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Wu XZ, Huang WJ, Liu W, Mándi A, Zhang Q, Zhang L, Zhang W, Kurtán T, Yuan CS, Zhang C. Penicisteckins A-F, Isochroman-Derived Atropisomeric Dimers from Penicillium steckii HNNU-5B18. JOURNAL OF NATURAL PRODUCTS 2021; 84:2953-2960. [PMID: 34787427 DOI: 10.1021/acs.jnatprod.1c00787] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Penicisteckins A-D (1-4), two pairs of atropodiastereomeric biaryl-type hetero- and homodimeric bis-isochromans with 7,5'- and 7,7'-linkages and a pair of atropodiastereomeric 2-(isochroman-5-yl)-1,4-benzoquinone derivatives [penicisteckins E (5) and F (6)], were isolated from the Penicillium steckii HNNU-5B18. Their structures including the absolute configuration were determined by extensive spectroscopic and single-crystal X-ray diffraction analysis and TDDFT-ECD calculations. Both the bis-isochromans and the isochroman/1,4-benzoquinone conjugates represent novel biaryl scaffolds containing both central and axial chirality elements. The monomer anserinone B (8) exhibited potent antibacterial activities against Staphylococcus aureus ATCC 29213 and methicillin-resistant Staphylococcus aureus with minimal inhibition concentration values ranging from 2 to 8 μg mL-1. Plausible biosynthetic pathways of 1-6 are proposed, which suggest how the absolute configurations of the isolates were established during the biosynthetic scheme.
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Jiang ZP, Sun SH, Yu Y, Mándi A, Luo JY, Yang MH, Kurtán T, Chen WH, Shen L, Wu J. Discovery of benthol A and its challenging stereochemical assignment: opening up a new window for skeletal diversity of super-carbon-chain compounds. Chem Sci 2021; 12:10197-10206. [PMID: 34447528 PMCID: PMC8336589 DOI: 10.1039/d1sc02810c] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Accepted: 06/25/2021] [Indexed: 12/28/2022] Open
Abstract
Super-carbon-chain compounds (SCCCs) are marine organic molecules featuring long polyol carbon chains with numerous stereocenters. Polyol-polyene compounds (PPCs) and ladder-frame polyethers (LFPs) are two major families. It is highly challenging to establish the absolute configurations of SCCCs. In this century, few new SCCC families have been reported. Benthol A, an aberrant SCCC, was obtained from a South China Sea benthic dinoflagellate that should belong to a new taxon. Its planar structure and absolute configuration, containing thirty-five carbon stereocenters, were unambiguously established by a combination of extensive NMR spectroscopic investigations, periodate degradation of the 1,2-diol groups, ozonolysis of the carbon-carbon double bonds, J-based configurational analysis, NOE interactions, modified Mosher's MTPA ester method, and DFT-NMR 13C chemical-shift calculations aided by DP4+ statistical analysis. Benthol A displayed potent antimalarial activity against Plasmodium falciparum 3D7 parasites. This new molecule combines extraordinary structural features, particularly eight scattered ether rings on a C72 backbone chain, which places it within a new SCCC family between PPCs and LFPs, herein termed polyol-polyether compounds. This suggestion was strongly supported by principal component analysis. The discovery of benthol A does not only provide new insights into the untapped biosynthetic potential of marine dinoflagellates, but also opens up a new window for skeletal diversity of SCCCs.
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Okoth DA, Hug JJ, Mándi A, Kurtán T, Garcia R, Müller R. Structure and biosynthesis of sorangipyranone - a new γ-dihydropyrone from the myxobacterial strain MSr12020. J Ind Microbiol Biotechnol 2021; 48:kuab029. [PMID: 34003283 PMCID: PMC9113121 DOI: 10.1093/jimb/kuab029] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 05/13/2021] [Indexed: 08/28/2024]
Abstract
Sorangipyranone was isolated as a novel natural product featuring a unique 2,3-dihydro-γ-4H-pyrone scaffold from cultures of the myxobacterial strain MSr12020. We report here the full structure elucidation of sorangipyranone by spectroscopic techniques including 2D NMR and high-resolution mass spectrometry together with the analysis of the biosynthetic pathway. Determination of the absolute configuration was performed by time-dependent density functional theory-electronic circular dichroism calculations and determination of the applicability of the Snatzke's helicity rule, to correlate the high-wavelength n→π* electronic circular dichroism (ECD) transition and the absolute configuration of the 2,3-dihydro-4H-γ-pyrone, was done by the analysis of low-energy conformers and the Kohn-Sham orbitals. Sorangipyranone outlines a new class of a γ-dihydropyrone-containing natural product comprised of malonyl-CoA-derived building blocks and features a unique polyketide scaffold. In silico analysis of the genome sequence of the myxobacterial strain MSr12020 complemented with feeding experiments employing stable isotope-labeled precursors allowed the identification and annotation of a candidate biosynthetic gene cluster that encodes a modular polyketide synthase assembly line. A model for the biosynthetic pathway leading to the formation of the γ-dihydropyrone scaffold is presented in this study.
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Peng GY, Kurtán T, Mándi A, He J, Cao ZY, Tang H, Mao SC, Zhang W. Neuronal Modulators from the Coral-Associated Fungi Aspergillus candidus. Mar Drugs 2021; 19:md19050281. [PMID: 34069724 PMCID: PMC8161303 DOI: 10.3390/md19050281] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Revised: 05/12/2021] [Accepted: 05/13/2021] [Indexed: 11/16/2022] Open
Abstract
Three new p-terphenyl derivatives, named 4″-O-methyl-prenylterphenyllin B (1) and phenylcandilide A and B (17 and 18), and three new indole-diterpene alkaloids, asperindoles E-G (22-24), were isolated together with eighteen known analogues from the fungi Aspergillus candidus associated with the South China Sea gorgonian Junceela fragillis. The structures and absolute configurations of the new compounds were elucidated on the basis of spectroscopic analysis, and DFT/NMR and TDDFT/ECD calculations. In a primary cultured cortical neuronal network, the compounds 6, 9, 14, 17, 18 and 24 modulated spontaneous Ca2+ oscillations and 4-aminopyridine hyperexcited neuronal activity. A preliminary structure-activity relationship was discussed.
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Shen L, Zou XP, Li WS, Mándi A, Kurtán T, Wu J. Granatripodins A-B, limonoids featuring a Tricyclo[3.3.1.0 2,8]nonane motif: Absolute configuration and agonistic effects on human pregnane-X-receptor. Bioorg Chem 2021; 111:104888. [PMID: 33862473 DOI: 10.1016/j.bioorg.2021.104888] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Revised: 03/31/2021] [Accepted: 03/31/2021] [Indexed: 01/10/2023]
Abstract
Two unprecedented limonoids incorporating a sterically encumbered cyclopropane ring, named granatripodins A (1) and B (2), featuring the presence of a tricyclo[3.3.1.02,8]nonane motif, were obtained from seeds of the Thai Xylocarpus granatum. The planar structures and absolute configurations of these limonoids were unambiguously established by NMR investigations, TDDFT-ECD and DFT-NMR calculations, and single-crystal X-ray diffraction analysis (Cu Kα). Most notably, granatripodin A (1) exhibited agonistic effects on human pregnane-X-receptor at the concentration of 100.0 nM. The biosynthetic origins of these limonoids via a radical cascade reaction are proposed. This study exemplifies a universal approach for the stereochemical assignment of polycyclic compounds with a cyclopropane-embedded cage scaffold.
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Tao LX, Ji SS, Szalóki D, Kovács T, Mándi A, Antus S, Ding X, Kurtán T, Zhang HY. An optically active isochroman-2H-chromene conjugate potently suppresses neuronal oxidative injuries associated with the PI3K/Akt and MAPK signaling pathways. Acta Pharmacol Sin 2021; 42:36-44. [PMID: 32393798 PMCID: PMC7921582 DOI: 10.1038/s41401-020-0391-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Accepted: 02/23/2020] [Indexed: 12/18/2022] Open
Abstract
Increasing evidence suggests that the use of potent neuroprotective agents featured with novel pharmacological mechanism would offer a promising strategy to delay or prevent the progression of neurodegeneration. Here, we provide the first demonstration that the chiral nonracemic isochroman-2H-chromene conjugate JE-133, a novel synthetic 1,3-disubstituted isochroman derivative, possesses superior neuroprotective effect against oxidative injuries. Pretreatment with JE-133 (1-10 μM) concentration-dependently prevented H2O2-induced cell death in SH-SY5Y neuroblastoma cells and rat primary cortical neurons. Pretreatment with JE-133 significantly alleviated H2O2-induced apoptotic changes. These protective effects could not be simply attributed to the direct free radical scavenging as JE-133 had moderate activity in reducing DPPH free radical. Further study revealed that pretreatment with JE-133 (10 μM) significantly decreased the phosphorylation of MAPK pathway proteins, especially ERK and P38, in the neuronal cells. In addition, blocking PI3K/Akt pathway using LY294002 partially counteracted the cell viability-enhancing effect of JE-133. We conclude that JE-133 exerts neuroprotection associated with dual regulative mechanisms and consequently activating cell survival and inhibiting apoptotic changes, which may provide important clues for the development of effective neuroprotective drug lead/candidate.
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Zhang L, De BC, Zhang W, Mándi A, Fang Z, Yang C, Zhu Y, Kurtán T, Zhang C. Mutation of an atypical oxirane oxyanion hole improves regioselectivity of the α/β-fold epoxide hydrolase Alp1U. J Biol Chem 2020; 295:16987-16997. [PMID: 33004437 PMCID: PMC7863881 DOI: 10.1074/jbc.ra120.015563] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 09/25/2020] [Indexed: 01/13/2023] Open
Abstract
Epoxide hydrolases (EHs) have been characterized and engineered as biocatalysts that convert epoxides to valuable chiral vicinal diol precursors of drugs and bioactive compounds. Nonetheless, the regioselectivity control of the epoxide ring opening by EHs remains challenging. Alp1U is an α/β-fold EH that exhibits poor regioselectivity in the epoxide hydrolysis of fluostatin C (compound 1) and produces a pair of stereoisomers. Herein, we established the absolute configuration of the two stereoisomeric products and determined the crystal structure of Alp1U. A Trp-186/Trp-187/Tyr-247 oxirane oxygen hole was identified in Alp1U that replaced the canonical Tyr/Tyr pair in α/β-EHs. Mutation of residues in the atypical oxirane oxygen hole of Alp1U improved the regioselectivity for epoxide hydrolysis on 1. The single site Y247F mutation led to highly regioselective (98%) attack at C-3 of 1, whereas the double mutation W187F/Y247F resulted in regioselective (94%) nucleophilic attack at C-2. Furthermore, single-crystal X-ray structures of the two regioselective Alp1U variants in complex with 1 were determined. These findings allowed insights into the reaction details of Alp1U and provided a new approach for engineering regioselective epoxide hydrolases.
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Bús C, Kulmány Á, Kúsz N, Gonda T, Zupkó I, Mándi A, Kurtán T, Tóth B, Hohmann J, Hunyadi A, Vasas A. Oxidized Juncuenin B Analogues with Increased Antiproliferative Activity on Human Adherent Cell Lines: Semisynthesis and Biological Evaluation. JOURNAL OF NATURAL PRODUCTS 2020; 83:3250-3261. [PMID: 33064469 PMCID: PMC7707621 DOI: 10.1021/acs.jnatprod.0c00499] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Phenanthrenes have become the subject of intensive research during the past decades because of their structural diversity and wide range of pharmacological activities. Earlier studies demonstrated that semisynthetic derivatization of these natural compounds could result in more active agents, and oxidative transformations are particularly promising in this regard. In our work, a natural phenanthrene, juncuenin B, was transformed by hypervalent iodine(III) reagents using a diversity-oriented approach. Eleven racemic semisynthetic compounds were produced, the majority containing an alkyl substituted p-quinol ring. Purification of the compounds was carried out by chromatographic techniques, and their structures were elucidated by 1D and 2D NMR spectroscopic methods. Stereoisomers of the bioactive derivatives were separated by chiral-phase HPLC and the absolute configurations of the active compounds, 2,6-dioxo-1,8a-dimethoxy-1,7-dimethyl-8-vinyl-9,10-dihydrophenanthrenes (1a-d), and 8a-ethoxy-1,7-dimethyl-6-oxo-8-vinyl-9,10-dihydrophenanthrene-2-ols (7a,b) were determined by ECD measurements and TDDFT-ECD calculations. The antiproliferative activities of the compounds were tested on different (MCF-7, T47D, HeLa, SiHa, C33A, A2780) human gynecological cancer cell lines. Compounds 1a-d, 4a, 6a, and 7a possessed higher activity than juncuenin B on several tumor cell lines. The structure-activity relationship studies suggested that the p-quinol (2,5-cyclohexadien-4-hydroxy-1-one) moiety has a considerable effect on the antiproliferative properties, and substantial differences could be identified in the activities of the stereoisomers.
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Gao Y, Stuhldreier F, Schmitt L, Wesselborg S, Guo Z, Zou K, Mándi A, Kurtán T, Liu Z, Proksch P. Induction of New Lactam Derivatives From the Endophytic Fungus Aplosporella javeedii Through an OSMAC Approach. Front Microbiol 2020; 11:600983. [PMID: 33250887 PMCID: PMC7672018 DOI: 10.3389/fmicb.2020.600983] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Accepted: 10/16/2020] [Indexed: 12/16/2022] Open
Abstract
Fermentation of the endophytic fungus Aplosporella javeedii on solid rice medium in presence of either 3.5% NaNO3 or 3.5% monosodium glutamate caused a significant change of the fungal metabolite pattern compared to fungal controls grown only on rice. Chemical investigation of the former fungal extracts yielded 11 new lactam derivatives, aplosporellins A-K (2-12), in addition to the known compound, pramanicin A (1). All of these compounds were not detected when the fungus was grown on rice medium without these activators thereby indicating the power of this OSMAC approach. The structures of the new compounds were elucidated by one- and two- dimensional NMR spectroscopy, DFT-NMR calculations and by mass spectrometry as well as by comparison with the literature whereas the absolute configuration of the lactam core was determined by TDDFT-ECD and OR calculations. Pramanicin A (1) showed strong cytotoxicity against human lymphoma (Ramos) and leukemia (Jurkat J16) cells with IC50 values of 4.7 and 4.4 μM, respectively. Mechanistic studies indicated that 1 activates caspase-3 and induces apoptotic cell death.
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Wang P, Huang J, Kurtán T, Mándi A, Jia H, Cheng W, Lin W. Aaptodines A-D, Spiro Naphthyridine-Furooxazoloquinoline Hybrid Alkaloids from the Sponge Aaptos suberitoides. Org Lett 2020; 22:8215-8218. [PMID: 33112152 DOI: 10.1021/acs.orglett.0c02645] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
LC-MS-oriented fractionation of the sponge Aaptos suberitoides resulted in the isolation of four heptacyclic alkaloids, aaptodines A-D (1-4), which contain 9,10-dihydrofuro[2,3-f][1,3]oxazolo[5,4-h]quinolone and 7,8-dihydrocyclopenta[de][1,6]naphthyridine subunits with a spiro carbon atom. The structures were determined on the basis of NMR spectroscopic and single-crystal X-ray diffraction data analysis aided by electronic circular dichroism calculations and Mosher's method. A biosynthetic pathway for the formation of aaptodines A-D is postulated. Aaptodine D exhibits potent inhibition against osteoclast formation.
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Harwoko H, Lee J, Hartmann R, Mándi A, Kurtán T, Müller WEG, Feldbrügge M, Kalscheuer R, Ancheeva E, Daletos G, Frank M, Liu Z, Proksch P. Azacoccones F-H, new flavipin-derived alkaloids from an endophytic fungus Epicoccum nigrum MK214079. Fitoterapia 2020; 146:104698. [PMID: 32745508 DOI: 10.1016/j.fitote.2020.104698] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 07/20/2020] [Accepted: 07/28/2020] [Indexed: 11/19/2022]
Abstract
Three new flavipin-derived alkaloids, azacoccones F-H (1-3), along with six known compounds (4-9) were isolated from the endophytic fungus Epicoccum nigrum MK214079 associated with leaves of Salix sp. The structures of the new compounds were established by analysis of their 1D/2D nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectroscopy (HRESIMS) data. The absolute configuration of azacoccones F-H (1-3) was determined by comparison of experimental electronic circular dichroism (ECD) data with reported ones and biogenetic considerations. Epicocconigrone A (4), epipyrone A (5), and epicoccolide B (6) exhibited moderate antibacterial activity against Staphylococcus aureus ATCC 29213 with minimal inhibitory concentration (MIC) values ranging from 25 to 50 μM. Furthermore, epipyrone A (5) and epicoccamide A (7) displayed mild antifungal activity against Ustilago maydis AB33 with MIC values of 1.6 and 1.8 mM, respectively. Epicorazine A (8) showed pronounced cytotoxicity against the L5178Y mouse lymphoma cell line with an IC50 value of 1.3 μM.
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Li W, Yan R, Yu Y, Shi Z, Mándi A, Shen L, Kurtán T, Wu J. Determination of the Absolute Configuration of Super‐Carbon‐Chain Compounds by a Combined Chemical, Spectroscopic, and Computational Approach: Gibbosols A and B. Angew Chem Int Ed Engl 2020; 59:13028-13036. [PMID: 32343023 DOI: 10.1002/anie.202004358] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Revised: 04/15/2020] [Indexed: 12/22/2022]
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Li W, Yan R, Yu Y, Shi Z, Mándi A, Shen L, Kurtán T, Wu J. Determination of the Absolute Configuration of Super‐Carbon‐Chain Compounds by a Combined Chemical, Spectroscopic, and Computational Approach: Gibbosols A and B. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202004358] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
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Csupor D, Kurtán T, Vollár M, Kúsz N, Kövér KE, Mándi A, Szűcs P, Marschall M, Senobar Tahaei SA, Zupkó I, Hohmann J. Correction to Pigments of the Moss Paraleucobryum longifolium: Isolation and Structure Elucidation of Prenyl-Substituted 8,8'-Linked 9,10-Phenanthrenequinone Dimers. JOURNAL OF NATURAL PRODUCTS 2020; 83:1355. [PMID: 32159347 PMCID: PMC7853632 DOI: 10.1021/acs.jnatprod.0c00243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Wang HL, Li R, Li J, He J, Cao ZY, Kurtán T, Mándi A, Zheng GL, Zhang W. Alternarin A, a Drimane Meroterpenoid, Suppresses Neuronal Excitability from the Coral-Associated Fungi Alternaria sp. ZH-15. Org Lett 2020; 22:2995-2998. [PMID: 32237750 DOI: 10.1021/acs.orglett.0c00746] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Alternarin A (1), a rearranged drimane meroterpenoid characterized by a thioglycerate moiety, was isolated together with two known analogues from the coral-associated fungi Alternaria sp. ZH-15. Its structure was determined based on spectroscopic analysis, modified Mosher's method, and TDDFT/ECD calculations. In a primary cultured cortical neuronal network, compound 1 effectively inhibited the activity of spontaneous synchronous Ca2+ oscillations and 4-aminopyridine induced epileptic discharges in the low micromolar concentration range.
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Szappanos Á, Mándi A, Gulácsi K, Lisztes E, Tóth BI, Bíró T, Antus S, Kurtán T. Synthesis and antiproliferative activity of 6-naphthylpterocarpans. Org Biomol Chem 2020; 18:2148-2162. [PMID: 32134098 DOI: 10.1039/d0ob00110d] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The Heck-oxyarylation of racemic 2-(1-naphthyl)- and 2-(2-naphthyl)-2H-chromene derivatives were carried out resulting diastereoselectively in (6S*,6aR*,11aR*)-6-(1-naphthyl)- and 6-(2-naphthyl)-pterocarpans as major products and bridged (6R*,12R*)-6,12-methanodibenzo[d,g][1,3]dioxocine derivatives as minor products. Antiproliferative activity of two 6-naphthylpterocarpans was identified by MTT assay against A2780 and WM35 human cancer cell lines with low micromolar IC50 values. The measured 0.80 and 3.51 μM IC50 values of the (6S*,6aR*,11aR*)-6-(1-naphthyl)pterocarpan derivative with 8,9-methylenedioxy substitution represent the best activities in the pterocarpan family. Enantiomers of the pterocarpan and dioxocine derivatives and their chiral 2-naphthylchroman-4-one and 2-naphthyl-2H-chromene precursors were separated by HPLC using chiral stationary phase. HPLC-ECD spectra were recorded and absolute configuration and low-energy solution conformations were determined by TDDFT-ECD calculations. Characteristic ECD transitions of the separated enantiomers were correlated with their absolute configuration.
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Szalóki Vargáné D, Tóth L, Buglyó B, Kiss-Szikszai A, Mándi A, Mátyus P, Antus S, Chen Y, Li D, Tao L, Zhang H, Kurtán T. [1,5]-Hydride Shift-Cyclization versus C(sp 2)-H Functionalization in the Knoevenagel-Cyclization Domino Reactions of 1,4- and 1,5-Benzoxazepines. Molecules 2020; 25:E1265. [PMID: 32168821 PMCID: PMC7144003 DOI: 10.3390/molecules25061265] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2020] [Revised: 03/05/2020] [Accepted: 03/07/2020] [Indexed: 02/07/2023] Open
Abstract
Domino cyclization reactions of N-aryl-1,4- and 1,5-benzoxazepine derivatives involving [1,5]-hydride shift or C(sp2)-H functionalization were investigated. Neuroprotective and acetylcholinesterase activities of the products were studied. Domino Knoevenagel-[1,5]-hydride shift-cyclization reaction of N-aryl-1,4-benzoxazepine derivatives with 1,3-dicarbonyl reagents having active methylene group afforded the 1,2,8,9-tetrahydro-7bH-quinolino [1,2-d][1,4]benzoxazepine scaffold with different substitution pattern. The C(sp3)-H activation step of the tertiary amine moiety occurred with complete regioselectivity and the 6-endo cyclization took place in a complete diastereoselective manner. In two cases, the enantiomers of the chiral condensed new 1,4-benzoxazepine systems were separated by chiral HPLC, HPLC-ECD spectra were recorded, and absolute configurations were determined by time-dependent density functional theory- electronic circular dichroism (TDDFT-ECD) calculations. In contrast, the analogue reaction of the regioisomeric N-aryl-1,5-benzoxazepine derivative did not follow the above mechanism but instead the Knoevenagel intermediate reacted in an SEAr reaction [C(sp2)-H functionalization] resulting in a condensed acridane derivative. The AChE inhibitory assays of the new derivatives revealed that the acridane derivative had a 6.98 μM IC50 value.
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Murillo E, Agócs A, Nagy V, Király SB, Kurtán T, Toribio EM, Lakey-Beitia J, Deli J. Isolation and identification of sapotexanthin 5,6-epoxide and 5,8-epoxide from red mamey (Pouteria sapota). Chirality 2020; 32:579-587. [PMID: 32126590 DOI: 10.1002/chir.23206] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 02/13/2020] [Accepted: 02/14/2020] [Indexed: 11/09/2022]
Abstract
Two new carotenoids, sapotexanthin 5,6-epoxide and sapotexanthin 5,8-epoxide, have been isolated from the ripe fruits of red mamey (Pouteria sapota). Sapotexanthin 5,6-epoxide was also prepared by partial synthesis via epoxidation of sapotexanthin, and the (5R,6S) and (5S,6R) stereoisomers were identified by high-performance liquid chromatography-electronic circular dichroism (HPLC-ECD) analysis. Spectroscopic data of the natural and semisynthetic derivatives obtained by acid-catalyzed rearrangement of cryptocapsin 5,8-epoxide stereoisomers were compared for structural elucidation.
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Tran-Cong NM, Mándi A, Király SB, Kurtán T, Lin W, Liu Z, Proksch P. Furoic acid derivatives from the endophytic fungus Coniothyrium sp. Chirality 2020; 32:605-610. [PMID: 32115775 DOI: 10.1002/chir.23209] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2019] [Revised: 01/19/2020] [Accepted: 02/17/2020] [Indexed: 11/06/2022]
Abstract
The endophytic fungus Coniothyrium sp. was isolated from leaves of Quercus robur. Fermentation of this fungus on solid rice medium yielded two new furoic acid derivatives (1 and 2) and two additional known compounds. The structures of the new compounds were determined by extensive analysis of 1D and 2D nuclear magnetic resonance spectra as well as high-resolution mass spectrometry data. Compound 1, containing three aromatic chromophores attached by rotatable sigma bonds and a chirality center in benzylic position, was found to be a scalemic mixture with an excess of the (S) enantiomer, the absolute configuration of which was elucidated as by the solution time-dependent density functional theory-electronic circular dichroism approach. The ωB97X/TZVP PCM/MeCN and SOGGA11-X/TZVP SMD/MeCN methods were used for geometry reoptimization to reproduce the solution conformational ensemble. All isolated compounds were tested for their cytotoxicity but proved to be inactive.
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Csupor D, Kurtán T, Vollár M, Kúsz N, Kövér KE, Mándi A, Szűcs P, Marschall M, Senobar Tahaei SA, Zupkó I, Hohmann J. Pigments of the Moss Paraleucobryum longifolium: Isolation and Structure Elucidation of Prenyl-Substituted 8,8'-Linked 9,10-Phenanthrenequinone Dimers. JOURNAL OF NATURAL PRODUCTS 2020; 83:268-276. [PMID: 32077277 PMCID: PMC7316407 DOI: 10.1021/acs.jnatprod.9b00655] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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In a search for new secondary metabolites from mosses, leucobryns
A–E, axially chiral 9,10-phenanthrenequinone dimers, were isolated
from Paraleucobryum longifolium (1–5), together with diosmetin triglycoside. Leucobryns B (2) and C (3) were proved to be homodimeric atropodiastereomers
containing both axial and central chirality elements, while leucobryns
D (4) and E (5) were found to be heterodimeric
atropodiastereomers containing central chirality in only one of the
two monomeric units. Axial chirality of the compounds was determined
by ECD measurements and sTDA ECD calculations, while the central chirality
elements were assigned by TDDFT-SOR calculations. Leucobryns represent
the first 9,10-phenanthrenequinone dimers, the monomers of which are
linked through their C-8 atoms. Leucobryns B–E contain an uncommon
C10 monoterpenoid side chain, in which isoprenoid units
are joined by 3,4 linkages. Leucobryns A and B exhibited weak antiproliferative
activity against several human cancer cell lines.
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Pan F, El-Kashef DH, Kalscheuer R, Müller WEG, Lee J, Feldbrügge M, Mándi A, Kurtán T, Liu Z, Wu W, Proksch P. Cladosins L-O, new hybrid polyketides from the endophytic fungus Cladosporium sphaerospermum WBS017. Eur J Med Chem 2020; 191:112159. [PMID: 32101782 DOI: 10.1016/j.ejmech.2020.112159] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Revised: 02/17/2020] [Accepted: 02/17/2020] [Indexed: 01/16/2023]
Abstract
The endophytic fungus Cladosporium sphaerospermum WBS017 was obtained from healthy bulbs of Fritillaria unibracteata var. wabuensis. Fermentation of C. sphaerospermum on solid rice medium yielded three new hybrid polyketides, cladosins L-N (1-3), and a known derivative cladodionen (4). Further cultivation of this fungus on white bean medium afforded an additional new hybrid polyketide, cladosin O (5) along with three known analogues (6-8). The structures of the new compounds were elucidated using a combination of NMR and HRESIMS data. The absolute configurations of compounds 2 and 3 were determined by Mosher's method and TDDFT-ECD calculations. All isolated compounds were evaluated for their cytotoxic and antimicrobial activities. Cladodionen (4) exhibited cytotoxicity against the mouse lymphoma cell line L5178Y with an IC50 value of 3.7 μM, and also exhibited antifungal activity against Ustilago maydis and Saccharomyces cerevisiae, while cladosin L (1) displayed week antibacterial activity against Staphylococcus aureus ATCC 29213 and S. aureus ATCC 700699 with MIC values of 50 and 25 μM, respectively.
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Línzembold I, Czett D, Böddi K, Kurtán T, Király SB, Gulyás-Fekete G, Takátsy A, Lóránd T, Deli J, Agócs A, Nagy V. Study on the Synthesis, Antioxidant Properties, and Self-Assembly of Carotenoid-Flavonoid Conjugates. Molecules 2020; 25:E636. [PMID: 32024181 PMCID: PMC7038153 DOI: 10.3390/molecules25030636] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Revised: 01/28/2020] [Accepted: 01/29/2020] [Indexed: 11/23/2022] Open
Abstract
Flavonoids and carotenoids possess beneficial physiological effects, such as high antioxidant capacity, anticarcinogenic, immunomodulatory, and anti-inflammatory properties, as well as protective effects against UV light. The covalent coupling of hydrophobic carotenoids with hydrophilic flavonoids, such as daidzein and chrysin, was achieved, resulting in new amphipathic structures. 7-Azidohexyl ethers of daidzein and chrysin were prepared in five steps, and their azide-alkyne [4 + 2] cycloaddition with pentynoates of 8'-apo-β-carotenol, zeaxanthin, and capsanthin afforded carotenoid-flavonoid conjugates. The trolox-equivalent antioxidant capacity against ABTS•+ radical cation and self-assembly of the final products were examined. The 1:1 flavonoid-carotenoid hybrids generally showed higher antioxidant activity than their parent flavonoids but lower than that of the corresponding carotenoids. The diflavonoid hybrids of zeaxanthin and capsanthin, however, were found to exhibit a synergistic enhancement in antioxidant capacities. ECD (electronic circular dichroism) and UV-vis analysis of zeaxanthin-flavonoid conjugates revealed that they form different optically active J-aggregates in acetone/water and tetrahydrofuran/water mixtures depending on the solvent ratio and type of the applied aprotic polar solvent, while the capsanthin derivatives showed no self-assembly. The zeaxanthin bis-triazole conjugates with daidzein and with chrysin, differing only in the position of a phenolic hydroxyl group, showed significantly different aggregation profile upon the addition of water.
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Zhu Q, Tang C, Mándi A, Kurtán T, Ye Y. Trigonostemons G and H, dinorditerpenoid dimers with axially chiral biaryl linkage from
Trigonostemon chinensis. Chirality 2020; 32:265-272. [DOI: 10.1002/chir.23170] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 12/02/2019] [Accepted: 12/22/2019] [Indexed: 11/05/2022]
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Ferenczi RK, Illyés TZ, Király SB, Hoffka G, Szilágyi L, Mándi A, Antus S, Kurtán T. Evaluation of Different Synthetic Routes to (2R,3R)-3-Hydroxymethyl-2-(4-hydroxy- 3-methoxyphenyl)-1,4-Benzodioxane-6-Carbaldehyde. CURR ORG CHEM 2020. [DOI: 10.2174/1385272823666191212113407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The reported enantioselective synthesis for the preparation of (+)-(2R,3R)-2-(4-
hydroxy-3-methoxyphenyl)-3-hydroxymethyl-1,4-benzodioxane-6-carbaldehyde, precursor
for the stereoselective synthesis of bioactive flavanolignans, could not be reproduced.
Thus, the target molecule was prepared via the synthesis and separation of diastereomeric
O-glucosides. TDDFT-ECD calculations and the 1,4-benzodioxane helicity rule were utilized
to determine the absolute configuration. ECD calculations also confirmed that the 1Lb
Cotton effect is governed by the helicity of the heteroring, while the higher-energy ECD
transitions reflect mainly the orientation of the equatorial C-2 aryl group.
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Mándi A, Wu J, Kurtán T. TDDFT-ECD and DFT-NMR studies of thaigranatins A–E and granatumin L isolated from Xylocarpus granatum. RSC Adv 2020; 10:32216-32224. [PMID: 35518141 PMCID: PMC9056630 DOI: 10.1039/d0ra03725g] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Accepted: 08/20/2020] [Indexed: 11/21/2022] Open
Abstract
TDDFT-ECD calculations were utilized to explain the mirror image or different ECD spectra of thaigranatins A–E and granatumin L.
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