| 1. |
- Deyou, Tsegaye, et al.
(författare)
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Isoflavones and Rotenoids from the Leaves of Millettia oblata ssp teitensis
- 2017
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Ingår i: Journal of Natural Products. - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025. ; 80:7, s. 2060-2066
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Tidskriftsartikel (refereegranskat)abstract
- A new isoflavone, 8-prenylmilldrone (1), and four new rotenoids, oblarotenoids A-D (2-5), along with nine known compounds (6-14), were isolated from the CH2Cl2/CH3OH (1:1) extract of the leaves of Millettia oblata ssp. teitensis by chromatographic separation. The purified compounds were identified by NMR spectroscopic and mass spectrometric analyses, whereas the absolute configurations of the rotenoids were established on the basis of chiroptical data and in some cases by single-crystal X-ray crystallography. Maximaisoflavone J (11) and oblarotenoid C (4) showed weak activity against the human breast cancer cell line MDA-MB-231 with IC50 values of 33.3 and 93.8 mu M, respectively.
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| 2. |
- Karim, A., et al.
(författare)
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The three-center-four-electron tetrel bond
- 2018
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Konferensbidrag (refereegranskat)abstract
- We present a thermodynamically stable complex that possesses a three-center-four-electron (3c4e) tetrel bond [1,2], formed by capturing a reactive carbenium ion with a bidentate Lewis base. We report NMR spectroscopic, titration calorimetric and reaction kinetic evidences for the structure of this pentacoordinate species and discuss the properties of its tetrel bond, [N˜˜˜∙∙∙C∙∙∙˜˜˜N]+, in comparison with the analogous halogen, [N˜˜˜∙∙∙X∙∙∙˜˜˜N]+ and hydrogen, [N∙∙∙˜˜˜H∙∙∙˜˜˜N]+, bonds [3]. The necessity of the involvement of a bidentate Lewis base for the formation of a stable 3c4e tetrel bond is demonstrated by providing spectroscopic and crystallographic evidence, that a monodentate Lewis base induces a reaction rather than stabilizing the reactive species. A vastly decreased Lewis basicity of the bidentate ligand or reduced Lewis acidity of the carbenium ion weakens — or even prohibits — the formation of the pentacoordinate species, whereas synthetic modifications facilitating attractive orbital overlaps promote it. As the geometry of the pentacoordinate complex resembles the SN2 transition state, it may provide a model system for the investigation of fundamental reaction mechanisms and chemical bonding theories [4].References1. G.C. Pimentel J. Chem. Phys. 1951, 19, 446-4482. R.H. Crabtree Chem. Soc. Rev. 2017, 46, 1720-1729.3. S.B. Hakkert, M. Erdelyi J. Phys. Org. Chem. 2015, 95, 2572-25784. Karim, N. Schultz, H. Andersson, B. Nekoueishahraki et al, 2018, submitted.
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| 3. |
- Abdissa, Negera, et al.
(författare)
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Naphthalene Derivatives from the Roots of Pentas parvifolia and Pentas bussei
- 2016
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Ingår i: Journal of natural products. - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025. ; 79:9, s. 2181-2187
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Tidskriftsartikel (refereegranskat)abstract
- The phytochemical investigation of the CH2Cl2/MeOH (1:1) extract of the roots of Pentas parvifolia led to the isolation of three new naphthalenes, parvinaphthols A (1), B (2), and C (3), two known anthraquinones, and five known naphthalene derivatives. Similar investigation of the roots of Pentas bussei afforded a new polycyclic naphthalene, busseihydroquinone E (4), a new 2,2′-binaphthralenyl-1,1′-dione, busseihydroquinone F (5), and five known naphthalenes. All purified metabolites were characterized by NMR and MS data analyses, whereas the absolute configurations of 3 and 4 were determined by single-crystal X-ray diffraction studies. The E-geometry of compound 5 was supported by DFT-based chemical shift calculations. Compounds 2-4 showed marginal cytotoxicity against the MDA-MB-231 human triple-negative breast cancer cell line with IC50 values ranging from 62.3 to 129.6 μM. © 2016 The American Chemical Society and American Society of Pharmacognosy.
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| 4. |
- Atilaw, Yoseph, et al.
(författare)
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Prenylated Flavonoids from the Roots of Tephrosia rhodesica
- 2020
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Ingår i: Journal of Natural Products. - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025. ; 83:8, s. 2390-2398
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Tidskriftsartikel (refereegranskat)abstract
- Five new compounds-rhodimer (1), rhodiflavan A (2), rhodiflavan B (3), rhodiflavan C (4), and rhodacarpin (5)-along with 16 known secondary metabolites, were isolated from the CH2Cl2-CH3OH (1:1) extract of the roots of Tephrosia rhodesica. They were identified by NMR spectroscopic, mass spectrometric, X-ray crystallographic, and ECD spectroscopic analyses. The crude extract and the isolated compounds 2-5, 9, 15, and 21 showed activity (100% at 10 mu g and IC50 = 5-15 mu M) against the chloroquine-sensitive (3D7) strain of Plasmodium falciparum.
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| 5. |
- Deyou, Tsegaye, et al.
(författare)
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Rotenoids, Flavonoids, and Chalcones from the Root Bark of Millettia usaramensis
- 2015
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Ingår i: Journal of Natural Products. - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025 .- 0974-5211. ; 78:12, s. 2932-2939
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Tidskriftsartikel (refereegranskat)abstract
- Five new compounds, 4-O-geranylisoliquiritigenin (1), 12-dihydrousararotenoid B (2), 12-dihydrousararotenoid C (3), 4'-O-geranyl-7-hydroxyflavanone (4), and 4'O-geranyl-7-hydroxydihydroflavanol (5), along with 12 known natural products (6-17) were isolated from the CH2Cl2/MeOH (1:1) extract of the root bark of Millettia usaramensis ssp. usaramensis by chromatographic separation. The purified metabolites were identified by NMR spectroscopic and mass spectrometric analyses, whereas their absolute configurations were established on the basis of chiroptical data and in some cases also by X-ray crystallography. The crude extract was moderately active (IC50 = 11.63 mu g/mL) against the ER-negative MDB-MB-231 human breast cancer cell line, and accordingly compounds 6, 8, 9, 10, 12, and 16 also showed moderate to low cytotoxic activities (IC50 25.7-207.2 mu M). The new natural product 1 exhibited antiplasmodial activity with IC50 values of 3.7 and 5.3 mu M against the chloroquine-sensitive 3D7 and the chloroquine-resistant Dd2 Plasmodium falciparum strains, respectively, and was also cytotoxic to the HEK293 cell line.
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| 6. |
- Nyandoro, Stephen S., 1975, et al.
(författare)
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Flavonoids from Erythrina schliebenii
- 2017
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Ingår i: Journal of Natural Products. - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025. ; 80:2, s. 377-383
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Tidskriftsartikel (refereegranskat)abstract
- Prenylated and O-methylflavonoids including one new pterocarpan (1), three new isoflavones (2-4), and nineteen known natural products (5-23) were isolated and identified from the root, stem bark, and leaf extracts of Erythrina schliebenii. The crude extracts and their constituents were evaluated for antitubercular activity against Mycobacterium tuberculosis (H37Rv strain), showing MICs of 32-64 mu g mL(-1) and 36.9-101.8 mu M, respectively. Evaluation of their toxicity against the aggressive human breast cancer cell line MDA-MB-231 indicated EC50 values of 13.0-290.6 mu M (pure compounds) and 38.3 to >100 mu g mL(-1) (crude extracts). RAMSON D, 1973, PHYTOCHEMISTRY, V12, P2211
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| 7. |
- Carlsson, Anna-Carin, 1976, et al.
(författare)
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Substituent Effects on the [N–I–N]+ Halogen Bond
- 2016
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 138:31
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the influence of electron density on the three-center [N–I–N]+ halogen bond. A series of [bis(pyridine)iodine]+ and [1,2-bis((pyridine-2-ylethynyl)benzene)iodine]+ BF4– complexes substituted with electron withdrawing and donating functionalities in the para-position of their pyridine nitrogen were synthesized and studied by spectroscopic and computational methods. The systematic change of electron density of the pyridine nitrogens upon alteration of the para-substituent (NO2, CF3, H, F, Me, OMe, NMe2) was confirmed by 15N NMR and by computation of the natural atomic population and the π electron population of the nitrogen atoms. Formation of the [N–I–N]+ halogen bond resulted in >100 ppm 15N NMR coordination shifts. Substituent effects on the 15N NMR chemical shift are governed by the π population rather than the total electron population at the nitrogens. Isotopic perturbation of equilibrium NMR studies along with computation on the DFT level indicate that all studied systems possess static, symmetric [N–I–N]+ halogen bonds, independent of their electron density. This was further confirmed by single crystal X-ray diffraction data of 4-substituted [bis(pyridine)iodine]+ complexes. An increased electron density of the halogen bond acceptor stabilizes the [N···I···N]+ bond, whereas electron deficiency reduces the stability of the complexes, as demonstrated by UV-kinetics and computation. In contrast, the N–I bond length is virtually unaffected by changes of the electron density. The understanding of electronic effects on the [N–X–N]+ halogen bond is expected to provide a useful handle for the modulation of the reactivity of [bis(pyridine)halogen]+-type synthetic reagents.
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| 8. |
- Nyandoro, Stephen S., 1975, et al.
(författare)
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N-Cinnamoyltetraketide Derivatives from the Leaves of Toussaintia orientalis
- 2015
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Ingår i: Journal of natural products. - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025. ; 78:8
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Tidskriftsartikel (refereegranskat)abstract
- Seven N-cinnamoyltetraketides (1–7), including the new Z-toussaintine E (2), toussaintine F (6), and toussaintine G (7), were isolated from the methanol extract of the leaves of Toussaintia orientalis using column chromatography and HPLC. The configurations of E-toussaintine E (1) and toussaintines A (3) and D (5) are revised based on single-crystal X-ray diffraction data from racemic crystals. Both the crude methanol extract and the isolated constituents exhibit antimycobacterial activities (MIC 83.3–107.7 μM) against the H37Rv strain of Mycobacterium tuberculosis. Compounds 1, 3, 4, and 5 are cytotoxic (ED50 15.3–105.7 μM) against the MDA-MB-231 triple negative aggressive breast cancer cell line.
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| 9. |
- Nyandoro, Stephen S., 1975, et al.
(författare)
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Polyoxygenated Cyclohexenes and Other Constituents of Cleistochlamys kirkii Leaves
- 2017
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Ingår i: Journal of natural products. - : American Chemical Society (ACS). - 0163-3864 .- 1520-6025. ; 80:1, s. 114-125
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Tidskriftsartikel (refereegranskat)abstract
- Thirteen new metabolites, including the polyoxygenated cyclohexene derivatives cleistodiendiol (1), cleistodienol B (3), cleistenechlorohydrins A (4) and B (5), cleistenediols A–F (6–11), cleistenonal (12), and the butenolide cleistanolate (13), 2,5-dihydroxybenzyl benzoate (cleistophenolide, 14), and eight known compounds (2, 15–21) were isolated from a MeOH extract of the leaves of Cleistochlamys kirkii. The purified metabolites were identified by NMR spectroscopic and mass spectrometric analyses, whereas the absolute configurations of compounds 1, 17, and 19 were established by single-crystal X-ray diffraction. The configuration of the exocyclic double bond of compound 2 was revised based on comparison of its NMR spectroscopic features and optical rotation to those of 1, for which the configuration was determined by X-ray diffraction. Observation of the co-occurrence of cyclohexenoids and heptenolides in C. kirkii is of biogenetic and chemotaxonomic significance. Some of the isolated compounds showed activity against Plasmodium falciparum (3D7, Dd2), with IC50 values of 0.2–40 μM, and against HEK293 mammalian cells (IC50 2.7–3.6 μM). While the crude extract was inactive at 100 μg/mL against the MDA-MB-231 triple-negative breast cancer cell line, some of its isolated constituents demonstrated cytotoxic activity with IC50 values ranging from 0.03–8.2 μM. Compound 1 showed the most potent antiplasmodial (IC50 0.2 μM) and cytotoxic (IC50 0.03 μM, MDA-MB-231 cell line) activities. None of the compounds investigated exhibited translational inhibitory activity in vitro at 20 μM.
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