Sinopestalotiollides A–D, cytotoxic diphenyl ether derivatives from plant endophytic fungus Pestalotiopsis palmarum

Endophytic Fungi: Cellular factories of novel medicinal chemistries

Inflammation and associated disorders have been a major contributing factor to mortality worldwide. The augmented mortality rate and emerging resistance against the approved therapeutics necessitate the discovery of novel chemistries destined for multiple clinical settings. Cellular factories including endophytic fungi have been tapped for chemical diversity with therapeutic potential. The emerging evidence has suggested the potential of bioactive compounds isolated from the endophytic fungi as putative agents to combat inflammation-associated disorders. The review summarizesand assists the readers in comprehending the structural and functional aspects of the medicinal chemistries identified from endophytic fungi as anticancer, antiobesity, antigout, and immunomodulatory agents.

Penicillides from Penicillium and Talaromyces: Chemical Structures, Occurrence and Bioactivities

Penicillide is the founder product of a class of natural products of fungal origin. Although this compound and its analogues have been identified from taxonomically heterogeneous fungi, they are most frequently and typically reported from the species of Talaromyces and Penicillium. The producing strains have been isolated in various ecological contexts, with a notable proportion of endophytes. The occurrence of penicillides in these plant associates may be indicative of a possible role in defensive mutualism based on their bioactive properties, which are also reviewed in this paper. The interesting finding of penicillides in fruits and seeds of Phyllanthus emblica is introductory to a new ground of investigation in view of assessing whether they are produced by the plant directly or as a result of the biosynthetic capacities of some endophytic associates.

Diphenyl ethers from endophytic fungus Rhexocercosporidium sp. Dzf14 and their antibacterial activity by affecting homeostasis of cell membranes

BACKGROUND

Phytopathogenic bacteria cause severe losses to crops every year. The management of crop bacterial diseases with chemical agents has been considered as the main strategy. In order to cope with the bactericide resistance made by the pathogens, new antibacterials need to be continuously developed.

RESULTS

A chemical investigation from the endophytic fungus Rhexocercosporidium sp. Dzf14 has led to the isolation of 12 diphenyl ethers including two new ones named rhexocerin E (1) and rhexocercosporin G (2), along with two new depsides named rhexocerdepsides A (3) and B (4). The structures and absolute configurations of the new compounds were determined through comprehensive analysis of spectroscopic data and quantum chemical ECD calculations. Diphenyl ethers showed obviously antibacterial activity on Gram-positive bacteria. The structure-activity relationship of diphenyl ethers revealed that prenylation was critical to the antibacterial activity. Among them, rhexocercosporin D (12) possessed the strongest activity against Clavibacter michiganensis and Bacillus subtilis, and was selected for further mechanistic studies. It was found that rhexocercosporin D displayed bactericidal activity by affecting homeostasis of cell membranes. In addition to its rapid bactericidal effects on Gram-positive bacteria, rhexocercosporin D could restore the susceptibility against Gram-negative Agrobacterium tumefaciens by synergistic action with colistin.

CONCLUSION

Twelve diphenyl ethers and two depsides were isolated from endophytic fungus Rhexocercosporidium sp. Dzf14. Isopentenyl was critical for diphenyl ethers against Gram-positive bacteria. Rhexocercosporin D could affect homeostasis of bacterial cell membrane to exert rapid bactericidal activity. These findings highlight the antibacterial potential of the diphenyl ethers in crop bacterial disease management. © 2024 Society of Chemical Industry.

MPoMA protects against lung epithelial cell injury via p65 degradation

Numerous cases of lung injury caused by viral infection were reported during the coronavirus disease-19 pandemic. While there have been significant efforts to develop drugs that block viral infection and spread, the development of drugs to reduce or reverse lung injury has been a lower priority. This study aimed to identify compounds from a library of compounds that prevent viral infection that could reduce and prevent lung epithelial cell damage. We investigated the cytotoxicity of the compounds, their activity in inhibiting viral spike protein binding to cells, and their activity in reducing IL-8 production in lung epithelial cells damaged by amodiaquine (AQ). We identified N-(4-(4-methoxyphenoxy)-3-methylphenyl)-N-methylacetamide (MPoMA) as a non-cytotoxic inhibitor against viral infection and AQ-induced cell damage. MPoMA inhibited the expression of IL-8, IL-6, IL-1β, and fibronectin induced by AQ and protected against AQ-induced morphological changes. However, MPoMA did not affect basal IL-8 expression in lung epithelial cells in the absence of AQ. Further mechanistic analysis confirmed that MPoMA selectively promoted the proteasomal degradation of inflammatory mediator p65, thereby reducing intracellular p65 expression and p65-mediated inflammatory responses. MPoMA exerted potent anti-inflammatory and protective functions in epithelial cells against LPS-induced acute lung injury in vivo. These findings suggest that MPoMA may have beneficial effects in suppressing viral infection and preventing lung epithelial cell damage through the degradation of p65 and inhibition of the production of inflammatory cytokines.

Synthesis of Novel Diphenyl Ether-Based Bis-Heterocycles as Novel Hybrid Molecules via Michael and Other Cyclocondensation Reactions

Molecular hybridization is a technique used in drug creation that involves combining the pharmacophoric moieties of multiple bioactive compounds to create a new hybrid molecule with better affinity and effectiveness. In this regard, we created unique hybrid molecules out of diphenyl ether-linked fused pyrans and other heterocycles. The Michael reaction of 4,4'-oxydibenzaldehyde with malononitrile and various active methylene derivatives, as well as enaminone derivatives, produced the matching bis-fused pyrans and fused pyridines, both connected to a diphenyl ether moiety. Furthermore, the acid-catalyzed reaction of 4,4'-oxydibenzaldehyde with dimedone or β-naphthol produced the corresponding new bis(hexahydro-1H-xanthene-1,8-dione) and bis(14H-dibenzo[a,j]xanthene). The processes by which the target products are formed were also examined.

Recent advances on Pestalotiopsis genus: chemistry, biological activities, structure-activity relationship, and biosynthesis

Strains of the fungal genus Pestalotiopsis are reported as large promising sources of structurally varied biologically active metabolites. Many bioactive secondary metabolites with diverse structural features have been derived from Pestalotiopsis. Moreover, some of these compounds can potentially be developed into lead compounds. Herein, we have systematically reviewed the chemical constituents and bioactivities of the fungal genus Pestalotiopsis, covering a period ranging from January 2016 to December 2022. As many as 307 compounds, including terpenoids, coumarins, lactones, polyketides, and alkaloids, were isolated during this period. Furthermore, for the benefit of readers, the biosynthesis and potential medicinal value of these new compounds are also discussed in this review. Finally, the perspectives and directions for future research and the potential applications of the new compounds are summarized in various tables.

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.

Two new sesquiterpenoids from plant endophytic fungus Flammulina velutipes

Two new sesquiterpenoids, flammupin A (1) and flammupin B (2), along with two known compounds, enokipodin C (3) and 5,5'-dibuthoxy-2,2'-bifuran (4) were obtained from Flammulina velutipes, an endophytic fungus isolated from the roots of Caulophyllum robustum Maxim. The structures were elucidated by the combination of HR-ESI-MS, NMR, and ECD analyses. Compound 3 exhibited moderate to potent cytotoxicity against A549, HeLa, and SMMC-7721 cells with IC₅₀ values ranged from 3.69 to 11.84 μM.

Pestalotiopsis Diversity: Species, Dispositions, Secondary Metabolites, and Bioactivities

Pestalotiopsis species have gained attention thanks to their structurally complex and biologically active secondary metabolites. In past decades, several new secondary metabolites were isolated and identified. Their bioactivities were tested, including anticancer, antifungal, antibacterial, and nematicidal activity. Since the previous review published in 2014, new secondary metabolites were isolated and identified from Pestalotiopsis species and unidentified strains. This review gathered published articles from 2014 to 2021 and focused on 239 new secondary metabolites and their bioactivities. To date, 384 Pestalotiopsis species have been discovered in diverse ecological habitats, with the majority of them unstudied. Some may contain secondary metabolites with unique bioactivities that might benefit pharmacology.

Sinomenium acutum: A Comprehensive Review of its Botany, Phytochemistry, Pharmacology and Clinical Application

Sinomenium acutumis the dry stem of Sinomenium acutum (Thunb.) Rehd et Wils. (S. acutum) and Sinomenium acutum(Thunb.) Rehd. et Wils. var. cinereumRehd. et Wils and is mainly distributed in China and Japan. As a traditional Chinese medicine (TCM) for dispelling wind and dampness in China, it is widely distributed and has a long history of drug use. In recent years, with the increase of the incidence of rheumatoid disease, S. acutum has become the focus of research. This paper reviews the literature on the chemical constituents, pharmacological effects, clinical applications and pharmacokinetics and safety of S. acutum from the past 60 years. At present, more than 210 natural compounds have been isolated from S. acutum, including alkaloids, lignans, triterpenoid saponins, steroids, and other structures. Pharmacological activities of S. acutum were mainly reported on anti-inflammatory, analgesic, anti-allergic, immunosuppressive, anti-tumor, liver-protective, anti-oxidative, and other effects, and clinical applications were mainly recorded on rheumatoid arthritis, ankylosing spondylitis, and other diseases. The clinical use of SIN has fewer side effects and more safety; only a small number of gastrointestinal reactions occurred, and the symptoms disappeared after the drug stopped. The purpose of this paper is to lay a foundation and provide reference for the follow-up research and wide application of S. acutum.

Acrocalyenes A and B, Two New Diterpenoids from Sinomenium acutum Associated Fungus Acrocalymma sp

We identified two new diterpenoidal acrocalyenes A (1) and B (2) through chemical investigation on Acrocalymma sp., a plant-associated fungus from the tender stem isolates of Sinomenium acutum collected from the Qinling Mountains, along with seven already-recognized compounds (3-9). The HR-ESI-TOF-MS and 1D/2D NMR data were utilized for structural elucidation of these compounds, and the single-crystal X-ray diffraction was employed for absolute configuration clarification of the novel acrocalyenes 1 and 2. Bioassays revealed that the cytotoxicities of compounds 2, 4, 6, 7, and 8 against three human carcinoma cells (RKO, HeLa and HCC-1806) were moderate to strong, with IC₅₀ between 6.70-38.82 μM. These isolates were also evaluated for their fungal resistant potentials against Botrytis cinerea, Fusarium culmorum and Fusarium solani, in which 3 displayed significant inhibitory effects on all three phytopathogenic fungi, showing respective MIC of 50, 25 and 25 μM.

Neopestolides A-D, Diphenyl Ether Derivatives from the Plant Endophytic Fungus Neopestalotiopsis sp

Four new diphenyl ether derivatives, neopestolides A-D (2-5), were isolated from cultures of the plant endophytic fungus Neopestalotiopsis sp., along with the known metabolite pestalotiollide A (1); their structures were elucidated primarily by NMR experiments. The absolute configurations of 2 and 3-5 were deduced by electronic circular dichroism calculations and via Snatzke's method, respectively. Compounds 2-4 incorporate tetrahydrofuran moieties attached to the dibenzo[b,g][1,5]dioxocin-5(7H)-one skeleton via C-C linkages. Compounds 1 and 2 showed modest cytotoxicity against HepG2 cells.

Endophytic fungi: A treasure trove of novel anticancer compounds

Cancer is a multifactorial disease with a convoluted genesis and progression. The emergence of multidrug resistance to presently be offered drug and relapse is by far, the most critical concern to tackle this deteriorating disease. Henceforth, there is undeniably an inflated necessity for safe, promising, and less harmful new anticancer drugs. Natural compounds from various sources like plants, animals, and microorganisms have occupied a center stage in drug discovery due to their tremendous chemical diversity and potential as therapeutic agents. Endophytic microbes are symbiotically associated with plants and have been proven to produce novel or analogues of host bioactive metabolites exhibiting a variety of biological activities including anticancer activity. This review emphasizes on structurally diverse unprecedented anticancer natural compounds that have been reported exclusively from endophytic fungi from 2016 to 2020. It covers chemical nature of metabolites, its fungal source associated with terrestrial, as well as marine plants and anticancer activity based on their cytotoxicity profile against various cancer cell lines. Many of these fungal metabolites with promising anticancer activity can be used as lead molecules for in silico experiments and deserve special attention from scientists for further in vitro and clinical research.

Penipyrols C-G and methyl-penipyrol A, α-pyrone polyketides from the mangrove derived fungus Penicillium sp. HDN-11-131

Six new α-pyrone polyketides, penipyrols C-G (1-5) and methyl-penipyrol A (6), together with one biogenetically related known compound, penipyrol A (7), were isolated from the extract of fungus Penicillium sp. HDN-11-131. Their structures including the absolute configurations were established by extensive spectroscopic analysis, Mosher's method, and ECD calculations as well as biogenic considerations. Compounds 1-4 possess a rare skeleton featuring γ-butyrolactone linked to α-pyrone ring through double bond. Compound 1 can induce pancreatic β-cell regeneration in zebrafish at 10 μM, which demonstrated promising anti-diabetes potential.

Expedient Discovery for Novel Antifungal Leads Targeting Succinate Dehydrogenase: Pyrazole-4-formylhydrazide Derivatives Bearing a Diphenyl Ether Fragment

The pyrazole-4-carboxamide scaffold containing a flexible amide chain has emerged as the molecular skeleton of highly efficient agricultural fungicides targeting succinate dehydrogenase (SDH). Based on the above vital structural features of succinate dehydrogenase inhibitors (SDHI), three types of novel pyrazole-4-formylhydrazine derivatives bearing a diphenyl ether moiety were rationally conceived under the guidance of a virtual docking comparison between bioactive molecules and SDH. Consistent with the virtual verification results of a molecular docking comparison, the in vitro antifungal bioassays indicated that the skeleton structure of title compounds should be optimized as an N'-(4-phenoxyphenyl)-1H-pyrazole-4-carbohydrazide scaffold. Strikingly, N'-(4-phenoxyphenyl)-1H-pyrazole-4-carbohydrazide derivatives 11o against Rhizoctonia solani, 11m against Fusarium graminearum, and 11g against Botrytis cinerea exhibited excellent antifungal effects, with corresponding EC₅₀ values of 0.14, 0.27, and 0.52 μg/mL, which were obviously better than carbendazim against R. solani (0.34 μg/mL) and F. graminearum (0.57 μg/mL) as well as penthiopyrad against B. cinerea (0.83 μg/mL). The relative studies on an in vivo bioassay against R. solani, bioactive evaluation against SDH, and molecular docking were further explored to ascertain the practical value of compound 11o as a potential fungicide targeting SDH. The present work provided a non-negligible complement for the structural optimization of antifungal leads targeting SDH.

Anti-inflammatory and cytotoxic agents from Xylaria sp. SWUF09-62 fungus

The ongoing search for anti-cancer agents from microorganisms led to the isolation of four new compounds including 6-ethyl-8-hydroxy-4H-chromen-4-one (1), 6-ethyl-7,8-dihydroxy-4H-chromen-4-one (2), (3S)-3,4-dihydro-8-hydroxy-7-methoxy-3-methylisocoumarin (3) and (3S)-3,4-dihydro-5,7,8-trihydroxy-3-methylisocoumarin (4), together with eleven known compounds (5-15) from Xylaria sp. SWUF09-62 fungus. The chemical structures were deduced from IR, 1D and 2D NMR, and MS data. The absolute configurations of 3 and 4 were determined by ECD experiment. Compounds 2 and 4 indicated possible chemo-prevention and chemo-therapeutic properties, exhibited anti-inflammatory properties by reducing nitric oxide production in LPS-stimulated RAW264.7 cells (IC₅₀ = 1.57 ± 0.25 and 3.02 ± 0.27 μg/mL) and cytotoxicity against HT29 cells (IC₅₀ = 16.46 ± 0.48 and 97.78 ± 7.14 μg/mL).

Diphenyl Ethers from a Marine-Derived Aspergillus sydowii

Six new diphenyl ethers (1⁻6) along with eleven known analogs were isolated from the ethyl acetate extract of a marine-derived Aspergillus sydowii guided by LC-UV-MS. Their structures were unambiguously characterized by HRESIMS, NMR, as well as chemical derivatization. Compounds 1 and 2 are rare diphenyl ether glycosides containing d-ribose. The absolute configuration of the sugar moieties in compounds 1⁻3 was determined by a LC-MS method. All the compounds were evaluated for their cytotoxicities against eight cancer cell lines, including 4T1, U937, PC3, HL-60, HT-29, A549, NCI-H460, and K562, and compounds 1, 5, 6, and 8⁻11 were found to exhibit selective cytotoxicity against different cancer cell lines.

Xylarianins A-D from the endophytic fungus Xylaria sp. SYPF 8246 as natural inhibitors of human carboxylesterase 2

Eighteen secondary metabolites were isolated from the fermentation broth of the endophytic fungus Xylaria sp. SYPF 8246, including four new compounds, xylarianins A-D (1-4), three new natural products, 6-methoxycarbonyl-2'-methyl-3,5,4',6'-tetramethoxy-diphenyl ether (5), 2-chlor-6-methoxycarbonyl-2'-rnethyl-3,5,4',6'-tetramethoxy-diphenyl ether (6), and 2-chlor-4'-hydroxy-6-methoxy carbonyl-2'-methyl-3,5,6'-trimethoxy-diphenyl ether (7), and eleven known compounds (8-18). Their structural elucidations were conducted by using 1D and 2D NMR, HRESIMS, and Rh₂(OCOCF₃)₄-induced electronic circular dichroism (ECD) spectra analyses. The integrated ¹H and ¹³C NMR data of three new natural products 5-7 were reported for the first time. All the isolated compounds were assayed for their inhibitory activities against human carboxylesterase 2 (hCE 2). Compounds 1, 5-9, and 18 displayed significant inhibitory activities against hCE 2 with IC₅₀ values of 10.43 ± 0.51, 6.69 ± 0.85, 12.36 ± 1.27, 18.25 ± 1.78, 29.78 ± 0.48, 18.86 ± 1.87, and 20.72 ± 1.51 µM, respectively. The interactions between compounds 1 and 5 with hCE 2 were anaylzed by molecular docking.

Novel natural compounds from endophytic fungi with anticancer activity

Plant endophytes are microorganisms that live in healthy plant tissues in part or all of their life history without causing obvious symptoms of infection in the host plants. Endophytes, a new type of microbial resource that can produce a variety of biological constituents, have great values for research and broad prospects for development. This article reviewed the research and development progress of endophytic fungi with cytotoxic activity between 2014 and 2017, including endophytic fungi sources, microbial taxonomy, compound classification and cytotoxic activity. The results showed that the 109 strains of endophytic fungi belong to 3 phyla, 7 classes and 50 genera. The secondary metabolites mainly contained alkaloids, terpenes, steroids, polyketides, quinones, isocoumarins, esters etc. The results of this study provide references for the development of new antitumor drugs and endophytes resources.