Endophytic Metabolites Research Articles

Antifungal Potential of Endophytic Metabolites Derived from Staphylococcus: An In-Vitro and In-Silico Approach

Introduction: Nature is full of surprises; it gives us problems along with solutions, but the only condition is that it needs to be explored. The ability of endophytes to tackle pathogens is one such example that falls within the context of the current work. In the current study, we have assessed the antifungal potential of endophytic bacterial metabolites of medicinal importance through in-vitro and in-silico studies. Materials and Methods: Bioactive metabolites from Staphylococcus species, an endophytic bacterium, were extracted to assess their antifungal potential through disc diffusion assays and minimum inhibitory concentration determination. Gas Chromatography-Mass Spectroscopy characterized the diverse composition of the endophytic extracts. The interactions between these metabolites and target proteins, such as CYP51B in Aspergillus fumigatus, were revealed by in-silico studies, which included molecular docking and dynamics simulations. This provided a thorough understanding of the antifungal qualities inherent in endophytic bacterial metabolites. Results: The research findings highlighted that the zone of inhibition (ZOI) exhibited by the crude extract from Staphylococcus endophytes (23.6±1.24 mm) is comparable to that of the control, Voriconazole (23±0.82 mm). Additionally, the minimum inhibitory concentration of the crude extract (0.21±0.06 mg/ml) is lower than the control (0.33±0.11 mg/ml). Notably, among the 45 identified endophytic metabolites, Pyrrolo [1,2-a]pyrazine-1,4-dione, hexahydro-3- (phenylmethyl), demonstrated superior inhibition efficacy against CYP51B (PDB Id: 4UYM) of Aspergillusfumigatusascompared to Voriconazole. These findings emphasized the potential of the identified metabolite as a promising antifungal agent. Conclusion: The endophytic metabolite, Pyrrolo [1,2-a]pyrazine-1,4-dione, hexahydro-3- (phenylmethyl), showcased significant antifungal potential as a therapeutic agent against fungal infections.

Exploring the diversity, bioactivity of endophytes, and metabolome in Synsepalum dulcificum.

Synsepalum dulcificum exhibits high edible and medicinal value; however, there have been no reports on the exploration of its endophyte resources. Here, we conducted analyses encompassing plant metabolomics, microbial diversity, and the biological activities of endophytic metabolites in S. dulcificum. High-throughput sequencing identified 4,913 endophytic fungal amplicon sequence variants (ASVs) and 1,703 endophytic bacterial ASVs from the roots, stems, leaves, flowers, and fruits of S. dulcificum. Fungi were classified into 5 phyla, 24 classes, 75 orders, 170 families, and 313 genera, while bacteria belonged to 21 phyla, 47 classes, 93 orders, 145 families, and 232 genera. Furthermore, there were significant differences in the composition and content of metabolites in different tissues of S. dulcificum. Spearman's correlation analysis of the differential metabolites and endophytes revealed that the community composition of the endophytes correlated with plant-rich metabolites. The internal transcribed spacer sequences of 105 isolates were determined, and phylogenetic analyses revealed that these fungi were distributed into three phyla (Ascomycota, Basidiomycota, and Mucoromycota) and 20 genera. Moreover, 16S rDNA sequencing of 46 bacteria revealed they were distributed in 16 genera in three phyla: Actinobacteria, Proteobacteria, and Firmicutes. The antimicrobial activities (filter paper method) and antioxidant activity (DPPH and ABTS assays) of crude extracts obtained from 68 fungal and 20 bacterial strains cultured in different media were evaluated. Additionally, the α-glucosidase inhibitory activity of the fungal extracts was examined. The results showed that 88.6% of the strains exhibited antimicrobial activity, 55.7% exhibited antioxidant activity, and 85% of the fungi exhibited α-glucosidase inhibitory activity. The research suggested that the endophytes of S. dulcificum are highly diverse and have the potential to produce bioactive metabolites, providing abundant species resources for developing antibiotics, antioxidants and hypoglycemic drugs.

Plant Growth Promoting Activity of Colletotrichum sp., an Endophyte of Helicteres isora L. and its Growth Optimization using Response Surface Methodology

Endophytes are the beneficial group of plant symbionts and are potent sources for producing novel metabolites with biotechnological applications. They are efficient sources for the synthesis of plant growth-promoting substances- Indole acetic acid, ammonia, solubilizing phosphates and thus open up sustainable agricultural opportunities. In the present investigation, twenty-two fungal endophytes were isolated from an ethnomedicinal plant-Helicteres isora L., collected from forests of Singbhum, Jhargram, India, and the isolate-Colletotrichum sp. HelS1, exhibited the most potent in vitro plant growth-promoting activities among all. HelS1 synthesized auxin (111.13 µg ml-1), ammonia, and solubilized phosphate (47.22 µg ml-1) in specific culture conditions. A treatment with fungal extract effectively increases the growth of the experimental plant (tomato seedlings) in terms of improvement in relative water contents, dry weight, nodal length, and pigment profiles compared to the untreated ones. There was an increase in root length by 27% compared to the control group. The isolate produced the maximum IAA after 7 days of incubation on Czepak Dox Broth supplemented with tryptophan (5 mg mL-1), sucrose (30 g L-1), and NaNO3 (2.2 g L-1) at pH 6.2. Fourier Transform Infrared Spectroscopic analysis of the crude fungal extract further confirmed the production of indole-like compounds. This investigation suggested that secondary metabolites of endophytes act as a potent plant growth inducer and can be utilized in bio-based crop management techniques.

Efficacy of ergosterol peroxide obtained from the endophytic fungus Acrophialophora jodhpurensis against Rhizoctonia solani.

To investigate antifungal activity of the extract and major metabolite of the endophytic fungus Acrophialophora jodhpurensis (belonging to Chaetomiaceae) against crown and root rot caused by Rhizoctonia solani (teleomorph: Thanatephorus cucumeris), as an important pathogen of tomato. The endophytic fungus A. jodhpurensis, has high inhibitory effect against R. solani AG4-HG II in vitro and in vivo. The media conditions were optimized for production of the endophyte's metabolites. The highest amounts of secondary metabolites were produced at pH 7, 30°C temperature, and in the presence of 0.5% glucose, 0.033% sodium nitrate, and 1 gl-1 asparagine as the best carbon, nitrogen, and amino acid sources, respectively. The mycelia were extracted by methanol and the obtained extract was submitted to various chromatography techniques. Phytochemical analysis via thin-layer chromatography (TLC) and nuclear magnetic resonance (NMR) spectroscopy showed that ergosterol peroxide was the major component in the extract of this endophyte. Antifungal activities of the methanolic extract and ergosterol peroxide in the culture media were studied against R. solani. Minimum inhibitory concentrations of the extract and ergosterol peroxide against the pathogen were 600 and 150µg ml-1, respectively. Ergosterol peroxide revealed destructive effects on the pathogen structures in microscopic analyses and induced sclerotia production. Histochemical analyses revealed that it induced apoptosis in the mycelia of R. solani via superoxide production and cell death. Application of ergosterol peroxide in the leaf disc assay reduced the disease severity in tomato leaves. Antifungal metabolites produced by A. jodhpurensis, such as ergosterol peroxide, are capable of controlling destructive Rhizoctonia diseases on tomato.

Terricoxanthones A–E, unprecedented dihydropyran-containing dimeric xanthones from the endophytic fungus Neurospora terricola HDF-Br-2 associated with the vulnerable conifer Pseudotsuga gaussenii

An investigation on the secondary metabolites from a rice culture broth of the endophytic fungus Neurospora terricola HDF-Br-2 derived from the vulnerable conifer Pseudotsuga gaussenii led to the isolation and characterization of 34 structurally diverse polyketides (1–34). Seven of them are previously undescribed, including five unprecedented dihydropyran-containing (terricoxanthones A–E, 1–5, resp.) and one rare tetrahydrofuran-containing (terricoxanthone F, 6) dimeric xanthones. The structures were elucidated by spectroscopic methods and single-crystal X-ray diffraction analyses. Terricoxanthones each were obtained as a racemic mixture. Their plausible biosynthetic relationships were briefly proposed. Compounds 6, aspergillusone A (8), and alatinone (27) displayed considerable inhibition against Candida albicans with MIC values of 8–16 μg/mL. 4-Hydroxyvertixanthone (12) and 27 exhibited significant inhibitory activities against Staphylococcus aureus, with MIC values of 4–8 μg/mL. Furthermore, compounds 8 and 27 could disrupt biofilm of S. aureus and C. albicans at 128 μg/mL. The findings not only extend the skeletons of xanthone dimers and contribute to the diversity of metabolites of endophytes associated with the endangered Chinese conifer P. gaussenii, but could further reveal the important role of protecting plant species diversity in support of chemical diversity and potential sources of new therapeutics.

Endophytic Microbial Community and its Potential Applications: A Review

Endophytes are present in all plant species across the world. They assist their hosts by producing several chemicals/metabolites that provide protection and, ultimately, survival value to their host plants. In various studies, endophytes have been demonstrated to be a new and potential source of novel natural chemicals for application in modern medicine, agriculture, and industry. Endophytes have developed a variety of natural chemicals that include antibacterial, antifungal, antiviral, anticancer, antiparasitic, cytotoxic, antidiabetic, immunosuppressive, antitubercular, anti-inflammatory, and antioxidants. These chemicals are involved in biodegradation and biofertilizers that promote the growth of plants. Screening these endophytic metabolites is regarded as a promising technique to combat drug-resistant human and plant disease strains. In this review, the basic concept of endophytes, the variety of endophytic microbiome, as well as the application of endophytes are presented. This knowledge may be used to extract improved bioactive compounds from endophytes and may serve as a foundation for future research.

Neuroprotective α-pyrones from Nigrospora oryzae, an endophytic fungus residing in Taxus chinensis var. mairei

Endophytes coevolve with plant hosts and thus are more probable to acquire the character (in favor) of producing undescribed bioactive metabolites. Consequently, the topic has been intensely investigated for over two decades, but endophytic metabolites with neuroprotective effect remain scarce. The study presents the discovery of eight undescribed (named solanapyrones U–Z and prosolanapyrones A and B) and six known pyrones (solanapyrones A–C and E–G) from the culture of Nigrospora oryzae, an endophytic fungus associated with Taxus chinensis var. mairei. The structures and absolute configurations of undescribed pyrones were elucidated by extensive spectroscopic analysis, modified Mosher's method, and induced circular dichroism (ICD) spectrum. Solanapyrones A and B and an undescribed pyrone (solanapyrone U) were demonstrated to be more neuroprotective than clenbuterol in inducing bone marrow mesenchymal stem cells (bMSCs) to secret nerve growth factor (NGF). The work updates the pyrone chemodiversity in nature and extends the biofunction repertoire of solanapyrone-related polyketides.

In vivo studies on evaluation of endophytic fungi extract from Trichoderma viride against cervical cancer

BackgroundThe crude ethyl acetate Trichoderma viride extract obtained from Ziziphus mauritiana was initially analyzed by HPLC for identification of major bioactive compounds, and then, it was subjected for in vivo acute and sub-acute toxicity, cervical cancer studies using Wistar albino rats.ResultDuring acute toxicity studies, animal groups treated with distinct dosage of 2000 mg/kg restrained toxicity signs in tested groups compared to controls for 14 days which established to be secure and non-toxic even at high dose. However, in terms of sub-acute toxicity studies, animals were given with repeated amount of (10 mg/kg, 20 mg/kg and 40 mg/kg) for a period of 28 days along with control group. Upon investigations of hematological, biochemical and histopathological studies repeated dose of 20 mg/kg and 40 mg/kg of T. viride extract found to be normal and no other major changes observed among treated groups. During in vivo studies, after treatment of T. viride extract (40 mg/kg) effectively inhibited the cervical cancer cell growth in DES-treated groups. Through HPLC analysis the major compound ursolic acid and 2,5-piperazinedione were mainly identified.ConclusionThe secondary metabolites of endophytes have been used substantially for the sustainable production of therapeutically important compounds. The limited availability of bioactive principles in plant sources could be surpassed by exploiting the chemical entities in the endophytes. In the present investigation, it has been accomplished that ethyl acetate extract of T. viride was safe at higher and lower dosage could be considered for pharmacological studies from plant may provide an excellent avenue for the discovery of drug candidates against deadly cancer diseases.

Chemical and Biological Review of Endophytic Fungi Associated with Morus sp. (Moraceae) and In Silico Study of Their Antidiabetic Potential

The chronic nature of diabetes mellitus motivates the quest for novel agents to improve its management. The scarcity and prior uncontrolled utilization of medicinal plants have encouraged researchers to seek new sources of promising compounds. Recently, endophytes have presented as eco-friendly leading sources for bioactive metabolites. This article reviewed the endophytic fungi associated with Morus species and their isolated compounds, in addition to the biological activities tested on their extracts and chemical constituents. The relevant literature was collected from the years 2008-2022 from PubMed and Web of Science databases. Notably, no antidiabetic activity was reported for any of the Morus-associated endophytic fungal extracts or their twenty-one previously isolated compounds. This encouraged us to perform an in silico study on the previously isolated compounds to explore their possible antidiabetic potential. Furthermore, pharmacokinetic and dynamic stability studies were performed on these compounds. Upon molecular docking, Colletotrichalactone A (14) showed a promising antidiabetic activity due to the inhibition of the α-amylase local target and the human sodium-glucose cotransporter 2 (hSGT2) systemic target with safe pharmacokinetic features. These results provide an in silico interpretation of the possible anti-diabetic potential of Morus endophytic metabolites, yet further study is required.

Investigations on the cytotoxicity and antimicrobial activities of terezine E and 14-hydroxyterezine D.

Secondary metabolites produced by endophytes are an excellent source of biologically active compounds. The newly isolated natural products terezine E and 14-hydroxyterezine D are endophytic metabolites exhibiting anticancer activity recently identified by our team (https://doi.org/10.1080/14786419.2018.1489393). In our current study, we evaluated their affinity for binding to the active site of histone deacetylase (PDB ID: 4CBT) and matrix metalloproteinase 9 (PDB ID: 4H3X) by molecular docking using AutoDock Vina software after having tested their cytotoxic activities on three cell lines (human ductal breast epithelial tumor cells (T47D)-HCC1937), human hepatocarcinoma cell line (HepG2)-HB8065), and human colorectal carcinoma cells (HCT-116)-TCP1006, purchased from ATCC, USA)). Additionally, their antimicrobial activities were investigated, and their minimum inhibitory concentration (MIC) values were determined against P. notatum and S. aureus by the broth microdilution method. Higher cytotoxicity was observed for terezine E against all tested cell lines compared to 14-hydroxyterezine D. Molecular docking results supported the high cytotoxicity of terezine E and showed higher binding affinity with 4CBT with an energy score of 9 kcal/mol. Terezine E showed higher antibacterial and antifungal activities than 14-hydroxyrerezine D: MIC values were 15.45 and 21.73 µg/mL against S. aureus and 8.61 and 11.54 µg/mL against P. notatum, respectively.

Evaluation of Culture Filtrates of Endophytic Microorganisms from Tomato against Ralstonia solanacearum

A novel approach to biological control using endophytes has gained immense potential in disease management. The endophytes constitute a valuable source of secondary metabolites such as alkaloids, terpenoids, sterols and phenolic compounds which play a major role in plant defense mechanisms. Therefore an experiment was carried out to study the effect of secondary metabolites of endophytes from tomatoes against the bacterial wilt pathogen Ralstonia solanacearum both in vitro and in vivo conditions using their culture filtrates. In vitro evaluation of the culture filtrates of the endophytes was carried out by inoculating the pathogen on a five per cent culture filtrate amended Potato Dextrose Agar medium. Complete inhibition of the pathogen was observed in all endophytes indicating the inhibitory effect of their culture filtrates. In order to study the effect of secondary metabolites of endophytes on R. solanacearum under in planta conditions, culture filtrates along with culture suspensions for comparison were used. The tomato seedlings dipped first in culture filtrate/suspension then in bacterial ooze showed lowest wilt incidence and among the two, seedling dip in filtrate was the effective one. The minimum wilt incidence was noticed with seedlings dipped first in culture filtrate of endophyte Trichoderma viride-2 recording 10.92, 15.68 and 19.84 per cent followed by T. harzianum-1 and Bacillus subtilis, which showed 12.5, 16.67 and 22.22 per cent at 7, 10 and 14 days after inoculation respectively. Thus the above findings clearly indicated the inhibitory effect of secondary metabolites of the endophytes on bacterial wilt pathogen.

Secondary Metabolites of Endophytes Associated with the Zingiberaceae Family and Their Pharmacological Activities

Zingiberaceae is commonly known as the ginger family and has been extensively studied in the last decades for its pharmacological purposes. The study of ginger includes microorganisms known as endophytes, which raise interest for the research community because they can produce a wide range of secondary metabolites. This review discusses the secondary metabolites of endophytes from the Zingiberaceae family and their pharmacological activities. We detail the group of secondary metabolites, updated for its absolute structures, source and part origins, and, especially, pharmacological divided properties. Zingiberaceae endophytes have 106 volatile compounds and 52 isolated constituents, including 17 polyketides, five nonribosomal peptides, five aromatic compounds, three alkaloids, and 21 terpene-alkaloids. They have antimicrobial, anticancer, antioxidant, and anti-inflammatory activities. Secondary metabolites from plant endophytes of the Zingiberaceae family have the potential to be therapeutic drugs in the future. Research on endophytic bacteria or fungi has been little performed. Therefore, this study supports a new drug discovery from Zingiberaceae endophytes and compares them for future drug development.

Ultra-high-performance liquid chromatography combined with electrospray ionization quadrupole time-of-flightmass spectrometryand molecular networking analysis to investigate the chemodiversity of bioactive extracts of Annona jahnii Saff. fungi from the Brazilian Amazon.

Annona species are of interest for the isolation of bioactive molecules; however, studies of Annona jahnii Saff. are limited. The exploration of bioactive metabolites of endophytes isolated from this species is unprecedented and allows the preservation of the host plant, in addition to enabling the discovery of compounds with promising biological activities. Ethyl acetate extracts from the cultured media of five fungi were obtained. The antioxidant capacity of the extracts was measured using the 1,1-diphenyl-2-picrylhydrazyl free radical method. Antimicrobial activity was determined using the microdilution method in broth in 96-well plates. The exploration of the metabolic profile of the extracts and dereplication of the compounds were performed using ultra-high-performance liquid chromatography/electrospray ionization/tandem mass spectrometry (UHPLC/ESI-MS/MS) combined with analysis using molecular networking (MN). A total of 1818 MS features were detected in the five selected extracts, of which 39 compounds were putatively identified. The secondary metabolites with the highest abundance were alkaloids, naphthopyrons, and cytochalasins. Other secondary metabolites include fumonisins, coumarin, and a meroterpenoid. Most of these compounds are related to specific biological properties such as antioxidant, anti-inflammatory, antimicrobial, antiviral, and antitumor activities. Extracts F398 and F403 showed inhibitory activity of the four pathogens tested. Extracts F475 and F506 did not inhibit the growth of Staphylococcus aureus, and F407 did not inhibit the growth of Escherichia coli in addition to having potent antioxidant activity, with IC50 values of 10μg/mL or less. The use of UHPLC/ESI-MS/MS data combined with MN proved useful in the dereplication of bioactive molecules of complex extracts that are still unexplored. These initial investigations should significantly assist in further research and increase the efficiency and speed in the discovery of new sources of secondary metabolites and new natural products.

Endophytes, a Potential Source of Bioactive Compounds to Curtail the Formation-Accumulation of Advanced Glycation End Products: A Review.

Endophytes, microorganisms that live in the internal tissues and organs of the plants, are known to produce numerous bioactive compounds, including, at times, some phytochemicals of their host plant. For such reason, endophytes have been quoted as a potential source for discovering bioactive compounds, particularly, of medical interest. Currently, many non-communicable diseases are threatening global human health, noticeably: diabetes, neurodegenerative diseases, cancer, and other ailment related to chronic inflammation and ageing. Intriguingly, the pathogenesis and development of these diseases have been linked to an excessive formation and accumulation of advanced glycation end products (AGEs). AGEs are a heterogeneous group of compounds that can alter the conformation, function, and lifetime of proteins. Therefore, compounds that prevent the formation and consequent accumulation of AGEs (AntiAGEs compounds) could be useful to delay the progress of some chronic diseases, and/or harmful effects of undue AGEs accumulation. Despite the remarkable ability of endophytes to produce bioactive compounds, most of the natural antiAGEs compounds reported in the literature are derived from plants. Accordingly, this work covers 26 plant antiAGEs compounds and some derivatives that have been reported as endophytic metabolites, and discusses the importance, possible advantages, and challenges of using endophytes as a potential source of antiAGEs compounds.

Broad-Spectrum Antimicrobial Action of Cell-Free Culture Extracts and Volatile Organic Compounds Produced by Endophytic Fungi Curvularia Eragrostidis.

Endophytes are the mutualistic microorganisms that reside within the host plant and promote plant growth in adverse conditions. Plants and their endophytes are engaged in a symbiotic relationship that enables endophytes to access bioactive genes of the ethnomedicinal plants, and, as a result, endophytes are constantly addressed in the sector of pharmaceuticals and agriculture for their multidomain bio-utility. The gradual increase of antimicrobial resistance can be effectively countered by the endophytic metabolites. In these circumstances, in the present investigation, endophytic Curvularia eragrostidis HelS1 was isolated from an ethnomedicinally valuable plant Helecteris isora from East India’s forests. The secondary volatile and non-volatile metabolites are extracted from HelS1 and are found to be effective broad-spectrum antimicrobials. A total of 26 secondary metabolites (9 volatiles and 17 non-volatiles) are extracted from the isolate, which exhibits effective antibacterial [against six Gram-positive and seven Gram-negative pathogens with a minimum inhibitory concentrations (MIC) value ranging from 12.5 to 400 μg ml–1] and antifungal (against seven fungal plant pathogens) activity. The secondary metabolite production was optimised by one variable at a time technique coupled with the response surface methodology. The results revealed that there was a 34% increase in antibacterial activity in parameters with 6.87 g L–1 of fructose (as a carbon source), 3.79 g L–1 of peptone (as a nitrogen source), pH 6.75, and an inoculation period of 191.5 h for fermentation. The volatile metabolite production was also found to be optimum when the medium was supplemented with yeast extract and urea (0.2 g L–1) along with dextrose (40 g L–1). Amongst extracted volatile metabolites, 1-H-indene 1 methanol acetate, tetroquinone, N, N-diphenyl-2-nitro-thio benzamide, Trans 1, 2-diethyl-trans-2-decalinol, naphthalene, and azulene are found to be the most effective. Our investigation opens up opportunities in the sector of sustainable agriculture as well as the discovery of novel antimicrobials against dreadful phyto and human pathogens.

Potential use of endophytes in the pharmaceutical industry

Endophytes are microorganisms, usually fungi or bacteria less commonly algae and viruses, that live in plant tissues without causing disease symptoms in their host. It is estimated that there are over one million endophytic fungal species, but because of their habitat, they have been discovered relatively recently and therefore poorly studied. (Gupta, Chaturvedi, Kulkarni, & Van Staden, 2019) It is estimated that less than 1 % of all endophytic species are currently known. When observing the mutual relationships of plants with endophytes, most researchers take the view that such associations are commensal (Ayswaria, Vasu, & Krishna, 2020). Nowadays, endophytic microorganisms are considered to be a potential source of compounds - secondary metabolites. Endophyte bioactive compounds can be used in the pharmaceutical industry. Endophytes are mainly used in the production of antibiotics, antioxidants, various enzymes, anti-inflammatory, antimicrobial, antiparasitics and antifungal drugs, immunosuppressors, and also as anticancer agents. The interest in biotechnology is great, as the application of secondary metabolites of endophytes is possible in the cosmetic industry, agricultural complex, textile production, and food industry besides pharmaceuticals. The relevance of this topic and its further research on the use of already available and the discovery of new bioactive components of endophytic microorganisms can help scientists in resolving the problems of resistance of some pathogenic strains to modern approaches in antibiotic therapy. The potential uses are great, as endophytes can be extracted from numerous plants worldwide. The properties and characteristics of extracted endophytes will vary due to their geographical location and environmental conditions. Besides the wide variety of endophytic microorganisms for production, an important factor is the ability to use the same fungus, bacterium, or algae to synthesize a significant number of different active compounds. These compounds are interesting because they can manifest their action in several directions. In this article we considered several options for classifying endophytic microorganisms, listed the possible applications in the pharmaceutical industry, also considered the most used bioactive compounds from the Streptomyces genus actinobacteria, in addition, we reviewed substances with anti-tumor activity, which are now used to treat cancer of various human organs and are available as drugs for preparing injection solutions, metabolites of endophytes equally found their application. The aim of this work was to describe the modern classification of endophytes and show their potential use in antibiotic drugs as active agents in cancer treatment and their use as sedative drugs.

The Multifunctions and Future Prospects of Endophytes and Their Metabolites in Plant Disease Management.

Endophytes represent a ubiquitous and magical world in plants. Almost all plant species studied by different researchers have been found to harbor one or more endophytes, which protect host plants from pathogen invasion and from adverse environmental conditions. They produce various metabolites that can directly inhibit the growth of pathogens and even promote the growth and development of the host plants. In this review, we focus on the biological control of plant diseases, aiming to elucidate the contribution and key roles of endophytes and their metabolites in this field with the latest research information. Metabolites synthesized by endophytes are part of plant disease management, and the application of endophyte metabolites to induce plant resistance is very promising. Furthermore, multi-omics should be more fully utilized in plant–microbe research, especially in mining novel bioactive metabolites. We believe that the utilization of endophytes and their metabolites for plant disease management is a meaningful and promising research direction that can lead to new breakthroughs in the development of more effective and ecosystem-friendly insecticides and fungicides in modern agriculture.

PHYTOCHEMICAL, ANTIOXIDANT AND ANTIMICROBIAL STUDIES OF THE CRUDE EXTRACT OF Curvulariasp. ISOLATED FROM THE LEAVES OF THE MEDICINAL PLANT Piliostigma thonningii (Fabaceae)

Recently, there is biotechnological interest in secondary metabolites of endophytes since they have been shown to be capable of producing substances of pharmacological importance. Piliostigmathonningii is a tree whose parts are widely employed in Nigeria for diverse medicinal applications. The aim of this study is to investigate the phytochemical composition, the antiradical and in vitro antimicrobial potentials of the crude ethyl acetate extract of Curvularia sp isolated from the leaves of the plant. The endophytic fungus was isolated, purified, and identified using conventional methods. While standard procedures was employed in the determination of the phytochemical constituents, quantitative estimation of the total phenol and flavonoid were done by spectrophotometric method using gallic acid and quercetin as standards respectively. While the antioxidant activity was determined by DPPH scavenging assay, the agar well diffusion method was employed to screen for its antimicrobial capabilities. Results showed the presence ofimportant phytoconstituents notably alkaloid, flavonoid, phenolics, tannin, saponins among others. While the antioxidant assay showed the total phenolic and flavonoid contents to be 212.55 ± 1.2 mgGAE/g extract and 143.16 ± 0.8 mgQE/g extract respectively, a 74.45 ± 0.11% free radical scavenging activity was observed compared to ascorbic acid standard that exhibited a 87.92 ± 0.17% inhibition. At the highest investigated concentration of 1 mg/mL, the extract produced antibacterial activity only against Escherichia coliandPseudomonas aeruginosa. The results showed that the extract exhibits marked antioxidant and selected antibacterial effects thus justifying the assertion that endophytic bioactive compounds have promising applications in the field of medicine.

Dynamic Changes in Endophytic Microorganisms and Metabolites During Natural Drying of Licorice.

The method of drying licorice is an important factor affecting the quality of the final product. To determine the best processing method of licorice postharvest, we investigated the interaction of increasing aridity between the endophytic microorganisms and the accumulation of metabolites. Samples from the roots of licorice growing along an aridity gradient during the natural drying process were collected, and the metabolic components, the content of the main active substances and the dynamic changes of the endophytic microbial community were assessed. The glycyrrhizic acid and liquiritin contents decreased slightly or remained flat during natural drying, whereas those of liquiritigenin and isoliquiritigenin increased slightly. Moreover, the Shannon index of endophytic microbial diversity of licorice was the highest in the fresh period and showed a downward trend during the drying process. When the licorice were fresh, Cladosporiaceae and Burkholderiaceae were the dominant family present, but after drying, Nectriaceae and Enterobacteriaceae were the dominant families. A similar trend was also found in which the differential metabolites of licorice were reduced during natural drying. Furthermore, correlation analysis between dominant families and differential metabolites showed that there was a correlation between the two. Therefore, fresh processing is an effective drying method to ensure the quality of licorice. This study revealed the relationship of endophytic microbiota and changes in the licorice metabolites during different stages of drying, which provided a scientific basis for the drying method of licorice.

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.