Cytotoxic cytochalasans from fungus Xylaria longipes

The Cytochalasins and Polyketides from a Mangrove Endophytic Fungus Xylaria arbuscula QYF

Twelve compounds, including four undescribed cytochalasins, xylariachalasins A-D (1-4), four undescribed polyketides (5-8), and four known cytochalasins (9-12), were isolated from the mangrove endophytic fungus Xylaria arbuscula QYF. Their structures and absolute configurations were established by extensive spectroscopic analyses (1D and 2D NMR, HRESIMS), electronic circular dichroism (ECD) calculations, 13C NMR calculation and DP4+ analysis, single-crystal X-ray diffraction, and the modified Mosher ester method. Compounds 1 and 2 are rare cytochalasin hydroperoxides. In bioactivity assays, Compound 2 exhibited moderate antimicrobial activities against Staphylococcus aureus and Candida albicans with MIC values of 12.5 μM for both Compound 10 exhibited significant cytotoxic activity against MDA-MB-435 with an IC50 value of 3.61 ± 1.60 μM.

Xylatolides A and B, new 10-membered macrolides from the endophytic fungus Xylaria sp

Chemical investigation of the fungal endophyte Xylaria sp. isolated from leaves of Moringa oleifera, collected in Cameroon, resulted in the previously undescribed 10-membered macrolide, and two known natural products. The structures of the xylatolides A and B were unambiguously identified by their mass spectra and by extensive 1D and 2D NMR spectroscopic analysis, featuring a 10-membered lactone core structure with oxygenated substituents and an unsubstituted 10-alkyl chain presenting seven carbon atoms. Compounds were screened for their cytotoxic potential against the human HepG2 hepatocellular carcinoma cells and HCT-116 cells (human colon carcinoma cell line). Moreover, the isolated compounds were also assayed against a small panel of sensitive strains including the bacterial species Escherichia coli, Staphylococcus aureus, and Mycobacterium tuberculosis as well as against the fungal species Candida albicans. However, no significant activities were found.

Cytotoxic cytochalasans from cultures of the fungus Metarhizium brunneum TBRC-BCC 79240

Fourteen new cytochalasans, brunnesins A-N (1-14), along with eleven known compounds, were isolated from the culture extracts of the insect pathogenic fungus Metarhizium brunneum strain TBRC-BCC 79240. The compound structures were established by spectroscopy, X-ray diffraction analysis, and electronic circular dichroism. Compound 4 exhibited antiproliferative activity against all cell lines tested (mammalian), with 50% inhibition concentration (IC₅₀) values ranging from 2.09 to 16.8 μg mL^-1. Compounds 6 and 16 were shown to be bioactive only against non-cancerous Vero cells (IC₅₀ 4.03 and 0.637 μg mL^-1, respectively) whereas compounds 9 and 12 were bioactive only against NCI-H187 small-cell lung cancer cells (IC₅₀ 18.59 and 18.54 μg mL^-1, respectively). Compounds 7, 13, and 14 showed cytotoxicity against NCI-H187 and Vero cell lines with IC₅₀ values ranging from 3.98-44.81 μg mL^-1.

Rare cytochalasans isolated from the mangrove endophytic fungus Xylaria arbuscula

Four new cytochalasans, arbuschalasins A-D (1-4), along with thirteen known analogues (5-17), were isolated from the solid rice medium of endophytic fungus Xylaria arbuscula. Arbuschalasins A-B feature a rare 5/6/6/6 fused ring system while arbuschalasin D was characterized as the first example of natural cytochalasans that possesses a 5/5/11 fused scaffold. The structures of 1-4 were assigned by spectroscopic data, with their absolute structures being determined by electronic circular dichroism (ECD) calculations. All of the isolates were evaluated against the human colorectal adenocarcinoma cell lines (HCT15). Compounds 6 and 7 showed significant inhibitory effects (IC₅₀ values were 13.5 and 13.4 μM, respectively), being more active than those of the positive control, fluorouracil (103.1 μM).

Asperflavipines C–E and aspermichalasine A: three cytochalasan heterotetramers and an unusual cytochalasan monomer from Aspergillus micronesiensis

Asperflavipines C–E, three new cytochalasin heterotetramers, possessing a highly complex tetradecacyclic ring system with continuous bridged ring systems, and aspermichalasine A, possessing an unusual 5/6/5/8 ring system, were isolated.

Zopfiellasins A-D, Two Pairs of Epimeric Cytochalasins from Kiwi-Associated Fungus Zopfiella sp. and Their Antibacterial Assessment

In our continuous search for antibacterial agents against Pseudomonas syringae pv. actinidiae (Psa) from kiwi-associated fungi, two pairs of epimeric cytochalasins, zopfiellasins A-D (1-4), were characterized from the fungus Zopfiella sp. The structures were established on the basis of spectroscopic data analysis, while the absolute configurations were determined by single-crystal X-ray diffraction. Compounds 1 and 3 exhibited antibacterial activity against Psa with MIC values of 25 and 50 μg/mL, respectively. This is the first report of anti-Psa activity of cytochalasin derivatives.

A critical review on the use of DP4+ in the structural elucidation of natural products: the good, the bad and the ugly. A practical guide

Covering: 2015 up to the end of 2020Even in the golden age of NMR, the number of natural products being incorrectly assigned is becoming larger every day. The use of quantum NMR calculations coupled with sophisticated data analysis provides ideal complementary tools to facilitate the elucidation process in challenging cases. Among the current computational methodologies to perform this task, the DP4+ probability is a popular and widely used method. This updated version of Goodman's DP4 synergistically combines NMR calculations at higher levels of theory with the Bayesian analysis of both scaled and unscaled data. Since its publication in late 2015, the use of DP4+ to solve controversial natural products has substantially grown, with several predictions being confirmed by total synthesis. To date, the structures of more than 200 natural products were determined with the aid of DP4+. However, all that glitters is not gold. Besides its intrinsic limitations, on many occasions it has been improperly used with potentially important consequences on the quality of the assignment. Herein we present a critical revision on how the scientific community has been using DP4+, exploring the strengths of the method and how to obtain optimal results from it. We also analyze the weaknesses of DP4+, and the paths to by-pass them to maximize the confidence in the structural elucidation.

Progress in the Chemistry of Cytochalasans

Cytochalasans are a group of fungal-derived natural products characterized by a perhydro-isoindolone core fused with a macrocyclic ring, and they exhibit a high structural diversity and a broad spectrum of bioactivities. Cytochalasans have attracted significant attention from the chemical and pharmacological communities and have been reviewed previously from various perspectives in recent years. However, continued interest in the cytochalasans and the number of laboratory investigations on these compounds are both growing rapidly. This contribution provides a general overview of the isolation, structural determination, biological activities, biosynthesis, and total synthesis of cytochalasans. In total, 477 cytochalasans are covered, including "merocytochalasans" that arise by the dimerization or polymerization of one or more cytochalasan molecules with one or more other natural product units. This contribution provides a comprehensive treatment of the cytochalasans, and it is hoped that it may stimulate further work on these interesting natural products.

Cytochalasins from Xylaria sp. CFL5, an Endophytic Fungus of Cephalotaxus fortunei

Three previously undescribed cytochalasins, named xylariasins A‒C (1‒3), together with six known ones (4‒9) were isolated from Xylaria sp. CFL5, an endophytic fungus of Cephalotaxus fortunei. The chemical structures of all new compounds were elucidated on the basis of extensive spectroscopic data analyses and electronic circular dichroism calculation, as well as optical rotation calculation. Biological activities of compounds 1, 4‒9 were evaluated, including cytotoxic, LAG3/MHC II binding inhibition and LAG3/FGL1 binding inhibition activities. Compounds 6 and 9 possessed cytotoxicity against AGS cells at 5 μM, with inhibition rates of 94% and 64%, respectively. In addition, all tested isolates, except compound 6, exhibited obvious inhibitory activity against the interaction of both LAG3/MHC II and LAG3/FGL1. Compounds 1, 5, 7, and 8 inhibited LAG3/MHC II with IC₅₀ values ranging from 2.37 to 4.74 μM. Meanwhile, the IC₅₀ values of compounds 1, 7, and 8 against LAG3/FGL1 were 11.78, 4.39, and 7.45 μM, respectively.

Biological Activities of Some New Secondary Metabolites Isolated from Endophytic Fungi: A Review Study

Secondary metabolites isolated from plant endophytic fungi have been getting more and more attention. Some secondary metabolites exhibit high biological activities, hence, they have potential to be used for promising lead compounds in drug discovery. In this review, a total of 134 journal articles (from 2017 to 2019) were reviewed and the chemical structures of 449 new metabolites, including polyketides, terpenoids, steroids and so on, were summarized. Besides, various biological activities and structure-activity relationship of some compounds were aslo described.

Cytochalasin H isolated from mangrove-derived endophytic fungus inhibits epithelial-mesenchymal transition and cancer stemness via YAP/TAZ signaling pathway in non-small cell lung cancer cells

Our previous studies have isolated cytochalasin H (CyH) from endophytic fungus derived from mangrove and found that CyH induced apoptosis and inhibited migration and angiogenesis in non-small cell lung cancer (NSCLC) cells. In this study, we further investigated the effect of CyH on epithelial-mesenchymal transition (EMT) and cancer stemness of A549 and NCI-H460 NSCLC cells and the underlying mechanisms, especially the role of YAP/ TAZ signaling pathway in the process. Our results showed that CyH significantly inhibited invasive ability and the sphere formation of NSCLC cells. The expression of E-cadherin, an EMT epithelial marker, was obviously up-regulated, while the expression of Vimentin and N-cadherin, the EMT mesenchymal markers, was dramatically down-regulated by CyH treatment in NSCLC cells. Moreover, the expression of EMT-associated transcription factors including Slug, Twist1, and Snail1 and stemness markers including Nanog, Sox-2, and Oct-4 was significantly down-regulated by CyH treatment in NSCLC cells. Additionally, CyH significantly down-regulated YAP and TAZ expression and up-regulated LAST1/2 and MST1/2 expression, and CyH inhibited the interaction between YAP and TEAD. Furthermore, YAP knockdown abolished the effect of CyH on the expression of EMT- and stemness-related markers in NSCLC cells. Taken together, these results suggest that CyH inhibits EMT and cancer stemness of NSCLC cells via the regulation of YAP/TAZ signaling pathway.

Recent progress in biodiversity research on the Xylariales and their secondary metabolism

The families Xylariaceae and Hypoxylaceae (Xylariales, Ascomycota) represent one of the most prolific lineages of secondary metabolite producers. Like many other fungal taxa, they exhibit their highest diversity in the tropics. The stromata as well as the mycelial cultures of these fungi (the latter of which are frequently being isolated as endophytes of seed plants) have given rise to the discovery of many unprecedented secondary metabolites. Some of those served as lead compounds for development of pharmaceuticals and agrochemicals. Recently, the endophytic Xylariales have also come in the focus of biological control, since some of their species show strong antagonistic effects against fungal and other pathogens. New compounds, including volatiles as well as nonvolatiles, are steadily being discovered from these ascomycetes, and polythetic taxonomy now allows for elucidation of the life cycle of the endophytes for the first time. Moreover, recently high-quality genome sequences of some strains have become available, which facilitates phylogenomic studies as well as the elucidation of the biosynthetic gene clusters (BGC) as a starting point for synthetic biotechnology approaches. In this review, we summarize recent findings, focusing on the publications of the past 3 years.

New curtachalasin from the Xylaria sp. DO 1801

One new cytochalasin, named curtachalasin Q (1), together with 8 known cytochalasins were isolated from the ethyl acetate extract of the Xylaria sp. DO1801. The structure of the new compound was elucidated on the basis of IR, UV, HR-ESI-MS, NMR spectra and X-ray diffraction. Compound 1 and 2 were not cytotoxic (IC₅₀>50uM) against four tumour cell lines (SW-1990, ASPC-1, HepG2 and Hep3B).