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

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.

Bioactive Compounds Produced by Endophytic Microorganisms Associated with Bryophytes—The “Bryendophytes”

The mutualistic coexistence between the host and endophyte is diverse and complex, including host growth regulation, the exchange of substances like nutrients or biostimulants, and protection from microbial or herbivore attack. The latter is commonly associated with the production by endophytes of bioactive natural products, which also possess multiple activities, including antibacterial, insecticidal, antioxidant, antitumor, and antidiabetic properties, making them interesting and valuable model substances for future development into drugs. The endophytes of higher plants have been extensively studied, but there is a dearth of information on the biodiversity of endophytic microorganisms associated with bryophytes and, more importantly, their bioactive metabolites. For the first time, we name bryophyte endophytes “bryendophytes” to elaborate on this important and productive source of biota. In this review, we summarize the current knowledge on the diversity of compounds produced by endophytes, emphasizing bioactive molecules from bryendophytes. Moreover, the isolation methods and biodiversity of bryendophytes from mosses, liverworts, and hornworts are described.

A validated high-throughput method for assaying rat lungworm (Angiostrongylus cantonensis) motility when challenged with potentially anthelmintic natural products from Hawaiian fungi

Parasitic nematodes devastate human and animal health. The limited number of anthelmintics available is concerning, especially because of increasing drug resistance. Anthelmintics are commonly derived from natural products, e.g. fungi and plants. This investigation aimed to develop a high-throughput whole organism screening method based on a motility assay using the wMicroTracker system. Anthelmintic activity of extracts from Hawaiian fungi was screened against third-stage larvae of the parasitic nematode Angiostrongylus cantonensis , categorized according to the degree of motility reduction. Of the 108 crude samples and fractionated products, 48 showed some level of activity, with 13 reducing motility to 0–25% of the maximum exhibited, including two pure compounds, emethacin B and epicoccin E, neither previously known to exhibit anthelmintic properties. The process of bioassay-guided fractionation is illustrated in detail based on analysis of one of the crude extracts, which led to isolation of lamellicolic anhydride, a compound with moderate activity. This study validates the wMicroTracker system as an economical and high-throughput option for testing large suites of natural products against A. cantonensis , adds to the short list of diverse parasites for which it has been validated and highlights the value of A. cantonensis and Hawaiian fungi for discovery of new anthelmintics.

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.