structures were elucidated by spectral analysis, as well as a direct comparison of spectral data with those of known compounds. Azaanthraquinones 2 and 3 showed cytotoxic activity against four human tumor cell lines, MDA MB 231, MIA PaCa2, HeLa, and NCI H1975. A molecular docking study suggested DNA interactions as the mode of action of these naphthoquinones and azaanthraquinones.

Potential allelopathic azaphilones produced by the endophytic Chaetomium globosum TY1 inhabited in Ginkgo biloba using the one strain-many compounds method

On the basis of the one strain-many compounds strategy, seven azaphilones, including Chaetomugilin A (1), D (2), S (3), I (4), J (5), Q (6) and O (7), were isolated from the endophytic Chaetomium globosum TY1. Their structures were identified by NMR and HRESIMS spectrometry data. All azaphilones were evaluated for plant growth regulation using eight species of herbaceous plant seeds seedling growth bioassay, which showed the plant growth influence of the seedling. Among these compounds tested, Chaetomugilin O (7) with tetrahydrofuran exhibited higher response index and lower IC50 values than positive control glyphosate, a broad-spectrum systemic herbicide. 1-3 also showed better or similar inhibit activity to glyphosate. The structure-allelopathic activity relationship analysis of these isolated azaphilones indicates that both tetrahydrofuran and tetrahydrofuran combine with lactones ring groups give potent inhibition of seedling growth. Chaetomugilin O and Chaetomugilin A, D, S could be used to develop natural eco-friendly herbicides.

Three cyclic pentapeptides and a cyclic lipopeptide produced by endophytic Fusarium decemcellulare LG53

Endophytic Fusarium decemcellulare LG53 harbored in Mahonia fortunei produces three cyclic pentapeptides (1–3) and the cyclic lipopeptide, fusaristatin A (4).

Secondary metabolites from the endophytic Botryosphaeria dothidea of Melia azedarach and their antifungal, antibacterial, antioxidant, and cytotoxic activities

Two new metabolites, an α-pyridone derivative, 3-hydroxy-2-methoxy-5-methylpyridin-2(1H)-one (1), and a ceramide derivative, 3-hydroxy-N-(1-hydroxy-3-methylpentan-2-yl)-5-oxohexanamide (2), and a new natural product, 3-hydroxy-N-(1-hydroxy-4-methylpentan-2-yl)-5-oxohexanamide (3), along with 15 known compounds including chaetoglobosin C (7) and chaetoglobosin F (8) were isolated from the solid culture of the endophytic fungus Botryosphaeria dothidea KJ-1, collected from the stems of white cedar (Melia azedarach L). The structures were elucidated on the basis of spectroscopic analysis (1D and 2D NMR experiments and by mass spectrometric measurements), and the structure of 1 was confirmed by X-ray single-crystal diffraction. These metabolites were evaluated in vitro for antimicrobial, antioxidant, and cytotoxicity activities. Pycnophorin (4) significantly inhibited the growth of Bacillus subtilis and Staphyloccocus aureus with equal minimum inhibitory concentration (MIC) values of 25 μM. Stemphyperylenol (5) displayed a potent antifungal activity against the plant pathogen Alternaria solani with MIC of 1.57 μM comparable to the commonly used fungicide carbendazim. Both altenusin (9) and djalonensone (10) showed markedly DPPH radical scavenging activities. In addition, stemphyperylenol (5) and altenuene (6) exhibited strong cytotoxicity against HCT116 cancer cell line with a median inhibitory concentration (IC50) value of 3.13 μM in comparison with the positive control etoposide (IC50 = 2.13 μM). This is the first report of the isolation of these compounds from the endophytic B. dothidea.