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1.
Int J Mol Sci ; 23(23)2022 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-36499338

RESUMO

Inflammation is implicated in a wide variety of physiological and pathological processes. Plants are an important source of active anti-inflammatory compounds. The compound 3, 5-diprenyl-4-hydroxyacetophenone (DHAP) was isolated from the dichloromethane extract of the aerial parts of Ageratina pazcuarensis by chromatography and identified by spectroscopic (IR, NMR) and spectrometric (GC-MS) methods. Anti-inflammatory activity was evaluated on ear edema mouse induced with 12-O-tetradecanoylphorbol 13-acetate (TPA) at 2 mg/ear. The antioxidant activity of DHAP was determined using DPPH assay. Cell viability was tested in J774A.1 macrophages, the levels of NO, TNF-α, IL-1ß, IL-6, and IL-10 production in macrophages stimulated with lipopolysaccharide (LPS), and membrane lysis induced by hypotonic solution in erythrocytes were evaluated. DHAP diminished the ear edema mouse in 70.10%, and it had scavenger effect against the radical with IC50 of 26.00 ± 0.37 µg/mL. Likewise, 91.78 µM of this compound inhibited the production of NO (38.96%), IL-1ß (55.56%), IL-6 (51.62%), and TNF-α (59.14%) in macrophages and increased the levels of IL-10 (61.20%). Finally, 25 and 50 µg/mL DHAP provided the greatest protection against erythrocyte membrane lysis. These results demonstrate that DHAP has anti-inflammatory activity.


Assuntos
Ageratina , Anti-Inflamatórios , Extratos Vegetais , Animais , Camundongos , Ageratina/química , Anti-Inflamatórios/farmacologia , Edema/induzido quimicamente , Interleucina-10 , Interleucina-6 , Lipopolissacarídeos , Extratos Vegetais/farmacologia , Fator de Necrose Tumoral alfa
2.
Pharmaceuticals (Basel) ; 15(7)2022 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-35890070

RESUMO

BACKGROUND: Inflammation is a complex process as a response to several stimuli, such as infection, a chemical irritant, and the attack of a foreign body. Piquerol was isolated from Piqueria trinervia, and its anti-inflammatory activity was evaluated using in vivo and in vitro models. METHODS: Piquerol is a monoterpene that was identified using NMR, FT-IR spectroscopy, and mass spectrometry analysis. The anti-inflammatory activity was tested in vivo in ear edema induced with TPA in mice. Piquerol was also tested on J774A.1 macrophages stimulated with lipopolysaccharide (LPS), and the levels of NO, NF-κB, TNF-α, IL-1ß, IL-6, and IL-10 were determined using ELISA. RESULTS: The results show that piquerol diminished ear edema (66.19%). At 150.51 µM, it also inhibited the levels of NO (31.7%), TNF-α (49.8%), IL-1ß (69.9%), IL-6 (47.5%), and NF-κB (26.7%), and increased the production of IL-10 (62.3%). Piquerol has a membrane stabilization property in erythrocyte, and at 100 µg/mL, the membrane protection was of 86.17%. CONCLUSIONS: Piquerol has anti-inflammatory activity, and its possible mechanism of action is through the inhibition of pro-inflammatory mediators. This compound could be a candidate in the development of new drugs to treat inflammatory problems.

3.
Nat Prod Res ; 36(4): 1123-1128, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33342288

RESUMO

Agave marmorata Roezl is an endemic succulent specie from the Oaxaca-Puebla area of Mexico. This plant is a medicinal recourse and contain a rich variety of saponins-type compounds with multiples biological effects. Some of them have been shown to be anticancer, antibacterial, or having anti-inflammatory and immunoregulation effects. This paper is the first scientific report to describe the pharmacological activity and chemistry of the saponin smilagenin-3-O-[ß-D-glucopyranosyl (1→2)-ß-D-galactopyranoside] (1), isolated from Agave marmorata Roezl. Saponin (1) displayed immunomodulating activity when assayed on cultured macrophages. It inhibits NO production (EC50 = 5.6 mg/ml, Emax = 101%), as well as NF-κB expression (EC50 = 0.086 mg/ml, Emax = 90%). Using bioinformatic molecular docking, we identified a new smilagenin- PI3K kinase interaction site.


Assuntos
Agave , NF-kappa B/antagonistas & inibidores , Saponinas , Fator de Transcrição AP-1/antagonistas & inibidores , Agave/química , Simulação de Acoplamento Molecular , Estrutura Molecular , Saponinas/química , Saponinas/farmacologia
4.
Nat Prod Res ; 35(23): 5344-5349, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32347111

RESUMO

Phytochemical research of the acetate and methanol extracts of the aerial parts (flowers, leaves and stems) of Salvia elegans allowed to obtain seventeen known compounds (1-17): three of them (4, 5, 14), had already been described for this species, while the others (1-3, 6-13, 15-17) are described for the first time for S. elegans. All isolated compounds were characterized using spectroscopic techniques and mass spectrometry and were evaluated in the Angiotensin I-converting enzyme (ACE) inhibition model, where the phenolic compounds (13, 14 and 15) had the same inhibitory effect as lisinopril at 0.02 mg/mL. The terpenes showed a moderate inhibitory capacity at a concentration of 0.2 mg/mL.


Assuntos
Inibidores da Enzima Conversora de Angiotensina , Salvia , Inibidores da Enzima Conversora de Angiotensina/farmacologia , Fenóis , Extratos Vegetais/farmacologia , Folhas de Planta
5.
Biomolecules ; 10(5)2020 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-32429307

RESUMO

Haemonchus contortus affect small ruminants all over the world. Anthelmintics cause resistance, contamination, and a risk of public health. Prosopis laevigata is a plant used as a home remedy against many diseases in Mexico. This study arose from a preliminary study where a P. laevigata hydroalcoholic extract (Pl-hae) showed anthelmintic activity (aa) against H. contortus. Searching for bioactive compounds (bac) with high aa, the Pl-hae was fractioned obtaining an aqueous (Aq-F) and an ethyl acetate fraction (EtAc-F), and a flavonoid with aa identified as isorhamnetin was obtained from EtAc-F. Both fractions were in vitro assessed by the egg hatch test (eht) and larval mortality (lm) assays. The bac obtained from EtAc-F were characterised by NMR analysis. The highest aa were recorded with EtAc-F, resulting in 100% eht and 80.45% lm at 0.75 and 30 mg/mL, respectively. Alterations in eggs and larvae attributed to isorhamnetin were recorded by environmental scanning electron microscopy, confocal laser scanning and by high-resolution digital-coupled camera. This flavonoid caused 100% eht at 0.07 mg/mL after 48 h and 100% lm at 7.5 mg/mL after 72 h exposure. Isorhamnetin has promising potential as an anthelmintic against sheep haemonchosis.


Assuntos
Anti-Helmínticos/farmacologia , Haemonchus/efeitos dos fármacos , Prosopis/química , Quercetina/análogos & derivados , Animais , Anti-Helmínticos/química , Haemonchus/crescimento & desenvolvimento , Larva/efeitos dos fármacos , Óvulo/efeitos dos fármacos , Folhas de Planta/química , Quercetina/química , Quercetina/farmacologia
6.
Food Chem ; 309: 125796, 2020 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-31706678

RESUMO

Interest in anthocyanins has increased remarkably in recent decades, although their wider application has been hampered by instability problems. Thus, this study aimed at developing a strategy to gain access to more stable anthocyanins via enzymatic esterification. For that purpose, three cyanidin derivatives were obtained from underutilized, but easily accessible sources, and their total anthocyanin content was quantified. The purity of cyanidins obtained ranged from 40% to 88% depending on their source. Subsequently, the critical enzymatic reaction conditions were established, and the best results were found using tert-butanol as a solvent, 20 g/L of lipase B from Candida Antarctica, and vinyl cinnamate as acyl donor at ratio 250:1 (acyl donor to anthocyanin). Finally, five new acylated anthocyanin derivatives were synthesized with improved antioxidant activity and thermostability, in comparison to the cyanidin-3-glucoside, which is an advantageous feature for industrial applications.


Assuntos
Antocianinas/metabolismo , Antioxidantes/química , Proteínas Fúngicas/metabolismo , Glucosídeos/metabolismo , Lipase/metabolismo , Acilação , Antocianinas/química , Cinamatos/química , Esterificação , Glucosídeos/química , Espectroscopia de Ressonância Magnética , Prunus domestica/química , Prunus domestica/metabolismo , Solventes/química , Temperatura
7.
Drug Dev Res ; 79(4): 165-172, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29989223

RESUMO

Salvia tiliifolia Vahl (Lamiaceae) is used for the empirical treatment of pain and inflammation. The diterpenoid tilifodiolide (TFD) was isolated from Salvia tiliifolia. The in vitro anti-inflammatory effects of TFD (0.1-200 µM) were assessed using murine macrophages stimulated with LPS and estimating the levels of pro-inflammatory mediators for 48 h. The in vivo anti-inflammatory activity of TFD was assessed using the carrageenan-induced paw edema test for 6 h. The antinociceptive effects of TFD were evaluated using the formalin test and the acetic acid induced-writhing test. The effects of TFD on locomotor activity were assessed using the open field test and the rotarod test. TFD inhibited the production of TNF-α (IC50 = 5.66 µM) and IL-6 (IC50 = 1.21 µM) in macrophages. TFD (200 mg/kg) showed anti-inflammatory effects with similar activity compared to 10 mg/kg indomethacin. The administration of TFD induced antinociception in the phase 1 (ED50 = 48.2 mg/kg) and the phase 2 (ED50 = 28.9 mg/kg) of the formalin test. In the acetic acid assay, TFD showed antinociceptive effects (ED50 = 32.3 mg/kg) with similar potency compared to naproxen (ED50 = 36.2 mg/kg). In the presence of different inhibitors in the acetic acid assay, only the co-administration of TFD and naloxone reverted the antinociceptive activity shown by TFD alone. TFD did not affect locomotor activity in mice. TFD exerts in vitro and in vivo anti-inflammatory activity and in vivo antinociceptive effects.


Assuntos
Analgésicos/farmacologia , Anti-Inflamatórios/farmacologia , Diterpenos/farmacologia , Medição da Dor/efeitos dos fármacos , Salvia/química , Animais , Diterpenos/química , Diterpenos/isolamento & purificação , Relação Dose-Resposta a Droga , Indometacina/farmacologia , Interleucina-6/metabolismo , Macrófagos/metabolismo , Masculino , Camundongos , Atividade Motora , Naloxona/farmacologia , Naproxeno/farmacologia , Teste de Desempenho do Rota-Rod , Fator de Necrose Tumoral alfa/metabolismo
8.
Rev. bras. farmacogn ; 27(3): 302-305, May-June 2017. tab, graf
Artigo em Inglês | LILACS | ID: biblio-898662

RESUMO

Abstract New compounds with chemotherapeutic activity are sought after, and plants are an important source of these compounds. Four diterpenes, 19-deoxyicetexone, 7,20-dihydroanastomosine, icetexone and 19-deoxyisoicetexone, were isolated from the hexane-washed chloroform extract of Salvia ballotiflora. The cytotoxic activity of the hexane-washed chloroform extract and its four diterpenes were tested using the MTT assay against three tumor cell lines: HeLa (cervical cancer), A549 (lung cancer) and MCF7 (breast cancer), and two murine cell line: J774A.1 (epithelial cancer) and CT26 (colon cancer), and their IC50 values were determined. 19-Deoxyisoicetexone had the greatest effect on HeLa cells with IC50 of 3.2 µg/ml (9.36 µM), whereas hexane-washed chloroform extract had the best cytotoxic effect on A549 cells with an IC50 of 2.29 µg/ml. These effects of 19-deoxyisoicetexone and hexane-washed chloroform extract were with similar activity compared to cisplatin (IC50 = 1.06 µg/ml in HeLa cells, and 4.6 µg/ml (15.21 µM) in A549 cells).

9.
Pharm Biol ; 55(1): 1467-1472, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28347190

RESUMO

CONTEXT: A previous study demonstrated that the chloroform extract of Salvia connivens Epling (Lamiaceae) has anti-inflammatory activity. OBJECTIVE: Identification of the active components in the dicholorometane extract (DESC), and, standardization of the extract based in ursolic acid. MATERIAL AND METHODS: DESC was prepared by percolation with dichlromethane and after washed with hot hexane, its composition was determined by CG-MS and NMR, and standardized by HPLC. The anti-inflammatory activity was tested on acute TPA-induced mouse ear oedema at doses of 2.0 mg/ear. The cell viability of macrophages was evaluated by MTT method, and pro- and anti-inflammatory interleukin levels were measured using an ELISA kit. RESULTS: Ursolic acid, oleanolic acid, dihydroursolic acid and eupatorin were identified in DESC, which was standardized based on the ursolic acid concentration (126 mg/g). The anti-inflammatory activities of DESC, the acid mixture, and eupatorin (2 mg/ear) were 60.55, 57.20 and 56.40% inhibition, respectively, on TPA-induced ear oedema. The IC50 of DESC on macrophages was 149.4 µg/mL. DESC (25 µg/mL) significantly reduced TNF-α (2.0-fold), IL-1ß (2.2-fold) and IL-6 (2.0-fold) in macrophages stimulated with LPS and increased the production of IL-10 (1.9-fold). DISCUSSION: Inflammation is a basic response to injuries, and macrophages are involved in triggering inflammation. Macrophage cells exhibit a response to LPS, inducing inflammatory mediators, and DESC inhibits the biosynthesis of the pro-inflammatory and promote anti-inflammatory cytokines. CONCLUSION: DESC has an anti-inflammatory effect; reduced the levels of IL-1ß, Il-6 and TNF-α; and increases IL-10 in macrophages stimulated with LPS. Ursolic acid is a good phytochemical marker.


Assuntos
Anti-Inflamatórios/farmacologia , Edema/prevenção & controle , Lipopolissacarídeos/farmacologia , Ativação de Macrófagos/efeitos dos fármacos , Macrófagos/efeitos dos fármacos , Cloreto de Metileno/química , Extratos Vegetais/farmacologia , Salvia/química , Solventes/química , Animais , Anti-Inflamatórios/isolamento & purificação , Linhagem Celular , Cromatografia Líquida de Alta Pressão , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Edema/induzido quimicamente , Edema/imunologia , Flavonoides/isolamento & purificação , Flavonoides/farmacologia , Cromatografia Gasosa-Espectrometria de Massas , Interleucina-1beta/metabolismo , Interleucina-6/metabolismo , Macrófagos/imunologia , Macrófagos/metabolismo , Espectroscopia de Ressonância Magnética , Masculino , Camundongos , Ácido Oleanólico/isolamento & purificação , Ácido Oleanólico/farmacologia , Fitoterapia , Componentes Aéreos da Planta/química , Extratos Vegetais/isolamento & purificação , Plantas Medicinais , Acetato de Tetradecanoilforbol , Triterpenos/isolamento & purificação , Triterpenos/farmacologia , Fator de Necrose Tumoral alfa/metabolismo , Ácido Ursólico
10.
Drug Dev Res ; 76(4): 185-93, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-26109468

RESUMO

Preclinical Research Krameria cytisoides is used for the treatment of inflammation, stomach pain, and gastric ulcers. The active ingredient from this plant is a peroxide, kramecyne (KACY) which has anti-inflammatory effects. The aim of the present study was to evaluate the anti-inflammatory activities of KACY in lipopolysaccharide (LPS)-induced systemic chronic inflammation in mice for 60 days, using dexamethasone (DEX) as the positive control, vehicle (the LPS group) as the negative control and the control group (mice without inflammation). KACY did not affect survival, body weight or relative organ weight in mice but it: decreased nitric oxide (NO) production by 68%; prostaglandin E2 (PGE2 ) by 67%; increased release of anti-inflammatory cytokine IL-10 (2.0-fold), and reduced production of the proinflammatory cytokines, IL-6 (2.0-fold), IL-1ß (2.4-fold), and TNF-α (2.0-fold). Furthermore, the gastroprotective effects of KACY in mice were evaluated in an ethanol-induced gastric ulcer model. The results showed that KACY at 50 and 100 mg/kg exerted gastroprotective effects with similar activity to 50 mg/kg ranitidine. In gastric tissues, KACY decreased the level of malondialdehyde (MDA) but increased the catalase (CAT) activity. KACY have potential for the treatment of chronic inflammatory diseases due its similar activity to that of DEX. It also has gastroprotective effects.


Assuntos
Anti-Inflamatórios/uso terapêutico , Antiulcerosos/uso terapêutico , Éteres Cíclicos/uso terapêutico , Peróxidos/uso terapêutico , Úlcera Gástrica/tratamento farmacológico , Animais , Anti-Inflamatórios/farmacologia , Antiulcerosos/farmacologia , Catalase/metabolismo , Citocinas/sangue , Dinoprostona/sangue , Etanol , Éteres Cíclicos/farmacologia , Glutationa Peroxidase/metabolismo , Glutationa Redutase/metabolismo , Lipopolissacarídeos , Masculino , Malondialdeído/metabolismo , Camundongos , Óxido Nítrico/metabolismo , Peróxidos/farmacologia , Úlcera Gástrica/induzido quimicamente , Úlcera Gástrica/metabolismo , Superóxido Dismutase/metabolismo
11.
Life Sci ; 121: 70-7, 2015 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-25476830

RESUMO

AIMS: The aim of this study was to evaluate the antinociceptive (acute assays) and anti-inflammatory (chronic assays) effects of kramecyne (KACY), a peroxide isolated from Krameria cytisoides. MAIN METHODS: The antinociceptive activity of KACY was evaluated using the hot plate, acetic acid and formalin tests. The effects of KACY on heat-induced hemolysis in rat erythrocytes were also evaluated. The in vivo anti-inflammatory assays were performed using the chronic TPA (12-O-tetradecanoylphorbol 13-acetate) method to induce ear edema and carrageenan-kaolin induced arthritis (CKIA). In the CKIA model, the hot plate test was performed, serum samples were obtained for the quantitation of pro-inflammatory (IL-1ß, IL-6, IL-12 and TNF-α) and anti-inflammatory (IL-4 and IL-10) cytokines. KEY FINDINGS: KACY possess antinociceptive effects with comparable activity to naproxen (NPX). KACY inhibited hemolysis (EC50 = 180 µg/mL), in comparison to the untreated group and with a higher potency than NPX (EC50 = 263 µg/mL). KACY at 50 mg/kg decreased inflammation by 38% (chronic TPA-induced edema model) and by 26% (CKIA model), in comparison with the vehicle group and with similar activity to the positive controls 8 mg/kg indomethacin (IND) and 1 mg/kg methotrexate (MTX), respectively. In the CKIA model, KACY increased the release of anti-inflammatory (IL-4 and IL-10) cytokines but reduced the production of pro-inflammatory cytokines (IL-1ß, IL-6, IL-12 and TNF-α). KACY at 50 and 100 mg/kg showed antinociceptive effects by 27% and 23%, respectively, in mice with mono-arthritis. SIGNIFICANCE: KACY might be a good alternative for the treatment of rheumatoid arthritis (RA) due its antinociceptive and anti-inflammatory activities.


Assuntos
Analgésicos/uso terapêutico , Anti-Inflamatórios não Esteroides/uso terapêutico , Artrite/tratamento farmacológico , Éteres Cíclicos/uso terapêutico , Peróxidos/uso terapêutico , Animais , Artrite/induzido quimicamente , Peso Corporal/efeitos dos fármacos , Citocinas/metabolismo , Edema/induzido quimicamente , Edema/tratamento farmacológico , Membrana Eritrocítica/efeitos dos fármacos , Hemólise/efeitos dos fármacos , Técnicas In Vitro , Krameriaceae/química , Masculino , Camundongos , Medição da Dor/efeitos dos fármacos , Ratos , Ratos Wistar
12.
Molecules ; 18(8): 8895-905, 2013 Jul 26.
Artigo em Inglês | MEDLINE | ID: mdl-23896615

RESUMO

The antidiarrheal properties of 19-deoxyicetexone, a diterpenoid isolated from Salvia ballotiflora were evaluated on castor oil-, arachidonic acid (AA)- and prostaglandin (PGE2)-induced diarrhea in rodent models. The structure of 19-deoxyicetexone was determined by X-ray crystallography, mass spectrometry (EI-MS), as well as ultraviolet (UV-Vis), infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopies. This compound significantly and dose-dependently reduced frequency of stooling in castor oil-induced diarrhea, and at dose of 25 mg/kg it also inhibited diarrhea induced with AA, while it had no effect on PGE2-induced diarrhea. This compound at doses of 25 mg/kg also diminished castor oil-induced enteropooling and intestinal motility, and inhibited the contraction of the rats' ileum induced by carbachol chloride at a concentration of 100 µg/mL. 19-Deoxyicetexone did not present acute toxicity at doses of 625 mg/kg. Its antidiarrheal activity may be due to increased reabsorption of NaCl and water and inhibition of the release of prostaglandins, gastrointestinal motility and fluid accumulation in the intestinal tracts of rats. These findings suggest that 19-deoxyicetexone may be used in the treatment of diarrhea, although more studies must be carried out to confirm this.


Assuntos
Diarreia/tratamento farmacológico , Diterpenos/isolamento & purificação , Medicamentos de Ervas Chinesas/química , Animais , Antidiarreicos/administração & dosagem , Antidiarreicos/química , Antidiarreicos/isolamento & purificação , Canfanos , Cristalografia por Raios X , Diarreia/induzido quimicamente , Diarreia/patologia , Diterpenos/administração & dosagem , Diterpenos/química , Medicamentos de Ervas Chinesas/administração & dosagem , Humanos , Espectroscopia de Ressonância Magnética , Camundongos , Panax notoginseng , Ratos , Salvia miltiorrhiza
13.
Molecules ; 17(2): 2049-57, 2012 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-22349895

RESUMO

In the present work we describe the structure and anti-inflammatory activity of a new compound, kramecyne, isolated from a methanol extract of Krameria cytisoides (Krameriaceae). The structure of kramecyne was determined by IR, NMR, MS, and elemental analysis, which indicated that the structure corresponded to a hexamer of cyclic peroxide monomers. This compound exhibited good anti-inflammatory activity in the 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced mouse ear edema (51.8 ± 6.9% inhibition) and carrageenan-induced rat paw edema models at doses of 50 mg/kg. The compound significantly reduced edema to 63.1% after 1.0 h, and the effect was unchanged for 5 h. Kramecyne did not present acute toxicity, even at doses of 5,000 mg/kg.


Assuntos
Anti-Inflamatórios/química , Anti-Inflamatórios/farmacologia , Éteres Cíclicos/química , Éteres Cíclicos/farmacologia , Krameriaceae/química , Peróxidos/química , Peróxidos/farmacologia , Extratos Vegetais/química , Extratos Vegetais/farmacologia , Animais , Edema/induzido quimicamente , Edema/tratamento farmacológico , Masculino , Camundongos , Ratos , Ratos Wistar , Relação Estrutura-Atividade
14.
Magn Reson Chem ; 48(11): 866-72, 2010 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-20821374

RESUMO

The indirect vicinal proton-proton coupling constants for pyrrole, furan, thiophene and 15 related heteroaromatic compounds were calculated using the Khon-Sham approximation. An analysis of the four Ramsey contributions to the coupling constants was carried out showing that the Fermi contact term is always positive and dominant, although the remaining contributions have a nonnegligible net negative contribution. The trends observed for the proton-proton coupling constants were rationalized in terms of the properties of the electron density. It was found that electron delocalization between the corresponding hydrogen atoms plays a major role on the observed behavior with the charges of the carbon atoms bonded to them and the accompanying geometric variations being also of importance in the coupling mechanism.


Assuntos
Compostos Heterocíclicos/química , Hidrocarbonetos Aromáticos/química , Prótons , Simulação por Computador , Furanos/química , Espectroscopia de Ressonância Magnética/normas , Estrutura Molecular , Pirróis/química , Teoria Quântica , Padrões de Referência , Estereoisomerismo , Tiofenos/química
15.
J Phys Chem A ; 111(33): 8264-70, 2007 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-17672442

RESUMO

We studied vicinal and long-range coupling constants for 9-anthracene derivatives, e.g., Br, CN, CHO, NO2, CH2Cl, CH2OH, and OCH3. We performed the accurate measurements using modified J doubling in the frequency domain, even for the smallest couplings immersed within the line width. Density functional theory allowed us to reproduce and exhaustively analyze the physical contributions to the values of these spectroscopic parameters. The theory of atoms in molecules defines a delocalization index that correlates linearly with vicinal and long-range coupling constants when they are grouped in terms of the number of bonds between the coupled nuclei. An exception to this behavior is obtained for 4J(H4,H10) values, which have a negative Fermi contact and the largest delocalization index for each molecule. This observation can be explained by a characteristic "gable roof" arrangement formed by the five nuclei involved in the coupling.


Assuntos
Antracenos/química , Prótons , Solventes/química
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