Substituent and ring effects on enthalpies of formation: 2-methyl- and 2-ethylbenzimidazoles versus benzene-and imidazole-derivatives

The enthalpies of combustion, heat capacities, enthalpies of sublimation and enthalpies of formation of 2-methylbenzimidazole (2MeBIM) and 2-ethylbenzimidazole (2EtBIM) are reported and the results compared with those of benzimidazole itself (BIM). Theoretical estimates of the enthalpies of formation were obtained through the use of atom equivalent schemes. The necessary energies were obtained in single-point calculations at the B3LYP/6-311+G(d,p) on B3LYP/6-31G* optimized geometries. The comparison of experimental and calculated values of benzenes, imidazoles and benzimidazoles bearing H (unsubstituted), methyl and ethyl groups shows remarkable homogeneity. The energetic group contribution transferability is not followed, but either using it or adding an empirical interaction term, it is possible to generate an enormous collection of reasonably accurate data for different substituted heterocycles (pyrazole-derivatives, pyridine-derivatives, etc.) from the large amount of values available for substituted benzenes and those of the parent (pyrazole, pyridine) heterocycles.We acknowledge the financial support of the DGI/MCyT (project nos. BQU-2003-00976, 01251 and 05827). This work has been partially supported by the DGI project no. BQU-2003-00894. A generous allocation of computational time at the CCC of the Universidad Auto´noma de Madrid is also gratefully acknowledged. Thanks are also due to Instituto de Cooperac¸a˜o Cientı´fica e Tecnolo´gica Internacional (ICCTI), Lisbon, Portugal, and Consejo Superior de Investigaciones Cientı´ficas (CSIC), Madrid, Spain, for a joint research project ICCTI/CSIC. MLPFA thanks Fundac¸a˜o para a Cieˆncia e Tecnologia (FCT), Lisbon, Portugal, for the award of a postdoctoral fellowship (PRAXIS XXI/BPD/16319/98) and MT thanks MECD/SEEU (AP 2002-0603), Spain, for financial support

Experimental thermochemical study of two 2-alkylbenzimidazole isomers (alkyl = propyl and isopropyl)

This paper reports the values of the standard (p∘=0.1 MPa) molar enthalpy of formation in the condensed, at T=298.15 K, for 2-R-benzimidazoles (R=propyl, isopropyl), derived from, the respective enthalpies of combustion in oxygen, measured by static bomb combustion calorimetry and the standard molar enthalpies of sublimation, at T=298.15 K, obtained using Calvet microcalorimetry in the case of 2-isopropylbenzimidazole and, by the variation of vapour pressures, determined by the Knudsen effusion technique, with temperatures between (344 and 365) K for 2-propylbenzimidazole. Heat capacities, in the temperature ranges from T=268 K to near their respective melting temperatures, T=421 K for 2-propylbenzimidazole and T=464 K for 2-isopropylbenzimidazole, were measured with a differential scanning calorimeter. These values were used to derive the standard molar enthalpies of formation, of the two 2-benzimidazole derivatives, in gaseous phase.Thanks are due to Instituto de Cooperação Cientı́fica e Tecnológica Industrial (ICCTI), Lisbon, Portugal, and Consejo Superior de Investigaciones Cientı́ficas (CSIC), Madrid, Spain for a joint research project CSIC/ICCTI; M.L.P.F.A. thanks Fundação para a Ciência e Tecnologia (FCT), Lisbon, Portugal, for the award of a postdoctoral fellowship (SRFH/BPD/5595/2001). The Spanish DGI/MCyT is acknowledged under projects BQU2000-0252, 0906 and 1497; M.T. thanks MECD/SEEU, AP2002-0603, Spain for financial support

Substituent effects on enthalpies of formation of nitrogen heterocycles: 2-substituted benzimidazoles and related compounds

The enthalpies of combustion, heat capacities, enthalpies of sublimation and enthalpies of formation of 2-tert-butylbenzimidazole (2tBuBIM) and 2-phenylimidazole (2PhIM) are reported and the results compared with those of benzene derivatives and a series of azoles (imidazoles, pyrazoles, benzimidazoles and indazoles). Theoretical estimates of the enthalpies of formation were obtained through the use of atom equivalent schemes. The necessary energies were obtained in single-point calculations at the B3LYP/6-311++G(d,p) on B3LYP/6-31G* optimized geometries. The comparison of experimental and calculated values of all studied compounds bearing H (unsubstituted), methyl (Me) ethyl (Et), propyl (Pr), isopropyl (iPr), tert-butyl (tBu), benzyl (Bn) and phenyl (Ph) groups show remarkable homogeneity. The remarkable consistency of both the calculated and experimental results allows us to predict with reasonable certainty the missing experimental values. The crystal and molecular structure of the 2-benzylbenzimidazole (2BnBIM) has been determined by X-ray analysis. The observed molecular conformation permits the crystal being built up through N−H···N hydrogen bonds and van der Waals contacts between the molecules. An attempt has been made to relate the crystal structure to the enthalpies of sublimation.Thanks are due to Instituto de Cooperac¸a˜o Cientı´fica e Tecnolo´gica International (ICCTI), Lisbon, Portugal, and Consejo Superior de Investigaciones Cientı´ficas (CSIC), Madrid, Spain. L.M.P.F.A. thanks Fundac¸a˜o para a Cieˆncia e Tecnologia (FCT), Lisbon, Portugal, for the award of a postdoctoral fellowship (PRAXIS XXI/BPD/16319/98). This work has also been financed by DGICYT (BQU-2003- 00894, -00976 and -01251)

Enthalpies of formation of N-substituted pyrazoles and imidazoles

Accurate experimental enthalpies of formation measured using static bomb combustion calorimetry, the “vacuum sublimation” drop calorimetry method, and the Knudsen-effusion method are reported for the first time for four azoles:  1-methylimidazole (1MeIMI), 1-methylpyrazole (1MePYR), 1-benzylimidazole (1BnIMI), and 1-benzylpyrazole (1BnPYR). These values and those corresponding to imidazole (1HIMI), pyrazole (1HPYR), 1-ethylimidazole (1EtIMI), 1-ethylpyrazole (1EtPYR), 1-phenylimidazole (1PhIMI), and 1-phenylpyrazole (1PhPYR) are compared with theoretical values using the G2(MP2) and the B3LYP/6-311*G(3df,2p)//6-31G(d) approaches. In general, there is a very good agreement between calculated and experimental values for the series of N-substituted imidazoles, while the agreement is less good for the series of the N-substituted pyrazoles. Experimentally, the gap between the enthalpies of formation of imidazoles and pyrazoles decreases significantly upon N-substitution, while the theoretical estimates indicate that this decrease is smaller.This work has been partially supported by the DGES Projects PB 96-0001-C03-03, PB96-0067, and PB96-0927-C02-01. A generous allocation of computational time at the Centro de Computacio´n Cientı´fica de la Facultad de Ciencias (CCCFC) de la UAM is also gratefully acknowledged. Thanks are due to Junta National de Investigac¸a˜o Cientı´fica e Tecnolo´gica (JNICT), Lisbon, Portugal and Consejo Superior de Investigaciones Cientı´ficas (CSIC), Madrid, Spain, for a joint research project CSIC/JNICT. Financial support from the Praxis XXI, Project 2/2.1/qui/54/94, is acknowledged. L.M.P.F.A. thanks Fundac¸aˆo para a Cieˆncia e Tecnologia, Lisbon, Portugal for the award of a postdoctoral fellowship (Praxis XXI/BDP/16319/98). J.F.L. acknowledges funding from “Dow Chemical Company” for partial support of his thermochemical studies

Microbiological quality of treated water by solar-driven oxidation processes

info:eu-repo/semantics/publishedVersio

Genetic diversity and structure of two species of Enyalius (Squamata: Leiosauridae) from neotropical biodiversity hotspots

Diversidade e estrutura genética de duas espécies de Enyalius (Squamata: Leiosauridae) em hotspots neotropicais de biodiversidade. Os lagartos do gênero Enyalius são endêmicos da América do Sul, sendo predominantemente encontrados no Cerrado e em fragmentos da Floresta Atlântica. Este é um gênero pouco estudado, e não foram encontrados dados relacionados à diversidade e à estrutura genética das espécies do gênero. Neste trabalho, investigamos a diversidade genética de populações de E. bilineatus (N = 20) e E. perditus (N = 28), usando um fragmento de 234-pb do citocromo b, e comparamos as sequências geradas com outras publicadas. Dezenove haplótipos distintos foram encontrados (11 de E. perditus e oito de E. bilineatus), sendo oito deles novos registros. Os valores de diversidade haplotípica foram muito similares para as duas espécies (0.684 para E. perditus e 0.647 para E. bilineatus). A distância genética entre as duas espécies foi de 20.3%, e as distâncias intraespecíficas foram 2.0% para E. perditus e 5.6% para E. bilineatus. Nossos dados sugerem que as populações de E. bilineatus são altamente divergentes e que a espécie deve apresentar diversidade críptica. Este é o primeiro estudo medindo a diversidade genética de espécies do gênero Enyalius oriundas de regiões consideradas hotspots da biodiversidade neotropical e apresenta dados relevantes para um melhor entendimento das relações inter e intrapopulacionais, assim como a distribuição das linhagens genéticas desse gênero endêmico.Genetic diversity and structure of two species of Enyalius (Squamata: Leiosauridae) from neotropical biodiversity hotspots. Enyalius, a lizard genus endemic to South America, is mostly distributed in the remains of the Atlantic Forest and in the Cerrado. The genus has been the topic of a few studies but none has quantified the genetic diversity and structure within and among populations of Enyalius. The genetic diversity and structure of populations of E. bilineatus (N = 20) and E. perditus (N = 28) are examined using a 234-bp fragment of the cytochrome b gene and compared with the sequences reported in other published data. Nineteen distinct haplotypes (eleven for E. perditus and eight for E. bilineatus) were found, eight of which were recorded for the first time. The haplotype diversities are highly similar for both species (0.684 for E. perditus and 0.647 for E. bilineatus). The genetic distance between the two species is 20.3% and the distance within species is 2.0% and 5.6% for E. perditus and E. bilineatus, respectively. Our data suggest that populations of E. bilineatus are genetically divergent and may reveal cryptic diversity. This is the first study to quantify the genetic diversity of species of Enyalius from Neotropical biodiversity hotspots. These data facilitate a better understanding of both within and among population variation, and highlight the distribution of genetic lineages of an endemic and poorly studied genus

Enzymatic inhibition studies of selected flavonoids and chemosystematic significance of polymethoxylated flavonoids and quinoline alkaloids in Neoraputia (Rutaceae)

Our taxonomic interest in the Neoraputia stimulated an investigation of N. paraensis searching for alkaloids. Fractions were monitored by ¹H NMR and ESI-MS/MS and only those which showed features of anthranilate alkaloids and flavonoids absent in the previous investigations were examined. Stems afforded the alkaloids flindersine, skimmianine, 8-methoxyflindersine and dictamnine; leaves yielded 3',4',7,8-tetramethoxy-5,6-(2,2-dimethylpyrano)-flavone, 3',4',5,7,8-pentamethoxyflavone, 5-hydroxy-3',4',6,7-tetramethoxyflavone, 3',4'-methylenedioxy-5,6,7-trimethoxyflavone and 5-hydroxy-3',4'-methylenedioxy-6,7-dimethoxyflavone. The alkaloids have remained undiscovered for 10 years. A number of flavonoids isolated from N. paraensis, N. magnifica, Murraya paniculata, Citrus sinensis graft (Rutaceae), Lonchocarpus montanus (Leguminosae) were evaluated for their ability to inhibit the enzymatic activity of the protein glyceraldehyde-3-phosphate dehydrogenase from Trypanosoma cruzi. Highly oxygenated flavones and isoflavone were the most actives.Nosso interesse quimiotaxonômico sobre Neoraputia nos estimulou a examinar N. paraensis, visando a busca de alcalóides. As frações foram monitoradas via RMN ¹H e ESI-EM/EM e foram analisadas somente aquelas cujos espectros apresentavam características de alcalóides do ácido antranílico e flavonóides não isolados anteriormente. Foram isolados do caule os alcalóides flindersina, skimmianina, 8-metoxiflindersina e dictamnina; das folhas os flavonóides 3',4',7,8-tetrametoxi-5,6-(2,2-dimetilpirano)-flavona, 3',4',5,7,8-pentametoxiflavona, 5-hidroxi-3',4',6,7-tetrametoxiflavona, 3',4'-metilenodioxi-5,6,7-trimetoxiflavona e 5-hidroxi-3',4'-metilenodioxi-6,7-dimetoxiflavona,. Os alcalóides do ácido antranílico não foram encontrados em dez anos. Vários flavonóides isolados de N. paraensis, N. magnifica, Murraya paniculata, enxerto de Citrus sinensis (Rutaceae) e Lonchocarpus montanus (Leguminosae) foram testados frente a gliceraldeído-3-fosfato desidrogenase de Trypanosoma cruzi, visando verificar seus potenciais em inibir a atividade da enzima. Os flavonóides polimetoxilados e um isoflavonóide foram os mais ativos.380387Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Flavanol-anthocyanin condensed pigments in plant extracts

Pigments resulting from the direct condensation of anthocyanins and flavanols are usually associated with reactions taking place during processing and storage of plant-derived foods and beverages and have been particularly studied in aged red wines. In this paper, small amounts of flavanol-anthocyanin condensed pigments are found in different plant extracts. Structures are suggested for 10 such condensed pigments detected in extracts of strawberry, runner beans, purple corn and grape skins, based on their MS" fragmentation patterns, following analyses by electrospray tandem mass spectrometry. All of them correspond to dimers containing a flavan-3-ol [either (epi)afzelechin, (epi)catechin or (epi)gallocatechin] as the upper unit carbon-carbon linked to a lower anthocyanin unit consisting of different delphinidin, cyanidin, pelargonidin, peonidin or malvidin derivatives. The detection of these pigments in plant extracts may suggest that they are natural pigments and not products exclusively formed during storage and ageing of processed foods and beverages, as was previously assumed.Comissão Europeia (Fundo Social Europeu) e Governo Português através do Programa PRODEP (III) - ref.ª 5.3/N/199.006/00-Doutoramento

Renovascular hypertension increases serum TNF and CX3CL1 in experimental Trypanosoma cruzi infection.

Trypanosoma cruzi triggers a progressive inflammatory response affecting cardiovascular functions in humans and experimental models. Angiotensin II, a key effector of the renin-angiotensin system, plays roles in mediating hypertension, heart failure, and inflammatory responses. T. cruzi and AngII can induce inflammatory responses by releasing inflammatory mediators. The aim of this study was to evaluate systemic AngII, tumor necrosis factor (TNF), and CX3CL1 mediators in a two-kidney one-clip (2K1C) renovascular hypertension model using Wistar rats infected with T. cruzi. Our data showed an increase in serum AngII in uninfected and T. cruzi-infected rats 1 week after 2K1C surgery compared to non-2K1C (Sham) animals. The baseline systolic blood pressure was higher in both uninfected and infected 2K1C rats. Despite no difference in circulating parasites in the acute phase of infection, elevated serum TNF and CX3CL1 were observed at 8 weeks post-infection in 2K1C rats in association with higher cardiac inflammatory infiltration. In summary, AngII-induced hypertension associated with T. cruzi infection may act synergistically to increase TNF and CX3CL1 in the 2K1C rat model, thereby intensifying cardiac inflammatory infiltration and worsening the underlying inflammation triggered by this protozoan