Bioprospecting endophytic fungi from Fusarium genus as sources of bioactive metabolites

Endophytic Fungi for Crops Adaptation to Abiotic Stresses

Endophytic fungi (EFs) have emerged as promising modulators of plant growth and stress tolerance in agricultural ecosystems. This review synthesizes the current knowledge on the role of EFs in enhancing the adaptation of crops to abiotic stress. Abiotic stresses, such as drought, salinity, and extreme temperatures, pose significant challenges to crop productivity worldwide. EFs have shown remarkable potential in alleviating the adverse effects of these stresses. Through various mechanisms, including the synthesis of osmolytes, the production of stress-related enzymes, and the induction of plant defense mechanisms, EFs enhance plant resilience to abiotic stressors. Moreover, EFs promote nutrient uptake and modulate the hormonal balance in plants, further enhancing the stress tolerance of the plants. Recent advancements in molecular techniques have facilitated the identification and characterization of stress-tolerant EF strains, paving the way for their utilization in agricultural practices. Furthermore, the symbiotic relationship between EFs and plants offers ecological benefits, such as improved soil health and a reduced dependence on chemical inputs. However, challenges remain in understanding the complex interactions between EFs and host plants, as well as in scaling up their application in diverse agricultural systems. Future research should focus on elucidating the mechanisms underlying endophytic-fungal-mediated stress tolerance and developing sustainable strategies for harnessing their potential in crop production.

GC-MS-Guided Antimicrobial Defense Responsive Secondary Metabolites from the Endophytic Fusarium solani Isolated from Tinospora cordifolia and Their Multifaceted Biological Properties

Medicinal plants are hosts to an infinite number of microorganisms, commonly referred to as endophytes which are rich in bioactive metabolites yielding favorable biological activities. The endophytes are known to have a profound impact on their host plant by promoting the accumulation of secondary metabolites which are beneficial to humankind. In the present study, the fungal endophyte, Fusarium solani (ABR4) from the medicinal plant Tinospora cordifolia, was assessed for its bioactive secondary metabolites employing fermentation on a solid rice medium. The crude ABR4 fungal extract was sequentially purified using the solvent extraction method and characterized using different spectroscopic and analytical techniques namely TLC, UV spectroscopic analysis, HRESI-MS, FTIR, and GC-MS analysis. The GC-MS analysis revealed the presence of pyridine, benzoic acid, 4-[(trimethylsilyl)oxy]-trimethylsilyl ester, hexadecanoic acid trimethylsilyl ester, and oleic acid trimethylsilyl ester. The cytotoxic ability of ABR4 was evaluated by MTT assay against lung cancer (A549) and breast cancer (MCF-7) cell lines. The compounds did not exhibit significant cytotoxicity against the tested cell lines. The endophytic ABR4 extract was evaluated for its antimicrobial potential against human pathogens (S. aureus, B. cereus, E. coli, S. typhimurium, P. aeruginosa, and C. albicans) by recording 47 to 54% inhibition. Taken together, the endophytic fungal strain ABR4 demonstrated a remarkable antimicrobial activity against the tested pathogens. Furthermore, the functional metabolites isolated from the endophytic strain ABR4 reveal its broader usage as antimicrobial agents for newer drug development in the pharmaceutical industry.

Purification of andibenin and a chromanone analogue from rhizospheric Aspergillus flavus and soil-borne Penicillium notatum exhibiting cytotoxic and antibacterial properties

The discovery of bioactive compounds from fungal natural sources holds immense potential for the development of novel therapeutics. The present study investigates the extracts of soil-borne Penicillium notatum and rhizosphere-inhabiting Aspergillus flavus for their antibacterial, antifungal, and cytotoxic potential. Additionally, two compounds were purified using chromatographic and spectroscopic techniques. The results demonstrated that the ethyl acetate fraction of A. flavus exhibited prominent cytotoxic activity against Artemia salina, whereas the ethyl acetate fraction of P. notatum displayed promising antibacterial potential. At dose concentrations of 10, 100, and 1000 µg mL-1, the ethyl acetate fraction of A. flavus showed mortality percentages of 7.6%, 66.4%, and 90%, respectively. The ethyl acetate fraction of P. notatum extract exhibited significant antibacterial activity, forming inhibition zones measuring 41, 38, 34, 34, and 30 mm against B. subtilis, S. flexneri, E. coli, K. pneumoniae, and S. aureus, respectively, at 1000 µg mL-1. At this concentration, inhibition zones of 28, 27, and 15 mm were recorded for P. vulgaris, S. typhi, and X. oryzae. Using bioassay-guided approach, one compound each was purified from the fungal extracts. The initial purification involved mass spectroscopic analysis, followed by structural elucidation using 500 MHz nuclear magnetic resonance (NMR) spectroscopy. Compound 1, derived from A. flavus, was identified as ethyl 2-hydroxy-5,6-dimethyl-4-oxocyclohex-2-ene-1-carboxylate, with a mass of 212, whereas compound 2, isolated from P. notatum, was identified as 3-amino-2-(cyclopenta-2,4-dien-1-ylamino)-8-methoxy-4H-chromen-4-one, with an exact mass of 270. Based on bioassay results, compound 1 was subjected to brine shrimp lethality assay and compound 2 was tested for its antibacterial potential. Compound 1 exhibited 30% lethality against brine shrimp larvae at a concentration of 100 µg mL-1, whereas at 1000 µg mL-1 the mortality increased to 70%. Compound 2 displayed notable antibacterial potential, forming inhibition zones of 30, 24, 19, and 12 mm against S. aureus, E. coli, B. subtilis, and S. flexneri, respectively. In comparison, the standard antibiotic tetracycline produced inhibition zones of 18, 18, 15, and 10 mm against the respective bacterial strains at the same concentration.

Protective effects of hepatic diseases by bioactive phytochemicals in Fusarium oxysporum - A review

Lately, liver diseases were categorized as one of the most prevalent health problems globally as it causes a severe threat to mankind all over the world due to the wide range of occurrence. There are multiple factors causing hepatic disorders, such as alcohol, virus, poisons, adverse effects of drugs, poor diet, inherited conditions and obesity. Liver diseases have various types including alcoholic liver disease, non-alcoholic fatty liver disease, autoimmune hepatitis, liver cancer, hepatocellular carcinoma, liver fibrosis and hepatic inflammation. Therefore, it is imperative to find effective and efficacious agents in managing liver diseases. Fusarium oxysporum, an endophytic fungus and containing many bioactive compounds, could be served as a forked medication for enormous number and types of maladies. It was characterized by producing biochemical compounds which had rare pharmacological properties as it may be found in a limit number of other medicinal plants. The majority of the past researches related to Fusarium oxysporum recited the fungal negative field either on the pathogenic effects of the fungus on economical crops or on the fungal chemical components to know how to resist it. The present review will highlight on the bright side of Fusarium oxysporum and introduce the functional activities of its chemical compounds for treating its target diseases. The key point of illustrated studies in this article is displaying wide range of detected bioactive compounds isolated from Fusarium oxysporum and in other illustrated studies it was elucidated the therapeutical and pharmacological potency of these biologically active compounds (isolated from medicinal plants sources) against different types of liver diseases including non-alcoholic fatty liver disease, alcoholic liver disease, cirrhosis and others. It was demonstrated that F. oxysporum contains unique types of isoflavones, flavonoids, phenols and another active chemical compounds, and these compounds showed recently a fabulous clinical contribution in the therapy of liver injury diseases, which opens new and unprecedented way for evaluating the maintaining efficacy of Fusarium oxysporum bioactive compounds in dealing with hepatic complications and its remedy impacting on liver diseases and injured hepatocytes through recommending implement a practical study.

Identification and application of an endophytic fungus Arcopilus aureus from Panax notoginseng against crop fungal disease

Endophytic fungi are important microbial resources for developing novel antibacterial and antifungal drugs to prevent and control crop diseases. Panax notoginseng has been used as a Chinese medicinal herb for a long time, as it has various bioactivities. However, information on endophytic fungi isolated from Panax notoginseng is rare. In this study, an endophytic fungus known as SQGX-6, which was later identified as the golden hair fungus Arcopilus aureus, was isolated from Panax notoginseng. SQGX-6 was extracted using ethyl acetate, and the active components of the fungus were identified using ultra-performance liquid chromatography-mass spectrometry (UHPLC-MS). The antifungal and antioxidant activities of the extract were determined and evaluated in vitro and in vivo. SQGX-6 and its extract inhibited the growth of Corn stalk rot (Fusarium graminearum), Corn southern leaf blight (Helminthosporium maydis), and Tomato gray mold (Botrytis cinerea) in vitro. The free radical scavenging rates for 2,2-Diphenyl-1-pyridinyl hydrazide (DPPH) radical scavenging activity, 3-Ethylbenzothiazoline-6-Sulfonic Acid Radical scavenging (ABTS) activity were also downregulated by the SQGX-6 extract. In vivo, the SQGX-6 extract inhibited the mycelial growth rates of the three aforementioned fungi and downregulated malondialdehyde (MDA) content and upregulated peroxidase (POD) and phenylalanine ammonia-lyase (PAL) content in fruits, leading to significant reduction in damage to cherry tomatoes caused by Botrytis cinerea. UHPLC-MS was performed to identify various active substances, including Alkaloids, Azoles, Benzofurans, Coumarins, Flavonoids, Organic acids, Phenols, and plant growth regulators contained in the extract. These results suggested that the endophytic fungus SQGX-6 of Panax notoginseng and its extract have excellent antifungal and antioxidant activities, and thus, it is an important microbial resource for the developing novel drugs against plant fungal infections.

Impact of bacterial and fungal inoculants on the resident rhizosphere microbiome and the volatilome of tomato plants under leaf herbivory stress

Various studies have addressed the impact of microbial inoculants on the composition of the resident microbiome. How microbial inoculants impact plant metabolism and interact with the resident rhizobiota under herbivory stress remains elusive. Here, we investigated the impact of two bacterial and two fungal inoculants, inoculated as single species and as a synthetic community, on the rhizosphere microbiome and volatilome of tomato plants (Solanum lycopersicum) comparing nonstress conditions to exposed to leaf herbivory by Spodoptera exigua. Based on amplicon sequencing analysis, rhizobacterial community composition was significantly affected by all four inoculants and the magnitude of this effect was dependent on herbivory stress. Fungal community composition was altered by the microbial inoculants but independent of herbivory stress. The rhizosphere volatilome was impacted by the microbial inoculation and differences between treatments were evened under herbivory stress. Each microbial inoculant caused unique changes in the volatilome of stressed plants but also shared similar responses, in particular the enhanced production of dimethyl disulfide and benzothiazole. In conclusion, the introduction of microbial inoculants in the tomato rhizosphere caused unique as well as common changes in the rhizosphere microbiome and volatilome, but these changes were minor compared to the microbiome changes induced by herbivory stress.

Virulence factors of the genus Fusarium with targets in plants

Fusarium spp. comprise various species of filamentous fungi that cause severe diseases in plant crops of both agricultural and forestry interest. These plant pathogens produce a wide range of molecules with diverse chemical structures and biological activities. Genetic functional analyses of some of these compounds have shown their role as virulence factors (VF). However, their mode of action and contributions to the infection process for many of these molecules are still unknown. This review aims to analyze the state of the art in Fusarium VF, emphasizing their biological targets on the plant hosts. It also addresses the current experimental approaches to improve our understanding of their role in virulence and suggests relevant research questions that remain to be answered with a greater focus on species of agroeconomic importance. In this review, a total of 37 confirmed VF are described, including 22 proteinaceous and 15 non-proteinaceous molecules, mainly from Fusarium oxysporum and Fusarium graminearum and, to a lesser extent, in Fusarium verticillioides and Fusarium solani.

Biotransformation of Sclareol by a Fungal Endophyte of Salvia sclarea

Microbial endophytes are known as versatile producers of useful metabolites, which have extensive applications in pharmacy, fragrance, agriculture and food. This study aims to screen sclareol-biotransforming microorganisms from Salvia sclarea, an untapped source of diverse endophytes. In this study, 50 culturable endophytes were isolated from S. sclarea grown in Xinjiang using sclareol as the sole carbon source and screened for their potential to transform sclareol into analogues. A fungal endophyte, identified as the generally recognized as safe (GRAS) strain Aspergillus tubingensis, can produce labd-14-ene-3β,8α,13β-triol and 8α,13β-dihydroxylabd-14-en-3-one from sclareol, involving hydroxylation and carbonylation at the C3 site. Structures of the two metabolites were elucidated by HR-ESI-MS and NMR analysis. S. sclarea was proven to be a good source of endophytes that are prospective producers of secondary metabolites with valuable chemical and biological properties. This study is the first report regarding the isolation of endophytes from S. sclarea.

Annotating Multiple Prebiotic Synthesizing Capabilities Through Whole Genome Sequencing of Fusarium Strain HFK-74

In the present study, seven fungal isolates from effluent treatment plants were screened for the production of prebiotic fructooligosaccharide synthesizing enzymes with the highest activity of fructofuranosidase (17.52 U/mL) and fructosyl transferase (18.92 U/mL) in strain HKF-74. Mining of genome sequence of strain revealed the annotation of genes providing multiple carbohydrate metabolizing capacities, such as amylases (AMY1), beta-galactosidase (BGAL), beta-xylosidase (Xyl), β-fructofuranosidase (ScrB), fructosyltransferase (FTF), and maltose hydrolases (malH). The annotated genes were further supported by β-galactosidase (15.90 U/mL), xylanase (17.91 U/mL), and α-amylase (14.05 U/mL) activities for synthesis of galactooligosaccharides, xylooligosaccarides, and maltooligosaccharides, respectively. In addition to genes encoding prebiotic synthesizing enzymes, four biosynthetic gene clusters (BGCs) including Type I polyketide synthase (PKS), non-ribosomal peptide synthetase (NRPS), NRPS-like, and terpene were also predicted in strain HKF-74. This was significant considering their potential role in pharmaceutical and therapeutic applications as well as in virulence. Accurate taxonomic assignment of strain HKF-74 by in silico genomic comparison indicated its closest identity to type strains Fusarium verticillioides NRRL 20984, and 7600. The average nucleotide identity (ANI) of strain HKF-74 with these strains was 92.5% which was close to the species threshold cut-off value (95-96%) while the DNA-DNA hybridization (DDH) value was 83-84% which was greater than both, species delineating (79-80%), and also sub-species delineating (70%) boundaries. Our findings provide a foundation for further research into the use of Fusarium strains and their prebiotic synthesizing enzymes for the development of novel prebiotic supplements.

In Vitro Evaluation of Antiviral Activities of Funicone-like Compounds Vermistatin and Penisimplicissin against Canine Coronavirus Infection

Recent studies have demonstrated that 3-O-methylfunicone (OMF), a fungal secondary metabolite from Talaromyces pinophilus belonging to the class of funicone-like compounds, has antiviral activity against canine coronaviruses (CCoV), which causes enteritis in dogs. Herein, we selected two additional funicone-like compounds named vermistatin (VER) and penisimplicissin (PS) and investigated their inhibitory activity towards CCoV infection. Thus, both compounds have been tested for their cytotoxicity and for antiviral activity against CCoV in A72 cells, a fibrosarcoma cell line suitable for investigating CCoV. Our findings showed an increase in cell viability, with an improvement of morphological features in CCoV-infected cells at the non-toxic doses of 1 μM for VER and 0.5 μM for PS. In addition, we observed that these compounds caused a strong inhibition in the expression of the aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor which is activated during CCoV infection. Our results also showed the alkalinization of lysosomes in the presence of VER or PS, which may be involved in the observed antiviral activities.

Enhanced podophyllotoxin production of endophyte Fusarium proliferatum TQN5T by host extract and phenylalanine

Fermentation technology using endophytes is considered a potential alternative approach for producing pharmaceutical compounds like podophyllotoxin (PTOX). In this study, fungus TQN5T (VCCM 44284) was selected from endophytic fungi isolated from Dysosma versipellis in Vietnam for PTOX production through TLC. The presence of PTOX in TQN5T was further confirmed by HPLC. Molecular identification indicated TQN5T as Fusarium proliferatum with 99.43% identity. This result was asserted by morphological characteristics such as white cottony, filamentous colony, layer and branched mycelium, and clear hyphae septa. Cytotoxic assay indicated both biomass extract and culture filtrate of TQN5T presented strong cytotoxicity on LU-1 and HepG2 with IC50 of 0.11, 0.20, 0.041, and 0071, respectively, implying anti-cancer compounds were accumulated in the mycelium and secreted into the medium. Further, the production of PTOX in TQN5T was investigated in the fermentation condition supplemented with 10 µg/ml of host plant extract or phenylalanine as elicitors. The results revealed a significantly higher amount of PTOX in the PDB + PE and PDB + PA at all studied time points in comparison with PDB (control). Especially, after 168 h of culture, PTOX content in the PDB with plant extract reached the peak with 314 µg/g DW which is 10% higher than the best yield of PTOX in previous studies, denoting F. proliferatum TQN5T as a promising PTOX producer. This is the first study on enhancing the PTOX production in endophytic fungi by supplementing phenylalanine-a precursor for PTOX biosynthesis in plants into fermented media, suggesting a common PTOX biosynthetic pathway between host plant and endophytes. KEY POINTS: • Fusarium proliferatum TQN5T was proven for PTOX production. • Both mycelia extract and spent broth extract of Fusarium proliferatum TQN5T presented strong cytotoxicity on cancer cell lines LU-1 and HepG2. • The supplementation of 10 µg/ml host plant extract and phenylalanine into fermentation media of F. proliferatum TQN5T improved the yield of PTOX.

Abutilon theophrasti's Resilience against Allelochemical-Based Weed Management in Sustainable Agriculture - Due to Collection of Highly Advantageous Microorganisms?

Abutilon theophrasti Medik. (velvetleaf) is a problematic annual weed in field crops which has invaded many temperate parts of the world. Since the loss of crop yields can be extensive, approaches to manage the weed include not only conventional methods, but also biological methods, for instance by microorganisms releasing phytotoxins and plant-derived allelochemicals. Additionally, benzoxazinoid-rich rye mulches effective in managing common weeds like Amaranthus retroflexus L. have been tested for this purpose. However, recent methods for biological control are still unreliable in terms of intensity and duration. Rye mulches were also ineffective in managing velvetleaf. In this review, we present the attempts to reduce velvetleaf infestation by biological methods and discuss possible reasons for the failure. The resilience of velvetleaf may be due to the extraordinary capacity of the plant to collect, for its own survival, the most suitable microorganisms from a given farming site, genetic and epigenetic adaptations, and a high stress memory. Such properties may have developed together with other advantageous abilities during selection by humans when the plant was used as a crop. Rewilding could be responsible for improving the microbiomes of A. theophrasti.

Depsipeptides Targeting Tumor Cells: Milestones from In Vitro to Clinical Trials

Cancer is currently considered one of the most threatening diseases worldwide. Diet could be one of the factors that can be enhanced to comprehensively address a cancer patient's condition. Unfortunately, most molecules capable of targeting cancer cells are found in uncommon food sources. Among them, depsipeptides have emerged as one of the most reliable choices for cancer treatment. These cyclic amino acid oligomers, with one or more subunits replaced by a hydroxylated carboxylic acid resulting in one lactone bond in a core ring, have broadly proven their cancer-targeting efficacy, some even reaching clinical trials and being commercialized as "anticancer" drugs. This review aimed to describe these depsipeptides, their reported amino acid sequences, determined structure, and the specific mechanism by which they target tumor cells including apoptosis, oncosis, and elastase inhibition, among others. Furthermore, we have delved into state-of-the-art in vivo and clinical trials, current methods for purification and synthesis, and the recognized disadvantages of these molecules. The information collated in this review can help researchers decide whether these molecules should be incorporated into functional foods in the near future.

Diversity of Culturable Endophytic Fungi in Crocus sativus and Their Correlation with Crocin Content

The presence and diversity of endophytic fungi associated with host plants are important not just for host plant growth and defense, but also impact the production of medicinal secondary metabolites. However, the correlation between endophytic fungi and crocin production in Crocus sativus (CS) remains underexplored. Here, we explore the relationship between endophytic fungal diversity and crocin content among different CS tissues and field sites. Specifically, we isolated endophytic fungi from five different field sites (Shanghai, Jiande, Huzhou, Anhui, and Hebei) and five different tissues (corm, scape, leaf, petal, and stigma) and analyzed fungal community diversity, richness, and evenness. We identified a total of 32 endophytic fungal taxa, assigned to 7 orders within 4 classes (Eurotiomycetes, Agaricomycetes, Dothideomycetes, and Sordariomycetes). The most dominant order was Eurotiales, and the most dominant genera were Penicillium and Talaromyces. Species richness tended to be highest in belowgrown tissues, such as corm and scape. Additionally, several fungal taxa were found to be either site- or tissue-specific. Three genera in particular were correlated with crocin content: Penicillium, Sistotrema, and Bjerkandera. Given the fact that endophytic microorganisms can both promote the production of secondary metabolites in host plants and potentially produce secondary metabolites themselves, further study is required to understand the mechanistic relationship between these and other fungal genera and crocin production.

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.

Methods used for the study of endophytic fungi: a review on methodologies and challenges, and associated tips

Endophytic fungi are microorganisms that colonize the interior of plant tissues (e.g. leaves, seeds, stem, trunk, roots, fruits, flowers) in intracellular and/or extracellular spaces without causing symptoms of disease in host plants. These microorganisms have been isolated from plant species in a wide variety of habitats worldwide, and it is estimated that all terrestrial plants are colonized by one or more species of endophytic fungus. In addition, these microorganisms have been drawing the attention of researchers because of their ability to synthesize a wide range of bioactive molecules with potential for applications in agriculture, medicine and biotechnology. However, several obstacles come up when studying the diversity and chemical potential of endophytic fungi. For example, the usage of an inappropriate surface disinfection method for plant tissue may not eliminate the epiphytic microbiota or may end up interfering with the endophytic mycobiota, which consequently generates erroneous results. Moreover, the composition of the culture medium and the culture conditions can favor the growth of certain species and inhibit others, which generates underestimated results. Other inconsistencies can arise from the fungus misidentification and consequent exploration of its chemical potential. Based on the methodological biases that may occur at all stages of studies dealing with endophytic fungi, the objective of this review is to discuss the main methods employed in these studies as well as highlight the challenges derived from the different approaches. We also report associated tips to help future studies on endophytic fungi as a contribution.

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.

Metabolites characterisation of endophytic Phyllosticta fallopiae L67 isolated from Aloe vera with antimicrobial activity on diabetic wound microorganisms

This study aimed to assess the antimicrobial activity of endophytic Phyllosticta fallopiae L67 isolated from Aloe vera against diabetic wound microorganisms and characterise their active fraction for biologically important metabolites. The dichloromethane (DCM) extract exhibited the most significant activity with inhibition zones ranging from 11.33 to 38.33 mm. The minimal inhibitory and lethality concentrations of DCM extract ranged from 78.13 to 2500.00 µg/ml and 625.00 to 5000.00 µg/ml, respectively. The extract showed teratogenicity and lethality in the zebrafish model, where peritoneal and hepatic oedema occurred at 62.50 µg/ml, and no abnormality appeared at 31.25 µg/ml. The extract also inhibited more than 82% biofilm formation. Bioassay-guided fractionation on DCM extract yielded 18 fractions and the most active fraction was subjected to UPLC-QTOF-MS/MS analysis. Flavones, stilbenes, flavanonols, isoflavonoids, phenolic glycosides and phenol derivatives were detected. In conclusion, endophytic P. fallopiae possessed bioactive metabolites with significant antimicrobial activity against diabetic wound microorganisms.

α-Glucosidase inhibitory effect of an anthraquinonoid produced by Fusarium incarnatum GDZZ-G2

α-Glucosidase is the key enzyme on carbohydrate metabolism, and its bioactive inhibitors are supposed to be an effective therapeutic for type 2 diabetes mellitus. During our continuing study for discovering α-glucosidase inhibitors, a fungus GDZZ-G2 which is derived from a medicinal plant Callicarpa kwangtungensis Chun, exhibited significant inhibition on α-glucosidase. The strain was identified as Fusarium incarnatum by morphological and molecular methods. Further bioassay-guided fractionation result in six known secondary metabolites (1-6). All the compounds except 4 were isolated from F. incarnatum for the first time. Among them, an anthraquinonoid (S)-1,3,6-trihydroxy-7-(1-hydroxyethyl)anthracene-9,10-dione (compound 1) exhibited strong inhibitory effect against α-glucosidase (IC₅₀  = 77.67 ± 0.67 μΜ), compared with acarbose (IC₅₀  = 711.8 ± 5 μΜ). An enzyme kinetics analysis revealed that compound 1 was an uncompetitive inhibitor. Besides, docking simulations predicted that compound 1 inhibited α-glucosidase substrate complex by binding Gln322, Gly306, Thr307, and Ser329 through hydrogen-bond interactions. Our findings suggested that compound 1 can be considered a lead compound for further modifications and the development of a new effective drug candidate in the treatment of type 2 diabetes mellitus.

Crude metabolites from endophytic fungi inhabiting Cameroonian Annona muricata inhibit the causative agents of urinary tract infections

Urinary tract infections (UTIs) are common bacterial infections. The global emergence of multidrug-resistant uropathogens in the last decade underlines the need to search for new antibiotics with novel mechanisms of action. In this regard, exploring endophytic fungi inhabiting medicinal plants used locally against urinary tract infections could be a promising strategy for novel drug discovery. This study investigates crude metabolites from endophytic fungi isolated from Annona muricata as potential sources of antibiotic drugs to fight against uropathogens and reduce related oxidative stress. Crude ethyl acetate extracts from 41 different endophytic fungi were screened against three bacterial strains using the broth microdilution method, and fungi producing active crude extracts were identified using ITS1-5.8S rRNA-ITS2 nucleotide sequences. The antibacterial modes of action of the five most active extracts were evaluated using Staphylococcus aureus ATCC 43300 and Klebsiella oxytoca strains. The DPPH and FRAP assays were used to investigate their antioxidant activity, and their cytotoxicity against the Vero cell line was evaluated using the MTT assay. Out of the 41 crude extracts tested, 17 were active with minimum inhibitory concentrations (MICs) ranging from 3.125 μg/mL to 100 μg/mL and were not cytotoxic against Vero cell lines with a cytotoxic concentration 50 (CC₅₀) >100 μg/mL. The more potent extracts (from Fusarium waltergamsii AMtw3, Aspergillus sp. AMtf15, Penicillium citrinum AMf6, Curvularia sp. AMf4, and Talaromyces annesophieae AMsb23) significantly inhibited bacterial catalase activity, lysed bacterial cells, increased outer membrane permeability, and inhibited biofilm formation, and the time-kill kinetic assay revealed concentration-dependent bactericidal activity. All seventeen extracts showed weak ferric iron-reducing power (1.06 to 12.37 μg equivalent NH₂OH/g of extract). In comparison, seven extracts exhibited DPPH free radical scavenging activity, with RSA₅₀ ranging from 146.05 to 799.75 μg/mL. The molecular identification of the seventeen active fungi revealed that they belong to six distinct genera, including Aspergillus, Curvularia, Fusarium, Meyerozyma, Penicillium, and Talaromyces. This investigation demonstrated that fungal endophytes from Cameroonian Annona muricata, a medicinal plant used locally to treat bacterial infections, might contain potent antibacterial metabolites with multiple modes of action. The antibacterial-guided fractionation of these active extracts is currently ongoing to purify and characterise potential antibacterial active ingredients.

Decalintetracids A and B, two pairs of unusual 3-decalinoyltetramic acid derivatives with phytotoxicity from Fusarium equiseti D39

The filamentous fungi Fusarium sp. are well-known for their ability to produce abundant specialised metabolites with attractive chemical structures and bioactivities. In this study, chemical analyses of the endophyte F. equiseti D39 led to the isolation and identification of two pairs of undescribed 3-decalinoyltetramic acids (3DTAs) E/Z diastereomers, decalintetracids A and B. Their structures were elucidated by comprehensive spectroscopic analysis and quantum-chemical calculations. Although 3DTAs were commonly reported from fungi, decalintetracid A possessed an unprecedented tricyclo [7.2.1.0^2,7] dodecane skeleton, which added the diversity of these fungal metabolites. In addition, decalintetracid B was featured by a unique 6/6/5 ring system core. A plausible biosynthetic pathway for decalintetracids A and B was proposed. Both compounds exhibited phytotoxicity toward Amaranthus retroflexus L. and Amaranthus hybrid, indicating their potential as natural herbicides.

Bioprospecting of fungal endophytes from Oroxylum indicum (L.) Kurz with antioxidant and cytotoxic activity

Oroxylum indicum (L.) Kurz, a medicinal plant, shows numerous pharmacological properties which may be attributed to the bioactive compounds produced by O. indicum or due to associated endophytes. In the present study, leaf of O. indicum was evaluated for the presence of associated fungal endophytes, and antioxidant and cytotoxic activities of bioactive compounds produced from them. Using culture-dependent approach, eight fungal endophytes belonging to five different genera were identified. Two endophytes Daldinia eschscholtzii and Ectophoma multirostrata have been reported for the first time from the leaf of O. indicum plant. High-performance thin-layer chromatography (HPTLC) of ethyl acetate (EA) extract of isolated fungal endophytes showed a distinct fingerprinting profile in EA extract of Colletotrichum gloeosporioides. Among identified endophytes, EA extract of C. gloeosporioides showed significant antioxidant activity against DPPH free radical, superoxide anion radical, nitric oxide radical and hydroxyl radical with EC₅₀ values of 22.24±1.302 μg/mL, 67.46±0.576 μg/mL, 80.10±0.706 μg/mL and 61.55±1.360 μg/mL, respectively. EA extract of C. gloeosporioides exhibited potential cytotoxicity against HCT116, HeLa and HepG2 cancer cell lines with IC₅₀ values of 76.59 μg/mL, 176.20 μg/mL and 1750.70 μg/mL, respectively. A comparative HPTLC fingerprinting and the antioxidant activity of C. gloeosporioides associated with two different hosts (leaf of O. indicum and dead twigs of other plant) showed that C. gloeosporioides produces bioactive compounds in a host-dependent manner.

Colonization with non-mycorrhizal culturable endophytic fungi enhances orchid growth and indole acetic acid production

BACKGROUND

Symbiotic associations of endophytic fungi have been proved by possessing an ability to produce hormones and metabolites for their host plant. Members of the Orchidaceae are obligate mycorrhizal species but a non-mycorrhizal association needs more investigation for their ability to promote plant growth and produce plant growth hormones. In the present study, endophytic fungi were isolated from the roots of Dendrobium longicornu Lindl., to investigate the root colonizing activity and role in plant growth and development.

RESULTS

Among 23 fungal isolates were identified both by morphological and molecular technique as Penicillium sp., Fusarium sp., Coniochaeta sp., Alternaria sp., and Cladosporium sp. The dominate species were Coniochaeta sp. and Cladosporium sp. The dominant species as per the isolation was Coniochaeta sp. These fungal strains were screened for growth-promoting activity of Cymbidium aloifolium (plantlet) consider as cross genus interaction and Dendrobium longicornu (protocorms) as a host plant in in-vitro condition. Importantly, Cladosporium sp., and Coniochaeta sp. showed successful colonization and peloton formation with roots of C. aloifolium. Moreover, it also enhanced acclimatization of plantlets. Fungal elicitors from nine fungal isolates enhanced the growth of the in vitro grown protocorms of D. longicornu. Key bioactive compounds detected in the fungal colonized plant extract were 2H-pyran-2-one, Cyclopropanecarboxylic acid, Oleic Acid and d-Mannitol, which may have a potential role in plant-microbe interaction. All fungal endophytes were able to synthesize the indole acetic acid (IAA) in presence of tryptophan. Moreover, fungal extract DLCCR7 treated with DL-tryptophan yielded a greater IAA concentration of 43 μg per ml than the other extracts. The iaaM gene involved in IAA synthesis pathway was amplified using iaaM gene primers successfully from Alternaria sp., Cladosporium sp., and Coniochaeta sp.

CONCLUSIONS

Hence, this study confirms the production of IAA by endophytes and demonstrated their host as well as cross-genus plant growth-promoting potential by producing metabolites required for the growth of the plant.

Interaction of the Fungal Metabolite Harzianic Acid with Rare-Earth Cations (La3+, Nd3+, Sm3+, Gd3+)

Rare-earth elements are emerging contaminants of soil and water bodies which destiny in the environment and effects on organisms is modulated by their interactions with natural ligands produced by bacteria, fungi and plants. Within this framework, coordination by harzianic acid (H₂L), a Trichoderma secondary metabolite, of a selection of tripositive rare-earth cations Ln³⁺ (Ln³⁺ = La³⁺, Nd³⁺, Sm^3+, and Gd³⁺) was investigated at 25 °C, and in a CH₃OH/0.1 M NaClO₄ (50/50 w/w) solvent, using mass spectrometry, circular dichroism, UV-Vis spectrophotometry, and pH measurements. Experimental data can be satisfactorily explained by assuming, for all investigated cations, the formation of a mono-complex (LnL⁺) and a bis-complex (LnL₂^-). Differences were found between the formation constants of complexes of different Ln³⁺ cations, which can be correlated with ionic radius. Since gadolinium is the element that raises the most concern among lanthanide elements, its effects on organisms at different levels of biological organization were explored, in the presence and absence of harzianic acid. Results of ecotoxicological tests suggest that harzianic acid can decrease gadolinium biotoxicity, presumably because of complex formation with Gd³⁺.

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.

Fungal Endophytes and Their Role in Agricultural Plant Protection against Pests and Pathogens

Virtually all examined plant species harbour fungal endophytes which asymptomatically infect or colonize living plant tissues, including leaves, branches, stems and roots. Endophyte-host interactions are complex and span the mutualist-pathogen continuum. Notably, mutualist endophytes can confer increased fitness to their host plants compared with uncolonized plants, which has attracted interest in their potential application in integrated plant health management strategies. In this review, we report on the many benefits that fungal endophytes provide to agricultural plants against common non-insect pests such as fungi, bacteria, nematodes, viruses, and mites. We report endophytic modes of action against the aforementioned pests and describe why this broad group of fungi is vitally important to current and future agricultural practices. We also list an extensive number of plant-friendly endophytes and detail where they are most commonly found or applied in different studies. This review acts as a general resource for understanding endophytes as they relate to potential large-scale agricultural applications.

Chemometric study on the biochemical marker of the manglicolous fungi to illustrate its potentiality as a bio indicator for heavy metal pollution in Indian Sundarbans

The study represents in vitro chemometric approach for assessing the heavy metal pollution in Indian Sundarbans. Physio-chemical and elemental characterisation of the sediment samples of Indian Sundarbans had shown high enrichments of toxic metal ions. It was characterised by elevated enrichment factors (2.16-10.12), geo-accumulation indices (0.03 -1.21), contamination factors (0.7-3.43) and pollution load indices (1.0-1.25) which showed progressive sediment quality deterioration and ecotoxicological risk due to metal ions contamination. The physio-chemical parameters of the sediments were replicated and computational chemometric modeling was utilized to assess fungal metabolic growth. All the fungi isolates had shown maximum metabolic activity in high temperature, alkaline pH, and high salinity. Further, the fungal metabolic activity was assessed in different gradient of heavy metal concentration. The significant deterioration of biochemical marker with increasing concentration of heavy metal indicates the status of the microbial health due to toxic metal pollution in the mangrove habitat.

The plant endosphere-hidden treasures: a review of fungal endophytes

The endosphere represents intracellular regions within plant tissues colonize by microbial endophytes without causing disease symptoms to host plants. Plants harbor one or two endophytic microbes capable of synthesizing metabolite compounds. Environmental factors determine the plant growth and survival as well as the kind of microorganisms associated with them. Some fungal endophytes that symbiotically colonize the endosphere of medicinal plants with the potential of producing biological products have been employed in traditional and modern medicine. The bioactive resources from endophytic fungi are promising; biotechnologically to produce cheap and affordable commercial bioactive products as alternatives to chemical drugs and other compounds. The exploration of bioactive metabolites from fungal endophytes has been found applicable in agriculture, pharmaceutical, and industries. Thus, fungal endophytes can be engineered to produce a substantive quantity of pharmacological drugs through the biotransformation process. Hence, this review shall provide an overview of fungal endophytes, ecology, their bioactive compounds, and exploration with the biosystematics approach.

Plant associated fungal endophytes as a source of natural bioactive compounds

Endophytes are a potent source of bioactive compounds that mimic plant-based metabolites. The relationship of host plant and endophyte is significantly associated with alteration in fungal colonisation and the extraction of endophyte-derived bioactive compounds. Screening of fungal endophytes and their relationship with host plants is essential for the isolation of bioactive compounds. Numerous bioactive compounds with antioxidant, antimicrobial, anticancer, and immunomodulatory properties are known to be derived from fungal endophytes. Bioinformatics tools along with the latest techniques such as metabolomics, next-generation sequencing, and metagenomics multilocus sequence typing can potentially fill the gaps in fungal endophyte research. The current review article focuses on bioactive compounds derived from plant-associated fungal endophytes and their pharmacological importance. We conclude with the challenges and opportunities in the research area of fungal endophytes.

Endophytic fungi inhabiting Physalis angulata L. plant: diversity, antioxidant, and antibacterial activities of their ethyl acetate extracts

OBJECTIVES

Endophytic fungi are an essential source of biologically active compounds. They have the ability to synthesize secondary metabolites which are the same or have a high degree of similarity to their host plants. In this study, we aimed to explore the biodiversity and the bioactivities of active metabolites produced by 14 endophytic fungi isolated from the medicinal plant Physalis angulata L. (PA).

METHODS

Fourteen endophytic fungi were isolated from the flowers, stems, leaves, and fruit husks of PA. The endophytic fungi were cultured and incubated in the PDB medium at room temperature. After three weeks, the cultures were extracted using ethyl acetate and dried using a rotary evaporator. The antioxidant activity was evaluated against DPPH while antibacterial activity was evaluated against Escherichia coli and Staphylococcus aureus using microdilution technique. TLC analysis was also done to profile the active compounds within the extract.

RESULTS

Hyphomycetes fungus isolated from the flower of PA exhibited a moderate antioxidant activity with an antioxidant index value of 0.59 (IC₅₀ = 52.43 μg/mL). Six isolates have strong antibacterial activity against E. coli and S. aureus with minimum inhibitory concentration (MIC) value ranging from 8-64 μg/mL. These endophytic fungi are one Hyphomycetes fungus isolated from the flower, one Fusarium sp. isolated from the stem, and four Colletotrichum sp. isolated from leaf and fruit husk of PA.

CONCLUSIONS

Endophytic fungi isolated from PA are potential novel sources of active metabolites especially for antibacterial compounds.

Diverse roles of microbial indole compounds in eukaryotic systems

Indole and its derivatives are widespread across different life forms, functioning as signalling molecules in prokaryotes and with more diverse roles in eukaryotes. A majority of indoles found in the environment are attributed to bacterial enzymes converting tryptophan into indole and its derivatives. The involvement of indoles among lower organisms as an interspecies and intraspecies signal is well known, with many reports showing that inter‐kingdom interactions involving microbial indole compounds are equally important as they influence defence systems and even the behaviour of higher organisms. This review summarizes recent advances in our understanding of the functional properties of indole and indole derivatives in diverse eukaryotes. Furthermore, we discuss current perspectives on the role of microbial indoles in human diseases such as diabetes, obesity, atherosclerosis, and cancers. Deciphering the function of indoles as biomarkers of metabolic state will facilitate the formulation of diet‐based treatments and open unique therapeutic opportunities.

Marine endophytic fungi associated with Halopteris scoparia (Linnaeus) Sauvageau as producers of bioactive secondary metabolites with potential dermocosmetic application

Marine fungi and, particularly, endophytic species have been recognised as one of the most prolific sources of structurally new and diverse bioactive secondary metabolites with multiple biotechnological applications. Despite the increasing number of bioprospecting studies, very few have already evaluated the cosmeceutical potential of marine fungal compounds. Thus, this study focused on a frequent seaweed in the Portuguese coast, Halopteris scoparia, to identify the endophytic marine fungi associated with this host, and assess their ability to biosynthesise secondary metabolites with antioxidative, enzymatic inhibitory (hyaluronidase, collagenase, elastase and tyrosinase), anti-inflammatory, photoprotective, and antimicrobial (Cutibacterium acnes, Staphylococcus epidermidis and Malassezia furfur) activities. The results revealed eight fungal taxa included in the Ascomycota, and in the most representative taxonomic classes in marine ecosystems (Eurotiomycetes, Sordariomycetes and Dothideomycetes). These fungi were reported for the first time in Portugal and in association with H. scoparia, as far as it is known. The screening analyses showed that most of these endophytic fungi were producers of compounds with relevant biological activities, though those biosynthesised by Penicillium sect. Exilicaulis and Aspergillus chevalieri proved to be the most promising ones for being further exploited by dermocosmetic industry. The chemical analysis of the crude extract from an isolate of A. chevalieri revealed the presence of two bioactive compounds, echinulin and neoechinulin A, which might explain the high antioxidant and UV photoprotective capacities exhibited by the extract. These noteworthy results emphasised the importance of screening the secondary metabolites produced by these marine endophytic fungal strains for other potential bioactivities, and the relevance of investing more efforts in understanding the ecology of halo/osmotolerant fungi.

Characterisation, pathogenicity and hydrolytic enzyme profiling of selected Fusarium species and their inhibition by novel coumarins

Three Fusarium species isolated locally were characterised by the amplification of their rDNA ITS region, host specificity, and hydrolytic enzyme production. The strains were identified as Fusarium pseudoanthophilum, which is being reported for the first time in South Africa, as well as F. foetens and F. fujikuroi. All the three strains were capable of infecting vegetables such as tomatoes, bell and cayenne peppers, belonging to the Solanaceae family. The Fusarium strains also showed significant production of cell wall degrading enzymes in vitro, such as amylase, cellulase, xylanase, and polygalacturonase, thus highlighting the possibilities of these enzymes as pathogenic factors. Subsequently, the strains were discovered to be susceptible to three halogenated coumarins. The most effective of the tested coumarins, 6-bromo3-2,2-dibromoacetyl-2H-chromen-2-one, showed MIC values of 0.125, 0.0625 and 0.125 mg/ml against F. foetens, F. pseudoanthophilum and F. fujikuroi, respectively. The antifungal potentials of the halogenated coumarins were confirmed in silico through PASS analysis, toxicity prediction and docking studies. Findings from this study demonstrate the use of these coumarins as potential control agents against the Fusarium species and other pathogenic fungi in general.

Marine endophytic fungal metabolites: A whole new world of pharmaceutical therapy exploration

The growing threat arises due to diseases such as cancer and the infections around the world leading to a critical requirement for novel and constructive compounds with unique ways of action capable of combating these deadly diseases. At present, it is evident that endophytic fungi constitute an enormous as well as comparatively untapped source of great biodiversity that can be considered as a wellspring of effective novel natural products for medical, agricultural and industrial use. Marine endophytic fungi have been found in every marine plants (algae, seagrass, driftwood, mangrove plants), marine vertebrates (mainly, fish) or marine invertebrates (mainly, sponge and coral) inter- and intra-cellular without causing any palpable symptoms of illness. Since evolution of microbes and eukaryotes to a higher level, coevolution has resulted in specific interaction mechanisms. Endophytic fungi are known to influence the life cycle and are necessary for the homeostasis of their eukaryotic hosts and the chemical signals of their host have been shown to activate gene expression in endophytes to induce expression of endophytic secondary metabolites. Marine endophytic fungi are receiving increasing attention by chemists because of their varied and structurally unmatched compounds that have strong biological roles in life as lead pharmaceutical compounds, including anticancer, antiviral, insulin mimetic, antineurodegenerative, antimicrobial, antioxidant and immuno-suppressant compounds. Moreover, fungal endophytes proved to have different biological activities for exploitation in the environmental and agricultural sustainability.

Revealing of biodiversity and antimicrobial effects of Artemisia asiatica endophytes

Endophytic fungi produce a plethora of secondary metabolites, which may open new avenues to study their applicability in pharmaceuticals. Therefore, the present study focuses on the fungal endophytic community of Artemisia asiatica. During our work, fungal endophytes were isolated from a medicinal plant, A. asiatica. The culturable endophytic fungi were identified using molecular techniques and biodiversity, richness and tissue specificity were examined. As these microorganisms have been generally identified as an abundant reservoir of novel antimicrobial compounds, the antimicrobial (i.e. antibacterial and antifungal) activities of the metabolites produced by the isolated fungi were studied. Numerous extracts containing the endophytic metabolites proved to be active against the applied test microorganisms including Gram-positive and Gram-negative bacteria, as well as yeasts and filamentous fungi, which can be examined in detail in the future and, based on the the chemical nature of these active metabolites, allow to discover novel bioactive metabolites.

Pharmacological Potential of Fungal Endophytes Associated with Medicinal Plants: A Review

Endophytic microbes are microorganisms that colonize the intracellular spaces within the plant tissues without exerting any adverse or pathological effects. Currently, the world population is facing devastating chronic diseases that affect humans. The resistance of pathogens to commercial antibiotics is increasing, thus limiting the therapeutic potential and effectiveness of antibiotics. Consequently, the need to search for novel, affordable and nontoxic natural bioactive compounds from endophytic fungi in developing new drugs with multifunction mechanisms to meet human needs is essential. Fungal endophytes produce invaluable bioactive metabolic compounds beneficial to humans with antimicrobial, anticancer, antidiabetic, anti-inflammatory, antitumor properties, etc. Some of these bioactive compounds include pestacin, taxol, camptothecin, ergoflavin, podophyllotoxin, benzopyran, isopestacin, phloroglucinol, tetrahydroxy-1-methylxanthone, salidroside, borneol, dibenzofurane, methyl peniphenone, lipopeptide, peniphenone etc. Despite the aforementioned importance of endophytic fungal metabolites, less information is available on their exploration and pharmacological importance. Therefore, in this review, we shall elucidate the fungal bioactive metabolites from medicinal plants and their pharmacological potential.

Untapped Potentials of Endophytic Fungi: A Review of Novel Bioactive Compounds with Biological Applications

Over the last century, endophytic fungi have gained tremendous attention due to their ability to produce novel bioactive compounds exhibiting varied biological properties and are, therefore, utilized for medicinal, pharmaceutical, and agricultural applications. Endophytic fungi reside within the plant tissues without showing any disease symptoms, thus supporting the physiological and ecological attributes of the host plant. Ground breaking lead compounds, such as paclitaxel and penicillin, produced by endophytic fungi have paved the way for exploring novel bioactive compounds for commercial usage. Despite this, limited research has been conducted in this valuable and unique niche area. These bioactive compounds belong to various structural groups, including alkaloids, peptides, steroids, terpenoids, phenols, quinones, phenols, and flavonoids. The current review focuses on the significance of endophytic fungi in producing novel bioactive compounds possessing a variety of biological properties that include antibacterial, antiviral, antifungal, antiprotozoal, antiparasitic, antioxidant, immunosuppressant, and anticancer functions. Taking into consideration the portal of this publication, special emphasis is placed on the antimicrobial and antiviral activities of metabolites produced by endophytes against human pathogens. It also highlights the importance of utilization of these compounds as potential treatment agents for serious life-threatening infectious diseases. This is supported by the fact that several findings have indicated that these bioactive compounds may significantly contribute towards the fight against resistant human and plant pathogens, thus motivating the need enhance the search for new, more efficacious and cost-effective antimicrobial drugs.

Differences in community composition of endophytic fungi between above- and below-ground tissues of Aristolochia chilensis in an arid ecosystem

Background

Endophytic fungi are diverse and ubiquitous in nature, yet studies simultaneously comparing endophyte communities in above- and below-ground plant tissues are relatively scarce. The main goal of our study was to compare the diversity and community composition of endophytic fungi associated with above- and below-ground tissues of the plant Aristolochia chilensis in an arid ecosystem. Endophytic fungi were isolated from healthy leaves and roots of A. chilensis, and the internal transcribed spacer (ITS) region was sequenced for phylogenetic and taxonomic analysis.

Results

A combined total of 457 fungal isolates were cultured from leaf and root tissues, belonging to 54 operational taxonomic units (OTUs). The genera Fusarium, Penicillium, Phialemonium and Trichoderma were the most representative endophyte taxa identified in A. chilensis tissues; nevertheless, Fusarium was significantly more dominant in the below-ground community, while foliar endophyte community was dominated by Penicillium. Whereas OTU richness and diversity were not different between below-ground and above-ground tissues, endophyte abundance was on average twice as high in below-ground tissue than in above-ground tissue. Fungal endophyte communities in the two tissue types were significantly dissimilar.

Conclusions

Results from this study indicate that A. chilensis harbors a similar diversity of endophytic fungi in above- and below-ground tissues. Dominant endophytic fungi were found to be dependent on tissue type, which potentially resulted in marked differences in community structure between above- and below-ground tissues. Ecological processes potentially affecting this pattern are discussed.

Fungi in mangrove ecosystems and their potential applications

Mangrove fungi, their ecological role in mangrove ecosystems, their bioproducts, and potential applications are reviewed in this article. Mangrove ecosystems can play an important role in beach protection, accretion promotion, and sheltering coastlines and creeks as barriers against devastating tropical storms and waves, seawater, and air pollution. The ecosystems are characterized by high average and constant temperatures, high salinity, strong winds, and anaerobic muddy soil. The mangrove ecosystems also provide the unique habitats for the colonization of fungi which can produce different kinds of enzymes for industrial uses, recycling of plants and animals in the ecosystems, and the degradation of pollutants. Many mangrove ecosystem-associated fungi also can produce exopolysaccharides, Ca²⁺-gluconic acid, polymalate, liamocin, polyunsaturated fatty acids, biofuels, xylitol, enzymes, and bioactive substances, which have many potential applications in the bioenergy, food, agricultural, and pharmaceutical industries. Therefore, mangrove ecosystems are rich bioresources for bioindustries and ecology. It is necessary to identify more mangrove fungi and genetically edit them to produce a distinct array of novel chemical entities, enzymes, and bioactive substances.

Elucidating Mechanisms of Endophytes Used in Plant Protection and Other Bioactivities With Multifunctional Prospects

Endophytes are abundant in plants and studies are continuously emanating on their ability to protect plants from pathogens that cause diseases especially in the field of agriculture. The advantage that endophytes have over other biocontrol agents is the ability to colonize plant's internal tissues. Despite this attributes, a deep understanding of the mechanism employed by endophytes in protecting the plant from diseases is still required for both effectiveness and commercialization. Also, there are increasing cases of antibiotics resistance among most causative agents of diseases in human beings, which calls for an alternative drug discovery using natural sources. Endophytes present themselves as a storehouse of many bioactive metabolites such as phenolic acids, alkaloids, quinones, steroids, saponins, tannins, and terpenoids which makes them a promising candidate for anticancer, antimalarial, antituberculosis, antiviral, antidiabetic, anti-inflammatory, antiarthritis, and immunosuppressive properties among many others, even though the primary function of bioactive compounds from endophytes is to make the host plants resistant to both abiotic and biotic stresses. Endophytes still present themselves as a peculiar source of possible drugs. This study elucidates the mechanisms employed by endophytes in protecting the plant from diseases and different bioactivities of importance to humans with a focus on endophytic bacteria and fungi.

Differences in Production, Composition, and Antioxidant Activities of Exopolymeric Substances (EPS) Obtained from Cultures of Endophytic Fusarium culmorum Strains with Different Effects on Cereals

Exopolymeric substances (EPS) can determine plant-microorganism interactions and have great potential as bioactive compounds. The different amounts of EPS obtained from cultures of three endophytic Fusarium culmorum strains with different aggressiveness-growth promoting (PGPF), deleterious (DRMO), and pathogenic towards cereal plants-depended on growth conditions. The EPS concentrations (under optimized culture conditions) were the lowest (0.2 g/L) in the PGPF, about three times higher in the DRMO, and five times higher in the pathogen culture. The EPS of these strains differed in the content of proteins, phenolic components, total sugars, glycosidic linkages, and sugar composition (glucose, mannose, galactose, and smaller quantities of arabinose, galactosamine, and glucosamine). The pathogen EPS exhibited the highest total sugar and mannose concentration. FTIR analysis confirmed the β configuration of the sugars. The EPS differed in the number and weight of polysaccharidic subfractions. The EPS of PGPF and DRMO had two subfractions and the pathogen EPS exhibited a subfraction with the lowest weight (5 kDa). The three EPS preparations (ethanol-precipitated EP, crude C, and proteolysed P) had antioxidant activity (particularly high for the EP-EPS soluble in high concentrations). The EP-EPS of the PGPF strain had the highest antioxidant activity, most likely associated with the highest content of phenolic compounds in this EPS.

Anti-leishmanial and Anti-inflammatory Agents from Endophytes: A Review

Leishmaniases and chronic inflammatory diseases are the cause of millions of deaths in the world each year. The treatment of leishmaniasis is facing serious drawbacks particularly due to the limited number of effective medicines, the resistance, and the toxicity of available drugs. On the other hand, many drugs are used for the management of inflammatory disorders. However, the most commonly prescribed although efficient is highly toxic with multiples side effects. New leads compounds for the development of new anti-leishmanial and anti-inflammatory drugs are needed. Over the past decade, several studies on the potential of endophytes to produce bioactive metabolites have been reported. We are presenting in the present review the status of research from 2000 to 2019 on the anti-leishmanial and anti-inflammatory metabolites isolated from endophytes from diverse habitats. An emphasis was put on existing gaps in the literature to inspire and guide future investigations. We hope that this review will help accelerate the drug discovery against leishmaniases and inflammation-associated disorders.