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Nagase Y, Naka Y, Nehira T. 6-Methoxy-2-Naphthoate as a Standard Chromophore for Chiroptical Studies by Fluorescence-Detected Exciton-Coupled Circular Dichroism. Chirality 2024; 36:e23718. [PMID: 39317444 DOI: 10.1002/chir.23718] [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: 04/12/2024] [Revised: 08/14/2024] [Accepted: 08/30/2024] [Indexed: 09/26/2024]
Abstract
This study investigated the applicability of fluorescent chromophores for exciton-coupled circular dichroism (ECCD) exploiting fluorescence-detected circular dichroism (FDCD). FDCD had been previously reported useful in allowing the sensitive detection of ECCD in favorable conditions. However, fluorescence detection may prevent applications of the combined method especially when solutions are polarized in emission. Even without polarization of emission, FDCD deviates from circular dichroism (CD) in some cases when the fluorophore of interest interacts with nonfluorescent chromophore. Herein, it was confirmed that employing 6-methoxy-2-naphthoate always yielded interpretable exciton-coupled FDCD spectra even when coupling with nonfluorescent p-substituted benzoates. The 6-methoxy-2-naphthoate chromophore (6-MN) is prescribed in special cases when only a small amount of sample is available for determining the absolute stereochemistry by the CD exciton chirality method observed by FDCD.
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Affiliation(s)
- Yui Nagase
- Faculty of Integrated Arts and Sciences, Hiroshima University, Higashihiroshima, Japan
| | - Yoshiki Naka
- Faculty of Integrated Arts and Sciences, Hiroshima University, Higashihiroshima, Japan
| | - Tatsuo Nehira
- Faculty of Integrated Arts and Sciences, Hiroshima University, Higashihiroshima, Japan
- Graduate School of Integrated Sciences for Life, Hiroshima University, Higashihiroshima, Japan
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2
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Potential anti-diabetic isoprenoids and a long-chain δ-lactone from frangipani (Plumeria rubra). Fitoterapia 2020; 146:104684. [PMID: 32634455 DOI: 10.1016/j.fitote.2020.104684] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2020] [Revised: 06/23/2020] [Accepted: 06/28/2020] [Indexed: 11/20/2022]
Abstract
A decoction of Plumeria rubra flowers has been used traditionally for the treatment of diabetes in China and Mexico. Chemical investigations on the bioactive constituents of these flowers led to the isolation of 30 compounds, including the four new compounds, one iridoiod (1), two triterpenoids (4, 5), and a long-chain δ-lactone (16). In addition, 26 known compounds (2, 3, 6-15, 17-30) are also reported. All of these compounds were identified on the basis of spectroscopic data interpretation and the absolute configurations of compound 4, 5, 16 were determined by Mosher's method. Compounds 1-4, 7, 8 and 16 showed moderate to significant inhibitory activities against α-glucosidase and protein tyrosine phosphatase 1B, with 4 having IC50 values of 19.45 μM and 0.21 μM, respectively.
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3
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Morais FS, Canuto KM, Ribeiro PRV, Silva AB, Pessoa ODL, Freitas CDT, Alencar NMN, Oliveira AC, Ramos MV. Chemical profiling of secondary metabolites from Himatanthus drasticus (Mart.) Plumel latex with inhibitory action against the enzymes α-amylase and α-glucosidase: In vitro and in silico assays. JOURNAL OF ETHNOPHARMACOLOGY 2020; 253:112644. [PMID: 32058007 DOI: 10.1016/j.jep.2020.112644] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2019] [Revised: 01/22/2020] [Accepted: 02/01/2020] [Indexed: 06/10/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Himatanthus drasticus is an important medicinal plant whose latex is traditionally used in Northeast Brazil to treat various diseases, including diabetes. The use of α-amylase and α-glucosidase inhibitors can be an effective strategy to modulate levels of postprandial hyperglycemia via control of starch metabolism. AIMS OF THE STUDY This study aimed to verify if H. drasticus latex has inhibitory activity against enzymes linked to type 2 diabetes, besides chemically characterizing the metabolites responsible for such activities. In addition, in silico analysis was performed to support the traditional claim of possible antidiabetic activity of this latex. MATERIALS AND METHODS Latex from H. drasticus stems was sequentially partitioned with n-hexane (FHDH), CHCl3 (FHDC) and EtOH (FHDHA). Wash extraction of the FHDHA fraction was performed to obtain the other extract fractions. The FHDHA was submitted to chromatography in a SPE C18 cartridge using gradient elution with MeOH/H2O to produce five fractions: FHDHA1, FHDHA2, FHDHA3, FHDHA4 and FHDHA5. The FHDHA1 was subjected to semi-preparative reverse phase HPLC. Lineweaver-Burk plots were used to investigate the kinetic parameters of α-amylase and α-glucosidase inhibitory activity. The interactions between plumieride and porcine pancreatic α-amylase and α-glucosidase were analyzed through an in silico molecular docking study. RESULTS Phytochemical identification of compounds present in the FHDHA fraction of H. drasticus latex was possible by 1H, 13C NMR analysis and mass spectrometry, and the results were compared with the literature. The identified compounds were α-ethyl glucoside, protocatechuic acid, 3-O-caffeoylquinic acid, 15-demethylplumieride acid, 5-O-caffeoylquinic acid, caffeic acid, vanillic acid, plumieride, and catechin. The inhibition results of the fractions tested against α-amylase and α-glucosidase showed inhibitory activities dependent on the increase of fractions and compound concentrations. The IC50 results obtained from FHDHA, FHDHA1 and plumieride fractions against α-amylase were 36.46, 72.61, 33.87 μg/mL respectively. The IC50 of plumieride was the closest to that of acarbose (22.52 μg/mL), a result similar to that obtained for α-glucosidase. The type of inhibition was competitive for both enzymes. CONCLUSIONS There was strong inhibition of α-amylase and α-glucosidase by FHDHA, FHDHA1 and plumieride, suggesting that these enzymes slow glucose absorption.
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Affiliation(s)
- Francimauro S Morais
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará. Fortaleza, Ceará, Brazil.
| | | | | | - Alison B Silva
- Departamento de Química Orgânica e Inorgânica, Universidade Federal do Ceará, Brazil
| | - Otilia D L Pessoa
- Departamento de Química Orgânica e Inorgânica, Universidade Federal do Ceará, Brazil
| | - Cleverson D T Freitas
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará. Fortaleza, Ceará, Brazil
| | - Nylane M N Alencar
- Departamento de Fisiologia e Farmacologia, Universidade Federal do Ceará, Brazil
| | - Ariclecio C Oliveira
- Instituto Superior de Ciências Biomédicas, Universidade Estadual do Ceará, Fortaleza, Ceará, Brazil
| | - Márcio V Ramos
- Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará. Fortaleza, Ceará, Brazil
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4
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Antitrypanosomal Activities and Mechanisms of Action of Novel Tetracyclic Iridoids from Morinda lucida Benth. Antimicrob Agents Chemother 2016; 60:3283-90. [PMID: 26953191 PMCID: PMC4879371 DOI: 10.1128/aac.01916-15] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 03/02/2016] [Indexed: 11/20/2022] Open
Abstract
Trypanosoma brucei parasites are kinetoplastid protozoa that devastate the health and economic well-being of millions of people in Africa through the disease human African trypanosomiasis (HAT). New chemotherapy has been eagerly awaited due to severe side effects and the drug resistance issues plaguing current drugs. Recently, there has been an emphasis on the use of medicinal plants worldwide. Morinda lucida Benth. is a popular medicinal plant widely distributed in Africa, and several research groups have reported on the antiprotozoal activities of this plant. In this study, we identified three novel tetracyclic iridoids, molucidin, ML-2-3, and ML-F52, from the CHCl3 fraction of M. lucida leaves, which possess activity against the GUTat 3.1 strain of T. brucei brucei. The 50% inhibitory concentrations (IC50) of molucidin, ML-2-3, and ML-F52 were 1.27 μM, 3.75 μM, and 0.43 μM, respectively. ML-2-3 and ML-F52 suppressed the expression of paraflagellum rod protein subunit 2, PFR-2, and caused cell cycle alteration, which preceded apoptosis induction in the bloodstream form of Trypanosoma parasites. Novel tetracyclic iridoids may be promising lead compounds for the development of new chemotherapies for African trypanosomal infections in humans and animals.
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5
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Determination of the absolute configuration of the novel anti-trypanosomal iridoid molucidin isolated from Morinda lucida by X-ray analysis. Tetrahedron Lett 2015. [DOI: 10.1016/j.tetlet.2015.11.031] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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6
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Dey A, Mukherjee A. Plumeria rubra L. (Apocynaceae): Ethnobotany, Phytochemistry and Pharmacology: A Mini Review. ACTA ACUST UNITED AC 2015. [DOI: 10.3923/jps.2015.54.62] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Hopmann KH, Šebestík J, Novotná J, Stensen W, Urbanová M, Svenson J, Svendsen JS, Bouř P, Ruud K. Determining the Absolute Configuration of Two Marine Compounds Using Vibrational Chiroptical Spectroscopy. J Org Chem 2012; 77:858-69. [DOI: 10.1021/jo201598x] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | - Jaroslav Šebestík
- Institute of Organic Chemistry
and Biochemistry, Academy of Sciences, Flemingovo nám. 2, 166
10 Prague, Czech Republic
| | | | - Wenche Stensen
- Lytix Biopharma AS, Tromsø Research
Park, N-9294 Tromsø, Norway
| | | | | | | | - Petr Bouř
- Institute of Organic Chemistry
and Biochemistry, Academy of Sciences, Flemingovo nám. 2, 166
10 Prague, Czech Republic
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8
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Waltenberger B, Rollinger JM, Griesser UJ, Stuppner H, Gelbrich T. Plumeridoid C from the Amazonian traditional medicinal plant Himatanthus sucuuba. Acta Crystallogr C 2011; 67:o409-12. [PMID: 21979978 PMCID: PMC3845386 DOI: 10.1107/s0108270111035761] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Accepted: 09/02/2011] [Indexed: 11/10/2022] Open
Abstract
The stereochemistry of the iridoid plumeridoid C, C(15)H(18)O(7), was established by X-ray single-crystal structure analysis, giving (2'R,3R,4R,4aS,7aR)-methyl 3-hydroxy-4'-[(S)-1-hydroxyethyl]-5'-oxo-3,4,4a,7a-tetrahydro-1H,5'H-spiro[cyclopenta[c]pyran-7,2'-furan]-4-carboxylate. The absolute structure of the title compound was determined on the basis of the Flack x parameter and Bayesian statistics on Bijvoet differences. The hydrogen-bond donor and acceptor functions of the two hydroxy groups are employed in the formation of O-H···O-bonded helical chains.
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Affiliation(s)
- Birgit Waltenberger
- Institute of Pharmacy, University of Innsbruck, Innrain 52c, 6020 Innsbruck, Austria
| | - Judith M. Rollinger
- Institute of Pharmacy, University of Innsbruck, Innrain 52c, 6020 Innsbruck, Austria
| | - Ulrich J. Griesser
- Institute of Pharmacy, University of Innsbruck, Innrain 52c, 6020 Innsbruck, Austria
| | - Hermann Stuppner
- Institute of Pharmacy, University of Innsbruck, Innrain 52c, 6020 Innsbruck, Austria
| | - Thomas Gelbrich
- Institute of Pharmacy, University of Innsbruck, Innrain 52c, 6020 Innsbruck, Austria
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9
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Mangoyi R, Hayeshi R, Ngadjui B, Ngandeu F, Bezabih M, Abegaz B, Razafimahefa S, Rasoanaivo P, Mukanganyama S. Glutathione transferase from Plasmodium falciparum – Interaction with malagashanine and selected plant natural products. J Enzyme Inhib Med Chem 2010; 25:854-62. [DOI: 10.3109/14756366.2010.486793] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Rumbidzai Mangoyi
- Biomolecular Interactions Analyses Group, Department of Biochemistry, University of Zimbabwe, P.O. Box MP 167, Mount Pleasant, Harare, Zimbabwe
| | - Rose Hayeshi
- Biomolecular Interactions Analyses Group, Department of Biochemistry, University of Zimbabwe, P.O. Box MP 167, Mount Pleasant, Harare, Zimbabwe
| | - Bonventure Ngadjui
- Department of Organic Chemistry, University of Yaounde, BP 812, Yaounde, Cameroon
| | - Francois Ngandeu
- Department of Organic Chemistry, University of Yaounde, BP 812, Yaounde, Cameroon
| | - Merhatibebe Bezabih
- Department of Chemistry, University of Botswana, Private Bag 00704, Gaborone, Botswana
| | - Berhanu Abegaz
- Department of Chemistry, University of Botswana, Private Bag 00704, Gaborone, Botswana
| | | | - Philippe Rasoanaivo
- Biomolecular Interactions Analyses Group, Department of Biochemistry, University of Zimbabwe, P.O. Box MP 167, Mount Pleasant, Harare, Zimbabwe
| | - Stanley Mukanganyama
- Biomolecular Interactions Analyses Group, Department of Biochemistry, University of Zimbabwe, P.O. Box MP 167, Mount Pleasant, Harare, Zimbabwe
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Dinda B, Chowdhury DR, Mohanta BC. Naturally occurring iridoids, secoiridoids and their bioactivity. An updated review, part 3. Chem Pharm Bull (Tokyo) 2009; 57:765-96. [PMID: 19652401 DOI: 10.1248/cpb.57.765] [Citation(s) in RCA: 108] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Naturally occurring new iridoids and secoiridoids published during 2005-2008 are reviewed with available physical and spectral data: mp, [alpha](D), UV, IR, (1)H- and (13)C-NMR and plant source. The works on biological and pharmacological activity of naturally occurring iridoids and secoiridoids reported during 2005-2008 are also reviewed. Bioactivities like antibacterial, anticancer, anticoagulant, antifungal, anti-inflammatory, antioxidative, antiprotozoal, hepatoprotective and neuroprotective activities are highlighted.
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Affiliation(s)
- Biswanath Dinda
- Department of Chemistry, Tripura University, Suryamaninagar, Agartala, India.
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11
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Ye G, Yang YL, Xia GX, Fan MS, Huang CG. Complete NMR spectral assignments of two new iridoid diastereoisomers from the flowers of Plumeria rubra L. cv. acutifolia. MAGNETIC RESONANCE IN CHEMISTRY : MRC 2008; 46:1195-1197. [PMID: 18802971 DOI: 10.1002/mrc.2331] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Two new iridoid diastereoisomers (1, 2), together with five known compounds, were isolated from the flowers of Plumerian rubra L. cv. acutifolia. Their structures were elucidated by the means of in-depth spectroscopic and mass-spectrometric analyses, particularly 1D and 2D NMR spectroscopy.
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Affiliation(s)
- Guan Ye
- Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 201203, PR China
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12
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Muleya V, Hayeshi R, Ranson H, Abegaz B, Bezabih MT, Robert M, Ngadjui BT, Ngandeu F, Mukanganyama S. Modulation of Anopheles gambiae Epsilon glutathione transferase activity by plant natural products in vitro. J Enzyme Inhib Med Chem 2008; 23:391-9. [PMID: 18569345 DOI: 10.1080/14756360701546595] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
Elevated glutathione transferase (GST) E2 activity is associated with DDT resistance in the mosquito Anopheles gambiae. The search for chemomodulators that inhibit the function of AgGSTE2 would enhance the insecticidal activity of DDT. Therefore, we examined the interaction of novel natural plant products with heterologously expressed An. gambiae GSTE 2 in vitro. Five of the ten compounds, epiphyllocoumarin (Tral-1), knipholone anthrone, isofuranonaphthoquinones (Mr 13/2, Mr13/4) and the polyprenylated benzophenone (GG1) were shown to be potent inhibitors of AgGSTE2 with IC(50) values of 1.5 microM, 3.5 microM, 4 microM, 4.3 microM and 4.8 microM respectively. Non-competitive inhibition was obtained for Tral 1 and GG1 with regards to GSH (K(i) of 0.24 microM and 0.14 microM respectively). Competitive inhibition for Tral1 was obtained with CDNB (K(i) = 0.4 microM) whilst GG1 produced mixed type of inhibition. The K(i) and K(i)' for GSH for Tral-1 and GG1 were 0.2 microM and 0.1 microM respectively. These results suggest that the novel natural plant products, particularly Tral-1, represent potent AgGSTE2 in vitro inhibitors.
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Affiliation(s)
- Victor Muleya
- Biomolecular Interactions Analyses Group, Department of Biochemistry, University of Zimbabwe, Harare, Zimbabwe
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Stephens PJ, Devlin FJ, Pan JJ. The determination of the absolute configurations of chiral molecules using vibrational circular dichroism (VCD) spectroscopy. Chirality 2008; 20:643-63. [PMID: 17955495 DOI: 10.1002/chir.20477] [Citation(s) in RCA: 267] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The vibrational circular dichroism (VCD) spectra of the two enantiomers of a chiral molecule are of equal magnitude and opposite sign: i.e. mirror-image enantiomers give mirror-image VCD spectra. In principle, the absolute configuration (AC) of a chiral molecule can therefore be determined from its VCD spectrum. In practice, the determination of the AC of a chiral molecule from its experimental VCD spectrum requires a methodology which reliably predicts the VCD spectra of its enantiomers. The only reliable methodology developed to date uses the Stephens quantum-mechanical theory of the rotational strengths of fundamental vibrational transitions, developed in the early 1980s, implemented using ab initio density functional theory in the GAUSSIAN program in the mid 1990s. This methodology has by now been widely used in determining ACs from experimental VCD spectra. In this article we discuss the protocol for determining the ACs of chiral molecules with optimum reliability and its implementation for a variety of molecules, including the D3 symmetry perhydrotriphenylene, a thiazino-oxadiazolone recently shown to be a highly active calcium entry channel blocker, the alkaloid natural products schizozygine, iso-schizogaline, and iso-schizogamine, and the iridoid natural products plumericin, iso-plumericin, and prismatomerin. The power of VCD spectroscopy in determining ACs, even for large organic molecules and for substantially conformationally-flexible organic molecules is clearly documented.
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Affiliation(s)
- Philip J Stephens
- Department of Chemistry, University of Southern California, Los Angeles, CA 90089-0482, USA.
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Stephens PJ, Pan JJ, Krohn K. Determination of the absolute configurations of pharmacological natural products via density functional theory calculations of vibrational circular dichroism: the new cytotoxic iridoid prismatomerin. J Org Chem 2007; 72:7641-9. [PMID: 17784774 DOI: 10.1021/jo071183b] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A new highly cytotoxic iridoid has very recently been isolated from Prismatomeris tetrandra and shown to have the structure 3, similar to that of the iridoid oruwacin, 2. We report the determination of the absolute configuration (AC) of the new iridoid, prismatomerin, using vibrational circular dichroism (VCD) spectroscopy. The VCD spectrum of the acetate derivative of 3, 4, is analyzed using the Stephens theory of VCD and density functional theory (DFT). The AC of the naturally occurring 3 is shown to be 1R,5S,8S,9S,10S, identical to that of the naturally occurring iridoid plumericin, 1, also determined using VCD spectroscopy. The [alpha]D values of the natural products 3 and 1 are negative and positive, respectively. Since the ACs of 3 and 1 are identical, it follows that the AC of 3 cannot be correctly determined by empirical comparison of the signs of the [alpha]D values of 3 and 1.
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Affiliation(s)
- Philip J Stephens
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, USA.
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Krohn K, Gehle D, Dey SK, Nahar N, Mosihuzzaman M, Sultana N, Sohrab MH, Stephens PJ, Pan JJ, Sasse F. Prismatomerin, a new iridoid from Prismatomeris tetrandra. Structure elucidation, determination of absolute configuration, and cytotoxicity. JOURNAL OF NATURAL PRODUCTS 2007; 70:1339-43. [PMID: 17665951 DOI: 10.1021/np070202+] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
A new complex iridoid, prismatomerin (1), has been isolated from the leaves of Prismatomeris tetrandra, together with the known glucoside gaertneroside (4). The structures of 1 and 4 were determined by spectroscopic analysis, notably 2D NMR techniques. The (1R,5S,8S,9S,10S)-(-) absolute configuration of prismatomerin (1) was determined by comparison of the vibrational circular dichroism (VCD) spectrum calculated using density functional theory and the experimental VCD spectrum of the O-acetyl derivative 3. Prismatomerin (1) showed remarkable antitumor activity and also interfered with mitotic spindle formation.
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Affiliation(s)
- Karsten Krohn
- Department of Chemistry, University of Paderborn, D-33098 Paderborn, Germany.
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Stephens PJ, Pan JJ, Devlin FJ, Krohn K, Kurtán T. Determination of the Absolute Configurations of Natural Products via Density Functional Theory Calculations of Vibrational Circular Dichroism, Electronic Circular Dichroism, and Optical Rotation: The Iridoids Plumericin and Isoplumericin. J Org Chem 2007; 72:3521-36. [PMID: 17388636 DOI: 10.1021/jo070155q] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The absolute configurations (ACs) of the iridoid natural products, plumericin (1) and isoplumericin (2), have been re-investigated using vibrational circular dichroism (VCD) spectroscopy, electronic circular dichroism (ECD) spectroscopy, and optical rotatory dispersion (ORD). Comparison of DFT calculations of the VCD spectra of 1 and 2 to the experimental VCD spectra of the natural products, (+)-1 and (+)-2, leads unambiguously to the AC (1R,5S,8S,9S,10S)-(+) for both 1 and 2. In contrast, comparison of time-dependent DFT (TDDFT) calculations of the ECD spectra of 1 and 2 to the experimental spectra of (+)-1 and (+)-2 does not permit definitive assignment of their ACs. On the other hand, TDDFT calculations of the ORD of (1R,5S,8S,9S,10S)-1 and -2 over the range of 365-589 nm are in excellent agreement with the experimental data of (+)-1 and (+)-2, confirming the ACs derived from the VCD spectra. Thus, the ACs initially proposed by Albers-Schönberg and Schmid are shown to be correct, and the opposite ACs recently derived from the ECD spectra of 1 and 2 by Elsässer et al. are shown to be incorrect. As a result, the ACs of other iridoid natural products obtained by chemical correlation with 1 and 2 are not in need of revision.
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Affiliation(s)
- P J Stephens
- Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, USA.
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Elsässer B, Krohn K, Flörke U, Root N, Aust HJ, Draeger S, Schulz B, Antus S, Kurtán T. X-ray Structure Determination, Absolute Configuration and Biological Activity of Phomoxanthone A. European J Org Chem 2005. [DOI: 10.1002/ejoc.200500265] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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