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Wennrich JP, Holzenkamp C, Kolařík M, Maier W, Mándi A, Kurtán T, Ashrafi S, Ebada SS, Stadler M. Dactylfungins and Tetralones: Bioactive Metabolites from a Nematode-Associated Laburnicola nematophila. JOURNAL OF NATURAL PRODUCTS 2024; 87:1860-1871. [PMID: 39012621 PMCID: PMC11287750 DOI: 10.1021/acs.jnatprod.4c00623] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2024] [Revised: 06/29/2024] [Accepted: 06/30/2024] [Indexed: 07/17/2024]
Abstract
A chemical investigation of Laburnicola nematophila, isolated from cysts of the plant parasitic nematode Heterodera filipjevi, affored three dactylfungin derivatives (1-3) and three tetralone congeners (4-6). Dactylfungin C (1), laburnicolin (4), and laburnicolenone (5) are previously undescribed natural products. Chemical structures of the isolated compounds were determined based on 1D and 2D NMR spectroscopic analyses together with HR-ESI-MS spectrometry and comparison with data reported in the literature. The relative configurations of compounds 1, 2, and 4-6 were determined based on their ROESY data and analysis of their coupling constants (J values). The absolute configurations of 4-6 were determined through the comparison of their measured and calculated TDDFT-ECD spectra. Compounds 1-3 were active against azole-resistant Aspergillus fumigatus.
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Mándi A, Rimóczi A, Vasas A, Hohmann J, Swamy MMM, Monde K, Barta RA, Kicsák M, Komáromi I, Fehér K, Kurtán T. Testing the Simplified Molecular Dynamics Approach to Improve the Reproduction of ECD Spectra and Monitor Aggregation. Int J Mol Sci 2024; 25:6453. [PMID: 38928181 PMCID: PMC11204327 DOI: 10.3390/ijms25126453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2024] [Revised: 05/30/2024] [Accepted: 06/06/2024] [Indexed: 06/28/2024] Open
Abstract
A simplified molecular-dynamics-based electronic circular dichroism (ECD) approach was tested on three condensed derivatives with limited conformational flexibility and an isochroman-2H-chromene hybrid, the ECD spectra of which could not be precisely reproduced by the conventional ECD calculation protocol. Application of explicit solvent molecules at the molecular mechanics (MD) level in the dynamics simulations and subsequent TDDFT-ECD calculation for the unoptimized MD structures was able to improve the agreements between experimental and computed spectra. Since enhancements were achieved even for molecules with limited conformational flexibility, deformations caused by the solvent molecules and multitudes of conformers produced with unoptimized geometries seem to be key factors for better agreement. The MD approach could confirm that aggregation of the phenanthrene natural product luzulin A had a significant contribution to a specific wavelength range of the experimental ECD. The MD approach has proved that dimer formation occurred in solution and this was responsible for the anomalous ECD spectrum. The scope and limitations of the method have also been discussed.
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Simons VE, Mándi A, Frank M, van Geelen L, Tran-Cong N, Albrecht D, Coort A, Gebhard C, Kurtán T, Kalscheuer R. Colletodiol derivatives of the endophytic fungus Trichocladium sp. Fitoterapia 2024; 175:105914. [PMID: 38508500 DOI: 10.1016/j.fitote.2024.105914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 02/21/2024] [Accepted: 03/16/2024] [Indexed: 03/22/2024]
Abstract
The OSMAC (one strain many compounds) concept is a cultivation-based approach to increase the diversity of secondary metabolites in microorganisms. In this study, we applied the OSMAC-approach to the endophytic fungus Trichocladium sp. by supplementation of the cultivation medium with 2.5% phenylalanine. This experiment yielded five new compounds, trichocladiol (1), trichocladic acid (2), colletodiolic acid (3), colletolactone (4) and colletolic acid (5), together with five previously described ones (6-10). The structures were elucidated via comprehensive spectroscopic measurements, and the absolute configurations of compound 1 was elucidated by using TDDFT-ECD calculations. For formation of compounds 3-5, a pathway based on colletodiol biosynthesis is proposed. Compound 6 exhibited strong antibacterial activity against methicillin-resistant Staphylococcus aureus with a minimal inhibitory concentration (MIC) of 0.78 μM as well as a strong cytotoxic effect against the human monocytic cell line THP1 with an IC50 of 0.7 μM. Compound 8 showed moderate antibacterial activity against Mycobacterium tuberculosis with a MIC of 25 μM and a weak cytotoxic effect against THP1 cells with an IC50 of 42 μM.
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Kajtár M, Király SB, Bényei A, Kiss-Szikszai A, Kónya-Ábrahám A, Zhang N, Horváth LB, Bősze S, Li D, Kotschy A, Paczal A, Kurtán T. Competing Domino Knoevenagel-Cyclization Sequences with N-Arylcinnamylamines. J Org Chem 2024; 89:6937-6950. [PMID: 38691817 DOI: 10.1021/acs.joc.4c00299] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2024]
Abstract
Domino Knoevenagel-cyclization reactions of N-arylcinnamylamines were carried out with active methylene reagents, which took place with five competing cyclization mechanisms: intramolecular hetero Diels-Alder reaction, stepwise polar [2 + 2] cycloaddition, styryl or aza-Diels-Alder reactions followed by rearomatization, and [1,5]-hydride shift-6-endo cyclization. In the stepwise aza-Diels-Alder reaction, the N-vinylpyridinium moiety acted as an azadiene, producing a condensed heterocycle with tetrahydroquinolizinium and tetrahydroquiniline subunits. Antiproliferative activity with low micromolar IC50 values was identified for some of the novel scaffolds.
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Wennrich JP, Ebada SS, Sepanian E, Holzenkamp C, Khalid SJ, Schrey H, Maier W, Mándi A, Kurtán T, Ashrafi S, Stadler M. Omnipolyphilins A and B: Chlorinated Cyclotetrapeptides and Naphtho-α-pyranones from the Plant Nematode-Derived Fungus Polyphilus sieberi. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2024; 72:6998-7009. [PMID: 38507729 PMCID: PMC10995996 DOI: 10.1021/acs.jafc.4c00572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Revised: 02/29/2024] [Accepted: 03/05/2024] [Indexed: 03/22/2024]
Abstract
Chemical exploration for two isolates of the recently described ascomycete species Polyphilus sieberi, derived from the eggs of the plant parasitic nematode Heterodera filipjevi, afforded the identification of many compounds that belong to various metabolite families: two previously undescribed chlorinated cyclotetrapeptides, omnipolyphilins A (1) and B (2), one new pyranonaphthoquinone, ventiloquinone P (3), a 6,6'-binaphto-α-pyranone dimer, talaroderxine D (4) in addition to nine known metabolites (5-13) were isolated from this biocontrol candidate. All isolated compounds were characterized by comprehensive 1D, 2D NMR, and HR-ESI-MS analyses. The absolute configurations of the cyclotetrapeptides were determined by a combination of advanced Marfey's method, ROE correlation aided by conformational analysis, and TDDFT-ECD calculations, while ECD calculations, Mosher's method, and experimental ECD spectra were used for ventiloquinone P (3) and talaroderxine D (4). Among the isolated compounds, talaroderxine D (4) showed potent antimicrobial activities against Bacillus subtilis and Staphylococcus aureus with MIC values of 2.1 and 8.3 μg mL-1, respectively. Additionally, promising inhibitory effects on talaroderxine D (4) against the formation of S. aureus biofilms were observed up to a concentration of 0.25 μg mL-1. Moreover, ophiocordylongiiside A (10) showed activity against the free-living nematode Caenorhabditis elegans.
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Tao L, Yu W, Liu Z, Zhao D, Lin S, Szalóki D, Kicsák M, Kurtán T, Zhang H. JE-133 Suppresses LPS-Induced Neuroinflammation Associated with the Regulation of JAK/STAT and Nrf2 Signaling Pathways. ACS Chem Neurosci 2024; 15:258-267. [PMID: 38181172 DOI: 10.1021/acschemneuro.3c00454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2024] Open
Abstract
Neuroinflammation plays an important role in the pathogenesis of neurodegenerative diseases, and interrupting the microglial-mediated neuroinflammation has been suggested as a promising strategy to delay or prevent the progression of neurodegeneration. In this study, we investigated the effects of JE-133, an optically active isochroman-2H-chromene conjugate containing a 1,3-disubstituted isochroman unit, on lipopolysaccharide (LPS)-induced microglial neuroinflammation and underlying mechanisms both in vitro and in vivo. First, JE-133 treatment decreased LPS-induced overproduction of interleukin-1 beta (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), nitrite, and nitric oxide synthase (iNOS) in BV2 microglial cells. Further study revealed that JE-133 downregulated the phosphorylation level of JAK/STAT and upregulated the protein level of Nrf2/HO-1 in LPS-stimulated BV2 microglial cells and verified that JE-133 directly bound to Keap1 by a pull-down assay. Next, JE-133 administration also inhibited neuroinflammation in vivo, as indicated by a reduced CD11b protein level and an overexpressed mRNA level of the pro-inflammatory cytokine TNF-α in the hippocampus of LPS-injected mice. Moreover, the regulative effects of JE-133 on the JAK/STAT and Nrf2/HO-1 pathways were also verified in the hippocampus of LPS-injected mice. Taken together, our study for the first time reports that JE-133 exhibits inhibitory effects against LPS-stimulated neuroinflammation both in vitro and in vivo, which might be associated with the simultaneous regulation of the JAK/STAT and Nrf2 pathways. Our findings may provide important clues for the discovery of effective drug leads/candidates against neuroinflammation-associated neurodegeneration.
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Varga E, Balázs VL, Sándor V, Agócs A, Nagy V, Király SB, Kurtán T, Molnár P, Deli J. Carotenoid Composition of Telekia speciosa. PLANTS (BASEL, SWITZERLAND) 2023; 12:4116. [PMID: 38140443 PMCID: PMC10747434 DOI: 10.3390/plants12244116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 12/05/2023] [Accepted: 12/06/2023] [Indexed: 12/24/2023]
Abstract
The carotenoid composition of the flower of Telekia speciosa was investigated for the first time by HPLC-DAD-MS. In addition to the main carotenoid lutein and its geometrical isomers, 5,6-epoxy-carotenoids, namely violaxanthin, lutein 5,6-epoxide and antheraxanthin, were detected in larger amounts. In addition, β-carotene 5,6-epoxide and β-carotene 5,6,5',6'-diepoxide were found, which occurs very rarely in plants. For unambigous identification, β-carotene 5,6-epoxide and β-carotene 5,6,5',6'-diepoxide were prepared semisynthetically, and they were characterized by 1H and 13C NMR and HPLC-CD methods.
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Sum W, Ebada SS, Kirchenwitz M, Wanga L, Decock C, Stradal TEB, Matasyoh JC, Mándi A, Kurtán T, Stadler M. Neurite Outgrowth-Inducing Drimane-Type Sesquiterpenoids Isolated from Cultures of the Polypore Abundisporus violaceus MUCL 56355. JOURNAL OF NATURAL PRODUCTS 2023; 86:2457-2467. [PMID: 37910033 PMCID: PMC10683085 DOI: 10.1021/acs.jnatprod.3c00525] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Indexed: 11/03/2023]
Abstract
Abundisporin A (1), together with seven previously undescribed drimane sesquiterpenes named abundisporins B-H (2-8), were isolated from a polypore, Abundisporus violaceus MUCL 56355 (Polyporaceae), collected in Kenya. Chemical structures of the isolated compounds were elucidated based on exhaustive 1D and 2D NMR spectroscopic measurements and supported by HRESIMS data. The absolute configurations of the isolated compounds were determined by using Mosher's method for 1-4 and TDDFT-ECD calculations for 4 and 5-8. None of the isolated compounds exhibited significant activities in either antimicrobial or cytotoxicity assays. Notably, all of the tested compounds demonstrated neurotrophic effects, with 1 and 6 significantly increasing outgrowth of neurites when treated with 5 ng/mL NGF.
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Anwar A, Elnaggar MS, Elissawy AM, Ibrahim N, Mándi A, Kurtán T, Liu Z, El-Ahmady SH, Kalscheuer R. New Meroterpenoid Derivatives from the Pomegranate-Derived Endophytic Fungus Talaromyces purpureogenus. Molecules 2023; 28:7650. [PMID: 38005373 PMCID: PMC10673506 DOI: 10.3390/molecules28227650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Revised: 11/05/2023] [Accepted: 11/14/2023] [Indexed: 11/26/2023] Open
Abstract
In this study, we report the isolation of two new meroterpenoids, miniolutelide D (1) and miniolutelide E (13-epi-miniolutelide C) (2), along with two meroterpenoidal analogues (3 and 4) and two phenolic compounds (5 and 6) from the endophytic fungus Talaromyces purpureogenus derived from Punica granatum fruits. Their structures were elucidated using extensive MS, 1D, and 2D NMR spectroscopic analyses as well as by comparing with data in the literature. The absolute configurations of 1 and 2 were determined using TDDFT-ECD calculations. Antimicrobial activity was evaluated. Compound 5 displayed significant activity against methicillin-resistant Staphylococcus aureus strain ATCC 700699 and moderate activity against S. aureus strain ATCC 29213.
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Sikandar A, Popoff A, Jumde RP, Mándi A, Kaur A, Elgaher WAM, Rosenberger L, Hüttel S, Jansen R, Hunter M, Köhnke J, Hirsch AKH, Kurtán T, Müller R. Revision of the Absolute Configurations of Chelocardin and Amidochelocardin. Angew Chem Int Ed Engl 2023; 62:e202306437. [PMID: 37466921 DOI: 10.1002/anie.202306437] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Revised: 07/17/2023] [Accepted: 07/18/2023] [Indexed: 07/20/2023]
Abstract
Even with the aid of the available methods, the configurational assignment of natural products can be a challenging task that is prone to errors, and it sometimes needs to be corrected after total synthesis or single-crystal X-ray diffraction (XRD) analysis. Herein, the absolute configuration of amidochelocardin is revised using a combination of XRD, NMR spectroscopy, experimental ECD spectra, and time-dependent density-functional theory (TDDFT)-ECD calculations. As amidochelocardin was obtained via biosynthetic engineering of chelocardin, we propose the same absolute configuration for chelocardin based on the similar biosynthetic origins of the two compounds and result of TDDFT-ECD calculations. The evaluation of spectral data of two closely related analogues, 6-desmethyl-chelocardin and its semisynthetic derivative 1, also supports this conclusion.
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Wennrich JP, Sepanian E, Ebada SS, Llanos-Lopez NA, Ashrafi S, Maier W, Kurtán T, Stadler M. Bioactive Naphtho-α-Pyranones from Two Endophytic Fungi of the Genus Polyphilus. Antibiotics (Basel) 2023; 12:1273. [PMID: 37627693 PMCID: PMC10451773 DOI: 10.3390/antibiotics12081273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 07/29/2023] [Accepted: 07/31/2023] [Indexed: 08/27/2023] Open
Abstract
In the course of our survey to study the metabolic potential of two species of a new helotialean genus Polyphilus, namely P. frankenii and P. sieberi, their crude extracts were obtained using different cultivation techniques, which led to the isolation and characterization of two new naphtho-α-pyranone derivatives recognized as a monomer (1) and its 6,6'-homodimer (2) together with two known diketopiperazine congeners, outovirin B (3) and (3S,6S)-3,6-dibenzylpiperazine-2,5-dione (4). The structures of isolated compounds were determined based on extensive 1D and 2D NMR and HRESIMS. The absolute configuration of new naphtho-α-pyranones was determined using a comparison of their experimental ECD spectra with those of related structural analogues. 6,6'-binaphtho-α-pyranone talaroderxine C (2) exhibited potent cytotoxic activity against different mammalian cell lines with IC50 values in the low micromolar to nanomolar range. In addition, talaroderxine C unveiled stronger antimicrobial activity against Bacillus subtilis rather than Staphylococcus aureus with MIC values of 0.52 µg mL-1 (0.83 µM) compared to 66.6 µg mL-1 (105.70 µM), respectively.
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Llanos-López NA, Ebada SS, Vasco-Palacios AM, Sánchez-Giraldo LM, López L, Rojas LF, Mándi A, Kurtán T, Marin-Felix Y. Panapophenanthrin, a Rare Oligocyclic Diterpene from Panus strigellus. Metabolites 2023; 13:848. [PMID: 37512554 PMCID: PMC10385786 DOI: 10.3390/metabo13070848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2023] [Revised: 07/03/2023] [Accepted: 07/11/2023] [Indexed: 07/30/2023] Open
Abstract
During the course of our search for biologically active secondary metabolites from fungal cultures, a new oligocyclic diterpenoidal derivative, panapophenanthrin (1), was isolated from Panus strigellus. In addition, two known metabolites, panepophenanthrin (2) and dihydrohypnophilin (3), were also obtained. The chemical structures of the isolated compounds were elucidated based on extensive 1D and 2D NMR spectral analyses together with high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). The absolute configuration was determined through TDDFT-ECD calculations. All of the compounds were assessed for their antimicrobial and cytotoxic activities. Compounds 1 and 3 showed moderate to weak activities in the performed antimicrobial assays, while compound 1 exhibited potent cytotoxic activity against the mammalian cell lines mouse fibroblast (L929) and human endocervical adenocarcinoma (KB3.1).
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Wang L, Kiffe-Delf AL, Ostermann PN, Simons VE, He D, Gao Y, van Geelen L, Dai HF, Zhao YX, Schaal H, Mándi A, Király SB, Kurtán T, Liu Z, Kalscheuer R. Asperphenalenones Isolated from the Biocontrol Agent Clonostachys rosea and Their Antimicrobial Activities. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2023. [PMID: 37436951 DOI: 10.1021/acs.jafc.3c00447] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/14/2023]
Abstract
Clonostachys rosea is a fungus widely distributed on Earth and has a high capacity to adapt to complex environments in soil, plants, or sea. It is an endophyte that can be used as a potential biocontrol agent to protect plants from pathogenic fungi, nematodes, and insects. However, the spectrum of secondary metabolites produced by C. rosea has only scarcely been studied. In the present study, eight new phenalenones, asperphenalenones F-M (1-8), together with two known derivatives, asperphenalenones E and B (9 and 10), were isolated from the axenic rice culture of this fungus. The structures of the new compounds were elucidated by nuclear magnetic resonance, high-resolution electrospray ionization mass spectrometry, electronic circular dichroism, and gas chromatography-mass spectrometry analyses. Asperphenalenones J-M (5-8) are unusual phenalenone adducts that are conjugated to diterpenoid glycosides. Asperphenalenones F and H showed moderate antibacterial activity against methicillin-resistant Staphylococcus aureus, with minimal inhibitory concentrations of 12.5 and 25 μM, respectively. Asperphenalenone B exhibited low antiviral activity against the human immunodeficiency virus replication. Furthermore, asperphenalenones F and H exhibited low cytotoxicity against Jurkat cells, while all other compounds were devoid of cytotoxicity.
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Elnaggar MS, Elissawy AM, Youssef FS, Kicsák M, Kurtán T, Singab ANB, Kalscheuer R. Austalide derivative from marine-derived Aspergillus sp. and evaluation of its cytotoxic and ADME/TOPKAT properties. RSC Adv 2023; 13:16480-16487. [PMID: 37274397 PMCID: PMC10233426 DOI: 10.1039/d3ra02632a] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2023] [Accepted: 05/22/2023] [Indexed: 06/06/2023] Open
Abstract
In-depth chemical investigation of an ethyl acetate extract of Aspergillus sp. isolated from the soft coral Sinularia species resulted in the isolation of one new meroterpenoid, austalide Z (1), one known austalide W (2), six known prenylated indole diketopiperazine alkaloids (3-8), and phthalic acid and its ethyl derivative (9-10). The structures were established by means of 1D and 2D NMR (one- and two-dimensional nuclear magnetic resonance) experiments supported by UV analysis and ESI-MS (electrospray ionization mass spectrometry). In vitro cytotoxic evaluation was performed against the Caco-2 cancer cell line using the MTT assay, which showed that the examined compounds had weak to moderate activities, with the new meroterpenoid austalide Z (1) displaying an IC50 value of 51.6 μg mL-1. ADME/TOPKAT (absorption, distribution, metabolism, excretion, and toxicity) predication performed in silico showed that most of the isolated compounds possessed reasonable pharmacokinetic, pharmacodynamic, and toxicity properties. Thus, it can be concluded that Aspergillus sp. could act as a source of drug leads for cancer prevention with promising pharmacokinetic and pharmacodynamic properties and thus could be incorporated in pharmaceutical dosage forms.
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Li YH, Mándi A, Li HL, Li XM, Li X, Meng LH, Yang SQ, Shi XS, Kurtán T, Wang BG. Isolation and characterization of three pairs of verrucosidin epimers from the marine sediment-derived fungus Penicillium cyclopium and configuration revision of penicyrone A and related analogues. MARINE LIFE SCIENCE & TECHNOLOGY 2023; 5:223-231. [PMID: 37275535 PMCID: PMC10232390 DOI: 10.1007/s42995-023-00173-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/18/2022] [Accepted: 01/27/2023] [Indexed: 06/07/2023]
Abstract
Verrucosidins, a methylated α-pyrone class of polyketides rarely reported upon, have been implicated in one or more neurological diseases. Despite the significance of verrucosidins as neurotoxins, the absolute configurations of most of the derivatives have not been accurately characterized yet. In this study, three pairs of C-9 epimeric verrucosidin derivatives, including the known compounds penicyrones A and B (1a/1b) and 9-O-methylpenicyrones A and B (2a/2b), the new compounds 9-O-ethylpenicyrones A and B (3a/3b), together with the related known derivative verrucosidin (4), were isolated and identified from the culture extract of Penicillium cyclopium SD-413, which was obtained from the marine sediment collected from the East China sea. Their structures were established based on an in-depth analysis of nuclear magnetic resonances (NMR) and mass spectroscopic data. Determination of the absolute configurations of these compounds was accomplished by Mosher's method and time-dependent density functional theory (TDDFT) calculations of electronic circular dichroism (ECD) and optical rotation (OR). The configurational assignment of penicyrone A demonstrated that the previously reported C-6 absolute configuration of verrucosidin derivatives needs to be revised from (6S) to (6R). The 9R/9S epimers of compounds 1-3 were found to exhibit growth inhibition against some pathogenic bacteria, indicating that they have potential as lead compounds for the creation of antimicrobial agents. Supplementary Information The online version contains supplementary material available at 10.1007/s42995-023-00173-2.
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Mazzone F, Simons VE, van Geelen L, Frank M, Mándi A, Kurtán T, Pfeffer K, Kalscheuer R. In Vitro Biological Activity of Natural Products from the Endophytic Fungus Paraboeremia selaginellae against Toxoplasma gondii. Antibiotics (Basel) 2022; 11:antibiotics11091176. [PMID: 36139955 PMCID: PMC9495004 DOI: 10.3390/antibiotics11091176] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 08/26/2022] [Accepted: 08/29/2022] [Indexed: 11/16/2022] Open
Abstract
Toxoplasma gondii is an apicomplexan pathogen able to infect a wide range of warm-blooded animals, including humans, leading to toxoplasmosis. Current treatments for toxoplasmosis are associated with severe side-effects and a lack efficacy to eradicate chronic infection. Thus, there is an urgent need for developing novel, highly efficient agents against toxoplasmosis with low toxicity. For decades, natural products have been a useful source of novel bioactive compounds for the treatment of infectious pathogens. In the present study, we isolated eight natural products from the crude extract of the endophytic fungus Paraboeremia selaginellae obtained from the leaves of the plant Philodendron monstera. The natural products were tested for inhibiting Toxoplasma gondii proliferation, and their cytotoxicity was evaluated in different human cell lines. Six natural products showed antitoxoplasma activity with low or no cytotoxicity in human cell lines. Together, these findings indicate that biphenyl ethers, bioxanthracenes, and 5S,6S-phomalactone from P. selaginellae are potential candidates for novel anti-toxoplasma drugs.
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Akone SH, Wang H, Misse Mouelle EN, Mándi A, Kurtán T, Koliye PR, Hartmann R, Bhatia S, Yang J, Müller WEG, Lai D, Kalscheuer R, Proksch P. Prenylated cyclohexene-type meroterpenoids and sulfur-containing xanthones produced by Pseudopestalotiopsis theae. PHYTOCHEMISTRY 2022; 197:113124. [PMID: 35144154 DOI: 10.1016/j.phytochem.2022.113124] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2021] [Revised: 01/30/2022] [Accepted: 01/31/2022] [Indexed: 06/14/2023]
Abstract
Chemical investigation of the fungal endophyte Pseudopestalotiopsis theae isolated from leaves of Caloncoba welwitschii, collected in Cameroon, resulted in two previously undescribed sulfur-containing xanthone derivatives sydoxanthones D and E, in addition to three previously undescribed monomeric diisoprenyl-cyclohexene-type meroterpenoids biscognienynes D-F and five known natural products. The structures of the undescribed compounds were unambiguously identified by their mass spectra and by extensive 1D and 2D NMR spectroscopic analysis. Mosher's reaction was performed to determine the absolute configuration of sydoxanthones D and E while TDDFT-ECD calculations were used to assign the configuration of biscognienyne D. Biscognienynes B and D showed significant cytotoxicity against the mouse lymphoma cell line L5178Y with IC50 values of 7.7 and 6.7 μM and against the human leukemic cell lines HL60, and Hal-01 with IC50 values ranging from 4.3 to 12.1 μM.
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Wang L, Linares-Otoya V, Liu Y, Mettal U, Marner M, Armas-Mantilla L, Willbold S, Kurtán T, Linares-Otoya L, Schäberle TF. Discovery and Biosynthesis of Antimicrobial Phenethylamine Alkaloids from the Marine Flavobacterium Tenacibaculum discolor sv11. JOURNAL OF NATURAL PRODUCTS 2022; 85:1039-1051. [PMID: 35416664 DOI: 10.1021/acs.jnatprod.1c01173] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
The bacterial genus Tenacibaculum has been associated with various ecological roles in marine environments. Members of this genus can act, for example, as pathogens, predators, or episymbionts. However, natural products produced by these bacteria are still unknown. In the present work, we investigated a Tenacibaculum strain for the production of antimicrobial metabolites. Six new phenethylamine (PEA)-containing alkaloids, discolins A and B (1 and 2), dispyridine (3), dispyrrolopyridine A and B (4 and 5), and dispyrrole (6), were isolated from media produced by the predatory bacterium Tenacibaculum discolor sv11. Chemical structures were elucidated by analysis of spectroscopic data. Alkaloids 4 and 5 exhibited strong activity against Gram-positive Bacillus subtilis DSM10, Mycobacterium smegmatis ATCC607, Listeria monocytogenes DSM20600, and Staphylococcus aureus ATCC25923, with minimum inhibitory concentration (MIC) values ranging from 0.5 to 4 μg/mL, and moderate activity against Candida albicans FH2173 and Aspergillus flavus ATCC9170. Compound 6 displayed moderate antibacterial activities against Gram-positive bacteria. Dispyrrolopyridine A (4) was active against efflux pump deficient Escherichia coli ATCC25922 ΔtolC, with an MIC value of 8 μg/mL, as well as against Caenorhabditis elegans N2 with an MIC value of 32 μg/mL. Other compounds were inactive against these microorganisms. The biosynthetic route toward discolins A and B (1 and 2) was investigated using in vivo and in vitro experiments. It comprises an enzymatic decarboxylation of phenylalanine to PEA catalyzed by DisA, followed by a nonenzymatic condensation to form the central imidazolium ring. This spontaneous formation of the imidazolium core was verified by means of a synthetic one-pot reaction using the respective building blocks. Six additional strains belonging to three Tenacibaculum species were able to produce discolins, and several DisA analogues were identified in various marine flavobacterial genera, suggesting the widespread presence of PEA-derived compounds in marine ecosystems.
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Szabó Z, Paczal A, Kovács T, Mándi A, Kotschy A, Kurtán T. Synthesis and Vibrational Circular Dichroism Analysis of N-Heterocyclic Carbene Precursors Containing Remote Chirality Centers. Int J Mol Sci 2022; 23:ijms23073471. [PMID: 35408831 PMCID: PMC8999040 DOI: 10.3390/ijms23073471] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 03/17/2022] [Accepted: 03/18/2022] [Indexed: 01/01/2023] Open
Abstract
VCD analysis of 16 diastereomeric pairs of NHC precursors containing two isolated chirality centers and different substitution patterns identified VCD transitions characteristic of the chirality center in the imidazolium ring or in the side chain, which, in contrast to ECD and OR, could be utilized to assign the two chirality centers separately by simple comparison, regardless of the type and position of achiral aromatic substituents. While the ECD and OR data showed great dependence on the position of an achiral substituent such as a methoxy group, characteristic experimental VCD transitions remained consistent and they could be used to determine the absolute configuration of all the regio- and stereoisomers and substituted analogues. VCD, ECD and OR approaches were evaluated, and several carbene precursors were found, for which only the VCD method could distinguish the four stereoisomers. With t-butyl, phenyl or 2-naphthyl substituents at the C-1′ chirality center, the ECD spectra of the C-1′ epimers were near-identical, and hence it was only the VCD approach that showed distinct differences suitable for the configurational assignment. The chiroptical characterization of our diastereomeric pairs of NHC precursors enables the future application of related derivatives having different substitution patterns in stereoselective transformations.
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Alekszi‐Kaszás A, Käfer‐Beke K, Varga TR, Bényei A, Kovács T, Mándi A, Kurtán T, Simon A, Nemes P. Regio‐ and Stereoselective Synthesis of Benzoquinolizidines. ChemistrySelect 2022. [DOI: 10.1002/slct.202104286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Huang SZ, Wang Q, Yuan JZ, Cai CH, Wang H, Mándi A, Kurtán T, Dai HF, Zhao YX. Hexahydroazulene-2(1 H)-one Sesquiterpenoids with Bridged Cyclobutane, Oxetane, and Tetrahydrofuran Rings from the Stems of Daphne papyracea with α-Glycosidase Inhibitory Activity. JOURNAL OF NATURAL PRODUCTS 2022; 85:3-14. [PMID: 34935371 DOI: 10.1021/acs.jnatprod.0c01394] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Chemical investigation of an alcoholic extract from the stem of Daphne papyracea ("Xuehuagou") led to the isolation of the tetracyclic sesquiterpenoid daphnepapytone A (1), containing a unique caged skeleton with a cyclobutane ring having three tetrasubstituted chirality centers. Also isolated were new guaiane sesquiterpenoids, namely, daphnepapytones B-H (2-8), and one 1,5-diphenylpentanone 2-hydroxy-5-oxo-daphneone (9), together with 26 known compounds. The cyclic metabolites share a 5-isoprenyl-hexahydroazulene-2(1H)-one skeleton with different substitution patterns and a bridged cyclobutane, oxetane, or tetrahydrofuran ring. The planar structures and relative configuration of the new compounds were elucidated on the basis of spectroscopic analysis aided by DFT 13C NMR calculations. The absolute configurations of 1-7 were determined by X-ray single-crystal diffraction or TDDFT-ECD calculations. Daphnepapytones A and C (1 and 3), 2-hydroxy-5-oxodaphneone (9), daphnenone (10), daphneone (11), and 3-methyldaphneolone (12) showed α-glycosidase inhibitory activity, with IC50 values of 159.0, 102.3, 139.3, 43.3, 145.0, and 126.1 μM, respectively.
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Yuan JZ, Yang YL, Li W, Yang L, Dai HF, Mándi A, Cai CH, Chen HQ, Dong WH, Kurtán T, Mei WL, Wang H. Zizaane-Type Sesquiterpenoids and Their Rearranged Derivatives from Agarwood of an Aquilaria Plant. Molecules 2021; 27:molecules27010198. [PMID: 35011431 PMCID: PMC8746309 DOI: 10.3390/molecules27010198] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2021] [Revised: 12/24/2021] [Accepted: 12/28/2021] [Indexed: 11/24/2022] Open
Abstract
Nine new sesquiterpenoids (1–9) were isolated from ethyl ether extract of agarwood originated from Aquilaria sp., including three novel sesquiterpenoids (1–3) derived from zizaane, together with six zizaane-type sesquiterpenoids (4–9). All structures were unambiguously elucidated based on 1D and 2D NMR spectra as well as by HRESIMS data. The absolute configuration of sesquiterpenoids was determined by comparison of the experimental and computed ECD spectra. In vitro anti-inflammatory assessment showed that compound 9 exhibited inhibition of NO production in LPS-stimulated RAW264.7 cells with an IC50 value of 62.22 ± 1.27 μM.
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Du F, Mándi A, Li X, Meng L, Kurtán T, Wang B. Experimental and Computational Analysis of the Solution and
Solid‐State
Conformations of Hexadepsipeptides from
Beauveria felina. CHINESE J CHEM 2021. [DOI: 10.1002/cjoc.202100586] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Király SB, Bényei A, Lisztes E, Bíró T, Tóth BI, Kurtán T. Knoevenagel‐Cyclization Cascade Reactions of Substituted 5,6‐Dihydro‐2
H
‐Pyran Derivatives. European J Org Chem 2021. [DOI: 10.1002/ejoc.202101277] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Vasas A, Lajter I, Kúsz N, Király SB, Kovács T, Kurtán T, Bózsity N, Nagy N, Schelz Z, Zupkó I, Krupitza G, Frisch R, Mándi A, Hohmann J. Isolation, Structure Determination of Sesquiterpenes from Neurolaena lobata and Their Antiproliferative, Cell Cycle Arrest-Inducing and Anti-Invasive Properties against Human Cervical Tumor Cells. Pharmaceutics 2021; 13:pharmaceutics13122088. [PMID: 34959370 PMCID: PMC8704432 DOI: 10.3390/pharmaceutics13122088] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 11/16/2021] [Accepted: 11/26/2021] [Indexed: 11/29/2022] Open
Abstract
Seven new germacranolides (1–3, 5–8), among them a heterodimer (7), and known germacranolide (4), eudesmane (9) and isodaucane (10) sesquiterpenes were isolated from the aerial parts of Neurolaena lobata. Their structures were determined by using a combination of different spectroscopic methods, including HR-ESIMS and 1D and 2D NMR techniques supported by DFT-NMR calculations. The enantiomeric purity of the new compounds was investigated by chiral HPLC analysis, while their absolute configurations were determined by TDDFT-ECD and OR calculations. Due to the conformationally flexible macrocycles and difficulties in assigning the relative configuration, 13C and 1H NMR chemical shift and ECD and OR calculations were performed on several stereoisomers of two derivatives. The isolated compounds (1–10) were shown to have noteworthy antiproliferative activities against three human cervical tumor cell line with different HPV status (HeLa, SiHa and C33A). Additionally, lobatolide C (6) exhibited substantial antiproliferative properties, antimigratory effect, and it induced cell cycle disturbance in SiHa cells.
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