Mycoleptodiscins A and B, cytotoxic alkaloids from the endophytic fungus Mycoleptodiscus sp. F0194

Modular Synthesis and Antimicrobial Investigation of Mycoleptodiscin A and Simplified Indolosesquiterpenoids

The structure-activity relationship of the unusual indolosesquiterpenoid mycoleptodiscin A is unknown due to natural scarcity and inefficient synthesis. A modular approach leveraging Larock indole synthesis has been established to access mycoleptodiscin A and a divergent collection of drimenyl indoles. It features the utilization of an inexpensive (+)-sclareolide, modularity, purification-economy, and scalability, which facilitates the first biological evaluation of mycoleptodiscin A and related precursors.

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

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

Putative Anticancer Compounds from Plant-Derived Endophytic Fungi: A Review

Endophytic fungi are microorganisms that exist almost ubiquitously inside the various tissues of living plants where they act as an important reservoir of diverse bioactive compounds. Recently, endophytic fungi have drawn tremendous attention from researchers; their isolation, culture, purification, and characterization have revealed the presence of around 200 important and diverse compounds including anticancer agents, antibiotics, antifungals, antivirals, immunosuppressants, and antimycotics. Many of these anticancer compounds, such as paclitaxel, camptothecin, vinblastine, vincristine, podophyllotoxin, and their derivatives, are currently being used clinically for the treatment of various cancers (e.g., ovarian, breast, prostate, lung cancers, and leukemias). By increasing the yield of specific compounds with genetic engineering and other biotechnologies, endophytic fungi could be a promising, prolific source of anticancer drugs. In the future, compounds derived from endophytic fungi could increase treatment availability and cost effectiveness. This comprehensive review includes the putative anticancer compounds from plant-derived endophytic fungi discovered from 1990 to 2020 with their source endophytic fungi and host plants as well as their antitumor activity against various cell lines.

Cure lies in nature: medicinal plants and endophytic fungi in curbing cancer

Success of targeted cancer treatment modalities has generated an ambience of plausible cure for cancer. However, cancer remains to be the major cause of mortality across the globe. The emergence of chemoresistance, relapse after treatment and associated adverse effects has posed challenges to the present therapeutic regimes. Thus, investigating new therapeutic agents of natural origin and delineating the underlying mechanism of action is necessary. Since ages and still in continuum, the phytochemicals have been the prime source of identifying bioactive agents against cancer. They have been exploited for isolating targeted specific compounds to modulate the key regulating signaling pathways of cancer pathogenesis and progression. Capsaicin (alkaloid compound in chilli), catechin, epicatechin, epigallocatechin and epigallocatechin-3-gallate (phytochemicals in green tea), lutein (carotenoid found in yellow fruits), Garcinol (phenolic compound present in kokum tree) and many other naturally available compounds are also very valuable to develop the drugs to treat the cancer. An alternate repository of similar chemical diversity exists in the form of endophytic fungi inhabiting the medicinal plants. There is a high diversity of plant associated endophytic fungi in nature which are potent producers of anti-cancer compounds and offers even stronger hope for the discovery of an efficient anti-cancer drug. These fungi provide various bioactive molecules, such as terpenoids, flavonoids, alkaloids, phenolic compounds, quinines, steroids etc. exhibiting anti-cancerous property. The review discusses the relevance of phytochemicals in chemoprevention and as modulators of miRNA. The perspective advocates the imperative role of anti-cancerous secondary metabolites containing repository of endophytic fungi, as an alternative route of drug discovery.

In silico study for prediction of novel bioactivities of the endophytic fungal alkaloid, mycoleptodiscin B for human targets

Mycoleptodiscin B is a natural product extracted from the endophytic fungus Mycoleptodiscus sp. found in Sri Lanka and Panama with experimentally unexplored activities for human targets. In this study, a computational methodology was applied to determine druggable targets of mycoleptodiscin B. According to the computational toxicity and pharmacokinetics assessment, mycoleptodiscin B was proven to be a suitable drug candidate. Druggable targets for this compound, aromatase, acidic plasma glycoprotein and androgen receptor, were predicted using reverse docking. A two-step validation of those targets was performed using conventional molecular docking and molecular dynamic (MD) simulations, resulting in aromatase being determined as the potential therapeutic target. Based on molecular mechanics/Generalized Born Surface Area (GBSA) free energies and ligand stability inside the active site cavity during its 120 ns MD run, it can be concluded that mycoleptodiscin B is a potent aromatase inhibitor and could be subjected to further in vitro and in vivo experiments in the drug development pipeline. Consequently, natural product chemists can quickly identify the hidden medicinal properties of their miracle compounds using the computational approach applied in this research.

Efficient Protocol for Accurately Calculating 13C Chemical Shifts of Conformationally Flexible Natural Products: Scope, Assessment, and Limitations

An efficient protocol for calculating ¹³C NMR chemical shifts for natural products with multiple degrees of conformational freedom is described. This involves a multistep procedure starting from molecular mechanics and ending with a large basis set density functional model to obtain accurate Boltzmann conformer weights, followed by empirically corrected density functional NMR calculations for the individual conformers. The accuracy of the protocol (average rms <4 ppm) was determined by application to ∼925 diverse natural products, the structures of which have been confirmed either by X-ray crystallography or independent synthesis. The protocol was then applied to ∼ 2275 natural products, the structures of which were elucidated mainly by NMR and MS data. Five to ten percent of the latter compounds exhibited rms errors significantly in excess of 4 ppm, suggesting possible structural or signal assignment errors. Both data sets are available from an online browser ( NMR.wavefun.com ). The procedure can be and has been fully automated and is practical using present-generation personal computers, requiring a few hours or days depending on the size of the molecule and number of accessible conformers.

Re-evaluation of Mycoleptodiscus species and morphologically similar fungi

Mycoleptodiscus includes plant pathogens, animal opportunists, saprobic and endophytic fungi. The present study presents the first molecular phylogeny and revision of the genus based on four loci, including ITS, LSU, rpb2, and tef1. An extensive collection of Mycoleptodiscus cultures, including ex-type strains from the CBS, IMI, MUCL, BRIP, clinical isolates from the USA, and fresh isolates from Brazil and Spain, was studied morphologically and phylogenetically to resolve their taxonomy. The study showed that Mycoleptodiscus sensu lato is polyphyletic. Phylogenetic analysis places Mycoleptodiscus in Muyocopronales (Dothideomycetes), together with Arxiella, Leptodiscella, Muyocopron, Neocochlearomyces, and Paramycoleptodiscus. Mycoleptodiscus terrestris, the type species, and M. sphaericus are reduced to synonyms, and one new species is introduced, M. suttonii. Mycoleptodiscus atromaculans, M. coloratus, M. freycinetiae, M. geniculatus, M. indicus, M. lateralis (including M. unilateralis and M. variabilis as its synonyms) and M. taiwanensis belong to Muyocopron (Muyocopronales, Dothideomycetes), and M. affinis, and M. lunatus to Omnidemptus (Magnaporthales, Sordariomycetes). Based on phylogenetic analyses we propose Muyocopron alcornii sp. nov., a fungus associated with leaf spots on Epidendrum sp. (Orchidaceae) in Australia, Muyocopron zamiae sp. nov. associated with leaf spots on Zamia (Zamiaceae) in the USA, and Omnidemptus graminis sp. nov. isolated from a grass (Poaceae) in Spain. Furthermore, Neomycoleptodiscus venezuelense gen. & sp. nov. is introduced for a genus similar to Mycoleptodiscus in Muyocopronaceae.

Total synthesis of natural productsviairidium catalysis

An overview of the highlights in total synthesis of natural products using iridium as a catalyst is given.

Fungal Identification Using Molecular Tools: A Primer for the Natural Products Research Community

Fungi are morphologically, ecologically, metabolically, and phylogenetically diverse. They are known to produce numerous bioactive molecules, which makes them very useful for natural products researchers in their pursuit of discovering new chemical diversity with agricultural, industrial, and pharmaceutical applications. Despite their importance in natural products chemistry, identification of fungi remains a daunting task for chemists, especially those who do not work with a trained mycologist. The purpose of this review is to update natural products researchers about the tools available for molecular identification of fungi. In particular, we discuss (1) problems of using morphology alone in the identification of fungi to the species level; (2) the three nuclear ribosomal genes most commonly used in fungal identification and the potential advantages and limitations of the ITS region, which is the official DNA barcoding marker for species-level identification of fungi; (3) how to use NCBI-BLAST search for DNA barcoding, with a cautionary note regarding its limitations; (4) the numerous curated molecular databases containing fungal sequences; (5) the various protein-coding genes used to augment or supplant ITS in species-level identification of certain fungal groups; and (6) methods used in the construction of phylogenetic trees from DNA sequences to facilitate fungal species identification. We recommend that, whenever possible, both morphology and molecular data be used for fungal identification. Our goal is that this review will provide a set of standardized procedures for the molecular identification of fungi that can be utilized by the natural products research community.

A new helvolic acid derivative from an endophytic Fusarium sp. of Ficus carica

A new helvolic acid derivative named helvolic acid methyl ester (1), together with two known helvolic acid compounds, helvolic acid (2) and hydrohelvolic acid (3), were isolated from the fermentation of endophytic fungus Fusarium sp. in Ficus carica leaves. Their structures were elucidated and identified by spectroscopic methods. Compounds 1-3 showed potent antifungal and antibacterial activities.

Cytotoxic and Antibiotic Cyclic Pentapeptide from an Endophytic Aspergillus tamarii of Ficus carica

A new cyclic pentapeptide, disulfide cyclo-(Leu-Val-Ile-Cys-Cys) (1), named malformin E, together with 13 known cyclic dipeptides, was isolated from the culture broth of endophytic fungus FR02 from the roots of Ficus carica. The strain FR02 was identified as Aspergillus tamarii on the basis of morphological characteristics and molecular analyses of internal transcribed spacer (ITS). Their structures were determined by the combination of 1D and 2D NMR spectroscopy, HRMS (ESI), UV, and Marfey's analysis. Compound 1 exhibited strong cytotoxic activities against human cancer cell strains MCF-7 and A549 with IC50 values of 0.65 and 2.42 μM, respectively. It also displayed remarkable antimicrobial activities against Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Penicillium chrysogenum, Candida albicans, and Fusarium solani with MIC values of 0.91, 0.45, 1.82, 0.91, 3.62, 7.24, and 7.24 μM, respectively.

Expanding Diversity without Protecting Groups: (+)-Sclareolide to Indolosesquiterpene Alkaloid Mycoleptodiscin A and Analogues

Short and scalable synthesis of the complex pentacyclic indolosesquiterpene natural product mycoleptodiscin A has been achieved from commercially available diterpenoid (+)-sclareolide in 19% overall yield. This approach allows one to prepare various analogues of mycoleptodiscin using McMurry cyclization as a key reaction with just three chromatographic purifications.

Chemical constituents and their antibacterial activity from the tropical endophytic fungus Diaporthe sp. F2934

AIMS

To isolate, characterize and determine the antibacterial activities of compounds produced by the endophytic fungus Diaporthe sp. F2934, cultivated on malt extract agar.

METHODS AND RESULTS

The fungus was cultivated aseptically in Petri dishes containing malt extract agar at 25°C for 15 days. Crude extract was obtained from mycelium using ethyl acetate and sonication, and was fractioned using classic chromatography and HPLC. The structures of phomosines and chromanones were established by NMR experiments including HMQC, HMBC and COSY. Their molecular formulas were determined by ESI-TOFMS. We obtained six compounds: (1) 4H-1-benzopyra-4-one-2,3-dihydro-5-hydroxy-2,8-dimetyl, (2) 4H-1-benzopyran-4-one-2,3-dihydro-5-hydroxy-8-(hydroxylmethyl)-2-methyl, (3) 4H-1-benzopyra-4-one-2,3-dihydro-5-methoxyl-2,8-dimetyl, (4) phomosine A, (5) phomosine D and (6) phomosine C. Isolated compounds 1, 2 and 5 were inactive against 15 micro-organisms, but phomosines A and C were active against diverse Gram-negative and Gram-positive bacteria.

CONCLUSIONS

A group of new chromanones and known phomosines have been isolated from the genus Diaporthe (Diaporthe sp. F2934). The results obtained confirm the wide chemical diversity produced by endophytic fungi, specifically the genus Diaporthe. In addition, phomosines A and C may be considered as antimicrobial agents that can be used to guide the development of new antibiotics.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our phylogenetic analysis places Diaporthe sp. F2934 as sister to the Diaporthe cynaroidis clade. Three chromanones were isolated and identified, for the first time, using crude extract obtained from Diaporthe F2934. From this extract phomosines A, C and D were also purified. Regarding Staphylococcus aureus, the inhibition zone diameter (IZD) for phomosine A was 20% higher than the standard drug, vancomycin. When cultivated as described here, Diaporthe sp. F2934 produced new and antimicrobial compounds.

Design, Synthesis, and Evaluation of Irciniastatin Analogues: Simplification of the Tetrahydropyran Core and the C(11) Substituents

The design, synthesis, and biological evaluation of irciniastatin A (1) analogues, achieved by removal of three synthetically challenging structural units, as well as by functional group manipulation of the C(11) substituent of both irciniastatins A and B (1 and 2), has been achieved. To this end, we first designed a convergent synthetic route toward the diminutive analogue (+)-C(8)-desmethoxy-C(11)-deoxy-C(12)-didesmethylirciniastatin (6). Key transformations include an acid-catalyzed 6-exo-tet pyran cyclization, a chiral Lewis acid mediated aldol reaction, and a facile amide union. The absolute configuration of 6 was confirmed via spectroscopic analysis (CD spectrum, HSQC, COSY, and ROESY NMR experiments). Structure–activity relationship (SAR) studies of 6 demonstrate that the absence of the three native structural units permits access to analogues possessing cytotoxic activity in the nanomolar range. Second, manipulation of the C(11) position, employing late-stage synthetic intermediates from our irciniastatin syntheses, provides an additional five analogues (7–11). Biological evaluation of these analogues indicates a high functional group tolerance at position C(11).

Host associations and beta diversity of fungal endophyte communities in New Guinea rainforest trees

Processes shaping the distribution of foliar fungal endophyte species remain poorly understood. Despite increasing evidence that these cryptic fungal symbionts of plants mediate interactions with pathogens and herbivores, there remain basic questions regarding the extent to which dispersal limitation and host specificity might shape fungal endophyte community composition in rainforests. To assess the relative importance of spatial pattern and host specificity, we isolated fungi from a sample of mapped trees in lowland Papua New Guinea. Sequences of the internal transcribed spacer (ITS) region were obtained for 2079 fungal endophytes from three sites and clustered into molecular operational taxonomic units (MOTUs) at 95% similarity. Multivariate analyses suggest that host affinity plays a significant role in structuring endophyte community composition whereas there was no evidence of endophyte spatial pattern at the scale of tens to hundreds of metres. Differences in endophyte communities between sampled trees were weakly correlated with variation in foliar traits but not with tree species relatedness. The dominance of relatively few generalist endophytes and the presence of a large number of rare MOTUs was a consistent observation at three sites separated by hundreds of kilometres and regional turnover was low. Host specificity appears to play a relatively weak but more important role than dispersal limitation in shaping the distribution of fungal endophyte communities in New Guinea forests. Our results suggest that in the absence of strong ecological gradients and host turnover, beta diversity of endophyte communities could be low in large areas of contiguous forest.

A new furan derivative from an endophytic Aspergillus flavus of Cephalotaxus fortunei

A new furan derivative named 5-acetoxymethylfuran-3-carboxylic acid (2), together with a known furan compound, 5-hydroxymethylfuran-3-carboxylic acid (1), were isolated from the fermentation of Aspergillus flavus, endophytic fungi in Cephalotaxus fortunei. The structures of 1 and 2 were elucidated by NMR, IR, UV and MS data, as well as compared with literature data. The compounds 1 and 2 exhibited potent antibacterial activity against Staphylococcus aureus with MIC values of 31.3 and 15.6 μg/mL, respectively. The compound 2 showed moderate antioxidant activity.

Endophytic fungi with antitumor activities: Their occurrence and anticancer compounds

Plant endophytic fungi have been recognized as an important and novel resource of natural bioactive products, especially in anticancer application. This review mainly deals with the research progress on the production of anticancer compounds by endophytic fungi between 1990 and 2013. Anticancer activity is generally associated with the cytotoxicity of the compounds present in the endophytic fungi. All strains of endophytes producing antitumor chemicals were classified taxonomically and the genera of Pestalotiopsis and Aspergillus as well as the taxol producing endophytes were focused on. Classification of endophytic fungi producing antitumor compounds has received more attention from mycologists, and it can also lead to the discovery of novel compounds with antitumor activity due to phylogenetic relationships. In this review, the structures of the anticancer compounds isolated from the newly reported endophytes between 2010 and 2013 are discussed including strategies for the efficient production of the desired compounds. The purpose of this review is to provide new directions in endophytic fungi research including integrated information relating to its anticancer compounds.