Natural product diversity from the endophytic fungi of the genus Aspergillus

Microbial allies: exploring fungal endophytes for biosynthesis of terpenoid indole alkaloids

Terpenoid indole alkaloids (TIAs) are natural compounds found in medicinal plants that exhibit various therapeutic activities, such as antimicrobial, anti-inflammatory, antioxidant, anti-diabetic, anti-helminthic, and anti-tumor properties. However, the production of these alkaloids in plants is limited, and there is a high demand for them due to the increasing incidence of cancer cases. To address this research gap, researchers have focused on optimizing culture media, eliciting metabolic pathways, overexpressing genes, and searching for potential sources of TIAs in organisms other than plants. The insufficient number of essential genes and enzymes in the biosynthesis pathway is the reason behind the limited production of TIAs. As the field of natural product discovery from biological species continues to grow, endophytes are being investigated more and more as potential sources of bioactive metabolites with a variety of chemical structures. Endophytes are microorganisms (fungi, bacteria, archaea, and actinomycetes), that exert a significant influence on the metabolic pathways of both the host plants and the endophytic cells. Bio-prospection of fungal endophytes has shown the discovery of novel, high-value bioactive compounds of commercial significance. The discovery of therapeutically significant secondary metabolites has been made easier by endophytic entities' abundant but understudied diversity. It has been observed that fungal endophytes have better intermediate processing ability due to cellular compartmentation. This paper focuses on fungal endophytes and their metabolic ability to produce complex TIAs, recent advancements in this area, and addressing the limitations and future perspectives related to TIA production.

Comparative metabolomics study on the secondary metabolites of the red alga, Corallina officinalis and its associated endosymbiotic fungi

Marine endosymbionts have gained remarkable interest in the last three decades in terms of natural products (NPs) isolated thereof, emphasizing the chemical correlations with those isolated from the host marine organism. The current study aimed to conduct comparative metabolic profiling of the marine red algae Corallina officinalis, and three fungal endosymbionts isolated from its inner tissues namely, Aspergillus nidulans, A. flavipes and A. flavus. The ethyl acetate (EtOAc) extracts of the host organism as well as the isolated endosymbionts were analyzed using ultra-high performance liquid chromatography coupled to high resolution tandem mass spectrometry (UHPLC-MS/MS)in both positive and negative ion modes, applying both full scan (FS) and all ion fragmentation (AIF) modes. Extensive interpretation of the LC-MS/MS spectra had led to the identification of 76 metabolites belonging to different phytochemical classes including alkaloids, polyketides, sesquiterpenes, butyrolactones, peptides, fatty acids, isocoumarins, quinones, among others. Metabolites were tentatively identified by comparing the accurate mass and fragmentation pattern with metabolites previously reported in the literature, as well as bioinformatics analysis using GNPS. A relationship between the host C. officinalis and its endophytes (A. flavus, A. nidulans, and A. flavipes) was discovered. C. officinalis shares common metabolites with at least one of the three endosymbiotic fungi. Some metabolites have been identified in endophytes and do not exist in their host. Multivariate analysis (MVA) revealed discrimination of A. flavipes from Corallina officinalis and other associated endophytic Aspergillus fungi (A. flavus and A. nidulans).

Endophytic Fungi Inoculation Reduces Ramulosis Severity in Gossypium hirsutum Plants

Biotic stress in cotton plants caused by the phytopathogenic fungus Colletotrichum gossypii var. cephalosporioides triggers symptoms of ramulosis, a disease characterized by necrotic spots on young leaves, followed by death of the affected branch's apical meristem, plant growth paralysis, and stimulation of lateral bud production. Severe cases of ramulosis can cause up to 85% yield losses in cotton plantations. Currently, this disease is controlled exclusively by using fungicides. However, few studies have focused on biological alternatives for mitigating the effects of contamination by C. gossypii var. cephalosporioides on cotton plants. Thus, the hypothesis raised is that endophytic fungi isolated from an Arecaceae species (Butia purpurascens), endemic to the Cerrado biome, have the potential to reduce physiological damage caused by ramulosis, decreasing its severity in these plants. This hypothesis was tested using plants grown from seeds contaminated with the pathogen and inoculated with strains of Gibberella moniliformis (BP10EF), Hamigera insecticola (BP33EF), Codinaeopsis sp. (BP328EF), G. moniliformis (BP335EF), and Aspergillus sp. (BP340EF). C. gossypii var. cephalosporioides is a leaf pathogen; thus, the evaluations were focused on leaf parameters: gas exchange, chlorophyll a fluorescence, and oxidative metabolism. The hypothesis that inoculation with endophytic strains can mitigate physiological and photochemical damage caused by ramulosis in cotton was confirmed, as the fungi improved plant growth and stomatal index and density, increased net photosynthetic rate (A) and carboxylation efficiency (A/Ci), and decreased photochemical stress (ABS/RC and DI0/RC) and oxidative stress by reducing enzyme activity (CAT, SOD, and APX) and the synthesis of malondialdehyde (MDA). Control plants developed leaves with a low adaxial stomatal index and density to reduce colonization of leaf tissues by C. gossypii var. cephalosporioides due to the absence of fungal antagonism. The Codinaeopsis sp. strain BP328EF can efficiently inhibit C. gossypii var. cephalosporioides in vitro (81.11% relative inhibition), improve gas exchange parameters, reduce photochemical stress of chlorophyll-a, and decrease lipid peroxidation in attacked leaves. Thus, BP328EF should be further evaluated for its potential effect as a biological alternative for enhancing the resistance of G. hirsutum plants and minimizing yield losses caused by C. gossypii var. cephalosporioides.

Exploring the antioxidant potential of endophytic fungi: a review on methods for extraction and quantification of total antioxidant capacity (TAC)

Endophytic fungi have emerged as a significant source of natural products with remarkable bioactivities. Recent research has identified numerous antioxidant molecules among the secondary metabolites of endophytic fungi. These organisms, whether unicellular or micro-multicellular, offer the potential for genetic manipulation to enhance the production of these valuable antioxidant compounds, which hold promise for promoting health, vitality, and various biotechnological applications. In this study, we provide a critical review of methods for extracting, purifying, characterizing, and estimating the total antioxidant capacity (TAC) of endophytic fungi metabolites. While many endophytes produce metabolites similar to those found in plants with established symbiotic associations, we also highlight the existence of novel metabolites with potential scientific interest. Additionally, we discuss how advancements in nanotechnology have opened new avenues for exploring nanoformulations of endophytic metabolites in future studies, offering opportunities for diverse biological and industrial applications.

Fungal endophytes from saline-adapted shrubs induce salinity stress tolerance in tomato seedlings

To meet the food and feed demands of the growing population, global food production needs to double by 2050. Climate change-induced challenges to food crops, especially soil salinization, remain a major threat to food production. We hypothesize that endophytic fungi isolated from salt-adapted host plants can confer salinity stress tolerance to salt-sensitive crops. Therefore, we isolated fungal endophytes from shrubs along the shores of saline alkaline Lake Magadi and evaluated their ability to induce salinity stress tolerance in tomato seeds and seedlings. Of 60 endophytic fungal isolates, 95% and 5% were from Ascomycetes and Basidiomycetes phyla, respectively. The highest number of isolates (48.3%) were from the roots. Amylase, protease and cellulase were produced by 25, 30 and 27 isolates, respectively; and 32 isolates solubilized phosphate. Only eight isolates grew at 1.5 M NaCl. Four fungal endophytes (Cephalotrichum cylindricum, Fusarium equiseti, Fusarium falciforme and Aspergilus puniceus) were tested under greenhouse conditions for their ability to induce salinity tolerance in tomato seedlings. All four endophytes successfully colonized tomato seedlings and grew in 1.5 M NaCl. The germination of endophyte-inoculated seeds was enhanced by 23%, whereas seedlings showed increased chlorophyll and biomass content and decreased hydrogen peroxide content under salinity stress, compared with controls. The results suggest that the the four isolates can potentially be used to mitigate salinity stress in tomato plants in salt-affected soils.

Endophytic Aspergillii and Penicillii from medicinal plants: a focus on antimicrobial and multidrug resistant pathogens inhibitory activity

The rise of multidrug resistance among microorganisms, where they develop resistance against formerly efficacious drugs, has led to increased disease prevalence and mortality rates, posing a growing challenge. Globally, antibiotic resistance has made a significant impact, causing millions of fatalities each year. Endophytic fungi have gained considerable attention in research due to their potential to produce a wide variety of secondary metabolites, including natural substances with antimicrobial capabilities. The genera Aspergillus and Penicillium stand out as the most prevalent species of endophytic fungi. Filamentous fungi, such as these are responsible for the production of 45% of known microbial metabolites. This review focuses on exploring the bioactive substances produced by endophytic fungi from these two genera, particularly in conjunction with medicinal plants. Emphasis is placed on their antimicrobial activity and their ability to inhibit multidrug-resistant pathogens. As the need for alternative treatments to combat drug-resistant infections continues to grow, endophytic fungi have the potential to provide a valuable source of bioactive molecules for medical applications.

Metabolic profiling, antimicrobial, anticancer, and in vitro and in silico immunomodulatory investigation of Aspergillus niger OR730979 isolated from the Western Desert, Egypt

Ten fungal species were isolated from soil in the Western Desert and Wadi El-Natron in Egypt. All fungal isolates were morphologically recognized down to the species level. Methanol extracts of fungal mycelia and ethyl acetate extracts of culture filtrate from the isolated fungi were evaluated for antimicrobial activity against six pathogenic bacteria and one pathogenic yeast (Candida albicans ATCC20231). Only ethyl acetate extracts of Fusarium circinatum, Aspergillus niger, and Aspergillus terreus culture filtrates showed significant antimicrobial activity against the majority of the investigated pathogens. The culture filtrate extract of Aspergillus niger exhibited notable cytotoxicity towards the breast cancer (MCF-7) cell line, with the lowest detected IC50 recorded at 8 μg/μl. Whereas Fusarium circinatum and Aspergillus terreus had IC50s of 15.91 μg/μl and 18 μg/μl, respectively. A gas chromatography-mass spectroscopy (GC-MS) investigation of A. niger's potent extract revealed 23 compounds with different biological activities. Glycidyleoleate was found to be the main extract component. Aspergillus niger extract was chosen to study its possible cytotoxic mechanism. The extract was found to induce apoptosis and cell cycle arrest at the < 2n stage. Despite a significant increase in caspases 8 and 9, the production levels of tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6) have shown a significant decrease. The high interaction of glycidyleoleate against the studied cytokines' binding receptors was demonstrated via docking studies. In conclusion, the available data revealed that the culture filtrate extract of A. niger possesses promising antimicrobial, cytotoxic, and immunomodulatory properties.

Phytochemical investigation of Nigrospora zimmermanii isolated from Poincianella pluviosa (Sibipiruna): metabolites characterisation and screening for anti-inflammatory activity

Endophytic fungi residing symbiotically in plant tissues are promising sources of bioactive natural products. This study explored the anti-inflammatory potential of an endophytic fungus isolated from the Brazilian medicinal plant Poincianella pluviosa (Sibipiruna). The extract from the endophyte FPD13 exhibited potential ex vivo anti-inflammatory effects by inhibiting prostaglandin E2 (PGE2) release by 75.22%. Phytochemical analysis using High-Performance Liquid Chromatography (HPLC), Nuclear Magnetic Resonance (NMR), and Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS) enabled the isolation and identification of three compounds, including the macrolide Nigrosporolide, the phenyl-propanol Tyrosol, and the terpene Decarestrictine A. Morphological characteristics and Internal Transcribed Spacers region (ITS) sequencing classified fungus FPD13 as Nigrospora zimmermanii. The results reveal the anti-inflammatory potential and chemical diversity of P. pluviosa endophytes, warranting further investigation into the bioactivity and structure elucidation of their bioactive metabolites.

Chemical Constituents and Bioactivities of the Plant-Derived Fungus Aspergillus fumigatus

A new bergamotane sesquiterpenoid, named xylariterpenoid H (1), along with fourteen known compounds (2-15), were isolated from the crude extract of Aspergillus fumigatus, an endophytic fungus isolated from Delphinium grandiflorum L. Their structures were elucidated mainly by extensive analyses of NMR and MS spectroscopic data. In addition, the screening results of antibacterial and cytotoxic activities of compounds 1-15 showed that compound 4 displayed antibacterial activities against Staphylococcus aureus and MRSA (methicillin-resistant S. aureus) with an MIC value of 3.12 µg/mL.

Long-Term Investigation of Marine-Derived Aspergillus Diversity in the Republic of Korea

Aspergillus species play a crucial role in terrestrial environments as degraders and are well known for producing various secondary metabolites. Recently, Aspergillus species have been discovered in marine environments, exhibiting adaptability to high salinity and producing diverse secondary metabolites with valuable properties. However, limited research has focused on their marine diversity, leading to inaccurate species identification. The current study addresses this gap by investigating diverse marine habitats in the Republic of Korea, including sediment, seawater, seaweed, and marine animals. From three coasts of the Korean Peninsula, 472 Aspergillus strains were isolated from the various marine habitats. A total of 41 species were accurately identified using multigenetic markers: internal transcribed spacer, calmodulin, and β-tubulin. The findings underscore the importance of accurate identification and provide a basis for elucidating the functional role of marine-derived Aspergillus species in marine ecosystems.

Evaluation of the anti-infective potential of the seed endophytic fungi of Corchorus olitorius through metabolomics and molecular docking approach

BACKGROUND

Endophytic fungi are very rich sources of natural antibacterial and antifungal compounds. The main aim of this study is to isolate the fungal endophytes from the medicinal plant Corchorus olitorius seeds (F. Malvaceae), followed by antimicrobial screening against various bacterial and fungal strains.

RESULTS

Seven endophytic fungal strains belonging to different three genera were isolated, including Penicillium, Fusarium, and Aspergillus. The seven isolated endophytic strains revealed selective noticeable activity against Escherichia coli (ATCC25922) with varied IC50s ranging from 1.19 to 10 µg /mL, in which Aspergillus sp. (Ar 6) exhibited the strongest potency against E. coli (ATCC 25,922) and candida albicans (ATCC 10,231) with IC50s 1.19 and 15 µg /mL, respectively. Therefore, the chemical profiling of Aspergillus sp. (Ar 6) crude extract was performed using LC-HR-ESI-MS and led to the dereplication of sixteen compounds of various classes (1-16). In-silico analysis of the dereplicated metabolites led to highlighting the compounds responsible for the antimicrobial activity of Aspergillus sp. extract. Moreover, molecular docking showed the potential targets of the metabolites; Astellatol (5), Aspergillipeptide A (10), and Emericellamide C (14) against E. coli and C. albicans.

CONCLUSION

These results will expand the knowledge of endophytes and provide us with new approaches to face the global antibiotic resistance problem and the future production of undiscovered compounds different from the antibiotics classes.

The anti-infective potential of the endophytic fungi associated with Allium cepa supported by metabolomics analysis and docking studies

Endophytic fungi are known to be a rich source of anti-infective drugs. In our study, Allium cepa was investigated for fungal diversity using different media to give 11 isolates which were identified morphologically. Out of the isolated fungal strains, Penicillium sp. (LCEF10) revealed potential anti-infective activity against the tested microbes (Fusarium solani ATTC 25922, Pseudomonas aeruginosa (ATTC 29231), Staphylococcus aureus ATTC 27853, Candida albicans ATTC 10231), besides, their MICs were measured by well diffusion method, therefore, it was subjected to molecular identification in addition to phylogenetic analysis. Moreover, the ITS sequence of strain LCEF10 showed a consistent assignment with the highest sequence similarity (99.81%) to Penicillium oxalicum NRRL 787. The crude ethyl acetate extract of Penicillium sp. LCEF10 was investigated for metabolomic analysis using LC-HR-ESI-MS. The metabolic profiling revealed the presence of polyketides, macrolides, phenolics and terpenoids. Furthermore, in silico molecular docking study was carried out to predict which compounds most likely responsible for the anti-infective activity.

Biological Control of Aspergillus parasiticus and Aspergillus ochraceus and Reductions in the Amount of Ochratoxin A and Aflatoxins in Bread by Selected Non-Conventional Yeast

Aspergillus parasiticus and Aspergillus ochraceus are important pathogenic fungi that pose a serious threat because of their ability to produce mycotoxins, including ochratoxin A (OTA) and aflatoxins (AFs). The main method of reducing these pathogens is the use of chemical fungicides, though recently there has been a focus on finding biological control agents. The obtained results from this study indicate the great potential of two wild yeast strains, Aureobasidium pullulans PP3 and Saitozyma podzolicus D10, in the biological control of A. parasiticus and A. ochraceus and reductions in the amount of OTA and AFs they produce. In vitro, the growth of the mycelium of pathogens was reduced by 41.21% to 53.64%, and spore germination was inhibited by 58.39% to 71.22%. Both yeast strains produced the enzymes chitinase, β-1,3-glucanase, and amylase, and A. pullulans PP3 additionally produced protease and cellulase. This yeast strain also had the ability to grow over a wide range of temperature (4-30 °C), salinity (0-12%) and pH (4-11) conditions. No growth of the yeast was observed at 37 °C, nor any biogenic amines or hydrogen sulfide production. Adding the tested yeast inoculum to the dough reduced OTA (within 14.55-21.80%) and AFs (within 18.10-25.02%) in the model bread.

Histone Deacetylase UvHST2 Is a Global Regulator of Secondary Metabolism in Ustilaginoidea virens

Ustilaginoidea virens, the causal agent of rice false smut, produces a large amount of mycotoxins, including ustilaginoidins and sorbicillinoids. However, little is known about the regulatory mechanism of mycotoxin biosynthesis inU. virens. Here, we demonstrate that the NAD+-dependent histone deacetylase UvHST2 negatively regulates ustilaginoidin biosynthesis. UvHst2 knockout caused retarded hypha growth and reduced conidiation and pathogenicity inU. virens. Transcriptome analysis revealed that the transcription factor genes, transporter genes, and other tailoring genes in eight biosynthetic gene clusters (BGCs) including ustilaginoidin and sorbicillinoid BGCs were upregulated in ΔUvhst2. Interestingly, the UvHst2 deletion affects alternative splicing. Metabolomics revealed that UvHST2 negatively regulates the biosynthesis of various mycotoxins including ustilaginoidins, sorbicillin, ochratoxin B, zearalenone, and O-M-sterigmatocystin. Combined transcriptome and metabolome analyses uncover that UvHST2 positively regulates pathogenicity but negatively modulates the expression of BGCs involved in secondary metabolism. Collectively, UvHST2 functions as a global regulator of secondary metabolism inU. virens.

Antimicrobial activities of metabolites isolated from endophytic Aspergillus flavus of Sarcophyton ehrenbergi supported by in-silico study and NMR spectroscopy

BACKGROUND

Endophytic Aspergillus species produce countless valuable bioactive secondary metabolites. In the current study, Aspergillus flavus an endophyte from the soft coral Sarcophyton ehrenbergi was chemically explored and the extracted phytoconstituents were subsequently evaluated for antimicrobial activity. This is accomplished by employing nuclear magnetic resonance (NMR) spectroscopy and computational techniques. Additionally, An in vitro anticancer analysis of A. flavus total extract against breast cancer cells (MCF-7) was investigated.

RESULT

Six compounds were separated from the crude alcohol extract of the endophytic Aspergillus flavus out of which anhydro-mevalonolactone was reported for the first time. The anti-fungal and anti-Helicobacter pylori properties of two distinct compounds (Scopularides A and B) were assessed. Additionally, computational research was done to identify the binding mechanisms for all compounds. Both the compounds were found to be active against H. pylori with minimum inhibitory concentration (MIC) values ranging from 7.81 to 15.63 µg/ mL as compared with clarithromycin 1.95 µg/ mL. Scopularides A was potent against both Candida albicans and Aspergillus niger with MIC values ranging from 3.9 to 31.25 µg/ mL, while scopularides B only inhibits Candida albicans with MIC value of 15.63 µg/ mL and weak inhibitory activity against A. niger (MIC = 125 µg/ mL). Furthermore, cytotoxic activity showed a significant effect (IC50: 30.46 mg/mL) against MCF-7 cells.

CONCLUSION

Our findings report that cytotoxic activity and molecular docking support the antimicrobial activity of Aspergillus flavus, which could be a promising alternative source as a potential antimicrobial agent.

Efficacy of Aspergillus tubingensis GX3' Fermentation against Meloidogyne enterolobii in Tomato (Solanum lycopersicum L.)

Meloidogyne enterolobii is one of the most virulent root-knot nematodes (RKNs). Aspergillus tubingensis Raoul Mosseray, 1934, is used to produce bioactive substances, enzymes, and secondary metabolites. However, no research has been conducted yet on the efficacy of A. tubingensis against plant-parasitic nematodes. Thus, the novel research was planned to evaluate the biocontrol efficacy of A. tubingensis fermentation against M. enterolobii. The findings showed that egg hatching inhibition and mortality of M. enterolobii increased with increasing concentration of fermentation and exposure time. The maximum second-stage juveniles (J2s) mortality was achieved via 100% fermentation at 72 h. Similarly, 100% fermentation inhibited 99.9% of egg hatching at 8 d. A. tubingensis fermentation increased plant biomass, decreased second-stage juvenile invasion, and inhibited nematode development and reproduction in greenhouse conditions. A. tubingensis reduced J2 invasion into tomato roots by 42.84% with CS+ (coated seeds plants with nematodes inoculum) and 27.04% with T+ (100% fermentation broth and nematodes inoculum both) treatments. Moreover, CS+ and T+ treatments decreased nematode development by 54.31% and 21.48%, respectively. It is concluded that the A. tubingensis GX3 strain can be used as a novel microbial biocontrol agent against M. enterolobii.

Production of L-Malic Acid by Metabolically Engineered Aspergillus nidulans Based on Efficient CRISPR-Cas9 and Cre-loxP Systems

Aspergillus nidulans has been more extensively characterized than other Aspergillus species considering its morphology, physiology, metabolic pathways, and genetic regulation. As it has a rapid growth rate accompanied by simple nutritional requirements and a high tolerance to extreme cultural conditions, A. nidulans is a promising microbial cell factory to biosynthesize various products in industry. However, it remains unclear for whether it is also a suitable host for synthesizing abundant L-malic acid. In this study, we developed a convenient and efficient double-gene-editing system in A. nidulans strain TN02A7 based on the CRISPR-Cas9 and Cre-loxP systems. Using this gene-editing system, we made a L-malic acid-producing strain, ZQ07, derived from TN02A7, by deleting or overexpressing five genes (encoding Pyc, pyruvate carboxylase; OahA, oxaloacetate acetylhydrolase; MdhC, malate dehydrogenase; DctA, C4-dicarboxylic acid transporter; and CexA, citric acid transporter). The L-malic acid yield in ZQ07 increased to approximately 9.6 times higher (up to 30.7 g/L titer) than that of the original unedited strain TN02A7, in which the production of L-malic acid was originally very low. The findings in this study not only demonstrate that A. nidulans could be used as a potential host for biosynthesizing organic acids, but also provide a highly efficient gene-editing strategy in filamentous fungi.

Natural Bacterial and Fungal Peptides as a Promising Treatment to Defeat Lung Cancer Cells

Despite the increasing availability of modern treatments, including personalized therapies, there is a strong need to search for new drugs that will be effective in the fight against cancer. The chemotherapeutics currently available to oncologists do not always yield satisfactory outcomes when used in systemic treatments, and patients experience burdensome side effects during their application. In the era of personalized therapies, doctors caring for non-small cell lung cancer (NSCLC) patients have been given a powerful weapon, namely molecularly targeted therapies and immunotherapies. They can be used when genetic variants of the disease qualifying for therapy are diagnosed. These therapies have contributed to the extension of the overall survival time in patients. Nevertheless, effective treatment may be hindered in the case of clonal selection of tumor cells with acquired resistance mutations. The state-of-the-art therapy currently used in NSCLC patients is immunotherapy targeting the immune checkpoints. Although it is effective, some patients have been observed to develop resistance to immunotherapy, but its cause is still unknown. Personalized therapies extend the lifespan and time to cancer progression in patients, but only those with a confirmed marker qualifying for the treatment (gene mutations/rearrangements or PD-L1 expression on tumor cells) can benefit from these therapies. They also cause less burdensome side effects than chemotherapy. The article is focused on compounds that can be used in oncology and produce as few side effects as possible. The search for compounds of natural origin, e.g., plants, bacteria, or fungi, exhibiting anticancer properties seems to be a good solution. This article is a literature review of research on compounds of natural origin that can potentially be used as part of NSCLC therapies.

GC-MS Based Characterization, Antibacterial, Antifungal and Anti-Oncogenic Activity of Ethyl Acetate Extract of Aspergillus niger Strain AK-6 Isolated from Rhizospheric Soil

Rhizospheric soil is the richest niche of different microbes that produce biologically active metabolites. The current study investigated the antimicrobial, antifungal and anticancer activities of ethyl acetate extract of the potent rhizospheric fungus Aspergillus niger AK6 (AK-6). A total of six fungal isolates were isolated, and isolate AK-6 was selected based on primary screening. Further, it exhibited moderate antimicrobial activity against pathogens such as Klebsiella pneumonia, Candida albicans, Escherichia coli, Shigella flexneri, Bacillus subtilis and Staphylococcus aureus. The morphological and molecular characterization (18S rRNA) confirmed that the isolate AK-6 belonged to Aspergillus niger. Further, AK-6 showed potent antifungal activity with 47.2%, 59.4% and 64.1% of inhibition against Sclerotium rolfsii, Cercospora canescens and Fusarium sambucinum phytopathogens. FT-IR analysis displayed different biological functional groups. Consequently, the GC-MS analysis displayed bioactive compounds, namely, n-didehydrohexacarboxyl-2,4,5-trimethylpiperazine (23.82%), dibutyl phthalate (14.65%), e-5-heptadecanol (8.98%), and 2,4-ditert-butylphenol (8.60%), among the total of 15 compounds isolated. Further, the anticancer activity of AK-6 was exhibited against the MCF-7 cell line of human breast adenocarcinoma with an IC₅₀ value of 102.01 μg/mL. Furthermore, flow cytometry depicted 17.3%, 26.43%, and 3.16% of early and late apoptosis and necrosis in the AK-6 extarct treated MCF-7 cell line, respectively. The results of the present analysis suggest that the isolated Aspergillus niger strain AK-6 extract has the potential to be explored as a promising antimicrobial, antifungal and anticancer drug for medical and agricultural applications.

Aspergillus Carneus metabolite Averufanin induced cell cycle arrest and apoptotic cell death on cancer cell lines via inducing DNA damage

Cancer is one of the leading causes of death worldwide, accounting for nearly 10 million deaths in 2020. Current treatment methods include hormone therapy, γ-radiation, immunotherapy, and chemotherapy. Although chemotherapy is the most effective treatment, there are major obstacles posed by resistance mechanisms of cancer cells and side-effects of the drugs, thus the search for novel anti-cancer compounds, especially from natural sources, is crucial for cancer pharmaceutics research. One natural source worthy of investigation is fungal species. In this study, the cytotoxicity of 5 metabolic compounds isolated from filamentous fungus Aspergillus Carneus. Arugosin C, Averufin, Averufanin, Nidurifin and Versicolorin C were analyzed using NCI-SRB assay on 10 different cell lines of breast cancer, ovarian cancer, glioblastoma and non-tumorigenic cell lines. Averufanin showed highest cytotoxicity with lowest IC₅₀ concentrations especially on breast cancer cells. Therefore, Averufanin was further investigated to enlighten cell death and molecular mechanisms of action involved. Cell cycle analysis showed increase in SubG1 phase suggesting apoptosis induction which was further confirmed by Annexin V and Caspase 3/7 Assays. H2A.X staining revealed accumulation of DNA damage in cells treated with Averufanin and finally western blot analysis validated DNA damage response and downstream effects of Averufanin treatment in various signaling pathways. Consequently, this study shows that Averufanin compound induces cell cycle arrest and cell death via apoptosis through causing DNA damage and can be contemplated and further explored as a new therapeutic strategy in breast cancer.

Aspergillus co-cultures: A recent insight into their secondary metabolites and microbial interactions

There is an urgent need for novel antibiotics to combat emerging resistant microbial strains. One of the most pressing resources is Aspergillus microbial cocultures. The genome of Aspergillus species comprises a far larger number of novel gene clusters than previously expected, and novel strategies and approaches are essential to exploit this potential source of new drugs and pharmacological agents. This is the first review consulting recent developments and chemical diversity of Aspergillus cocultures and highlighting its untapped richness. The analyzed data revealed that cocultivation of several Aspergillus species with other microorganisms, including bacteria, plants, and fungi, is a source of novel bioactive natural products. Various vital chemical skeleton leads were newly produced or augmented in Aspergillus cocultures, among which were taxol, cytochalasans, notamides, pentapeptides, silibinin, and allianthrones. The possibility of mycotoxin production or complete elimination in cocultivations was detected, which pave the way for better decontamination strategies. Most cocultures revealed a remarkable improvement in their antimicrobial or cytotoxic behavior due to their produced chemical patterns; for instance, weldone and asperterrin whose antitumor and antibacterial activities, respectively, were superior. Microbial cocultivation elicited the upregulation or production of specific metabolites whose importance and significance are yet to be revealed. With more than 155 compounds isolated from Aspergillus cocultures in the last 10 years, showing overproduction, reduction, or complete suppression under the optimized coculture circumstances, this study filled a gap for medicinal chemists searching for new lead sources or bioactive molecules as anticancer agents or antimicrobials.

Sulochrins and alkaloids from a fennel endophyte Aspergillus sp. FVL2

The fungal endophyte Aspergillus sp. strain FVL2, isolated from the traditional medicinal fennel plant, Foeniculum vulgare, was investigated for secondary metabolites. Fermentation on rice medium followed by chromatographic separation delivered three new natural products, 7-demethyl-neosulochrin (1), fumigaclavine I (3) and N-benzoyl-tryptophan (6) together with further 14 known metabolites, 1-O-methyl-sulochrin-4'-sulfate, questin, laccaic acid, isorhodoptilometrin, fumigaclavine A, fumigaclavine C, fumitremorgin C, fumigaquinazoline C, tryptoquivaline J, trypacidin, 3'-O-demethyl-sulochrin, 1-O-methyl-sulochrin, protocatechuic acid, and vermelone. The chemical structures of the new metabolites were determined by NMR spectroscopy and ESI HR mass spectrometry. For fumigaclavine I, we observed the partial deuterium transfer from the solvent to the enol form with a remarkable high stereo selectivity. The discovery of the new seco-anthraquinone 7-demethyl-neosulochrin (1) revealed a second type of ring cleavage by a questin oxygenase. The discovery of diverse secondary metabolites broadens the chemical space of Aspergillus.

Unearthing the fungal endophyte Aspergillus terreus for chemodiversity and medicinal prospects: a comprehensive review

Aspergillus terreus microorganism represents a promising prospective source for drug discovery since it is rich in diverse kinds of bioactive secondary metabolites. It contributed to many biotechnological applications and its metabolites are used in the synthesis of certain pharmaceuticals and food products, in addition to its useful uses in fermentation processes. There are about 346 compounds identified from marine and terrestrial-derived A. terreus from 1987 until 2022, 172 compounds of them proved a vast array of bioactivity. This review aimed to create an up-to-date comprehensive literature data of A. terreus's secondary metabolites classes supported by its different bioactivity data to be a scientific record for the next work in drug discovery.

Systematic Description of the Content Variation of Natural Products (NPs): To Prompt the Yield of High-Value NPs and the Discovery of New Therapeutics

Natural products (NPs) have long been associated with human production and play a key role in the survival of species. Significant variations in NP content may severely affect the "return on investment" of NP-based industries and render ecological systems vulnerable. Thus, it is crucial to construct a platform that relates variations in NP content to their corresponding mechanisms. In this study, a publicly accessible online platform, NPcVar (http://npcvar.idrblab.net/), was developed, which systematically described the variations of NP contents and their corresponding mechanisms. The platform comprises 2201 NPs and 694 biological resources, including plants, bacteria, and fungi, curated using 126 diverse factors with 26,425 records. Each record contains information about the species, NP, and factors involved, as well as NP content data, parts of the plant that produce NPs, the location of the experiment, and reference information. All factors were manually curated and categorized into 42 classes which belong to four mechanisms (molecular regulation, species factor, environmental condition, and combined factor). Additionally, the cross-links of species and NP to well-established databases and the visualization of NP content under various experimental conditions were provided. In conclusion, NPcVar is a valuable resource for understanding the relationship between species, factors, and NP contents and is anticipated to serve as a promising tool for improving the yield of high-value NPs and facilitating the development of new therapeutics.

The endophytic Fusarium strains: a treasure trove of natural products

The complexity and structural diversity of the secondary metabolites produced by endophytes make them an attractive source of natural products with novel structures that can help in treating life-changing diseases. The genus Fusarium is one of the most abundant endophytic fungal genera, comprising about 70 species characterized by extraordinary discrepancy in terms of genetics and ability to grow on a wide range of substrates, affecting not only their biology and interaction with their surrounding organisms, but also their secondary metabolism. Members of the genus Fusarium are a source of secondary metabolites with structural and chemical diversity and reported to exhibit diverse pharmacological activities. This comprehensive review focuses on the secondary metabolites isolated from different endophytic Fusarium species along with their various biological activities, reported in the period from April 1999 to April 2022.

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.

Molecular mechanism of Cu metal and drought stress resistance triggered by Porostereum spadiceum AGH786 in Solanum lycopersicum L

Rapid industrialization and global warming have threatened the plants with multiple abiotic stresses, such as heavy metals and drought stress. For crop cultivation, the conventional approach of cleaning the soils by excavation is very costly and not feasible for large scale. Establishing toxin-free and drought-resistant crops is a major challenge in the environment under natural and anthropogenic pressure. In the past decades, copper contamination of agricultural land has become an emerging concern. For dry land reclamation, several new strategies, including bioremediation (phytoremediation and microbial remediation), have been used. Owing to the potential of Cu hyperaccumulators, the current project aims to enhance the drought tolerance and the phytoremediation potential of Solanum lycopersicum L. with the inoculation of copper and 12% polyethylene glycol (PEG)-induced drought stress-tolerant endophytic fungus Porostereum spadiceum AGH786 under the combined stress of copper heavy metal and PEG-induced drought stress. When S. lycopersicum L. was watered with individual stress of copper (Cu) concentration (400 ppm) in the form of copper sulfate (CuSO₄.5H₂O), 12% PEG-induced drought stress and the combined stress of both negatively affected the growth attributes, hormonal, metabolic, and antioxidant potential, compared with control. However, the multistress-resistant AGH786 endophytic fungus ameliorated the multistress tolerance response in S. lycopersicum L. by positively affecting the growth attributes, hormonal, metabolic, and antioxidant potential, and by restricting the root-to-shoot translocation of Cu and inducing its sequestration in the root tissues of affected plants. AGH786-associated plants exhibited a reduction in the severity of copper (Cu) and drought stress, with higher levels of SlCOPT (Cu transporters) and SlMT (metallothionine) gene expressions in root and shoot tissues, indicating that AGH786 contributed to resistance to copper metal toxicity and drought stress in the host S. lycopersicum L.

Antimicrobial potentials of natural products against multidrug resistance pathogens: a comprehensive review

Antibiotic resistance is one of the critical issues, describing a significant social health complication globally. Hence, the discovery of novel antibiotics has acquired an increased attention particularly against drug-resistant pathogens. Natural products have served as potent therapeutics against pathogenic bacteria since the glorious age of antibiotics of the mid 20th century. This review outlines the various mechanistic candidates for dealing with multi-drug resistant pathogens and explores the terrestrial phytochemicals isolated from plants, lichens, insects, animals, fungi, bacteria, mushrooms, and minerals with reported antimicrobial activity, either alone or in combination with conventional antibiotics. Moreover, newly established tools are presented, including prebiotics, probiotics, synbiotics, bacteriophages, nanoparticles, and bacteriocins, supporting the progress of effective antibiotics to address the emergence of antibiotic-resistant infectious bacteria. Therefore, the current article may uncover promising drug candidates that can be used in drug discovery in the future.

Metabolites of medicine food homology-derived endophytic fungi and their activities

Medicine food homology (MFH) substances not only provide essential nutrients as food but also have corresponding factors that can prevent and help treat nutritional imbalances, chronic disease, and other related issues. Endophytic fungi associated with plants have potential for use in drug discovery and food therapy. However, the endophytic fungal metabolites from MFH plants and their effects have been overlooked. Therefore, this review focuses on the various biological activities of 108 new metabolites isolated from 53 MFH-derived endophytic fungi. The paper explores the potential nutritional and medicinal value of metabolites of MFH-derived endophytic fungi for food and medical applications. This research is important for the future development of effective, safe, and nontoxic therapeutic nutraceuticals for the prevention and treatment of human diseases.

Improved seed germination and plant growth mediated by compounds synthesized by endophytic Aspergillus niger (isolate 29) isolated from Albizia lebbeck (L.) Benth

Plant-microbe interactions are remarkably diverse and dynamic. These interactions can be in the form of endophytic association. Colonization of endophytic microflora in crop plants improves crop health leading to crop enhancement. They stimulate the overall growth of plants by facilitating nutrient uptake and regulating various hormones. This eventually improves the plant biomass and grain yield. Owing to the assistance of the endophytes to the host plants, augmentation of crop plants with potential fungal endophytes or their extracted bioactive compound can upsurge the overall crop production and provide promising solutions for environmentally sustainable agriculture. In this light, the present study deals with the prospects of bioactive metabolites produced by endophytic fungi in Albizia lebbeck (L.) Benth, a medicinal native plant of Rajasthan. The metabolomic analysis of a partially purified extract of Aspergillus niger (isolate 29) showed the presence of a total of 919 compounds using UHPLC-MS/MS. The metabolic pathway analysis revealed that these compounds were influencing super pathway of gibberellin and isoflavonoid biosynthesis. Significant increase in seed germination percentage (73-93%), seed vigour index (834.44-1498.21) and germination index (2.54-3.67 seeds/day) was found in treated seeds compared to untreated. There was a significant improvement in root (45-185%) and shoot length (215-295%) of wheat, barley and millet and a significant increase in root number (38-97%) in wheat and barley. Positive correlation was observed in the growth parameters of all the crops upon treatment. Overall, the results indicated that the partially purified fraction of A. niger (isolate 29) improved seed germination and promoted plant growth in cash crops. The results emphasize towards the importance of secondary metabolites in seed germination and enhancement of plant growth. These results also suggest a probable mutualistic role of endophyte with the host plant.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03332-x.

Phenyl Ethers from the Marine-Derived Fungus Aspergillus tabacinus and Their Antimicrobial Activity Against Plant Pathogenic Fungi and Bacteria

Marine fungi produce various secondary metabolites with unique chemical structures and diverse biological activities. In the continuing search for new antifungal agents from fungi isolated from marine environments, the culture filtrate of a fungus Aspergillus tabacinus SFC20160407-M11 exhibited the potential to control plant diseases caused by fungi. From the culture filtrate of A. tabacinus SFC20160407-M11, a total of seven compounds were isolated and identified by activity-guided column chromatography and spectroscopic analysis: violaceol I (1), violaceol II (2), diorcinol (3), versinol (4), orcinol (5), orsellinic acid (6), and sydowiol C (7). Based on in vitro bioassays against 17 plant pathogenic fungi and bacteria, violaceols and diorcinol (1-3) showed a broad spectrum of antimicrobial activity with minimum inhibitory concentration values in the range of 6.3-200 μg mL^-1. These compounds also effectively reduced the development of rice blast, tomato late blight, and pepper anthracnose caused by plant pathogenic fungi in a dose-dependent manner. Our results suggest that A. tabacinus SFC20160407-M11 and its phenyl ether compounds could be used for developing new antimicrobial agents to protect crops from plant pathogens.

Zinc Oxide Nanoparticles as Potential Delivery Carrier: Green Synthesis by Aspergillus niger Endophytic Fungus, Characterization, and In Vitro/In Vivo Antibacterial Activity

We aimed to synthesize zinc oxide nanoparticles (ZnO NPs) using the endophytic fungal extract of Aspergillus niger. The prepared ZnO NPs were characterized, and their in vitro and in vivo antibacterial activity was investigated. Isolated endophytic fungus identification was carried out using 18S rRNA. A. niger endophytic fungal extract was employed for the green synthesis of ZnO NPs. The in vitro antibacterial activity of the prepared ZnO NPs was elucidated against Staphylococcus aureus using the broth microdilution method and quantitative real-time polymerase chain reaction (qRT-PCR). Additionally, the in vivo antibacterial activity was elucidated using a systemic infection model in mice. The biosynthesized ZnO NPs showed a maximum optical density at 380 nm with characteristic peaks on the Fourier-transform infrared spectrum. The X-ray diffraction pattern was highly matched with a standard platform of zinc oxide crystals. Energy-dispersive X-ray analysis confirmed that the main composition of nanoparticles was zinc and oxygen atoms. Scanning and transmission electron microscopies showed spherical geometry with a smooth surface. Zeta potential measurements (26.6 ± 0.56 mV) verified the adequate stability of ZnO NPs. Minimum inhibitory concentrations of ZnO NPs against S. aureus isolates ranged from 8 to 128 µg/mL. Additionally, ZnO NPs revealed antibiofilm activity, resulting in the downregulation of the tested biofilm genes in 29.17% of S. aureus isolates. Regarding the in vivo experiment, ZnO NPs reduced congestion and fibrosis in liver and spleen tissues. They also improved liver function, increased the survival rate, and significantly decreased inflammatory markers (p < 0.05). ZnO NPs synthesized by A. niger endophytic fungus revealed a promising in vivo and in vitro antibacterial action against S. aureus isolates.

In Vitro Phytobiological Investigation of Bioactive Secondary Metabolites from the Malus domestica-Derived Endophytic Fungus Aspergillus tubingensis Strain AN103

Endophytic fungi including black aspergilli have the potential to synthesize multiple bioactive secondary metabolites. Therefore, the search for active metabolites from endophytic fungi against pathogenic microbes has become a necessity for alternative and promising strategies. In this study, 25 endophytic fungal isolates associated with Malus domestica were isolated, grown, and fermented on a solid rice medium. Subsequently, their ethyl acetate crude extracts were pretested for biological activity. One endophytic fungal isolate demonstrated the highest activity and was chosen for further investigation. Based on its phenotypic, ITS ribosomal gene sequences, and phylogenetic characterization, this isolate was identified as Aspergillus tubingensis strain AN103 with the accession number (KR184138). Chemical investigations of its fermented cultures yielded four compounds: Pyranonigrin A (1), Fonsecin (2), TMC 256 A1 (3), and Asperazine (4). Furthermore, 1H-NMR, HPLC, and LC-MS were performed for the identification and structure elucidation of these metabolites. The isolated pure compounds showed moderate-to-potent antibacterial activities against Pseudomonas aeruginosa and Escherichia coli (MIC value ranged from 31 and 121 to 14.5 and 58.3 μg/mL), respectively; in addition, the time−kill kinetics for the highly sensitive bacteria against isolated compounds was also investigated. The antifungal activity results show that (3) and (4) had the maximum effect against Fusarium solani and A. niger with inhibition zones of 16.40 ± 0.55 and 16.20 ± 0.20 mm, respectively, and (2) had the best effect against Candida albicans, with an inhibition zone of 17.8 ± 1.35 mm. Moreover, in a cytotoxicity assay against mouse lymphoma cell line L5178Y, (4) exhibited moderate cytotoxicity (49% inhibition), whereas (1−3) reported weak cytotoxicity (15, 26, and 19% inhibition), respectively. Our results reveal that these compounds might be useful to develop potential cytotoxic and antimicrobial drugs and an alternative source for various medical and pharmaceutical fields.

The Endophytic Aspergillus Strains: A Bountiful Source of Natural Products

Fungi that invade plant inner tissues without inducing disease symptoms are known as fungal endophytes. They represent a promising and tremendous reservoir of natural products with valuable biological potentials for application in medicine, agriculture and industry. Among the numerous existing endophytic fungi, Aspergillus strains constitute one of the most prolific sources of secondary metabolites with diverse chemical classes and interesting biological activities. This review covers the literature of the year 2020, reporting the isolation of 202 compounds obtained from more than ten different endophytic Aspergillus species associated with different host plants. Analysis and interpretation of the collected data revealed that chemical investigation of endophytes belonging to the genus Aspergillus may greatly contribute in the discovery of potential drug leads. The isolated metabolites were chemically various and exhibited diverse biological activities such as antibacterial, anti-cancer, anti-plasmodial, anti-inflammatory, antioxidant, immunosuppressive and antifungal activities. Moreover, adoption of advanced technology in molecular biology together with modern chemical tools is anticipated to improve the discovery of new biopharmaceuticals from this valuable microbial world in the future.

Fungal Endophytes: A Potential Source of Antibacterial Compounds

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

Biocontrol Activity of Aspergillus terreus ANU-301 against Two Distinct Plant Diseases, Tomato Fusarium Wilt and Potato Soft Rot

To screen antagonistic fungi against plant pathogens, dual culture assay (DCA) and culture filtrate assay (CFA) were performed with unknown soil-born fungi. Among the different fungi isolated and screened from the soil, fungal isolate ANU-301 successfully inhibited growth of different plant pathogenic fungi, Colletotrichum acutatum, Alternaria alternata, and Fusarium oxysporum, in DCA and CFA. Morphological characteristics and rDNA internal transcribed spacer sequence analysis identified ANU-301 as Aspergillus terreus. Inoculation of tomato plants with Fusarium oxysporum f. sp. lycopersici (FOL) induced severe wilting symptom; however, co-inoculation with ANU-301 significantly enhanced resistance of tomato plants against FOL. In addition, culture filtrate (CF) of ANU-301 not only showed bacterial growth inhibition activity against Dickeya chrysanthemi (Dc), but also demonstrated protective effect in potato tuber against soft rot disease. Gas chromatography-tandem mass spectrometry analysis of CF of ANU-301 identified 2,4-bis(1-methyl-1-phenylethyl)-phenol (MPP) as the most abundant compound. MPP inhibited growth of Dc, but not of FOL, in a dose-dependent manner, and protected potato tuber from the soft rot disease induced by Dc. In conclusion, Aspergillus terreus ANU-301 could be used and further tested as a potential biological control agent.

Biocontrol Potential of Aspergillus Species Producing Antimicrobial Metabolites

Microbial metabolites have been recognized as an important source for the discovery of new antifungal agents because of their diverse chemical structures with novel modes of action. In the course of our screening for new antifungal agents from microbes, we found that culture filtrates of two fungal species Aspergillus candidus SFC20200425-M11 and Aspergillus montenegroi SFC20200425-M27 have the potentials to reduce the development of fungal plant diseases such as tomato late blight and wheat leaf rust. From these two Aspergillus spp., we isolated a total of seven active compounds, including two new compounds (4 and 6), and identified their chemical structures based on the NMR spectral analyses: sphaeropsidin A (1), (R)-formosusin A (2), (R)-variotin (3), candidusin (4), asperlin (5), montenegrol (6), and protulactone A (7). Based on the results of the in vitro bioassays of 11 plant pathogenic fungi and bacteria, sphaeropsidin A (1), (R)-formosusin A (2), (R)-variotin (3), and asperlin (5) exhibited a wide range of antimicrobial activity. Furthermore, when plants were treated with sphaeropsidin A (1) and (R)-formosusin A (2) at a concentration of 500 μg/ml, sphaeropsidin A (1) exhibited an efficacy disease control value of 96 and 90% compared to non-treated control against tomato late blight and wheat leaf rust, and (R)-formosusin A (2) strongly reduced the development of tomato gray mold by 82%. Asperlin (5) at a concentration of 500 μg/ml effectively controlled the development of tomato late blight and wheat leaf rust with a disease control value of 95%. Given that culture filtrates and active compounds derived from two Aspergillus spp. exhibited disease control efficacies, our results suggest that the Aspergillus-produced antifungal compounds could be useful for the development of new natural fungicides.

Nematicidal Activity of Cyclopiazonic Acid Derived From Penicillium commune Against Root-Knot Nematodes and Optimization of the Culture Fermentation Process

Among 200 fungal strains isolated from the soil, only one culture filtrate of Aspergillus flavus JCK-4087 showed strong nematicidal activity against Meloidogyne incognita. The nematicidal metabolite isolated from the culture filtrate of JCK-4087 was identified as cyclopiazonic acid (CPA). Because JCK-4087 also produced aflatoxins, six strains of Penicillium commune, which have been reported to be CPA producers, were obtained from the bank and then tested for their CPA productivity. CPA was isolated from the culture filtrate of P. commune KACC 45973. CPA killed the second-stage juveniles of M. incognita, M. hapla, and M. arearia with EC50-3 days 4.50, 18.82, and 60.51 μg mL-1, respectively. CPA also significantly inhibited egg hatch of M. incognita and M. hapla after a total of 28 days of treatment with the concentrations > 25 μg mL-1. The enhancement of CPA production by P. commune KACC 45973 was explored using an optimized medium based on Plackett-Burman design (PBD) and central composite design (CCD). The highest CPA production (381.48 μg mL-1) was obtained from the optimized medium, exhibiting an increase of 7.88 times when compared with that from potato dextrose broth culture. Application of the wettable power-type formulation of the ethyl acetate extract of the culture filtrate of KACC 45973 reduced gall formation and nematode populations in tomato roots and soils under greenhouse conditions. These results suggest that CPA produced by P. commune KACC 45973 can be used as either a biochemical nematicide or a lead molecule for developing chemical nematicides to control root-knot nematodes.

Comparative fungal diversity and dynamics in plant compartments at different developmental stages under root-zone restricted grapevines

BACKGROUND

The root-zone restriction cultivation technique is used to achieve superior fruit quality at the cost of limited vegetative and enhanced reproductive development of grapevines. Fungal interactions and diversity in grapevines are well established; however, our knowledge about fungal diversity under the root-zone restriction technique is still unexplored. To provide insights into the role of mycobiota in the regulation of growth and fruit quality of grapevine under root-zone restriction, DNA from rhizosphere and plant compartments, including white roots (new roots), leaves, flowers, and berries of root-zone restricted (treatment) and conventionally grown plants (control), was extracted at three growth stages (full bloom, veraison, and maturity).

RESULTS

Diversity analysis based on the ITS1 region was performed using QIIME2. We observed that the root-zone restriction technique primarily affected the fungal communities of the soil and plant compartments at different growth stages. Interestingly, Fusarium, Ilyonectria, Cladosporium and Aspergillus spp observed in the rhizosphere overlapped with the phyllosphere at all phenological stages, having distinctive abundance in grapevine habitats. Peak richness and diversity were observed in the rhizosphere at the full bloom stage of control plants, white roots at the veraison stage of treatment, leaves at the maturity stage of treatment, flowers at the full bloom stage and berries at the veraison stage of control plants. Except for white roots, the diversity of soil and plant compartments of treated plants tended to increase until maturity. At the maturity stage of the treated and control plants, the abundance of Aspergillus spp. was 25.99 and 29.48%, respectively. Moreover, the total soluble sugar content of berries was 19.03 obrix and 16 obrix in treated and control plants, respectively, at the maturity stage.

CONCLUSIONS

This is the first elucidative study targeting the fungal diversity of conventional and root-restricted cultivation techniques in a single vineyard. Species richness and diversity are affected by stressful cultivation known as root zone restriction. There is an association between the abundance of Aspergillus spp. and fruit quality because despite causing stress to the grapevine, superior quality of fruit is retrieved in root-zone restricted plants.

Novel Antioxidants and α-Glycosidase and Protein Tyrosine Phosphatase 1B Inhibitors from an Endophytic Fungus Penicillium brefeldianum F4a

Oxidative stress plays a very important role in the progression of diabetes and its complications. A therapeutic agent that is both antidiabetic and antioxidant would be the preferred choice for the treatment of diabetes. The crude extract of the endophytic fungus Penicillium brefeldianum F4a has significant antioxidant and α-glycosidase and protein tyrosine phosphatase 1B (PTP1B) inhibition activities. Chemical investigation of P. brefeldianum F4a using an activity-guided isolation led to the discovery of three new compounds called peniorcinols A-C (1-3) along with six known compounds: penialidins A (4), penialidin F (5), myxotrichin C (6), riboflavin (7), indole-3-acetic acid (8), and 2-(4-hydroxy-2-methoxy-6-methylphenyl) acetic acid (9). Their chemical structures were established by their NMR and HRESIMS. The absolute configurations of 1 and 3 were determined by experimental and calculated electronic circular dichroism (ECD). Their antioxidant activities were evaluated by DPPH• and ABTS•+ scavenging assays. Compounds 1-6 and 8-9 showed moderate to strong free radical scavenging activities. Significantly, 4-6 exhibited more potent ABTS•+ scavenging activity than that of the positive control. Their α-glycosidase and PTP1B inhibition activities were tested. Among them, compound 3 showed α-glucosidase inhibition activity, and compounds 7 and 8 showed PTP1B inhibitory activity for the first time. It is worth noting that 3 and 8 displayed both antioxidant and α-glycosidase or PTP1B inhibition activities. These finding suggest that compounds 3 and 8 could be used as lead compounds to generate new potent drugs for the treatment of oxidative stress-related diabetes.

Antimicrobial, Antioxidant, Cytotoxic Activities and Phytochemical Analysis of Fungal Endophytes Isolated from Ocimum Basilicum

Fungal endophytes are living inside plants without any harmful effects; the prospecting about them is increased day by day because they can produce bioactive compounds which can be used in different applications. Herein, the current study was aimed to isolate the endophytic fungi from the Ocimum basilicum plant as safe microorganisms and evaluate their biological activities. The results illustrated that three endophytic fungal strains were isolated and identified morphologically and genetically as Aspergillus nidulans, Aspergillus fumigatus, and Aspergillus flavus and deposited in gene bank under accession numbers MZ045561, MZ045562, and MZ045563 respectively. Moreover, cell-free filtrates of endophytic fungal strains were extracted using ethyl acetate, where these crude extracts exhibited promising antimicrobial activity against Staphylococcus aureus, Bacillus cereus, Bacillus subtilis, Escherichia coli, Salmonella typhimurium, Pseudomonas aeruginosa, Klebsiella pneumonia, and Candida albicans at a concentration of 1000 µg/mL. Furthermore, these endophytic strains exhibited a potential antioxidant activity where IC₅₀ of the crude extract of A. nidulans, A. fumigatus, and A. flavus were (166.3, 68.4, and 347.1 µg/mL) and (151.2, 77.9, and 246.3 µg/mL) using DPPH and ABTS methods, respectively. Furthermore, the ethyl acetate crude extracts of these endophytic fungi did not exhibit any cytotoxic effect against Vero and Wi 38 normal cells. GC-MS analysis of the crude extract of A. nidulans, A. fumigatus, and A. flavus indicated the presence of 22, 22, and 20 active compounds, respectively. The major compounds in the fungal extracts are belonging to fatty acids, fatty acid esters, tetrahydrofurans, and sterols. In conclusion, the isolated endophytic A. nidulans, A. fumigatus, and A. flavus from Ocimum basilicum are promising sources for bioactive compounds.

Chemical epigenetic modifiers enhance the production of immunosuppressants from the endophytic fungus Aspergillus fumigatus isolated from Cynodon dactylon

Chemical epigenetic modifiers applied on a plant endophytic fungus Aspergillus fumigatus isolated from a healthy stem of terrestrial plant Cynodon dactylon, significantly changed of metabolic profile and resulted in the isolation of nineteen compounds, including ten alkaloids (1-10), six polyketides (11-16), and three benzene derivatives (17-19). This is the first report of 14, 18 and 19 being isolated from this fungal species. And compound 14 was known as a synthetic product and isolated as a natural product for the first time. HPLC profiles of the control and treated samples indicated that compounds 11, 16, 18 are belonged to the newly induced secondary metabolites. Their structures were elucidated on the basis of extensive NMR spectroscopic and mass spectrometric analyses. The immunosuppressive and cytotoxic activities of all isolated compounds were evaluated.

Z, Cubilla-Rios L. Structurally Uncommon Secondary Metabolites Derived from Endophytic Fungi

Among microorganisms, endophytic fungi are the least studied, but they have attracted attention due to their high biological diversity and ability to produce novel and bioactive secondary metabolites to protect their host plant against biotic and abiotic stress. These compounds belong to different structural classes, such as alkaloids, peptides, terpenoids, polyketides, and steroids, which could present significant biological activities that are useful for pharmacological or medical applications. Recent reviews on endophytic fungi have mainly focused on the production of novel bioactive compounds. Here, we focus on compounds produced by endophytic fungi, reported with uncommon bioactive structures, establishing the neighbor net and diversity of endophytic fungi. The review includes compounds published from January 2015 to December 2020 that were catalogued as unprecedented, rare, uncommon, or possessing novel structural skeletons from more than 39 different genera, with Aspergillus and Penicillium being the most mentioned. They were reported as displaying cytotoxic, antitumor, antimicrobial, antiviral, or anti-inflammatory activity. The solid culture, using rice as a carbon source, was the most common medium utilized in the fermentation process when this type of compound was isolated.

Aspochalasin H1: A New Cyclic Aspochalasin from Hawaiian Plant-Associated Endophytic Fungus Aspergillus sp. FT1307

Aspergillus is one of the most diverse genera, and it is chemically profound and known to produce many biologically active secondary metabolites. In the present study, a new aspochalasin H1 (1), together with nine known compounds (2-10), were isolated from a Hawaiian plant-associated endophytic fungus Aspergillus sp. FT1307. The structures were elucidated using nuclear magnetic resonance (NMR) (1H, 1H-1H COSY, HSQC, HMBC, ROESY and 1D NOE), high-resolution electrospray ionization mass spectroscopy (HRESIMS), and comparisons with the reported literature. The absolute configuration of the new compound was established by electronic circular dichroism (ECD) in combination with NMR calculations. The new compound contains an epoxide moiety and an adjacent trans-diol, which has not been reported before in the aspochalasin family. The antibacterial screening of the isolated compounds was carried out against pathogenic bacteria (Staphylococcus aureus, Methicillin-resistant S. aureus and Bacillus subtilis). The antiproliferative activity of compounds 1-10 was evaluated against human breast cancer cell lines (MCF-7 and T46D) and ovarian cancer cell lines (A2780).

Alkaloids from endophytic fungus Aspergillus fumigatus HQD24 isolated from the Chinese mangrove plant Rhizophora mucronata

Chemical investigation of endophytic fungus Aspergillus fumigatus HQD24, isolated from the flower of Rhizophora mucronata led to the isolation of eight alkaloids, including pyripyropene A (1), 1,11-dideacetyl-pyripyropene A (2), pyripyropene E (3), chaetominine (4), tryptoquivaline J (5), fumitremorgin C (6), 1-acetyl-β-carboline (7), and nicotinic acid (8). Their structures were unambiguously elucidated on the basis of extensive spectroscopic data and comparison with the data of literature. Compound 2 was known as a synthetic product and isolated as a natural product for the first time. The immunosuppressive and cytotoxic activities of all isolated compounds were evaluated.

Asperflaloids A and B from Aspergillus flavipes DZ-3, an Endophytic Fungus of Eucommia ulmoides Oliver

The fungus strain DZ-3 was isolated from twigs of the well-known medicinal plant Eucommia ulmoides Oliver and identified as Aspergillus flavipes. Two new alkaloids, named asperflaloids A and B (1 and 2), together with 10 known compounds (3-12) were obtained from the EtOAc extract of the strain. Interestingly, the alkaloids 1-4 with different frameworks are characterized by the presence of the same anthranilic acid residue. The structures were established by detailed analyses of the spectroscopic data. The absolute configuration of asperflaloids A and B was resolved by quantum chemistry calculation. All compounds were screened for their inhibitions against α-glucosidase and the antioxidant capacities. The results were that compound 3 had an IC50 value of 750.8 μM toward α-glucosidase, and the phenol compounds 7 and 8 exhibited potent antioxidant capacities with IC50 values 14.4 and 27.1 μM respectively.

Bioremoval capacity of phenol by some selected endophytic fungi isolated from Hibiscus sabdariffa and batch biodegradation of phenol in paper and pulp effluents

BACKGROUND AND OBJECTIVES

The use of endophytic fungi for management of phenol residue in paper and pulp industries has been shown as cost-effective and eco-friendly approach. In this study, isolation of endophytic fungi from roots, stems, and leaves of Hibiscus sabdariffa was conducted. Additionally, the isolated fungi were examined for their ability to degrade phenol and its derivatives in paper and pulp industrial samples, using different growth conditions.

MATERIALS AND METHODS

Out of 35 isolated endophyitc fungi, 31 were examined for their phenol biodegradation capacity using Czapek Dox broth medium containing Catechol and Resorcinol as a sole carbon source at final concentrations of 0.4, 0.6 and 0.8%.

RESULTS

A total of 35 fungal species belonging to 18 fungal genera were isolated and identified from different parts of H. sabdariffa plants. All strains have the capability for degrading phenol and their derivatives with variable extents. The optimum condition of degrading phenol in paper and pulp effluent samples by Fusarium poae11r7 were at pH 3-5, temperature at 28-35°C, good agitation speed at no agitation and 100 rpm.

CONCLUSION

All endophytic fungal species can utilize phenol and its derivatives as a carbon source and be the potential to degrade phenol in industrial contaminants.

Re-examination of species limits in Aspergillus section Flavipedes using advanced species delimitation methods and description of four new species

Since the last revision in 2015, the taxonomy of section Flavipedes evolved rapidly along with the availability of new species delimitation techniques. This study aims to re-evaluate the species boundaries of section Flavipedes members using modern delimitation methods applied to an extended set of strains (n = 90) collected from various environments. The analysis used DNA sequences of three house-keeping genes (benA, CaM, RPB2) and consisted of two steps: application of several single-locus (GMYC, bGMYC, PTP, bPTP) and multi-locus (STACEY) species delimitation methods to sort the isolates into putative species, which were subsequently validated using DELINEATE software that was applied for the first time in fungal taxonomy. As a result, four new species are introduced, i.e. A. alboluteus, A. alboviridis, A. inusitatus and A. lanuginosus, and A. capensis is synonymized with A. iizukae. Phenotypic analyses were performed for the new species and their relatives, and the results showed that the growth parameters at different temperatures and colonies characteristics were useful for differentiation of these taxa. The revised section harbors 18 species, most of them are known from soil. However, the most common species from the section are ecologically diverse, occurring in the indoor environment (six species), clinical samples (five species), food and feed (four species), droppings (four species) and other less common substrates/environments. Due to the occurrence of section Flavipedes species in the clinical material/hospital environment, we also evaluated the susceptibility of 67 strains to six antifungals (amphotericin B, itraconazole, posaconazole, voriconazole, isavuconazole, terbinafine) using the reference EUCAST method. These results showed some potentially clinically relevant differences in susceptibility between species. For example, MICs higher than those observed for A. fumigatus wild-type were found for both triazoles and amphotericin B for A. ardalensis, A. iizukae, and A. spelaeus whereas A. lanuginosus, A. luppiae, A. movilensis, A. neoflavipes, A. olivimuriae and A. suttoniae were comparable to or more susceptible as A. fumigatus. Finally, terbinafine was in vitro active against all species except A. alboviridis.