Antibacterial secondary metabolites from an endophytic fungus, Eupenicillium sp. LG41

Andrastin-type meroterpenoids, α-pyrone polyketides, and sesquicarane derivatives from Penicillium sp., a fungus isolated from Pinus koraiensis seed

The genus Penicillium has provided us with the household antibiotic penicillin and the well-known lipid-lowering agent mevastatin. The strain Penicillium sp. SZ-1 was found to grow vigorously in an intact Pinus koraiensis seed, it is inferred that the strain may develop unique mechanisms associated with the biosynthesis of rare metabolites. Further fermentation of the strain on solid rice medium yielded thirteen undescribed compounds, including three andrastin-type meroterpenoids (1-3), two α-pyrone polyketides (4 and 5), and eight sesquicarane derivatives (6-13), along with seven known compounds (14-20). Their structures were determined by detailed analysis of the spectroscopic and spectrometric data (NMR and HRESIMS), in addition to comparisons of the experimental and calculated ECD data for absolute configurational assignments. The hemiacetal moiety in compounds 1 and 2 and the 3α-hydroxy group in compound 3 were rarely found in the andrastin-type meroterpenoid family. The sesquicaranes belong to a small group of sesquiterpenoid that are rarely reported. Bioassay study showed that compound 1 exhibited inhibitory effects against Staphylococcus aureus ATCC 29213 and Escherichia coli ATCC 25922 with MIC values of 64 and 32 μg/mL, respectively. In addition, compounds 1 and 3 displayed weak DPPH radical scavenging activities. The andrastins and sesquicaranes in this study enriched the structural diversity of these classes of terpenoids. Of note, this study is the first report on the metabolites of a fungus isolated from P. koraiensis seed.

OSMAC Strategy: A promising way to explore microbial cyclic peptides

Microbial secondary metabolites are pivotal for the development of novel drugs. However, conventional culture techniques, have left a vast array of unexpressed biosynthetic gene clusters (BGCs) in microorganisms, hindering the discovery of metabolites with distinct structural features and diverse biological functions. To address this limitation, several innovative strategies have been emerged. The "One Strain Many Compounds" (OSMAC) strategy, which involves altering microbial culture conditions, has proven to be particularly effective in mining numerous novel secondary metabolites for the past few years. Among these, microbial cyclic peptides stand out. These peptides often comprise rare amino acids, unique chemical structures, and remarkable biological function. With the advancement of the OSMAC strategy, a plethora of new cyclic peptides have been identified from diverse microbial genera. This work reviews the progress in mining novel compounds using the OSMAC strategy and the applications of this strategy in discovering 284 microbial cyclic peptides from 63 endophytic strains, aiming to offer insights for the further explorations into novel active cyclic peptides.

Discovery of a novel anti-osteoporotic agent from marine fungus-derived structurally diverse sirenins

Thirteen new sirenin derivatives named eupenicisirenins C-O (1-13), along with a biosynthetically related known one (14), were isolated from the mangrove sediment-derived fungus Penicillium sp. SCSIO 41410. The structures, which possessed a rare cyclopropane moiety, were confirmed by extensive analyses of the spectroscopic data, quantum chemical calculations, and X-ray diffraction. Among them, eupenicisirenin C (1) exhibited the strongest NF-κB inhibitory activities, as well as suppressing effects on cGAS-STING pathway. Moreover, 1 showed the significant inhibitory effect on RANKL-induced osteoclast differentiation in bone marrow macrophages cells, and also displayed the therapeutic potential on prednisolone-induced zebrafish osteoporosis. Transcriptome analysis and the following verification tests suggested that its anti-osteoporotic mechanism is related to the extracellular matrix receptor interaction-related pathways. This study provided a promising marine-derived anti-osteoporotic agent for the treatment of skeletal disease.

Fungal Endophytes: Microfactories of Novel Bioactive Compounds with Therapeutic Interventions; A Comprehensive Review on the Biotechnological Developments in the Field of Fungal Endophytic Biology over the Last Decade

The seminal discovery of paclitaxel from endophytic fungus Taxomyces andreanae was a milestone in recognizing the immense potential of endophytic fungi as prolific producers of bioactive secondary metabolites of use in medicine, agriculture, and food industries. Following the discovery of paclitaxel, the research community has intensified efforts to harness endophytic fungi as putative producers of lead molecules with anticancer, anti-inflammatory, antimicrobial, antioxidant, cardio-protective, and immunomodulatory properties. Endophytic fungi have been a valuable source of bioactive compounds over the last three decades. Compounds such as taxol, podophyllotoxin, huperzine, camptothecin, and resveratrol have been effectively isolated and characterized after extraction from endophytic fungi. These findings have expanded the applications of endophytic fungi in medicine and related fields. In the present review, we systematically compile and analyze several important compounds derived from endophytic fungi, encompassing the period from 2011 to 2022. Our systematic approach focuses on elucidating the origins of endophytic fungi, exploring the structural diversity and biological activities exhibited by these compounds, and giving special emphasis to the pharmacological activities and mechanism of action of certain compounds. We highlight the tremendous potential of endophytic fungi as alternate sources of bioactive metabolites, with implications for combating major global diseases. This underscores the significant role that fungi can play in the discovery and development of novel therapeutic agents that address the challenges posed by prevalent diseases worldwide.

Distribution, cytotoxicity, and antioxidant activity of fungal endophytes isolated from Tsuga chinensis (Franch.) Pritz. in Ha Giang province, Vietnam

Purpose

An endangered Tsuga chinensis (Franch.) Pritz. is widely used as a natural medicinal herb in many countries, but little has been reported on its culturable endophytic fungi capable of producing secondary metabolites applied in modern medicine and pharmacy. The present study aimed to evaluate the distribution of fungal endophytes and their cytotoxic and antioxidant properties.

Methods

This study used the surface sterilization method to isolate endophytic fungi which were then identified using morphological characteristics and ITS sequence analysis. The antimicrobial and cytotoxic potentials of fungal ethyl acetate extracts were evaluated by the minimum inhibitory concentration (MIC) and sulforhodamine B (SRB) assays, respectively. Paclitaxel-producing fungi were primarily screened using PCR-based molecular markers. Additionally, biochemical assays were used to reveal the antioxidant potencies of selected strains.

Results

A total of sixteen endophytic fungi that belonged to 7 known and 1 unknown genera were isolated from T. chinensis. The greatest number of endophytes was found in leaves (50%), followed by stems (31.3%) and roots (18.7%). Out of 16 fungal strains, 33.3% of fungal extracts showed significant antimicrobial activities against at least 4 pathogens with inhibition zones ranging from 11.0 ± 0.4 to 25.8 ± 0.6 mm. The most prominent cytotoxicity against A549 and MCF7 cell lines (IC50 value < 92.4 μg/mL) was observed in Penicillium sp. SDF4, Penicillium sp. SDF5, Aspergillus sp. SDF8, and Aspergillus sp. SDF17. Out of three key genes (dbat, bapt, ts) involved in paclitaxel biosynthesis, strains SDF4, SDF8, and SDF17 gave one or two positive hits, holding the potential for producing the billion-dollar anticancer drug paclitaxel. Furthermore, four bioactive strains also displayed remarkable and wide-range antioxidant activity against DPPH, hydroxyl radical, and superoxide anion, which was in relation to the high content of flavonoids and polyphenols detected.

Conclusion

The present study exploited for the first time fungal endophytes from T. chinensis as a promising source for the discovery of new bioactive compounds or leads for the new drug candidates.

Endophytic Fungi as a Source of Antibacterial Compounds-A Focus on Gram-Negative Bacteria

Bacterial resistance has become one of the main motives in the worldwide race for undescribed antibacterial agents. The difficulties in the treatment of bacterial infections are a public health issue that increasingly highlights the need for antimicrobial agents. Endophytic microorganisms are a promising alternative in the search for drugs, due to the vast number of metabolites produced with unique characteristics and bioactive potential. This review highlights the importance of endophytic microorganisms as a source of secondary metabolites in the search for active molecules against bacteria of medical importance, with a special focus on gram-negative species. This fact is supported by the findings raised in this review, which brings an arsenal of 166 molecules with characterized chemical structures and their antibacterial activities. In addition, the low cost, ease of maintenance, and optimization-controlled fermentation conditions favor reproducibility in commercial scale. Given their importance, it is necessary to intensify the search for new molecules from endophytic microorganisms, and to increasingly invest in this very promising font.

Exploring the potential of endophytes and their metabolites for bio-control activity

In the current scenario, extensive use of synthetic chemicals in agriculture is creating notable problems such as disease and pest resistance, residues, yield loss, and soil unproductiveness. These harmful chemicals are eventually reaching our food plate through bioaccumulation and biomagnification in a crop. As a result, beneficial microorganisms are regularly being explored as a safer option in the agriculture sector for their ability to produce valuable bioactive secondary metabolites, particularly for crop protection. Such natural (bio) products are harmless to plants, humans, and the environment. In our quest for the search of the sources of bioactive constituents from the microorganisms, endophytes are the front-runner. They mutually reside inside the plant providing support against phytopathogens by releasing an array of bioactive secondary metabolites building climate reliance of the host plant. The purpose of this review is to examine the biocontrol potential of endophytes against bacterial and fungal pathogens in sustainable agriculture. We also attempt to explain the structure and activity of the secondary metabolites produced by bacterial and fungal endophytes in conjunction with their biocontrol function. Additionally, we address potential future research directions for endophytes as biopesticides.

Altereporenes A-E, five epoxy octa-hydronaphthalene polyketides produced by an endophytic fungus Alternaria sp. YUD20002

Five previously undescribed epoxy octa-hydronaphthalene polyketides, altereporenes A-E (1-5) were isolated from rice culture of the endophytic fungus Alternaria sp. YUD20002 derived from the tubers of Solanum tuberosum. Their structures were determined on the basis of comprehensive spectroscopic analyses, while the absolute configurations were elucidated by the comparison of experimental and calculated specific rotations. Meanwhile, the antimicrobial, cytotoxic, anti-inflammatory and acetylcholinesterase inhibitory activities of compounds 1-5 were also investigated.

Three new pyrrole alkaloids from the endophytic fungus Albifimbria viridis

Three new pyrrole alkaloids albifipyrrols A-C (1-3), were isolated from the endophytic fungus Albifimbria viridis collected from the Chinese medicinal plant. Their structures were elucidated by extensive NMR and HRESIMS spectrometric analyses. All compounds were evaluated for immunosuppressive activity. Fortunately, compound 2 exhibits certain inhibition specifically against the LPS-induced proliferation of B lymphocyte cells with IC₅₀ value 16.16 μM.

α-Pyrone and decalin derivatives from the marine-derived fungus Trichoderma harzianum PSU-MF79

Two new compounds, one α-pyrone (trichoharzianone) and one decalin (trichoharzianin), along with eight known compounds including three decalins, two δ-lactones, two carboxylic acids and one isochroman were isolated from the marine-derived fungus Trichoderma harzianum PSU-MF79. The structures were determined by spectroscopic methods. The relative configuration of trichoharzianin was assigned based on NOEDIFF data and coupling constants whereas the absolute configurations were established by comparison of electronic circular dichroism data with those of the co-metabolites. Known (-)-massoia lactone exhibited mild antifungal activity against Cryptococcus neoformans ATCC90113 flucytosine-resistant, Candida albicans ATCC90028 and C. albicans NCPF3153 with MIC values of 128, 200 and 200 µg/mL, respectively, and weak cytotoxic activity against HCT-116 and MCF-7 cell lines with the respective IC₅₀ values of 17 and 32 µM. In addition, it was noncytotoxic against noncancerous Vero cells with an IC₅₀ value of >100 µM.

Peniterpenoids A-C, new sesquiterpenoid metabolites from a wheat cyst nematode Penicillium janthinellum

Three new sesquiterpenoids, peniterpenoids A - C (1-3), together with six known metabolites (4-9) were isolated from an entomogenous fungus Penicillium janthinellum (LB1.20090001) collected from a wheat cyst nematode. The structures of the new compounds were elucidated based on NMR and HRESIMS spectroscopic analyses. The absolute configuration of the C-8 secondary alcohol of peniterpenoid B (2) was determined by [Rh₂(OCOCF₃)₄]-induced ECD experiment. Subsequently, the antimicrobial and DPPH scavenging activities were determined. Compounds 6-8 exhibited moderate antibacterial activities against Staphylococcus aureus (CGMCC1.2465) with MIC values of 25.0, 50.0 and 12.5 μg/mL, respectively.

Itaconic acid derivatives: structure, function, biosynthesis, and perspectives

Itaconic acid possessing a vinylidene group, which is mainly produced by fungi, is used as a biobased platform chemical and shows distinctive bioactivities. On the other hand, some fungi and lichens produce itaconic acid derivatives possessing itaconic acid skeleton, and the number of the derivatives is currently more than seventy. Based on the molecular structures, they can be categorized into two groups, alkylitaconic acids and α-methylene-γ-butyrolactones. Interestingly, some itaconic acid derivatives show versatile functions such as antimicrobial, anti-inflammatory, antitumor, and plant growth-regulating activities. The vinylidene group of itaconic acid derivatives likely participates in these functions. It is suggested that α-methylene-γ-butyrolactones are biosynthesized from alkylitaconic acids which are first biosynthesized from acyl-CoA and oxaloacetic acid. Some modifying enzymes such as hydroxylase and dehydratase are likely involved in the further modification after biosynthesis of their precursors. This contributes to the diversity of itaconic acid derivatives. In this review, we summarize their structures, functions, and biosynthetic pathways together with a discussion of a strategy for the industrial use. KEY POINTS: • Itaconic acid derivatives can be categorized into alkylitaconic acids and α-methylene-γ-butyrolactones. • The vinylidene group of itaconic acid derivatives likely participates in their versatile function. • It is suggested that α-methylene-γ-butyrolactones are biosynthesized from alkylitaconic acids which are first synthesized from acyl-CoA and oxaloacetic acid.

New paraconic acids from the endophytic fungus Xylariaceae sp. J4

Three new paraconic acids, xylariacinics A-C (1-3), were isolated from the endophyte Xylariaceae sp. J4 harbored in the medicinal plant Blumea balsamifera. Their structures were elucidated on the basis of extensive spectroscopic data including HRMS, and NMR. The antibacterial efficacies of compounds 1-3 were evaluated against a panel of bacteria such as Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa. Their antifungal activities were also tested against Colletotrichum gloeosporioides. Unfortunately, all of them were inactive.

Microbial Screening Based on the Mizoroki-Heck Reaction Permits Exploration of Hydroxyhexylitaconic-Acid-Producing Fungi in Soils

Recently, we developed a unique microbial screening method based on the Mizoroki–Heck reaction for itaconic acid (IA)-producing fungi. This method revealed that 37 out of 240 fungal strains isolated from soils produce vinyl compounds, including IA. In this study, we further characterized these compounds in order to verify that the screening method permits the isolation of fungi that produce other vinyl compounds, excluding IA. HPLC analysis showed that 11 out of 37 isolated strains produced IA, similar to Aspergillus terreus S12-1. Surprisingly, the other 8 isolated strains produced two vinyl compounds with HPLC retention times different from that of IA. From these strains, the vinyl compounds of Aspergillus niger S17-5 were characterized. Mass spectrometric and NMR analyses showed that they were identical to 8-hydroxyhexylitaconic acid (8-HHIA) and 9-HHIA. This finding showed that 8-HHIA- and 9-HHIA-producing fungi, as well as IA-producing fungi, are ubiquitously found in soils. Neither 8-HHIA nor 9-HHIA showed antibacterial or anti-inflammatory activities. Interestingly, 8-HHIA and 9-HHIA showed cytotoxicity against the human cervical cancer cell line (HeLa) and human diploid cell line (MRC-5), and MRC-5 only, respectively, compared to IA at the same concentration. This study indicates that the screening method could easily discover fungi producing 8-HHIA and 9-HHIA in soils.

Bioactive Secondary Metabolites from Endophytic Fungi

Background:

Endophytes represent a complex community of microorganisms colonizing asymptomatically internal tissues of higher plants. Several reports have shown that endophytes enhance the fitness of their host plants by direct production of bioactive secondary metabolites, which are involved in protecting the host against herbivores and pathogenic microbes. In addition, it is increasingly apparent that endophytes are able to biosynthesize medicinally important “phytochemicals”, originally believed to be produced only by their host plants.

Objective:

The present review provides an overview of secondary metabolites from endophytic fungi with pronounced biological activities covering the literature between 2010 and 2017. Special focus is given on studies aiming at exploration of the mode of action of these metabolites towards the discovery of leads from endophytic fungi. Moreover, this review critically evaluates the potential of endophytic fungi as alternative sources of bioactive “plant metabolites”.

Results:

Over the past few years, several promising lead structures from endophytic fungi have been described in the literature. In this review, 65 metabolites are outlined with pronounced biological activities, primarily as antimicrobial and cytotoxic agents. Some of these metabolites have shown to be highly selective or to possess novel mechanisms of action, which hold great promises as potential drug candidates.

Conclusion:

Endophytes represent an inexhaustible reservoir of pharmacologically important compounds. Moreover, endophytic fungi could be exploited for the sustainable production of bioactive “plant metabolites” in the future. Towards this aim, further insights into the dynamic endophyte - host plant interactions and origin of endophytic fungal genes would be of utmost importance.

Biological Activity of Endophytic Fungi from the Roots of the Medicinal Plant Vernonia anthelmintica

Endophytic fungi were first isolated from the fresh root of the Chinese medicinal plant Vernonia anthelmintica collected from the Hotan Prefecture within the Xinjiang Autonomous region of the People’s Republic of China. This plant has been used in Uyghur traditional medicine to treat vitiligo, a skin condition characterized by patches of the skin losing their pigment. In total, fifteen fungal strains were isolated. Among these, four endophytic fungi were identified by their DNA sequences and registered to GenBank with accession numbers. The isolates were identified as Schizophyllum commune XJA1, Talaromyces sp. XJA4, Aspergillus sp. XJA6, Aspergillus terreus XJA8. Ethyl acetate extracts of all fungal strains were used to quantify melanin content and to identify in vitro biological activity assays including antimicrobial, antioxidant, cytotoxic, antidiabetic and tyrosinase activity on B16 cells. Among the extracts of all four identified strains, the ethyl acetate extract of the Aspergillus sp. XJA6 was chosen for further characterization because it presented the highest biological activity against these tests. In addition, twenty four volatile compounds from the petroleum ether fraction were characterized by GC–MS.

Wood-decaying fungi found in Southern Ghana: A potential source of new anti-infective compounds

Background: Discovery of bioactive natural products are instrumental for development of novel antibiotics. The discovery and development of natural products such as penicillin represented a major milestone in the treatment of bacterial infections. Currently, many antibiotics have lost their relevance in clinics due to the emergence of drug-resistant microbial pathogens. Hence, there is the need for continuous search of new compounds endowed with potent antimicrobial activity. In this study, wood-decaying fungi (WDF) from Southern Ghana were explored for their potential as sources of novel antimicrobial compounds with intent of expanding the effort into a drug discovery programme in the near future. Methods: A total of 54 WDF isolates were fermented in potato dextrose broth and the secondary metabolites obtained were analyzed for the presence of antimicrobial agents using the disc diffusion assay. Chromatography techniques were used for preliminary analysis of the chemical composition of the extracts and for fractionation of the extracts that showed antimicrobial activity. Results: The extracts from 40 out of the 54 WDF isolates exhibited significant antimicrobial activity against either Staphylococcus aureus, Escherichia coli or Candida albicans. Fractionation of these bioactive extracts, followed by bioassay of the organic fractions obtained, indicate that extracts exhibiting antimicrobial activity against more than one of the three test organisms could be attributed to the presence of different bioactive compounds. Analysis of the composition of the extracts revealed that terpenes were predominant. Conclusions: This study suggests that a significant proportion of WDF in Southern Ghana produce antimicrobial compounds which could be potential sources of novel anti-infective agents and support the plans of developing a drug discovery programme in Ghana based on the fermentation of WDF.

Dimeric 1,4-benzoquinone Derivatives with Cytotoxic Activities from the Marine-Derived Fungus Penicillium sp. L129

Two new dimeric 1,4-benzoquinone derivatives, peniquinone A (1) and peniquinone B (2), a new dibenzofuran penizofuran A (3), and a new pyrazinoquinazoline derivative quinadoline D (4), together with 13 known compounds (5-17), were isolated from a marine-derived fungus Penicillium sp. L129. Their structures, including absolute configurations, were elucidated by extensive spectroscopic data and electronic circular dichroism calculations. Compound 1 exhibited cytotoxicity against the MCF-7, U87 and PC3 cell lines with IC₅₀ values of 12.39 µM, 9.01 µM and 14.59 µM, respectively, while compound 2 displayed relatively weak cytotoxicity activities against MCF-7, U87 and PC3 cell lines with IC₅₀ values of 25.32 µM, 13.45 µM and 19.93 µM, respectively. Furthermore, compound 2 showed weak quorum sensing inhibitory activity against Chromobacterium violaceum CV026 with an MIC value of 20 μg/well.

Induced production of steroids by co-cultivation of two endophytes from Mahonia fortunei

A new ergosterol derivative, 23R-hydroxy-(20Z,24R)-ergosta-4,6,8(14),20(22)-tetraen-3-one (1), and a biosynthetically related known compound, (22E,24R)-ergosta-4,6,8(14),22-tetraen-3-one (2), were isolated from the co-culture between endophytic fungus Pleosporales sp. F46 and endophytic bacterium Bacillus wiedmannii Com1 both inhibiting in the medicinal plant Mahonia fortunei. The structure of the new compound 1 was determined by extensive spectroscopic analysis using HRMS and NMR, together with the modified Mosher's ester method. This is the first example of isolation of a ergosterol derivative with a Δ²⁰⁽²²⁾-double bond in the side chain. Compound 1 exhibited moderate antibacterial efficacy against Staphylococcus aureus and no obvious cytotoxic activities against the cancer cell lines A549, MDA-MB-231 and Hct116. Our results not only reveal that compound 1 is a potent antibacterial lead compound, but also highlight the powder of co-cultivation for inducing the production of cryptic natural products from endophytes derived from the same host plant.

A new griseofulvin derivative from a soft coral-derived fungus Eupenicillium sp. SCSIO41208

A new griseofulvin derivative, eupenigriseofulvin (1), together with six known compounds, griseofulvin (2), dechlorogriseofluvin (3), dechloroisogriseofulvin (4), trichopyrone (5), 2-(4-hydroxyphenyl)-ethanol (6), and 1-phenylethane-1,2-diol (7), were isolated from the EtOAc extract of Eupenicillium sp. SCSIO41208. The structures of these compounds were elucidated by spectroscopic methods including NMR and mass spectrometry. The absolute configuration of 1 was determined on the basis of electronic circular dichroism (ECD) data analysis.

New Alkylitaconic Acid Derivatives from Nodulisporium sp. A21 and Their Auxin Herbicidal Activities on Weed Seeds

Five alkylitaconic acid (AA) derivatives, including two novel compounds, epideoxysporothric acid (2) and sporochartine F (5), and three known compounds, deoxysporothric acid (1), deoxyisosporothric acid (3), and 1-undecen-2,3-dicarboxylic acid (4), were obtained from the fermentation culture of the endophytic fungus Nodulisporium sp. A21. The auxin herbicidal activities of compounds 1-4 against weed seeds were investigated under laboratory conditions. In general, the tested compounds displayed radicle growth promoting activity at low doses and inhibitory activity at higher doses. Compounds 1 and 2 could significantly inhibit the radicle growth of dicotyledon weeds, Eclipta prostrata and Veronica persica, at a concentration range from 50 to 200 μg mL^-1, while 3 notably stimulated radicle growth at the same concentration range. The results suggested that these AA derivatives have the potential to be used as the lead scaffold for novel auxin herbicide development. In addition, the biosynthetic pathways of 1-4 were deduced based on ¹³C labeling experiment.

Acrepyrone A, a new γ-pyrone derivative from an endophytic fungus, Acremonium citrinum SS-g13

A new γ-pyrone derivative, acrepyrone A (1), and three known sorbicillinoids, trichodimerol (2), dihydrotrichodimerol (3) and tetrahydrotrichodimerol (4) were isolated from an endophytic fungus, Acremonium citrinum SS-g13, harboured in the roots of the Chinese medicinal plant Fructus mori. Their structures were determined by analysing MS, NMR, and ECD data. Compound 1 was evaluated for its cytotoxic effect, antibacterial activity and quorum sensing inhibitory potential.

New α-pyrones from an endophytic fungus, Hypoxylon investiens J2

Four new α-pyrones, hypotiens A–D (1–4), were isolated from a fungal endophyte, Hypoxylon investiens J2, harbored in the medicinal plant Blumea balsamifera. Their structures were determined through detailed HRMS and NMR spectroscopic data. Compounds 1–4 are new α-pyrone derivatives containing an unusual dimethyl substitution in the highly unsaturated side chain. Their plausible biosynthetic pathway was discussed. Biological assay indicated that compounds 1–4 showed no antimicrobial, quorum sensing inhibitory, and cytotoxic activities. The specific side chain in α-pyrone derivatives 1–4 might be responsible for the weak pharmacological activities.

Four new α-pyrones, hypotiens A–D (1–4), were isolated from a fungal endophyte, Hypoxylon investiens J2, harbored in the medicinal plant Blumea balsamifera.

Onydecalins, Fungal Polyketides with Anti- Histoplasma and Anti-TRP Activity

We report an unusual 3-substituted pyridine polyketide, onydecalin A (1), which was obtained along with 2 as a major constituent from the fungus Aioliomyces pyridodomos (order: Onygenales) following a two-month fermentation. Feeding studies demonstrated that the pyridine subunit originates via an unprecedented biosynthetic process in comparison to other polyketide-linked pyridines or derivatives such as pyridones. The slow growth of the fungus led us to perform a one-year fermentation, leading to production of compounds 2-4 as the major constituents. These compounds showed modest but selective inhibition against a variety of transient receptor potential channels, as well as against the human pathogenic fungus Histoplasma capsulatum.

Endophytic Fungus Isolated From Achyrocline satureioides Exhibits Selective Antiglioma Activity-The Role of Sch-642305

Glioblastoma is the most devastating primary brain tumor. Current treatment is palliative, making necessary the development of new therapeutic strategies to offer alternatives to patients. Therefore, endophytes represent an interesting source of natural metabolites with anticancer potential. These microorganisms reside in tissues of living plants and act to improve their growth. Evidence revealed that several medicinal plants are colonized by endophytic fungi producer of antitumor metabolites. Achyrocline satureioides is a Brazilian medicinal plant characterized by its properties against gastrointestinal disturbances, anticancer and antioxidant effects. However, there are no reports describing the endophytic composition of A. satureioides. The present study proposes the isolation of endophytic fungus from A. satureioides, extract preparation, phytochemical characterization and evaluation of its antiglioma potential. Our data showed that crude extracts of endophyte decreased glioma viability with IC50 values of 1.60-1.63 μg/mL to eDCM (dichloromethane extract) and 37.30-55.12 μg/mL to eEtAc (ethyl acetate extract), respectively. Crude extracts induced cell death by apoptosis with modulation of redox status. In order to bioprospect anticancer metabolites, endophytic fungus extracts were subjected to guided fractionation and purification yielded five fractions of each extract. Six of ten fractions showed selective antiproliferative activity against glioma cells, with IC50 values ranged from 0.95 to 131.3 μg/mL. F3DCM (from eDCM) and F3EtAc (from eEtAc) fractions promoted C6 glioma toxicity with IC50 of 1.0 and 27.05 μg/mL, respectively. F3EtAc fraction induced late apoptosis and arrest in G2/M stage, while F3DCM promoted apoptosis with arrest in Sub-G1 phase. Moreover, F3DCM increased antioxidant defense and decreased ROS production. Additionally, F3DCM showed no cytotoxic activity against astrocytes, revealing selective effect. Based on promising potential of F3DCM, we identified the production of Sch-642305, a lactone, which showed antiproliferative properties with IC50 values of 1.1 and 7.6 μg/mL to C6 and U138MG gliomas, respectively. Sch-642305 promoted arrest on cell cycle in G2/M inducing apoptosis. Furthermore, this lactone decreased glioma cell migration and modulated redox status, increasing superoxide dismutase and catalase activities and enhancing sulfhydryl content, consequently suppressing reactive species of oxygen generation. Taken together, these results indicate that metabolites produced by endophytic fungus isolated from A. satureioides have therapeutic potential as antiglioma agent.

Endophytic Fungi: A Source of Potential Antifungal Compounds

The emerging and reemerging forms of fungal infections encountered in the course of allogeneic bone marrow transplantations, cancer therapy, and organ transplants have necessitated the discovery of antifungal compounds with enhanced efficacy and better compatibility. A very limited number of antifungal compounds are in practice against the various forms of topical and systemic fungal infections. The trends of new antifungals being introduced into the market have remained insignificant while resistance towards the introduced drug has apparently increased, specifically in patients undergoing long-term treatment. Considering the immense potential of natural microbial products for the isolation and screening of novel antibiotics for different pharmaceutical applications as an alternative source has remained largely unexplored. Endophytes are one such microbial community that resides inside all plants without showing any symptoms with the promise of producing diverse bioactive molecules and novel metabolites which have application in medicine, agriculture, and industrial set ups. This review substantially covers the antifungal compounds, including volatile organic compounds, isolated from fungal endophytes of medicinal plants during 2013⁻2018. Some of the methods for the activation of silent biosynthetic genes are also covered. As such, the compounds described here possess diverse configurations which can be a step towards the development of new antifungal agents directly or precursor molecules after the required modification.

Comprehensive Secondary Metabolite Profiling Toward Delineating the Solid and Submerged-State Fermentation of Aspergillus oryzae KCCM 12698

Aspergillus oryzae has been commonly used to make koji, meju, and soy sauce in traditional food fermentation industries. However, the metabolic behaviors of A. oryzae during fermentation in various culture environments are largely uncharacterized. Thus, we performed time resolved (0, 4, 8, 12, 16 day) secondary metabolite profiling for A. oryzae KCCM 12698 cultivated on malt extract agar and broth (MEA and MEB) under solid-state fermentation (SSF) and submerged fermentation (SmF) conditions using the ultrahigh performance liquid chromatography-linear trap quadrupole-ion trap-mass spectrometry (UHPLC-LTQ-IT-MS/MS) followed by multivariate analyses. We observed the relatively higher proportions of coumarins and oxylipins in SSF, whereas the terpenoids were abundant in SmF. Moreover, we investigated the antimicrobial efficacy of metabolites that were extracted from SSF and SmF. The SSF extracts showed higher antimicrobial activities as compared to SmF, with higher production rates of bioactive secondary metabolites viz., ketone-citreoisocoumarin, pentahydroxy-anthraquinone, hexylitaconic acid, oxylipins, and saturated fatty acids. The current study provides the underpinnings of a metabolomic framework regarding the growth and bioactive compound production for A. oryzae under the primarily employed industrial cultivation states. Furthermore, the study holds the potentials for rapid screening and MS-characterization of metabolites helpful in determining the consumer safety implications of fermented foods involving Koji mold.

Epigenetic Modulation of Endophytic Eupenicillium sp. LG41 by a Histone Deacetylase Inhibitor for Production of Decalin-Containing Compounds

An endophytic fungus, Eupenicillium sp. LG41, isolated from the Chinese medicinal plant Xanthium sibiricum, was subjected to epigenetic modulation using an NAD⁺-dependent histone deacetylase (HDAC) inhibitor, nicotinamide. Epigenetic stimulation of the endophyte led to enhanced production of two new decalin-containing compounds, eupenicinicols C and D (3 and 4), along with two biosynthetically related known compounds, eujavanicol A (1) and eupenicinicol A (2). The structures and stereochemistry of the new compounds were elucidated by extensive spectroscopic analysis using LC-HRMS, NMR, optical rotation, and ECD calculations, as well as single-crystal X-ray diffraction. Compounds 3 and 4 exist in chemical equilibrium with two and three cis/trans isomers, respectively, as revealed by LC-MS analysis. Compound 4 was active against Staphylococcus aureus with an MIC of 0.1 μg/mL and demonstrated marked cytotoxicity against the human acute monocytic leukemia cell line (THP-1). We have shown that the HDAC inhibitor, nicotinamide, enhanced the production of compounds 3 and 4 by endophytic Eupenicillium sp. LG41, facilitating their isolation, structure elucidation, and evaluation of their biological activities.

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.

Antibacterial Azaphilones from an Endophytic Fungus, Colletotrichum sp. BS4

Three new compounds, colletotrichones A-C (1-3), and one known compound, chermesinone B (4a), were isolated from an endophytic fungus, Colletotrichum sp. BS4, harbored in the leaves of Buxus sinica, a well-known boxwood plant used in traditional Chinese medicine (TCM). Their structures were determined by extensive spectroscopic analyses including 1D and 2D NMR, HRMS, ECD spectra, UV, and IR, as well as single-crystal X-ray diffraction, and shown to be azaphilones sharing a 3,6a-dimethyl-9-(2-methylbutanoyl)-9H-furo[2,3-h]isochromene-6,8-dione scaffold. Owing to the remarkable antibacterial potency of known azaphilones coupled to the usage of the host plant in TCM, we evaluated the antibacterial efficacy of the isolated compounds against two commonly dispersed environmental strains of Escherichia coli and Bacillus subtilis, as well as against two human pathogenic clinical strains of Staphylococcus aureus and Pseudomonas aeruginosa. Compound 1 exhibited marked antibacterial potencies against the environmental strains that were comparable to the standard antibiotics. Compound 3 was also active against E. coli. Finally, compound 2a exhibited the same efficacy as streptomycin against the clinically relevant bacterium S. aureus. The in vitro cytotoxicity of these compounds on a human acute monocytic leukemia cell line (THP-1) was also assessed. Our results provide a scientific rationale for further investigations into endophyte-mediated host chemical defense against specialist and generalist pathogens.

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).

Endophytic Diaporthe sp. LG23 Produces a Potent Antibacterial Tetracyclic Triterpenoid

A new lanostanoid, 19-nor-lanosta-5(10),6,8,24-tetraene-1α,3β,12β,22S-tetraol (1), characterized by the presence of an aromatic B ring and hydroxylated at C-1, C-3, C-12, and C-22, was isolated from an endophytic fungus, Diaporthe sp. LG23, inhabiting leaves of the Chinese medicinal plant Mahonia fortunei. Six biosynthetically related known steroids were also isolated in parallel. Their structures were confirmed on the basis of detailed spectroscopic analysis in conjunction with the published data. Compound 1, an unusual fungus-derived 19-nor-lanostane tetracyclic triterpenoid with an aromatic B-ring system, exhibited pronounced antibacterial efficacy against both Gram-positive and -negative bacteria, especially the clinical isolates of Streptococcus pyogenes and Pseudomonas aeruginosa as well as a human pathogenic strain of Staphylococcus aureus. Our results reveal the potential of endophytes not only in conferring host fitness but also in contributing toward traditional host plant medicines.

A useful methoxyvinyl cation equivalent: α-t-butyldimethylsilyl-α-methoxyacetaldehyde

Described are the synthesis and application of α-t-butyldimethylsilyl-α-methoxyacetaldehyde as a formal methoxyvinyl cation equivalent. Addition of Grignard reagents to the title aldehyde, followed by treatment of the intermediate β-hydroxysilanes with KH, gives good yields of large Z-methoxyvinylated products. Assuming a Peterson-like elimination mechanism, one can infer that the Grignard addition proceeds with high syn selectivity. These results are consistent with a chelation control model involving coordination to the α-methoxy group in the title aldehyde rather than an alternative stereoelectronic Felkin-Anh-type model. It must be noted that a steric Felkin-Anh model also accounts for the observed stereochemistry. All told, the title reagent can be employed to efficiently append a Z-configured methoxyvinyl group to an appropriate R-M species, in two steps.