Dzf14 and their antibacterial activity by affecting homeostasis of cell membranes

BACKGROUND

Phytopathogenic bacteria cause severe losses to crops every year. The management of crop bacterial diseases with chemical agents has been considered as the main strategy. In order to cope with the bactericide resistance made by the pathogens, new antibacterials need to be continuously developed.

RESULTS

A chemical investigation from the endophytic fungus Rhexocercosporidium sp. Dzf14 has led to the isolation of 12 diphenyl ethers including two new ones named rhexocerin E (1) and rhexocercosporin G (2), along with two new depsides named rhexocerdepsides A (3) and B (4). The structures and absolute configurations of the new compounds were determined through comprehensive analysis of spectroscopic data and quantum chemical ECD calculations. Diphenyl ethers showed obviously antibacterial activity on Gram-positive bacteria. The structure-activity relationship of diphenyl ethers revealed that prenylation was critical to the antibacterial activity. Among them, rhexocercosporin D (12) possessed the strongest activity against Clavibacter michiganensis and Bacillus subtilis, and was selected for further mechanistic studies. It was found that rhexocercosporin D displayed bactericidal activity by affecting homeostasis of cell membranes. In addition to its rapid bactericidal effects on Gram-positive bacteria, rhexocercosporin D could restore the susceptibility against Gram-negative Agrobacterium tumefaciens by synergistic action with colistin.

CONCLUSION

Twelve diphenyl ethers and two depsides were isolated from endophytic fungus Rhexocercosporidium sp. Dzf14. Isopentenyl was critical for diphenyl ethers against Gram-positive bacteria. Rhexocercosporin D could affect homeostasis of bacterial cell membrane to exert rapid bactericidal activity. These findings highlight the antibacterial potential of the diphenyl ethers in crop bacterial disease management. © 2024 Society of Chemical Industry.

GDGJ-77B

Two new open-chain cytochalasins, xylarchalasins A and B (1 and 2), together with six known analogues (3-8), were isolated from the endophytic fungus Xylaria sp. GDGJ-77B from the Chinese medicinal plant Sophora tonkinensis. Their structures were elucidated on the basis of comprehensive spectroscopic analysis. Compound 2 displayed moderate antibacterial activities against Bacillus subtilis and Escherichia coli with MIC values of 25 and 12.5 μg/mL, respectively.

CB10100: α-Glucosidase Inhibitory Activity, Molecular Docking, and Molecular Dynamics Studies

Two α-pyrone analogs were isolated from the endophytic fungus Diaporthe sp. CB10100, which is derived from the medicinal plant Sinomenium acutum. These analogs included a new compound, diaporpyrone F (3), and a known compound, diaporpyrone D (4). The structure of 3 was identified by a comprehensive examination of HRESIMS, 1D and 2D NMR spectroscopic data. Bioinformatics analysis revealed that biosynthetic gene clusters for α-pyrone analogs are common in fungi of Diaporthe species. The in vitro α-glucosidase inhibitory activity and antibacterial assay of 4 revealed that it has a 46.40% inhibitory effect on α-glucosidase at 800 μM, while no antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA), Mycolicibacterium (Mycobacterium) smegmatis or Klebsiella pneumoniae at 64 μg/mL. Molecular docking and molecular dynamics simulations of 4 with α-glucosidase further suggested that the compounds are potential α-glucosidase inhibitors. Therefore, α-pyrone analogs can be used as lead compounds for α-glucosidase inhibitors in more in-depth studies.

Roles of endophytic fungi in medicinal plant abiotic stress response and TCM quality development

Medicinal plants, as medicinal materials and important drug components, have been used in traditional and folk medicine for ages. However, being sessile organisms, they are seriously affected by extreme environmental conditions and abiotic stresses such as salt, heavy metal, temperature, and water stresses. Medicinal plants usually produce specific secondary metabolites to survive such stresses, and these metabolites can often be used for treating human diseases. Recently, medicinal plants have been found to partner with endophytic fungi to form a long-term, stable, and win-win symbiotic relationship. Endophytic fungi can promote secondary metabolite accumulation in medicinal plants. The close relationship can improve host plant resistance to the abiotic stresses of soil salinity, drought, and extreme temperatures. Their symbiosis also sheds light on plant growth and active compound production. Here, we show that endophytic fungi can improve the host medicinal plant resistance to abiotic stress by regulating active compounds, reducing oxidative stress, and regulating the cell ion balance. We also identify the deficiencies and burning issues of available studies and present promising research topics for the future. This review provides guidance for endophytic fungi research to improve the ability of medicinal plants to resist abiotic stress. It also suggests ideas and methods for active compound accumulation in medicinal plants and medicinal material development during the response to abiotic stress.

HK-08 originated from leaves of Nerium indicum

Objective

To study secondary metabolites from endophytic fungus Colletotruchum sp. HK-08 originated from the leaves of Nerium indicum.

Methods

The compounds were isolated by various column chromatographic techniques, and their structures were elucidated by spectroscopic techniques [high resolution electrospray ionization mass spectroscopy (HRESIMS), one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance spectroscopy (NMR)], as well as comparison with literature data. The Ellman method was used to determine the acetylcholinesterase (AChE) inhibitory activity.

Results

Four indole derivatives were identified from Colletotruchum sp. HK-08, including 6'-hydroxymonaspiloindole (1), 2-(2-oxoindolin-3-yl)ethyl 2-(4-hydroxyphenyl) acetate (2), 2-(2-oxoindolin-3-yl)ethyl 2-(2-hydroxyphenyl)acetate (3), and monaspiloindole (4). Compound 4 presented weak AChE inhibitory activity with IC50 value of (69.30 ± 6.27) μmol/L [tacrine as the positive control, with IC50 value of (0.61 ± 0.07) μmol/L].

Conclusion

Compounds 1-3 were new compounds, and compound 4 had weak AChE inhibitory activity.

An Investigation of Quorum Sensing Inhibitors against Bacillus cereus in The Endophytic Fungus Pithomyces sacchari of the Laurencia sp

Bacillus cereus, a common food-borne pathogen, forms biofilms and generates virulence factors through a quorum sensing (QS) mechanism. In this study, six compounds (dankasterone A, demethylincisterol A3, zinnimidine, cyclo-(L-Val-L-Pro), cyclo-(L-Ile-L-Pro), and cyclo-(L-Leu-L-Pro)) were isolated from the endophytic fungus Pithomyces sacchari of the Laurencia sp. in the South China Sea. Among them, demethylincisterol A3, a sterol derivative, exhibited strong QS inhibitory activity against B. cereus. The QS inhibitory activity of demethylincisterol A3 was evaluated through experiments. The minimum inhibitory concentration (MIC) of demethylincisterol A3 against B. cereus was 6.25 μg/mL. At sub-MIC concentrations, it significantly decreased biofilm formation, hindered mobility, and diminished the production of protease and hemolysin activity. Moreover, RT-qPCR results demonstrated that demethylincisterol A3 markedly inhibited the expression of QS-related genes (plcR and papR) in B. cereus. The exposure to demethylincisterol A3 resulted in the downregulation of genes (comER, tasA, rpoN, sinR, codY, nheA, hblD, and cytK) associated with biofilm formation, mobility, and virulence factors. Hence, demethylincisterol A3 is a potentially effective compound in the pipeline of innovative antimicrobial therapies.

Phomopamide A, a cyclic pentadepsipeptide with α-glucosidase inhibition activity from the endophytic fungus Diaporthe sp

An undescribed cytotoxic cyclopeptide named phomopamide A (1) was isolated from Diaporthe sp., which is an endophytic fungus from Artemisia argyi. Phomopamide A (1) featured an pentadepsipeptide skeleton and composed of two Phe, one Val, one Leu, and one 2-hydroxyoctanoic acid units. The structure of this new compound was fully characterised on the basis of extensive spectroscopic analysis. Moreover, phomopamide A was evaluated for in vitro cyctotoxic and α-glucosidase inhibitory activity. As a result, phomopaminde A exhibited no cytotoxic activity against four tumour cell lines, while it showed a potent α-glucosidase inhibition effect with IC50 value of 62.35 µM.

The schizotrophic lifestyle of Sclerotinia sclerotiorum

Sclerotinia sclerotiorum is a cosmopolitan and typical necrotrophic phytopathogenic fungus that infects hundreds of plant species. Because no cultivars highly resistant to S. sclerotiorum are available, managing Sclerotinia disease caused by S. sclerotiorum is still challenging. However, recent studies have demonstrated that S. sclerotiorum has a beneficial effect and can live mutualistically as an endophyte in graminaceous plants, protecting the plants against major fungal diseases. An in-depth understanding of the schizotrophic lifestyle of S. sclerotiorum during interactions with plants under different environmental conditions will provide new strategies for controlling fungal disease. In this review, we summarize the pathogenesis mechanisms of S. sclerotiorum during its attack of host plants as a destructive pathogen and discuss its lifestyle as a beneficial endophytic fungus.

Anti-Inflammatory Properties of Oxygenated Isocoumarins and Xanthone from Thai Mangrove-Associated Endophytic Fungus Setosphaeria rostrata

Chronic inflammation plays a crucial role in the development and progression of numerous chronic diseases. To search for anti-inflammatory metabolites from endophytic fungi isolated from plants growing in Thai mangrove areas, a chemical investigation of those fungi was performed. Five new oxygenated isocoumarins, setosphamarins A-E (1-5) were isolated from the EtOAc extract of an endophytic fungus Setosphaeria rostrata, along with four known isocoumarins and one xanthone. Their structures were determined by extensive spectroscopic analysis. The absolute configurations of the undescribed compounds were established by comparative analysis between experimental and calculated circular dichroism (ECD) spectroscopy. All the compounds were evaluated for their anti-inflammatory activity by monitoring nitric oxide inhibition in lipopolysaccharide-induced macrophage J774A.1 cells. Only a xanthone, ravenelin (9), showed potent activity, with an IC50 value of 6.27 μM, and detailed mechanistic study showed that it suppressed iNOS and COX-2 expression.

In Vitro Analysis of the Antagonistic Biological and Chemical Interactions between the Endophyte Sordaria tomento-alba and the Phytopathogen Botrytis cinerea

Plant pathogenic infections causing substantial global food losses are a persistent challenge. This study investigates a potential biocontrol strategy against the necrotrophic fungus Botrytis cinerea using the endophytic fungus Sordaria tomento-alba isolated from Gliricidia sepium in Colombia. Today, synthetic fungicides dominate B. cinerea control, raising environmental and health concerns. S. tomento-alba exhibits notable in vitro effects, inhibiting B. cinerea growth by approximately 60% during co-culture and 50% in double disc co-culture. Additionally, it suppresses botryanes production and produces the compound heptacyclosordariolone, which has proven effective in inhibiting B. cinerea mycelial growth and spore germination in vitro. This biocontrol agent could be a potential eco-friendly alternative to replace synthetic fungicides. Our study provides insights into the chemical and biological mechanisms underpinning the antagonistic activity of S. tomento-alba, emphasizing the need for further research to understand its biosynthesis pathways and optimize its biocontrol potential. It also contributes molecular evidence of fungal interactions with implications for advanced forums in molecular studies in biology and chemistry, particularly in addressing plant pathogenic infections and promoting sustainable agriculture.

Caryophyllene-type sesquiterpenes from the endophytic fungus Pestalotiopsis lespedezae through an OSMAC approach

Two new caryophyllene-type sesquiterpenes pestalotiopsins U and V (1 and 2) and three known compounds pestalotiopsin B (7), pestaloporinate B (8), and pestalotiopsin C (9) were isolated by the cultivation of the endophytic fungus Pestalotiopsis lespedezae on solid rice medium, while four additional new caryophyllene pestalotiopsins W-Z (3-6) were obtained when 3.5% NaI was added to the fungal culture medium. The structures of the new compounds were determined by HRESIMS and 1D/2D nuclear magnetic resonance data. Compounds 1-9 were tested for cytotoxicity against the mouse lymphoma cell line L5178Y, but only 6 displayed significant activity with an IC50 value of 2.4 μM.

Two new lactam derivatives from a Sphagneticola trilobata derived fungus Penicillium rubens PQJ-2

A new bicyclic lactam derivatives penicilactam B (1) and a new monocyclic amide penicillamide D (2), along with four known compounds (3-6), were isolated from the fermentation broth of the derived fungus Penicillium rubens PQJ-2. Their structures and stereochemistry were elucidated by comprehensive spectroscopic analyses and quantum ECD calculations. All the compounds were evaluated for their antibacterial activities against Staphylococcus aureus subsp, Candida albicans, Escherichia coli and insecticidal activity against Helicoverpa armigera Hubner. Compounds 1-3 exhibited modest insecticidal activity against H. armigera Hubner.

Botryorhodine J, a new anti-MRSA depsidone isolated from endophytic fungus Alternaria alternata Pas11

A new depsidone derivative botryorhodine J (1), along with six known compounds (2-7) were obtained from solid rice cultures of Alternaria alternata Pas11 that was isolated from leaves of Phragmites australis. The structure of the new compound was elucidated on the basis of combination of NMR spectroscopic data and high resolution mass spectrometry (HRMS). All the isolated compounds were evaluated for their antibacterial activities against a panel of Gram-positive bacterial strains (methicillin-resistant Staphylococcus aureus [MRSA], Bacillus subtilis and S. aureus). Compounds 1 and 6 displayed antibacterial activity against the three bacterial strains with the minimum inhibitory concentration values (MICs) of 14 - 32 μg/mL, while compound 5 showed good antibacterial activity against above bacterial strains with MIC values of 5 - 8 μg/mL.

Indole Diterpene Derivatives from the Aspergillus flavus GZWMJZ-288, an Endophytic Fungus from Garcinia multiflora

A new indole diterpene, 26-dihydroxyaflavininyl acetate (1), along with five known analogs (2-6) were isolated from the liquid fermentation of Aspergillus flavus GZWMJZ-288, an endophyte from Garcinia multiflora. The structures of these compounds were identified through NMR, MS, chemical reaction, and X-ray diffraction experiments. Enzyme inhibition activity screening found that compounds 1, 4, and 6 have a good binding affinity with NPC1L1, among which compound 6 exhibited a stronger binding ability than ezetimibe at a concentration of 10 µM. Moreover, compound 5 showed inhibitory activity against α-glucosidase with an IC50 value of 29.22 ± 0.83 µM, which is 13 times stronger than that of acarbose. The results suggest that these aflavinine analogs may serve as lead compounds for the development of drugs targeting NPC1L1 and α-glucosidase. The binding modes of the bioactive compounds with NPC1L1 and α-glucosidase were also performed through in silico docking studies.

GXNU-MA

A new sulphur-containing metabolite, asperiguxidione A (1), was isolated from a mangrove endophytic fungus Aspergillus sp. GXNU-MA, and four known alkaloids 2-5, were isolated together from this strain. Their structures were determined by the com-bination of 1D and 2D NMR spectroscopy, HR-ESI-MS, and ECD analysis. Compounds 1 and 2 exhibited mediate activity against Staphylococcus aureus and Enterobacter aerogenes with equal MIC values of 12.5 μg/mL. Compound 3 reduced NO production in LPS-stimulated cells with an IC50 value of 13.329 ± 0.53 μg/mL in the anti-inflammatory assay.

New Dipyrroloquinones from a Plant-Derived Endophytic Fungus Talaromyces sp

Two new dipyrroloquinones, namely talaroterreusinones A (1) and B (2), together with four known secondary metabolites, terreusinone A (3), penicillixanthone A (4), isorhodoptilometrin (5), and chrysomutanin (6), were isolated from the solid culture of the endophytic fungus Talaromyces sp. by integrating mass spectrometry-based metabolic profiling and a bioassay-guided method. Their planar structures and stereochemistry were elucidated by comprehensive spectroscopic analysis including NMR and MS. The absolute configuration at C-1″ of terreusinone A (1) was established by applying the modified Mosher's method. Compounds 1-6 were evaluated for anti-inflammatory activity and cytotoxicity. As a result, 1-3 inhibited the LPS-stimulated NO production in macrophage RAW264.7 cells, with IC50 values of 20.3, 30.7, and 20.6 µM, respectively. Penicillixanthone A (4) exhibited potent cytotoxic activity against Hep G2 and A549 cell lines, with IC50 values of 117 nM and 212 nM, respectively, and displayed significant antitumour effects in A549 cells by inhibiting the PI3K-Akt-mTOR signalling pathway.

and Its Effect on Alzheimer's Disease Control

BACKGROUND

Common ginsenosides can be transformed into rare ginsenosides through microbial fermentation, and some rare ginsenosides can prevent Alzheimer's disease (AD). This study aimed to transform common ginsenosides into rare ginsenosides through solid-state fermentation of American ginseng stems and leaves (AGSL) by an endophytic fungus and to explore whether fermented saponin extracts prevent AD.

METHODS

The powders of AGSL were fermented in a solid state by endophytic fungus. Total saponins were extracted from fermentation products using the methanol extraction method. The types of saponins were analyzed by liquid chromatography mass spectrometry (LC/MS). The Aβ42 concentration and β-secretase activity were measured by ELISA for the prevention of AD.

RESULTS

After AGSL was fermented by an endophytic fungus NSJG, the total saponin concentration of the fermented extract G-SL was higher than the unfermented CK-SL. Rare ginsenoside Rh1 was newly produced and the yield of compound K (561.79%), Rh2 (77.48%), and F2 (40.89%) was increased in G-SL. G-SL had a higher inhibition rate on Aβ42 concentration (42.75%) and β-secretase activity (42.22%) than CK-SL, possibly because the rare ginsenoside Rh1, Rh2, F2, and compound K included in it have a strong inhibitory effect on AD.

CONCLUSION

The fermented saponin extracts of AGSL show more inhibition effects on AD and may be promising therapeutic drugs or nutrients for AD.

Genomic Characteristics and Comparative Genomics Analysis of the Endophytic Fungus Paraphoma chrysanthemicola DS-84 Isolated from Codonopsis pilosula Root

Paraphoma chrysanthemicola is a newly identified endophytic fungus. The focus of most studies on P. chrysanthemicola has been on its isolation, identification and effects on plants. However, the limited genomic information is a barrier to further research. Therefore, in addition to studying the morphological and physiological characteristics of P. chrysanthemicola, we sequenced its genome and compared it with that of Paraphoma sp. The results showed that sucrose, peptone and calcium phosphate were suitable sources of carbon, nitrogen and phosphorus for this strain. The activities of amylase, cellulase, chitosanase, lipase and alkaline protease were also detected. Sequencing analysis revealed that the genome of P. chrysanthemicola was 44.1 Mb, with a scaffold N50 of 36.1 Mb and 37,077 protein-coding genes. Gene Ontology (GO) annotation showed that mannose-modified glycosylation was predominant in monosaccharide utilisation. The percentage of glycoside hydrolase (GH) modules was the highest in the carbohydrate-active enzymes database (CAZy) analysis. Secondary metabolite-associated gene cluster analysis identified melanin, dimethylcoprogen and phyllostictine A biosynthetic gene clusters (>60% similarity). The results indicated that P. chrysanthemicola had a mannose preference in monosaccharide utilisation and that melanin, dimethylcoprogen and phyllostictine A were important secondary metabolites for P. chrysanthemicola as an endophytic fungus.

Serendipita indica mitigates drought-triggered oxidative burst in trifoliate orange by stimulating antioxidant defense systems

Soil drought is detrimental to plant growth worldwide, particularly by triggering reactive oxygen species (ROS) burst. Serendipita indica (Si), a culturable root-associated endophytic fungus, can assist host plants in dealing with abiotic stresses; however, it is unknown whether and how Si impacts the drought tolerance of citrus plants. To unravel the effects and roles of Si on drought-stressed plants, trifoliate orange (Poncirus trifoliata L. Raf.; a citrus rootstock) seedlings were inoculated with Si and exposed to soil drought, and growth, gas exchange, ROS levels, antioxidant defense systems, and expression of genes encoding antioxidant enzymes and fatty acid desaturases in leaves were measured. Soil drought suppressed plant biomass, whereas Si inoculation significantly increased plant biomass (10.29%-22.47%) and shoot/root ratio (21.78%-24.68%) under ample water and drought conditions, accompanied by improved net photosynthetic rate (105.71%), water use efficiency (115.29%), chlorophyll index (55.34%), and nitrogen balance index (63.84%) by Si inoculation under soil drought. Soil drought triggered an increase in leaf hydrogen peroxide and superoxide anion levels, while Si inoculation significantly reduced these ROS levels under soil drought, resulting in lower membrane lipid peroxidation with respect to malondialdehyde changes. Furthermore, Si-inoculated seedlings under soil drought had distinctly higher levels of ascorbate and glutathione, as well as catalase, peroxidase, and glutathione peroxidase activities, compared with no-Si-inoculated seedlings. Si inoculation increased the expression of leaf PtFAD2, PtFAD6, PtΔ9, PtΔ15, PtFe-SOD, PtCu/Zn-SOD, PtPOD, and PtCAT1 genes under both ample water and soil drought conditions. Overall, Si-inoculated trifoliate orange plants maintained a low oxidative burst in leaves under drought, which was associated with stimulation of antioxidant defense systems. Therefore, Si has great potential as a biostimulant in enhancing drought tolerance in plants, particularly citrus.

Optimization of the Fermentation Conditions of Metarhizium robertsii and Its Biological Control of Wolfberry Root Rot Disease

Fusarium solani is the main pathogenic fungus causing the root rot of wolfberry (Lycium barbarum). The endophytic fungus Metarhizium robertsii has been widely used for the biocontrol of plant pathogenic fungi, but the biocontrol effects of this fungus on wolfberry root rot and its antifungal mechanism against F. solani have not been reported. In this study, the antagonism of endophytic fungus M. robertsii against F. solani was verified. Further, we optimized the fermentation conditions of M. robertsii fermentation broth based on the inhibition rate of F. solani. In addition, the effects of M. robertsii fermentation broth on the root rot of wolfberry and its partial inhibition mechanism were investigated. The results showed that M. robertsii exhibited good antagonism against F. solani. Glucose and beef extracts were the optimal carbon and nitrogen sources for the fermentation of M. robertsii. Under the conditions of 29 °C, 190 rpm, and pH 7.0, the fermentation broth of M. robertsii had the best inhibition effect on F. solani. Furthermore, the fermentation broth treatment decreased the activities of superoxide dismutase, catalase, and peroxidase of F. solani; promoted the accumulation of malondialdehyde; and accelerated the leakage of soluble protein and the decrease in soluble sugar. In addition, inoculation with M. robertsii significantly reduced the decay incidence and disease index of wolfberry root rot caused by F. solani. These results indicate that M. robertsii could be used as a biological control agent in wolfberry root rot disease management.

Leaf

Six compounds were isolated from the ethyl acetate extract of endophytic fungus Colletotrichum queenslandicum derived from Morus australis Poir. leaf. Based on NMR and MS data led to characterised of these compounds including one new indole alkaloid Morucolletotricin (1) along with two other indole alkaloids; tryptopol (2) and indole-3-acetic acid (3), phomopyronol (4), 2-(3-aminophenyl)acetic acid (5) and ergosterol (6). phomopyronol (4) and 2-(3-aminophenyl)acetic acid (5) were first reported from Colletotrichum fungi. The cytotoxic activity of compounds 1-6 was evaluated against murine leukaemia P-388 cells and showed that all compounds were moderate cytotoxic. phomopyronol (4) was the most active among the five other compounds with IC50 = 37.17 μg/mL.

Two New Eudesmane-Type Sesquiterpene from Clonostachys sp. Y6-1and Their Cytotoxic Activity

Two undescribed eudesmane-type sesquiterpenoids together with four known compounds were isolated from Clonostachys sp. Y6-1 associated. Their chemical structures were unambiguously determined by NMR, mass spectrometry, and 13 C-NMR calculation as well as DP4+ probability analyses. The absolute configurations of compounds 1 and 2 were determined by ECD calculation and X-ray single-crystal diffraction methods. Furthermore, all isolates were evaluated for in vitro cytotoxic activities against MCF-7, HCT-116, MDA-MB-231, and SW620 cancer cells. Among them, bioactivity evaluation of compound 5 revealed that weak activity (IC50 =66.55±0.82 μM) against SW620.

Aspergillus nomiae and fumigatus Ameliorating the Hypoxic Stress Induced by Waterlogging through Ethylene Metabolism in Zea mays L

Transient and prolonged waterlogging stress (WS) stimulates ethylene (ET) generation in plants, but their reprogramming is critical in determining the plants' fate under WS, which can be combated by the application of symbiotically associated beneficial microbes that induce resistance to WS. The present research was rationalized to explore the potential of the newly isolated 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase-producing fungal endophytic consortium of Aspergillus nomiae (MA1) and Aspergillus fumigatus (MA4) on maize growth promotion under WS. MA1 and MA4 were isolated from the seeds of Moringa oleifera L., which ably produced a sufficient amount of IAA, proline, phenols, and flavonoids. MA1 and MA4 proficiently colonized the root zone of maize (Zea mays L.). The symbiotic association of MA1 and MA4 promoted the growth response of maize compared with the non-inoculated plants under WS stress. Moreover, MA1- and MA4-inoculated maize plants enhanced the production of total soluble protein, sugar, lipids, phenolics, and flavonoids, with a reduction in proline content and H2O2 production. MA1- and MA4-inoculated maize plants showed an increase in the DPPH activity and antioxidant enzyme activities of CAT and POD, along with an increased level of hormonal content (GA3 and IAA) and decreased ABA and ACC contents. Optimal stomatal activity in leaf tissue and adventitious root formation at the root/stem junction was increased in MA1- and MA4-inoculated maize plants, with reduced lysigenous aerenchyma formation, ratio of cortex-to-stele, water-filled cells, and cell gaps within roots; increased tight and round cells; and intact cortical cells without damage. MA1 and MA4 induced a reduction in deformed mesophyll cells, and deteriorated epidermal and vascular bundle cells, as well as swollen metaxylem, phloem, pith, and cortical area, in maize plants under WS compared with control. Moreover, the transcript abundance of ethylene-responsive gene ZmEREB180, responsible for the induction of the WS tolerance in maize, showed optimally reduced expression sufficient for induction in WS tolerance, in MA1- and MA4-inoculated maize plants under WS compared with the non-inoculated control. The existing research supported the use of MA1 and MA4 isolates for establishing the bipartite mutualistic symbiosis in maize to assuage the adverse effects of WS by optimizing ethylene production.

Maize Genotypes Sensitive and Tolerant to Low Phosphorus Levels Exhibit Different Transcriptome Profiles under Talaromyces purpurogenus Symbiosis and Low-Phosphorous Stress

Talaromyces purpurogenus, an endophytic fungus, exhibits beneficial effects on plants during plant-fungus interactions. However, the molecular mechanisms underlying plants' responses to T. purpurogenus under low-phosphorous (P) stress are not fully understood. In this study, we investigated the transcriptomic changes in maize with low-P-sensitive (31778) and -tolerant (CCM454) genotypes under low-P stress and its symbiotic interaction with T. purpurogenus. Its colonization enhanced plant growth and facilitated P uptake, particularly in 31778. Transcriptome sequencing revealed that 135 DEGs from CCM454 and 389 from 31778 were identified, and that only 6 DEGs were common. This suggested that CCM454 and 31778 exhibited distinct molecular responses to T. purpurogenus inoculation. GO and KEGG analysis revealed that DEGs in 31778 were associated with nicotianamine biosynthesis, organic acid metabolic process, inorganic anion transport, biosynthesis of various secondary metabolites and nitrogen metabolism. In CCM454, DEGs were associated with anthocyanin biosynthesis, diterpenoid biosynthesis and metabolic process. After T. purpurogenus inoculation, the genes associated with phosphate transporter, phosphatase, peroxidase and high-affinity nitrate transporter were upregulated in 31778, whereas AP2-EREBP-transcription factors were detected at significantly higher levels in CCM454. This study provided insights on the molecular mechanisms underlying plant-endophytic fungus symbiosis and low-P stress in maize with low-P-sensitive and -tolerant genotypes.

Purification of ursolic acid and β-sitosterol from endophytic Alternaria alternata for their alpha-amylase inhibitory activity

Fungal endophytes are a known warehouse of bioactive compounds with multifarious applications. In the present investigation two compounds, β-Sitosterol (1) and ursolic acid (2), were isolated from Alternaria alternata, an endophytic fungus associated with Morus alba Linn for the first time. The structure of the compounds was elucidated on the basis of comprehensive spectral analysis (UV, IR, 1 H-, 13 C- and 2D-NMR, as well as HRESI-MS). In the in vitro alpha amylase inhibitory assay both compounds (1) and (2) show potent antidiabetic activity. In support, Docking studies indicate significant binding affinity of the isolated compounds. Hence from the present study, it can be concluded that endophytic fungi in Morus alba Linn can find use in antidiabetic drug development in the medicinal industry.Communicated by Ramaswamy H. Sarma.

VM-40 Isolated from the Medicinal Plant Vinca minor

The genus Fusarium is well-known to comprise many pathogenic fungi that affect cereal crops worldwide, causing severe damage to agriculture and the economy. In this study, an endophytic fungus designated Fusarium sp. VM-40 was isolated from a healthy specimen of the traditional European medicinal plant Vinca minor. Our morphological characterization and phylogenetic analysis reveal that Fusarium sp. VM-40 is closely related to Fusarium paeoniae, belonging to the F. tricinctum species complex (FTSC), the genomic architecture and secondary metabolite profile of which have not been investigated. Thus, we sequenced the whole genome of Fusarium sp. VM-40 with the new Oxford Nanopore R10.4 flowcells. The assembled genome is 40 Mb in size with a GC content of 47.72%, 15 contigs (≥50,000 bp; N 50~4.3 Mb), and 13,546 protein-coding genes, 691 of which are carbohydrate-active enzyme (CAZyme)-encoding genes. We furthermore predicted a total of 56 biosynthetic gene clusters (BGCs) with antiSMASH, 25 of which showed similarity with known BGCs. In addition, we explored the potential of this fungus to produce secondary metabolites through untargeted metabolomics. Our analyses reveal that this fungus produces structurally diverse secondary metabolites of potential pharmacological relevance (alkaloids, peptides, amides, terpenoids, and quinones). We also employed an epigenetic manipulation method to activate cryptic BGCs, which led to an increased abundance of several known compounds and the identification of several putative new compounds. Taken together, this study provides systematic research on the whole genome sequence, biosynthetic potential, and metabolome of the endophytic fungus Fusarium sp. VM-40.

Design, Synthesis, Antibacterial Activity, and Mechanism of Novel Mesoionic Compounds Based on Natural Pyrazole Isolated from an Endophytic Fungus Colletotrichum gloeosporioides

Xanthomonas oryzae pv. oryzicola (Xoo) is a type of bacteria that causes bacterial leaf blight disease in rice plants. This disease is substantially harmful, and the current prevention and control measures are facing challenges. This study has investigated the effectiveness of the control activity that the endophytic fungus NS7 fermented from Dendrobium candidum possessed against Xoo. Twenty-eight novel mesoionic compounds were designed and synthesized based on the natural compound D. These compounds displayed moderate to excellent anti-Xoo activity in vitro. Notably, compound 24 exhibited prominent anti-Xoo activity in vitro with an EC₅₀ value of 40.3 mg/L, which was better than that of the positive control thiodiazole copper (TC)(71.2 mg/L) and the lead compound D (108.1 mg/L). In vivo pot experiments on Xoo showed that compound 24 exhibited protective and curative activities of 39.4 and 30.4%, respectively, which were better than those of TC (35.7 and 28.8%, respectively). Further, a preliminary mechanism study indicated that compound 24 could enhance the activity of defense enzymes to improve the ability for anti-Xoo. Meanwhile, compound 24 could also regulate the carbon fixation in photosynthetic organisms, which might be related to the enhanced immune function of rice. This study offers a new strategy for discovering antibacterial agents based on natural products.

Isolation, identification, and antibacterial evaluation of endophytic fungi from Gannan navel orange

Gannan navel orange is a famous brand in China but the isolation of its endophytic fungi was rarely reported. In this study, a total of 54 strains of endophytic fungi were successfully isolated from the pulp, peel, twig, and leaf of Gannan navel orange; they were successfully identified to belong to 17 species of 12 genera. All these strains were fermented using potato-dextrose agar (PDA) medium, and their secondary metabolites were then extracted with ethyl acetate (EtOAc). The antibacterial assays of Escherichia coli (E. coli), methicillin-resistant Staphylococcus aureus (MRSA), and Xanthomonas citri subsp. citri (Xcc) were also performed for the EtOAc extracts of these strains. As a result, the extracts of both Geotrichum sp. (gc-1-127-30) and Diaporthe biconispora (gc-1-128-79) demonstrated significant antibacterial activities against Xcc, and the MIC value for the extract of Colletotrichum gloeosporioides against MRSA was low to 62.5 μg/mL. Moreover, the chemical components of the extracts of Colletotrichum sp., Diaporthe biconispora, and Annulohypoxylon atroroseum were primarily investigated, and they successfully led to the isolation of 24 compounds involving a new botryane sesquiterpene. Among the isolated products, compound 2 showed significant inhibitory activities toward SA, MRSA, E. coli, and Xcc with MIC values of 12.5, 3.1, 125, and 12.5 μg/mL, respectively. This study revealed that the endophytic fungi of Gannan navel orange showed high potency to produce secondary metabolites with significant antibacterial effects.

Three new furanones from endophytic fungus Hypoxylon vinosopulvinatum DYR-1-7 from Cinnamomum cassia with their antifungal activity

Hypoxylon vinosopulvinatum DYR-1-7 is a endophytic fungus isolated from the Cinnamomum cassia Presl and has an inhibitory effect on Lasiodiplodia pseudotheobromae. Three new furanones, hypoxylonone A-C (1-3), as well as three known compounds (4-6), were isolated from an EtOAc extract of H. vinosopulvinatum DYR-1-7. The structures were determined by spectroscopic data analysis using UV, IR, 1D-, 2D-NMR and HR-ESI-MS. The absolute configurations of 1-3 were elucidated by electronic circular dichroism (ECD) analyses. In the antifungal bioassay, Hypoxylonone B and C exhibited strong inhibitory effects on L. pseudotheobromae with IC₅₀ value at the concentration of 1.01 and 2.40 μg/mL, respectively. Compound 6 showed medium antifungal activity with IC₅₀ value at the concentration of 10.67 μg/mL on Fusarium oxysporum. Compounds 3 and 4 displayed medium antifungul effects on Candida albicans.

A New Hypoglycemic Prenylated Indole Alkaloid N-Oxide from Endophytic Fungus Pallidocercospora crystalline

A new prenylated indole alkaloid-Penicimutamide C N-oxide (1), a new alkaloid penicimutamine A (2), along with six known alkaloids were isolated from an endophytic fungus Pallidocercospora crystallina. A simple and accurate method was used to determine the N-O bond in the N-oxide group of 1. By using a β-cell ablation diabetic zebrafish model, compounds 1, 3, 5, 6 and 8 showed significantly hypoglycemic activities under the concentration of 10 μM. Further studies revealed that compounds 1 and 8 lowered the glucose level through promoting glucose uptake in zebrafish. In addition, all eight compounds showed no acute toxicity, teratogenicity, nor vascular toxicity in zebrafish under the concentrations range from 2.5 μΜ to 40 μM. Importantly, these results provide new lead compounds for the development of antidiabetes strategies.

Diketopiperazine Alkaloids and Bisabolene Sesquiterpenoids from Aspergillus versicolor AS-212, an Endozoic Fungus Associated with Deep-Sea Coral of Magellan Seamounts

Two new quinazolinone diketopiperazine alkaloids, including versicomide E (2) and cottoquinazoline H (4), together with ten known compounds (1, 3, and 5-12) were isolated and identified from Aspergillus versicolor AS-212, an endozoic fungus associated with the deep-sea coral Hemicorallium cf. imperiale, which was collected from the Magellan Seamounts. Their chemical structures were determined by an extensive interpretation of the spectroscopic and X-ray crystallographic data as well as specific rotation calculation, ECD calculation, and comparison of their ECD spectra. The absolute configurations of (-)-isoversicomide A (1) and cottoquinazoline A (3) were not assigned in the literature reports and were solved in the present work by single-crystal X-ray diffraction analysis. In the antibacterial assays, compound 3 exhibited antibacterial activity against aquatic pathogenic bacteria Aeromonas hydrophilia with an MIC value of 18.6 μM, while compounds 4 and 8 exhibited inhibitory effects against Vibrio harveyi and V. parahaemolyticus with MIC values ranging from 9.0 to 18.1 μM.

New Isocoumarin and Pyrone Derivatives from the Chinese Mangrove Plant Rhizophora mangle-Associated Fungus Phomopsis sp. DHS-11

Mangrove-associated fungi are important sources for the discovery of new bioactive natural products. Three new isocoumarins (1-3) and one new pyrone derivative (4) were isolated from the ethyl acetate extract of the fermentation broth of the mangrove endophytic fungus Phomopsis sp. DHS-11. Nuclear magnetic resonance (NMR) spectroscopy (one-dimensional and two-dimensional) and mass spectrometry were used to determine the structures of these new compounds. The absolute configurations for the new isocoumarins 1-3 were determined by comparing their experimental and calculated electronic circular dichroism (ECD) spectra, while the configuration for the new pyrone-derivative 4 was tentatively solved by comparison of its ¹³C NMR data with reported data. In the biological activity test, compounds 1 and 3 showed cytotoxic activity against HeLa cells with IC₅₀ values of 11.49 ± 1.64 µM and 8.70 ± 0.94 µM, respectively. The initial structure and activity relationship (SAR) analysis revealed that the length of the side chain at C-3 for isocoumarin-type compounds 1-3 could affect the cytotoxicity against HeLa cells. Compound 4 exhibited cytotoxic activities against human hepatoma cells HepG2 with an IC₅₀ value of 34.10 ± 2.92 µM. All compounds have no immunosuppressive activity.

Polyketones from the endophytic fungus Cytospora rhizophorae

Cytosporaphenones D (1) and E (2), two new polyketones, and one new natural product 1,7-dihydroxy-6-methyl-8-formylxanthone (3), along with four known compounds, were isolated from Cytospora rhizophorae, an endophytic fungus from Morinda officinalis. Their structures were elucidated by extensive spectroscopic analyses and X-ray diffraction technique.

New Guaiane-Type Sesquiterpenoids Biscogniauxiaols A-G with Anti-Fungal and Anti-Inflammatory Activities from the Endophytic Fungus Biscogniauxia Petrensis

Seven undescribed guaiane-type sesquiterpenoids named biscogniauxiaols A-G (1-7) were isolated from the endophytic fungus Biscogniauxia petrensis on Dendrobium orchids. Their structures were determined by extensive spectroscopic analyses, electronic circular dichroism (EC) and specific rotation (SR) calculations. Compound 1 represented a new family of guaiane-type sesquiterpenoids featuring an unprecedented [5/6/6/7] tetracyclic system. A plausible biosynthetic pathway for compounds 1-7 was proposed. The anti-fungal, anti-inflammatory and multidrug resistance reversal activities of the isolates were evaluated. Compounds 1, 2 and 7 exhibited potent inhibitory activities against Candida albicans with MIC values ranging from 1.60 to 6.30 μM, and suppressed nitric oxide (NO) production with IC50 ranging from 4.60 to 20.00 μM. Additionally, all compounds (100 μg/mL) enhanced the cytotoxicity of cisplatin in cisplatin-resistant non-small cell lung cancer cells (A549/DDP). This study opened up a new source for obtaining bioactive guaiane-type sesquiterpenoids and compounds 1, 2, and 7 were promising for further optimization as multifunctional inhibitors for anti-fungal (C. albicans) and anti-inflammatory purposes.

Bioactive secondary metabolites from endophytic strains of Neocamarosporium betae collected from desert plants

Endophytic fungi from desert plants belong to a unique microbial community that has been scarcely investigated chemically and could be a new resource for bioactive natural products. In this study, 13 secondary metabolites (1-13) with diverse carbon skeletons, including a novel polyketide (1) with a unique 5,6-dihydro-4H,7H-2,6-methanopyrano[4,3-d][1,3]dioxocin-7-one ring system and three undescribed polyketides (2, 7, and 11), were obtained from the endophytic fungus Neocamarosporium betae isolated from two desert plant species. Different approaches, including HR-ESI-MS, UV spectroscopy, IR spectroscopy, NMR, and CD, were used to determine the planar and absolute configurations of the compounds. The possible biosynthetic pathways were proposed based on the structural characteristics of compounds 1-13. Compounds 1, 3, 4, and 9 exhibited strong cytotoxicity toward HepG2 cells compared with the positive control. Several metabolites (2, 4-5, 7-9, and 11-13) were phytotoxic to foxtail leaves. The results support the hypothesis that endophytic fungi from special environments, such as desert areas, produce novel bioactive secondary metabolites.

An endophytic fungus, Piriformospora indica, enhances drought tolerance of trifoliate orange by modulating the antioxidant defense system and composition of fatty acids

A cultivable endophytic fungus, Piriformospora indica, improves growth and enhances stress tolerance of host plants, but the underlying mechanisms remain unknown. We hypothesized that P. indica enhanced the drought tolerance of the host by regulating the antioxidant defense system and composition of fatty acids. Trifoliate orange (Poncirus trifoliata) seedlings were inoculated with P. indica under ample water and drought stress to analyze the change in plant growth, reactive oxygen species (ROS) levels, antioxidant enzyme activities, non-enzymatic antioxidant concentrations, fatty acid compositions, and expressions of both antioxidant enzyme genes and fatty acid desaturase (FAD) genes. The 9-week soil water deficit significantly increased the colonization of P. indica to roots, and P. indica promoted the increase of shoot biomass under drought. Soil drought triggered an elevation of hydrogen peroxide in roots, while the inoculated plants had lower levels of ROS (hydrogen peroxide and superoxide anion radicals) and lower degree of membrane lipid peroxidation (based on malondialdehyde levels) under drought. Drought treatment also elevated ascorbic acid and glutathione concentrations, and the elevation was further amplified after P. indica inoculation. Inoculated plants under drought also recorded significantly higher iron-superoxide dismutase (Fe-SOD), manganese-superoxide dismutase (Mn-SOD), peroxidases, catalase, glutathione reductase and ascorbate peroxidase activities, accompanied by up-regulation of PtFe-SOD and PtCu/Zn-SOD expressions. Inoculation with P. indica significantly increased total saturated fatty acids (e.g., C6:0, C15:0, C16:0, C23:0 and C24:0) concentration and reduced total unsaturated fatty acids (e.g., C18:1N9C, C18:2N6, C18:3N3, C18:1N12 and C19:1N9T) concentrations, leading to a decrease in the unsaturation index of fatty acids, which may be associated with the up-regulation of PtFAD2 and PtFAD6 and down-regulation of PtΔ9. It was concluded that the colonization of P. indica can activate enzyme and non-enzyme defense systems and regulate the composition of fatty acids under drought, thus alleviating the oxidative damage to the host caused by drought.

GZWMJZ-606 Endophytic with Houttuynia cordata Thunb

Two new 4-hydroxy-2-pyridone alkaloids furanpydone A and B (1 and 2), along with two known compounds N-hydroxyapiosporamide (3) and apiosporamide (4) were isolated from the endophytic fungus Arthrinium sp. GZWMJZ-606 in Houttuynia cordata Thunb. Furanpydone A and B had unusual 5-(7-oxabicyclo[2.2.1]heptane)-4-hydroxy-2-pyridone skeleton. Their structures including absolute configurations were determined on the basis of spectroscopic analysis, as well as the X-ray diffraction experiment. Compound 1 showed inhibitory activity against ten cancer cell lines (MKN-45, HCT116, K562, A549, DU145, SF126, A-375, 786O, 5637, and PATU8988T) with IC₅₀ values from 4.35 to 9.72 µM. Compounds 1, 3 and 4 showed moderate inhibitory effects against four Gram-positive strains (Staphylococcus aureus, methicillin-resistant S. aureus, Bacillus Subtilis, Clostridium perfringens) and one Gram-negative strain (Ralstonia solanacarum) with MIC values from 1.56 to 25 µM. However, compounds 1-4 showed no obvious inhibitory activity against two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and two pathogenic fungi (Candida albicans and Candida glabrata) at 50 µM. These results show that compounds 1-4 are expected to be developed as lead compounds for antibacterial or anti-tumor drugs.

Secondary metabolites from an endophytic fungus Trichoderma erinaceum with antimicrobial activity towards Pythium ultimum

Chemical investigation of the endophytic fungus, Trichoderma erinaceum, isolated from healthy and asymptomatic common bean field crop, resulted in the isolation of a new alkene, (Z)-5-amino-5-(1,1,2-trihydroxybuta-1,3-dienyloxy)pentane-6,7,8,9-tetraol (1), together with five known compounds (2-6). The structures of the compounds were elucidated by analysis of their spectroscopic data including 1 D, 2 D NMR, ESI-HRMS and literature data. The organic crude extract and the compound isolated from T. erinaceum significantly (p ≤ 0.05) inhibited the mycelial growth of Pythium ultimum.

Identification of a Novel Coumarins Biosynthetic Pathway in the Endophytic Fungus Fusarium oxysporum GU-7 with Antioxidant Activity

Coumarins are generally considered to be produced by natural plants. Fungi have been reported to produce coumarins, but their biosynthetic pathways are still unknown. In this study, Fusarium oxysporum GU-7 and GU-60 were isolated from Glycyrrhiza uralensis, and their antioxidant activities were determined to be significantly different. Abundant dipeptide, phenolic acids, and the plant-derived coumarins fraxetin and scopoletin were identified in GU-7 by untargeted metabolomics, and these compounds may account for its stronger antioxidant activity compared to GU-60. Combined with metabolome and RNA sequencing analysis, we identified 24 potentially key genes involved in coumarin biosynthesis and 6 intermediate metabolites. Interestingly, the best hit of S8H, a key gene involved in hydroxylation at the C-8 position of scopoletin to yield fraxetin, belongs to a plant species. Additionally, nondestructive infection of G. uralensis seeds with GU-7 significantly improved the antioxidant activity of seedlings compared to the control group. This antioxidant activity may depend on the biological characteristics of endophytes themselves, as we observed a positive correlation between the antioxidant activity of endophytic fungi and that of their nondestructively infected seedlings. IMPORTANCE Plant-produced coumarins have been shown to play an important role in assembly of the plant microbiomes and iron acquisition. Coumarins can also be produced by some microorganisms. However, studies on coumarin biosynthesis in microorganisms are still lacking. We report for the first time that fraxetin and scopoletin were simultaneously produced by F. oxysporum GU-7 with strong free radical scavenging abilities. Subsequently, we identified intermediate metabolites and key genes in the biosynthesis of these two coumarins. This is the first report on the coumarin biosynthesis pathway in nonplant species, providing new strategies and perspectives for coumarin production and expanding research on new ways for plants to obtain iron.

Chemical Investigation of Endophytic Diaporthe unshiuensis YSP3 Reveals New Antibacterial and Cytotoxic Agents

Chemical investigation of the plant-derived endophytic fungus Diaporthe unshiuensis YSP3 led to the isolation of four new compounds (1-4), including two new xanthones (phomopthane A and B, 1 and 2), one new alternariol methyl ether derivative (3) and one α-pyrone derivative (phomopyrone B, 4), together with eight known compounds (5-12). The structures of new compounds were interpreted on the basis of spectroscopic data and single-crystal X-ray diffraction analysis. All new compounds were assessed for their antimicrobial and cytotoxic potential. Compound 1 showed cytotoxic activity against HeLa and MCF-7 cells with IC₅₀ values of 5.92 µM and 7.50 µM, respectively, while compound 3 has an antibacterial effect on Bacillus subtilis (MIC value 16 μg/mL).

Differential Colonization of the Plant Vasculature Between Endophytic Versus Pathogenic Fusarium oxysporum Strains

Plant xylem colonization is the hallmark of vascular wilt diseases caused by phytopathogens within the Fusarium oxysporum species complex. Recently, xylem colonization has also been reported among endophytic F. oxysporum strains, resulting in some uncertainty. This study compares xylem colonization processes by pathogenic versus endophytic strains in Arabidopsis thaliana and Solanum lycopersicum, using Arabidopsis pathogen Fo5176, tomato pathogen Fol4287, and the endophyte Fo47, which can colonize both plant hosts. We observed that all strains were able to advance from epidermis to endodermis within 3 days postinoculation (dpi) and reached the root xylem at 4 dpi. However, this shared progression was restricted to lateral roots and the elongation zone of the primary root. Only pathogens reached the xylem above the primary-root maturation zone (PMZ). Related to the distinct colonization patterns, we also observed stronger induction of callose at the PMZ and lignin deposition at primary-lateral root junctions by the endophyte in both plants. This observation was further supported by stronger induction of Arabidopsis genes involved in callose and lignin biosynthesis during the endophytic colonization (Fo47) compared with the pathogenic interaction (Fo5176). Moreover, both pathogens encode more plant cell wall-degrading enzymes than the endophyte Fo47. Therefore, observed differences in callose and lignin deposition could be the combination of host production and the subsequent fungal degradation. In summary, this study demonstrates spatial differences between endophytic and pathogenic colonization, strongly suggesting that further investigations of molecular arm-races are needed to understand how plants differentiate friend from foe. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

YT2019-3321, an endophytic fungus derived from Lonicera Japonica

Introduction

Endophytic fungi associated with medicinal plants have proven to possess a high potential to produce structurally diverse metabolites, some of which are valuable for medicinal applications. In this study, Penicillium sp. YT2019-3321, an endophytic fungus derived from traditional Chinese medicine Lonicera japonica, was chemically studied.

Methods

The chemical structures of the isolated compounds were established by a correlative interpretation of HRESIMS and NMR spectroscopic data. The optical resolution of (±)-1 by chiral HPLC yielded individual enantiomers (+)-1 and (-)-1, and their stereochemistry were solved by X-ray diffraction crystallography, respectively.

Results and discussion

Eight structurally diversified secondary metabolites, including two previously unreported polyketides, named (±)-chrysoalide B (1) and penicidone E (2), were isolated and identified from Penicillium sp. YT2019-3321. Compound 2 possessed the γ-pyridone nucleus, which is rarely found in natural products. Cytotoxic assay revealed that the new compound 2 demonstrated a dose-dependent cytotoxicity against the human pancreatic tumor cells PATU8988T with the IC₅₀ value of 11.4 μM. Further studies indicated that 2 significantly induced apoptosis of PATU8988T cell lines, characterized by the morphologies abnormity, the reduction of cell number, the upregulation of proportion of apoptotic cells, and the ratio of Bcl-2 to Bax. Our study demonstrates that fungal secondary metabolites may have important significance in the discovery of drug leads.

Cytotoxic Potential of Bioactive Compounds from Aspergillus flavus, an Endophytic Fungus Isolated from Cynodon dactylon, against Breast Cancer: Experimental and Computational Approach

Endophytic fungi are a diverse group of microorganisms that colonize the inter- or intracellular spaces of plants and exhibit mutual benefits. Their interactions with the host plant and other microbiomes are multidimensional and play a crucial role in the production of secondary metabolites. We screened bioactive compounds present in the extracts of Aspergillus flavus, an endophytic fungus isolated from the roots of the medicinal grass Cynodon dactylon, for its anticancer potential. An in vitro analysis of the Ethyl acetate extract from A. flavus showed significant cytostatic effects (IC₅₀: 16.25 μg/mL) against breast cancer cells (MCF-7). A morphological analysis of the cells and a flow cytometry of the cells with annexin V/Propidium Iodide suggested that the extract induced apoptosis in the MCF-7 cells. The extract of A. flavus increased reactive oxygen species (ROS) generation and caused a loss of mitochondrial membrane potential in MCF-7 cells. To identify the metabolites that might be responsible for the anticancer effect, the extract was subjected to a gas chromatography-mass spectrometry (GC-MS) analysis. Interestingly, nine phytochemicals that induced cytotoxicity in the breast cancer cell line were found in the extract. The in silico molecular docking and molecular dynamics simulation studies revealed that two compounds, 2,4,7-trinitrofluorenone and 3α, 5 α-cyclo-ergosta-7,9(11), 22t-triene-6beta-ol exhibited significant binding affinities (-9.20, and -9.50 Kcal/mol, respectively) against Bcl-2, along with binding stability and intermolecular interactions of its ligand-Bcl-2 complexes. Overall, the study found that the endophytic A. flavus from C. dactylon contains plant-like bioactive compounds that have a promising effect in breast cancer.

Serendipita indica-A Review from Agricultural Point of View

Fulfilling the food demand of a fast-growing population is a global concern, resulting in increased dependence of the agricultural sector on various chemical formulations for enhancing crop production. This leads to an overuse of chemicals, which is not only harmful to human and animal health, but also to the environment and the global economy. Environmental safety and sustainable production are major responsibilities of the agricultural sector, which is inherently linked to the conservation of the biodiversity, the economy, and human and animal health. Scientists, therefore, across the globe are seeking to develop eco-friendly and cost-effective strategies to mitigate these issues by putting more emphasis on the use of beneficial microorganisms. Here, we review the literature on Serendipita indica, a beneficial endophytic fungus, to bring to the fore its properties of cultivation, the ability to enhance plant growth, improve the quality of produced crops, mitigate various plant stresses, as well as protect the environment. The major points in this review are as follows: (1) Although various plant growth promoting microorganisms are available, the distinguishing character of S. indica being axenically cultivable with a wide range of hosts makes it more interesting for research. (2) S. indica has numerous functions, ranging from promoting plant growth and quality to alleviating abiotic and biotic stresses, suggesting the use of this fungus as a biofertiliser. It also improves the soil quality by limiting the movement of heavy metals in the soil, thus, protecting the environment. (3) S. indica's modes of action are due to interactions with phytohormones, metabolites, photosynthates, and gene regulation, in addition to enhancing nutrient and water absorption. (4) Combined application of S. indica and nanoparticles showed synergistic promotion in crop growth, but the beneficial effects of these interactions require further investigation. This review concluded that S. indica has a great potential to be used as a plant growth promoter or biofertiliser, ensuring sustainable crop production and a healthy environment.

Antioxidant activity of mycelia methanolic extracts of endophytic fungi BvFV and BvFIX isolated from leaves of Bauhinia variegata

Endophytes are considered an essential source of natural products. Skin is the body's largest organ; its primary function is the protection of other organs, and aging is one of the most relevant problems associated with this organ. UV radiation generates reactive oxygen species (ROS), which lead to skin degeneration and consequent aging. The main endogenous antioxidants that neutralize ROS are enzymatic antioxidants such as superoxide dismutase (SOD), catalase, glutathione peroxidase, and glutathione reductase, and non-enzymatic antioxidants, such as glutathione and α-tocopherol. Nuclear receptors are involved in molecular mechanisms that control the aging process, especially peroxisome proliferator-activated receptors (PPAR), which regulate the function and expression of genes that modulate the balance between matrix metalloproteinases (MMP) activity and the expression of collagen. Some natural compounds, such as polyphenols, can activate PPAR and reduce the activation of MMP and collagen degradation. In this work, the antioxidant activity of the mycelia methanolic extracts of two endophytic fungi isolated from leaves of Bauhinia variegata, named BvFV and BvFIX, their action as PPAR agonists, and their effect on the activity of antioxidant defense system enzymes were evaluated. The mycelia methanolic extract of BvFV showed a weak agonist effect on PPARβ/δ, a high capability to inhibit lipid peroxidation, increased catalase activity, and increased superoxide dismutase activity by approximately 64%. In contrast, BvFIX increased catalase activity and increased superoxide dismutase activity in a dose-dependent manner, with an increase of 49.62% ± 7.87%, 56.64% ± 12.27%, and 240.46% ± 26.11% at concentrations of 25 µg/mL, 50 µg/mL and 100 µg/mL, respectively, in human dermal fibroblasts submitted to oxidative stress. These results suggest that the metabolites of the mycelia of endophytic fungi studied are promising to act in the chemoprevention of skin aging.

SZSJ-7B

Two previously undescribed lactones, phomolides A and B (1 and 2), and three new sesquiterpenoids, phomenes A-C (3-5), together with one known compound, colletotricholide A (6), were isolated from the endophytic fungus Phomopsis sp. SZSJ-7B. Their chemical structures, including the absolute configurations, were comprehensively established by extensive analyses of NMR, high-resolution electrospray ionization mass spectrometry, electronic circular dichroism powered by theoretical calculations, and X-ray diffractions. Moreover, the cytotoxic and antibacterial activities of compounds 1-6 were also evaluated, and the results demonstrated that compound 2 showed significant antibacterial effects towards methicillin-resistant Staphylococcus aureus and S. aureus strains with minimum inhibitory concentration as low as 6.25 μg/ml, which was comparable to that of the clinical drug vancomycin. Moreover, all compounds showed no cytotoxic activity.

Phytotoxic Metabolites Isolated from Aspergillus sp., an Endophytic Fungus of Crassula arborescens

Aspergillus sp., an endophytic fungus isolated from Crassula arborescens, displayed potent inhibitory activity against the seed germination of Arabidopsis thaliana. The bioactivity-guided fractionation of the culture extract of Aspergillus sp. MJ01 led to the isolation of nine compounds, including one previously undescribed furanone, namely aspertamarinoic acid (1), and eight known compounds, (-)-dihydrocanadensolide (2), kojic acid (3), citreoisocoumarin (4), astellolide A (5), astellolide B (6), astellolide G (7), cyclo-N-methylphenylalanyltryptophenyl (8) and (-)-ditryptophenaline (9). In the evaluation of the phytotoxic activities of compounds 1-9, the results suggested that 1 and 5 showed significant inhibitory activity on the seed germination of A. thaliana. This is the first report to disclose the phytotoxic activity of these compounds.

[Metabolites of endophytic fungus Nigrospora sphaerica S5 from Myoporum bontioides]

The endophytic fungus Nigrospora sphaerica S5 derived from the semi-mangrove plant Myoporum bontioides was fermented. Its metabolites were purified by column chromatography. Nine compounds were obtained and identified as terezine P(1), 3-(1-hydroxyethyl)-4-methyl dihydrofuran-2(3H)-one(2), methylhydroheptelidate(3), hydroheptelidic acid(4), 5, 7-dimethoxy-4, 6-dimethylphthalide(5),(3R,4S)-(-)-4-hydroxymellein(6), pestalopyrone(7), indole-3-formaldehyde(8) and p-hydroxybenzaldehyde(9) by spectroscopic techniques. Terezine P(1) was a new alkaloid belonging to the terezine class with a pyrazine ring. Compounds 2-7 were lactones, of which 3 and 4 belonged to sesquiterpenes. Compounds 8 and 9 were indole alkaloids and phenols, respectively. Compounds 3-6 were purified from Nigrospora sp. for the first time. These compounds showed different degrees of antibacterial activity against Staphylococcus aureus, Escherichia coli of O6 serotype and E. coli of O78 serotype.

Interactive Effects of Water Deficiency and Endophytic Beauveria bassiana on Plant Growth, Nutrient Uptake, Secondary Metabolite Contents, and Antioxidant Activity of Allium cepa L

The main aim of this research study was to assess the interactive effects of water deficiency and the inoculation of a growth medium with Beauveria bassiana on plant growth, nutrient uptake, secondary metabolite contents, and antioxidant capacity of Allium cepa. A. cepa seedlings were simultaneously exposed to one of three watering regime treatments (3-day, 5-day, and 7-day watering intervals) and B. bassiana or no-fungus treatment. While the longest watering interval induced reduced plant growth, plants inoculated with B. bassiana had better results than those in the no-fungus treatment. Significant interactive effects (DF = 2.0; p < 0.05) between fungus and the watering regime on P, K, and Fe contents were observed. Remarkably, at the 7-day watering interval, the polyphenol content (64.0 mg GAE/L) was significantly higher in the plants treated with B. bassiana than in the no-fungus-treated plants. The watering interval significantly affected (DF = 2, 6; F = 7.4; p < 0.05) total flavonol contents among the fungus-treated plants. The interaction of the watering interval and B. bassiana inoculation (DF = 2.0; F = 3.8; p < 0.05) significantly influenced the flavonol content in the onion bulbs and the antioxidant activities of onion bulbs in the FRAP assay (DF = 2.0; F = 4.1; p < 0.05).

Metabolites with antioxidant and α-glucosidase inhibitory activities produced by the endophytic fungi Aspergillus niger from Pachysandra terminalis

One new compound and 13 known compounds were isolated from Aspergillus niger, a plant endophytic fungus of Pachysandra terminalis collected from Qinling Mountains, Xi'an, China. The structure of new compound 1 was classically determined by extensive spectroscopic analysis. Compounds 5, 6, 8, and 14 were firstly reported from Aspergillus, while compound 2 was isolated from A. niger for the first time. All isolated compounds were further evaluated for their antioxidant and α-glucosidase inhibitory activities. Compounds 2 and 3 exhibited significant antioxidant activities with IC50 values of 31.64 μm and 24.32 μm, respectively, similar to the positive control ascorbic acid. Additionally, compound 1 displayed remarkable inhibitory activity against α-glucosidase with an IC50 value of 96.25 μm, which was 3.4-fold more potent than that of the positive control acarbose. Compound 1 has great potential for development as a new lead compound owing to its simple structure and remarkable biological activity.