Fusartricin, a sesquiterpenoid ether produced by an endophytic fungus Fusarium tricinctum Salicorn 19

Antimicrobials from endophytes as novel therapeutics to counter drug-resistant pathogens

The rapid increase in antimicrobial resistance (AMR) projects a "global emergency" and necessitates a need to discover alternative resources for combating drug-resistant pathogens or "superbugs." One of the key themes in "One Health Concept" is based on the fact that the interconnected network of humans, the environment, and animal habitats majorly contribute to the rapid selection and spread of AMR. Moreover, the injudicious and overuse of antibiotics in healthcare, the environment, and associated disciplines, further aggravates the concern. The prevalence and persistence of AMR contribute to the global economic burden and are constantly witnessing an upsurge due to fewer therapeutic options, rising mortality statistics, and expensive healthcare. The present decade has witnessed the extensive exploration and utilization of bio-based resources in harnessing antibiotics of potential efficacies. The discovery and characterization of diverse chemical entities from endophytes as potent antimicrobials define an important yet less-explored area in natural product-mediated drug discovery. Endophytes-produced antimicrobials show potent efficacies in targeting microbial pathogens and synthetic biology (SB) mediated engineering of endophytes for yield enhancement, forms a prospective area of research. In keeping with the urgent requirements for new/novel antibiotics and growing concerns about pathogenic microbes and AMR, this paper comprehensively reviews emerging trends, prospects, and challenges of antimicrobials from endophytes and their effective production via SB. This literature review would serve as the platform for further exploration of novel bioactive entities from biological organisms as "novel therapeutics" to address AMR.

Contribution of endophytes towards improving plant bioactive metabolites: a rescue option against red-taping of medicinal plants

Medicinal plants remain a valuable source for natural drug bioprospecting owing to their multi-target spectrum. However, their use as raw materials for novel drug synthesis has been greatly limited by unsustainable harvesting leading to decimation of their wild populations coupled with inherent low concentrations of constituent secondary metabolites per unit mass. Thus, adding value to the medicinal plants research dynamics calls for adequate attention. In light of this, medicinal plants harbour endophytes which are believed to be contributing towards the host plant survival and bioactive metabolites through series of physiological interference. Stimulating secondary metabolite production in medicinal plants by using endophytes as plant growth regulators has been demonstrated to be one of the most effective methods for increasing metabolite syntheses. Use of endophytes as plant growth promotors could help to ensure continuous supply of medicinal plants, and mitigate issues with fear of extinction. Endophytes minimize heavy metal toxicity in medicinal plants. It has been hypothesized that when medicinal plants are exposed to harsh conditions, associated endophytes are the primary signalling channels that induce defensive reactions. Endophytes go through different biochemical processes which lead to activation of defence mechanisms in the host plants. Thus, through signal transduction pathways, endophytic microorganisms influence genes involved in the generation of secondary metabolites by plant cells. Additionally, elucidating the role of gene clusters in production of secondary metabolites could expose factors associated with low secondary metabolites by medicinal plants. Promising endophyte strains can be manipulated for enhanced production of metabolites, hence, better probability of novel bioactive metabolites through strain improvement, mutagenesis, co-cultivation, and media adjustment.

Fusarium-Derived Secondary Metabolites with Antimicrobial Effects

Fungal microbes are important in the creation of new drugs, given their unique genetic and metabolic diversity. As one of the most commonly found fungi in nature, Fusarium spp. has been well regarded as a prolific source of secondary metabolites (SMs) with diverse chemical structures and a broad spectrum of biological properties. However, little information is available concerning their derived SMs with antimicrobial effects. By extensive literature search and data analysis, as many as 185 antimicrobial natural products as SMs had been discovered from Fusarium strains by the end of 2022. This review first provides a comprehensive analysis of these substances in terms of various antimicrobial effects, including antibacterial, antifungal, antiviral, and antiparasitic. Future prospects for the efficient discovery of new bioactive SMs from Fusarium strains are also proposed.

Research advances on endophytic fungi and their bioactive metabolites

Endophytic fungi, as a kind of fungi living in the healthy plant tissues and organs, are important sources of natural bioactive products and new microbial resources with high developing value. Therefore, exploration and utilization of endophytic fungi can not only alleviate the problems of resource shortage and ecological balance destruction caused by extracting large number of useful bioactive products from natural plants, but also benefit the protection of rare and endangered plant resources, which is of great significance and economic value. This review mainly expounds the concept of endophytic fungi, analyzes the research advances of endophytic fungi from antioxidant, antibacterial, insecticidal, regulating plant growth, anticancer and antitumor bioactivities and, furthermore, summarizes the existing problems in present research of endophytic fungi and corresponding solutions. We hope that this review could provide references for the development and utilization of endophytic fungi and their bioactive metabolites.

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.

Bioactive terpenoids derived from plant endophytic fungi: An updated review (2011-2020)

Plant endophytes have been considered as novel sources of naturally occurring compounds with various biological activities, including cytotoxic, antimicrobial, anti-inflammatory, anticancer, herbicides, antileishmanial and antioxidant. A variety of specialised products, comprising terpenoids, alkaloids, polyketides, phenolic compounds, coumarins, and quinone derivatives have been reported from various strains. An increasing number of products, especially terpenoids, are being isolated from endophytes. Herein, the isolated new terpenoids from plant endophytic fungi, their hosts, as well as biological activities, from January 2011 until the end of 2020 are reviewed. In this period, 516 terpenoids are classified into monoterpenes (5), sesquiterpenes (299), diterpenes (76), sesterterpens (22), meroterpenes (83), triterpenes (29), and other terpenoids (2), were isolated from different plant endophytic fungi species.

Natural imidazole alkaloids as antibacterial agents against Pseudomonas syringae pv. actinidiae isolated from kiwi endophytic fungus Fusarium tricinctum

Kiwi (Actinidia chinensis) plants are severely destroyed by canker disease which is caused by the bacterium Pseudomonas syringae pv. actinidiae (Psa). This program tries to find anti-Psa agents among secondary metabolites of endophytic fungi from kiwi plant itself. The chemical investigation on one kiwi endophytic fungi, Fusarium tricinctum, resulted in the isolation of nine new imidazole alkaloids, fusaritricines A-I (1-9) together with seven known analogues (10-16). The structures of new compounds were established by extensive spectroscopic methods. Compounds 2, 3, 9, and 13 showed good antibacterial activity against Psa with MIC values between 25 and 50 μg/mL. It is suggested that imidazole alkaloids should be potential anti-Psa agents.

Cosmosporasides F-H, three new sugar alcohol conjugated acyclic sesquiterpenes from a Fusarium oxysporum fungus

Three new sugar alcohol conjugated acyclic sesquiterpenes, cosmosporasides F-H (1-3), were isolated from the fermented cultures of Fusarium oxysporum SC0002. Their structures were elucidated by extensive analysis of spectroscopic data, including ¹H-¹³C long-range coupling constants (J_C,H). Their antibacterial, cytotoxic and anti-inflammatory activities were evaluated.

Fusarium: a treasure trove of bioactive secondary metabolites

Covering up to December 2019Fusarium, one of the most common fungal genera, has received considerable attention because of its biosynthetic exuberance, the result of many unique gene clusters involved in the production of secondary metabolites. This review provides the first comprehensive analysis of the secondary metabolites unique to the genus Fusarium, describing their occurrence, bioactivity, and genome features.

Bioprospecting endophytic fungi from Fusarium genus as sources of bioactive metabolites

Endophytic fungi became an attractive source for the discovery of new leads, because of the complexity and the structural diversity of their secondary metabolites. The genus Fusarium comprising about 70 species is extremely variable in terms of genetics, biology, ecology, and consequently, secondary metabolism and have been isolated from countless plants genera from diverse habitats. These endophytic microbes may provide protection and survival strategies in their host plants with production of a repertoire of chemically diverse and structurally unprecedented secondary metabolites reported to exhibit an incredible array of biological activities including antimicrobial, anticancer, antiviral, antioxidants, antiparasitics, immunosuppressants, immunomodulatory, antithrombotic, and biocontrol ability against plants pathogens and nematodes. This review comprehensively highlights over the period 1981-2019, the bioactive potential of metabolites produced by endophytes from Fusarium genus. Abbreviations: AIDS: Acquired immune deficiency syndrome; BAPT: C-13 phenylpropanoid side chain-CoA acyltransferase; CaBr2: Calcium bromide; DBAT: 10-deacetylbaccatin III-10-O-acetyl transferase; DNA: Deoxyribonucleic acid; EI-MS: Electron ionization mass spectrometer; EN: Enniatin; ERK: Extracellular regulated protein kinase; EtOAc: Ethyl acetate; FDA: Food and Drug Administration; GAE/g: Gallic acid equivalent per gram; GC-MS: Gas chromatography-mass spectrometry; HA: Hyperactivation; HCV: Hepatitis C Virus; HCVPR: Hepatitis C Virus protease; HeLa: Human cervical cancer cell line; HIV: Human immunodeficiency viruses; HPLC: High Performance Liquid Chromatography; IAA: Indole-3-acetic acid; IARC: International Agency for Research on Cancer; IC50: Half maximal inhibitory concentration; LC50: Concentration of the compound that is lethal for 50% of exposed population; LC-MS: Liquid chromatography-mass spectrometry; MCF-7: Human breast cancer cell line; MDR: Multidrug-resistant; MDRSA: Multidrug-resistant S. aureus; MFC: Minimum fungicidal concentration; MIC: Minimum inhibitory concentration; MRSA: Multidrug-resistant S. aureus; MTCC: Microbial type culture collection; PBMCs: Peripheral blood mononuclear cells; PCR: Polymerase chain reaction; TB: Tuberculosis; TLC: Thin layer chromatography; TNF: Tumor necrosis factor; WHO: World Health Organization http://www.zoobank.org/urn:lsid:zoobank.org:pub:D0A7B2D8-5952-436D-85C8-C79EAAD1013C.

Two New Alkaloids from Fusarium tricinctum SYPF 7082, an Endophyte from the Root of Panax notoginseng

Panax notoginseng (Araliaceae) is a famous traditional Chinese medicine mainly cultivated in Yunnan and Guangxi provinces of China. Two new alkaloids, rigidiusculamide E (1) and [-(α-oxyisohexanoyl-N-methyl-leucyl)₂-] (2), together with two known ones, (-)-oxysporidinone (3) and (-)-4,6'-anhydrooxysporidinone (4) were isolated from the mycelia culture of Fusarium tricinctum SYPF 7082, an endophytic fungus obtained from the healthy root of P. notoginseng. Their structures were determined on the basis of extensive spectroscopic analyses. Compounds 1-4 were tested for their inhibitory effects against NO production on Murine macrophage cell line, and the new compound 2 showed significant inhibitory activity on NO production with the IC₅₀ value of 18.10 ± 0.16 μM.

OSMAC approach leads to new fusarielin metabolites from Fusarium tricinctum

Using the OSMAC (One Strain MAny Compounds) approach, the fungal endophyte Fusarium tricinctum was cultivated on fruit and vegetable juice-supplemented solid rice media. This led to an up to 80-fold increase in the accumulation of the new natural product fusarielin J (1), as well as to the induction of two new natural products fusarielin K (2) and fusarielin L (3) and the known derivatives fusarielins A (4) and B (5). Compounds 2-5 were not detected when the fungus was grown on rice media lacking either fruit or vegetable juice. The highest increase in the accumulation of compound 1 was observed in the presence of apple and carrot juice, whereas the stimulating effect was weaker for banana juice. Compound 1 exhibited cytotoxicity against the human ovarian cancer cell line A2780, with an IC₅₀ value of 12.5 μM.