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Química Nova, Volume: 31, Número: 4, Publicado: 2008
  • Helena Ferraz e Química Nova: um exemplo de relacionamento Editorial

    Silva Jr., Luiz F.; Aguilar, Andrea M.; Cunha, Silvio do Desterro
  • Composição química dos óleos essenciais das folhas de seis espécies do gênero Baccharis de "Campos de Altitude" da mata atlântica paulista Artigo

    Lago, João Henrique G.; Romoff, Paulete; Fávero, Oriana A.; Soares, Marisi G.; Baraldi, Patrícia T.; Corrêa, Arlene G.; Souza, Fátima O.

    Resumo em Inglês:

    The essential oils from the leaves of six species of the Baccharis genus (B. dracunculifolia, B. microdonta, B. regnelli, B. schultzii, B. trimera, and B. uncinella), collected in the "Campos de Altitude" of the Atlantic Forest (SP), were extracted using hydrodistillation procedures and analyzed by GC and GC/MS. There was a predominance of sesquiterpenes in all studied oils as b-elemene in B. dracunculifolia and B. regnelli, a-humulene in B. trimera, g-gurjunene in B. schultzii, bicyclogermacrene in B. regnelli, d-cadinene in B. regnelli and B. uncinella, spathulenol in B. schultzii, caryophyllene oxide in B. microdonta and guaiol in B. uncinella. However, a high amount of monoterpenes was also observed in B. uncinella (a-pinene), B. regnelli (d-car-3-ene) and B. schultzii (limonene). The chemical compounds of the essential oils of B. schultzii, B. regnelli and B. microdonta are described for the first time in this work.
  • Desenvolvimento de um spot test para o monitoramento da atividade da peroxidase em um procedimento de purificação Artigo

    Zeraik, Ana Eliza; Souza, Fernanda Sant'Ana de; Fatibello-Filho, Orlando; Leite, Oldair D.

    Resumo em Inglês:

    In this work we describe both a chromatographic purification procedure and a spot test for the enzyme peroxidase (POD: EC 1.11.1.7). The enzyme was obtained from crude extracts of sweet potatoes and the chromatographic enzyme purification procedure resulted in several fractions. Therefore a simple, fast and economic spot test for monitoring peroxidase during the purification procedure was developed. The spot test is based on the reaction of hydrogen peroxide and guaiacol, which is catalyzed by the presence of peroxidase yielding the colored tetraguaiacol.
  • Monoterpenos di-hidroxilados e hidróxi-nitrogenados 1,2 e 1,3 como ligantes quirais em reação de reformatsky assimétrica Artigo

    Ribeiro, Carlos Magno R.; Morita, Cristina M.; Maia, Mônica P.

    Resumo em Inglês:

    This study describes the use of three (-)-alpha-pinene derivatives, one diol-1,2 [(-)-(1R, 2R, 3S, 5R)-2,6,6-trimethylbicyclo[3.1.1]heptane-2,3-diol 4] and two piridine-hydroxy derivatives [(+)-(1R,2S,3R,5S)-2,6,6-trimethyl-3-(2-pyridinylmethyl)bicyclo[3.1.1]heptan-3-ol 7 and (-)-(1R,2S,3R,5S)-2,6,6-trimethyl-3-[2-(2-pyridinyl) ethyl]bicyclo[3.1.1]heptan-3-ol 8]; one diol-1,3 [(-)-(1S,2R,5S)-2-(1-hydroxy-1-methylethyl)-5-methylcyclohexanol 5] derived from (+)-isopulegol 2 and one diol-1,3 [(+)-(1R,2R,5R)-2-(1-hydroxy-1-methylethyl)-5-methylcyclohexanol 6] derived from (+)-neo-isopulegol 3, as ligands in the asymmetric Reformatsky reaction. The best enantiomeric excess of beta-hydroxy ester obtained in the Reformatsky asymmetric reaction was 18% using ligand 6, and the chemical yield of the reactions was 65% on average.
  • Piranoflavonas inéditas e atividades tripanocidas das substâncias isoladas de conchocarpus heterophyllus Artigo

    Ambrozin, Alessandra Regina Pepe; Vieira, Paulo Cezar; Fernandes, João Batista; Silva, Maria Fátima das Graças Fernandes da; Albuquerque, Sérgio de

    Resumo em Inglês:

    The phytochemical investigation of trypanocidal extracts from leaves and stems of Conchocarpus heterophyllus (A. St.-Hil.) Kallunki & Pirani (Rutaceae) afforded new pyranoflavones along with the known compounds flavone, 7-methoxyflavone, 5-hydroxyflavone, haplotusine, 1-methyl-2-phenyl-4-quinolone alkaloid, beta-sitosterol, stigmasterol, and beta-sitosteryl benzoate. Their structures were established based on their spectral data. NMR data for the alkaloid haplotusine and the new pyranoflavones are described for the first time herein. These compounds were assayed on the tripomastigote forms of Trypanosoma cruzi. Among them, haplotusine and 1-methyl-2-phenyl-4-quinolone showed moderate values of IC50 136.9 and 144.9 mM, respectively.
  • Constituintes químicos e atividade antiedematogênica de Peltodon radicans (Lamiaceae) Artigo

    Costa, Habdel Nasser Rocha da; Santos, Maria Cristina dos; Alcântara, Antônio Flavio de Carvalho; Silva, Marilda Conceição; França, Roberta Cabral; Piló-Veloso, Dorila

    Resumo em Inglês:

    Most of the snakebite incidents in the Amazon region involve Bothrops atrox, whose venom presents the most potent edematogenic and necrotic activities in the genus. This work describes the studies of isolation of the chemical constituents and antiedematogenic activity of the species Peltodon radicans (Lamiaceae), which is used in the treatment of snakebites and scorpion stings in the region. The extracts presented aliphatic hydrocarbons, 3beta-OH,beta-amirin (1), 3beta-OH,alpha-amirin (2), beta-sitosterol (3), stigmasterol (4), ursolic acid (5), 2alpha,3beta,19alpha-trihydroxy-urs-12-en-28-oic acid (tormentic acid, 6), methyl 3beta-hydroxy,28-methyl-ursolate (7), sitosterol-3-O-beta-D-glucopyranoside (8), and stigmasterol-3-O-beta-D-glucopyranoside (9). The flower extracts presented the higher antiedematogenic activity. This is the first report on the study of the flowers, stem, and roots of this plant.
  • Constituintes químicos de Ipomoea subincana Meisn. (Convolvulaceae) Artigo

    Meira, Marilena; David, Jorge M.; David, Juceni P.; Araújo, Sinara V.; Regis, Tatiara L.; Giulietti, Ana Maria; Queiróz, Luciano P. de

    Resumo em Inglês:

    The chloroform extract of aerial parts of Ipomoea subincana was submitted to different chromatographic procedures which afforded methyl caffeate, ethyl caffeate, methyl 3,4-dimethoxycinnamate, lupeol, alpha-amyrin, beta-amyrin, 3-beta-O-beta-D-glycopiranosyl-sitosterol, beta-sitosterol, stigmasterol, scopoletin, aromadendrane-4beta,10alpha-diol, n-docosyl-cis-p-coumarate and n-icosyl-trans-p-coumarate, vanilin, cinamic acid and vanillic acid. However, from the ethyl acetate extract besides quercetin and 3-O-beta-D-glycopiranosyl-quercetin were isolated methyl 4-O-E-feruloyl-5-O-E-caffeoyl-quinate, methyl 3,5-di-O-E-caffeoyl-quinate and methyl 4-O-E-caffeoyl-quinate. The structures of the compounds were established on the basis of spectral data.
  • Saponinas triterpênicas das raízes de guettarda pohliana müll. Arg. (Rubiaceae) Artigo

    Oliveira, Paulo Roberto Neves de; Testa, Gláucio; Sena, Simone Bortolotti de; Costa, Willian Ferreira da; Sarragiotto, Maria Helena; Santin, Silvana Maria de Oliveira; Souza, Maria Conceição de

    Resumo em Inglês:

    The phytochemical investigation of Guettarda pohliana roots led to the isolation of 28-O-beta-D-glycopyranosyl-3-O-beta-D-quinovopyranosyl quinovic acid, 28-O-beta-D-glycopyranosyl-3-O-beta-D-glycopyranosyl quinovic acid, 3-O-beta-D-glycopyranosyl quinovic acid, 28-O-beta-D-glycopyranosyl-3-O-beta-D-glycopyranosyl cincholic acid along with quinovic acid, daucosterol and 4,5-O-dicaffeoyl quinic acid. The structures of the isolated compounds were assigned on the basis of spectroscopic data, including two-dimensional NMR methods. The antiradical activity of the crude methanolic extract and of its fractions was evaluated.
  • Ciclização do lapachol induzida por sais de tálio III Artigo

    Ribeiro, Carlos Magno R.; Souza, Pablo P. de; Ferreira, Letícia L. D. M.; Pinto, Lia A.; Almeida, Leonardo S. de; Jesus, Janaina G. de

    Resumo em Inglês:

    This work describes the cyclization of lapachol (1) induced by thallium triacetate (TTA) and thallium trinitrate (TTN) in several solvents using magnetic stirring and under microwave irradiation. alpha-Xyloidone (2) - dehydro-alpha-lapachone - was obtained as the main product in these reactions in 20 75% yield. However, rhinacanthin-A (4) was isolated as main product in a 40% yield, using TTA and acetic anhydride:water (1:1) as solvent, and dehydro-iso-alpha-lapachone (3) in 21% yield, using TTA and dichloromethane as solvent. The reaction time decreased drastically under microwave conditions, but the yields of these reactions were not the expected.
  • Síntese de 1-indanonas através da reação de acilação de Friedel-Crafts intramolecular utilizando NbCl5 como ácido de Lewis Artigo

    Polo, Ellen Christine; Silva-Filho, Luiz Carlos da; Silva, Gil Valdo José da; Constantino, Mauricio Gomes

    Resumo em Inglês:

    The intramolecular Friedel-Crafts acylation reaction of 3-arylpropanoic acids to give 1-indanones can be effected in good yields under mild conditions (room temperature) by using niobium pentachloride. Our results indicate that NbCl5 acts both as reagent (to transform carboxylic acids into acyl chlorides) and as catalyst in the Friedel-Crafts cyclization.
  • HPLC-ESI-MS/MS analysis of oxidized di-caffeoylquinic acids generated by metalloporphyrin-catalyzed reactions

    Santos, Michel D.; Lopes, Norberto P.; Iamamoto, Yassuko

    Resumo em Inglês:

    This paper reports an HPLC-ESI-MS/MS investigation on the oxidation of 3,5- and 4,5- dicaffeoylquinic acid using iron(III) tetraphenylporphyrin chloride as catalyst. Two major mono-oxidised products of the quinic acid moiety have been identified for both compounds. However, only the 4,5-derivative afforded two different tri-oxo products. Thus, it seems that the oxidation pattern depends on the number and positions of the caffeic acid moieties present in caffeoylquinic acid molecules.
  • Stereoselective syntheses of (+)- isoretronecanol and (+)-5-epi-tashiromine via addition of chiral titanium (iv) enolates to cyclic n-acyliminium ions

    Pereira, Elaine; Alves, Conceição de Fátima; Böckelmann, Maria Alice; Pilli, Ronaldo A.

    Resumo em Inglês:

    The stereoselective addition of the titanium (IV) enolates derived from (S)-4-isopropyl-N-4-chlorobutyryl-1,3-thiazolidine-2-thione (8) and from (S)-4-isopropyl-N-4-chloropentanoyl-1,3-thiazolidine-2-thione (9) to N-Boc-2-methoxypyrrolidine (5b) afforded the addition products (+)-10 and (+)-11 in 84% yield in both cases, as 8.6:1 and 10:1 diastereoisomeric mixtures, respectively. A three-step sequence allowed to convert these adducts to (+)-isoretronecanol (1) and (+)-5-epi-tashiromine (2) in 43% and 49% overall yield, respectively.
  • Síntese de aminoálcoois derivados do D-manitol Artigo

    Oliveira, Pedro S. M. de; Ferreira, Vitor F.; Souza, Marcus Vinicius N. de; Carvalho, Erika Martins de

    Resumo em Inglês:

    Aminoalcohols have found important applications in synthetic and medicinal chemistry, being used as chiral building blocks for the synthesis of many biologically active compounds. This class of compounds has been also used as chiral auxiliaries and ligands in asymmetric synthesis. Due to the importance of aminoalcohols in the treatment of several diseases, such as tuberculosis, the aim of this article is the synthesis and preliminary evaluation against tuberculosis of six aminoalcohols in 5 or 6 steps using D-mannitol as starting material, which is a useful carbohydrate employed in many syntheses.
  • Reações de oxidação de derivados de cis-octalinas promovidas por trinitrato de tálio (TTN) Artigo

    Ferraz, Helena M. C.; Carneiro, Vânia M. T.; Vieira, Tiago O.; Silva Jr., Luiz F.

    Resumo em Inglês:

    The reaction of ten cis-octalins and cis-octalones with thallium trinitrate (TTN) leads to different products, depending mainly on the substitution pattern of the substrate. Functionalized cis-hydrindanes were obtained from the reaction of 1,2,3,4,4a,5,8,8a-octahydro-4a-methylnaphthalene and of 1,2,3,4,4a,5,8,8a-octahydro-4a,7-dimethylnaphthalene with TTN in acetonitrile, whereas a cyclic ether was formed treating 1,2,3,4,4a,5,8,8a-octahydro-6,8a-dimethylnaphthalen-1-ol with TTN in trimethylorthoformate (TMOF).
  • Reatividade de ciclopropenonas frente a nucleófilos e sua correlação com potenciais de redução em meio aprótico Artigo

    Cunha, Silvio; Rocha, Zênis Novais da

    Resumo em Inglês:

    In this work we studied the reactivity of isopropylphenylcyclopropenone towards some nitrogen nucleophiles whose reactions with methylphenylcyclopropenone and diphenylcyclopropenone were previously studied. The electrochemical behavior of these cyclopropenones was evaluated for the first time, and a correlation between electrochemical parameters and reactivity of this class of compounds was done.
  • Diastereosseletividade na redução de enonas bicíclicas com hidretos volumosos Artigo

    Camozzato, Andreza C.; Tenius, Beatriz S. M.; Oliveira, Eduardo R. de; Viegas Jr., Cláudio; Victor, Maurício M.; Silveira, Leandro G. da

    Resumo em Inglês:

    Reduction of five substituted octalones employing lithium tri-sec-butylborohydride (L-selectride®) in THF and ethyl ether led to allylic alcohols with moderate diastereoselectivity. The stereoselectivity of addition of bulky hydrides showed to be different from most examples in the literature and was strongly influenced by substitution on the octalone ring.
  • Uma metodologia simples e eficiente para a cloração de compostos aromáticos ativados utilizando o ácido tricloro-isocianúrico Artigo

    Mendonça, Gabriela F.; Mattos, Marcio C. S. de

    Resumo em Inglês:

    The chlorination of activated aromatic rings is efficiently achieved under mild conditions by reaction of aromatic compounds with trichloroisocyanuric acid in acetonitrile, at room temperature, leading to products in 60-95% isolated yields and good regioselectivity.
  • Constituintes químicos das flores de Pterogyne nitens (Caesalpinioideae) Artigo

    Regasini, Luis Octávio; Fernandes, Daniara Cristina; Castro-Gamboa, Ian; Silva, Dulce Helena Siqueira; Furlan, Maysa; Bolzani, Vanderlan da Silva; Barreiro, Eliezer Jesus; Cardoso-Lopes, Elaine Monteiro; Young, Maria Cláudia Marx; Torres, Luce Brandão; Vellosa, José Carlos Rebuglio; Oliveira, Olga Maria Mascarenhas de

    Resumo em Inglês:

    The phytochemical investigation of the flowers of Pterogyne nitens (Caesalpinioideae) resulted in the isolation and identification of nine phenolic derivatives, quercetin 3-O-sophoroside, taxifolin, astilbin, ourateacatechin, caffeic, ferulic, sinapic, chlorogenic and gallic acid, besides two guanidine alkaloids, pterogynine, pterogynidine. This is the first time these compounds have been reported in P. nitens flowers. As this is a monospecific genus, these secondary metabolites may have taxonomical significance. Their structures were assigned on the basis of spectroscopic analyses, including two-dimensional NMR techniques.
  • Sobre uma degenerescência acidental nos deslocamentos químicos de RMN de 31P{¹H} em complexos difosfínicos de rutênio Artigo

    Valle, Eliana Maira Agostini; Nascimento, Fabio Batista do; Ferreira, Antonio Gilberto; Batista, Alzir A.; Monteiro, Marcos Cláudio Rodrigues; Machado, Sérgio de Paula; Ellena, Javier; Castellano, Eduardo E.; Azevedo, Eduardo Ribeiro de

    Resumo em Inglês:

    The [RuCl(bipy)(dppb)(4-pic)]PF6 complex was prepared and fully characterized. The X-ray crystal structure of this complex was determined in order to make an unambiguous distinction between the two possible positions of the 4-methylpyridine ligand (4-pic) in the compound: trans to phosphorus atom or trans to nitrogen atom. The [RuCl(bipy)(dppb)(4-pic)]PF6 complex exhibits an unusual temperature-dependent accidental degeneracy of the 31P chemical shifts in its solution NMR spectrum.
  • Bioreduction of substituted a-tetralones promoted by Daucus carota root

    Ferraz, Helena M. C.; Bianco, Graziela G.; Bombonato, Fernanda I.; Andrade, Leandro H.; Porto, André L. M.

    Resumo em Inglês:

    The bioreduction of a series of substituted a-tetralones, carried out using Daucus carota root (carrot), afforded the corresponding homochiral a-tetralols in variable conversions (9 to 90%) and excellent enantiomeric excesses. Two of the assayed a-tetralones were resistant to the bioreduction conditions. The absolute configurations of four a-tetralols were assigned as being (S), by comparison to the (S)-enantiomers obtained by kinetic resolution promoted by CALB-catalysed acetylation. Additionally, the new 5-methoxy-6-methyl-1-tetralone was synthesized in seven steps from 3-methylsalicylic acid.
  • Epoxidação do óleo de mamona e derivados empregando o sistema catalítico VO(acac)2/TBHP Artigo

    Nunes, Marta Regina dos Santos; Martinelli, Marcia; Pedroso, Marcelo Monteiro

    Resumo em Inglês:

    The alternative system VO(acac)2/TBHP was investigated for the epoxidation reaction of castor oil and its derivatives. Results of 88% of conversion, 73% of epoxidation and 82% of selectivity were obtained for the system containing 20% excess of TBHP and 1% of VO(acac)2 catalyst, during 3 h under toluene reflux. The product was characterized by GC/MS as methyl-cis-9, 10-epoxi, 12-hydroxystearate and quantitative ¹H NMR was used to calculate the data above. Preliminary results indicate that the heterogeneous system VO(acac)2 grafted on K10 clay can also promote epoxidation of castor oil.
  • Análise conformacional por cálculos teóricos da distinctina, peptídeo antimicrobiano isolado de anuros da espécie Phyllomedusa distincta Artigo

    Munhoz, Victor H. de Oliveira; Alcântara, Antônio F. de Carvalho; Piló-Veloso, Dorila

    Resumo em Inglês:

    Various studies demonstrate that different frog species produce distinct classes of biologically active peptides. These peptides can act as alternative agents against pathogenic bacteria and fungi by membrane permeability. Although studies have recently demonstrated that this process is utterly related to the secondary structure adopted by the peptide (in this case, the a-helical structure) when in contact with the bacterial membrane, the detailed mechanism is still unknown. In this work we describe a conformational analysis of distinctin, a heterodimeric peptide isolated from the skin of Phyllomedusa distincta, an anuran found in the Brazilian Atlantic Forest. The study yielded a stable geometry with a high content of the a-helical structure both in chains 1 and 2 of distinctin, showing strong interaction between them.
  • Saponinas antifúngicas de Swartzia langsdorffii Artigo

    Marqui, Sara Regina de; Lemos, Renata Brionízio; Santos, Luciana Ávila; Castro-Gamboa, Ian; Cavalheiro, Alberto José; Bolzani, Vanderlan da Silva; Silva, Dulce Helena Siqueira; Scorzoni, Liliana; Fusco-Almeida, Ana Maria; Mendes-Giannini, Maria José Soares; Young, Maria Claudia Marx; Torres, Luce Maria Brandão

    Resumo em Inglês:

    Chromatographic fractionation of the EtOH extract from the leaves of Swartzia langsdorffii afforded the pentacyclic triterpenes oleanolic acid and lupeol, and two saponins: oleanolic acid 3-sophoroside and the new ester 3-O-b-D-(6'-methyl)-glucopyranosyl-28-O-b-D-glucopyranosyl-oleanate. Their structures were elucidated from spectral data, including 2D NMR and HRESIMS experiments. Antifungal activity of all isolated compounds was evaluated, using phytopathogens Cladosporium cladosporioides and C. sphaerospermum, and human pathogens Candida albicans, C. krusei, C. parapsilosis and Cryptococcus neoformans.
  • Reação entre fenilnitrometanos e enoato derivado do D-manitol na presença de TBAF ou DBU: adição conjugada sin-seletiva e reação de NEF consecutiva Artigo

    Dias, Ayres G.; Pinho, Vagner D.; Costa, Paulo R. R.

    Resumo em Inglês:

    A tandem syn-selective conjugate addition - Nef reaction was observed when phenylnitromethane and oxygenated derivatives were allowed to react with an enoate derived from D-mannitol at rt in the presence of TBAF or DBU. While nitro-adducts predominate after 4h of reaction, the corresponding ketones were the main products after 12-24h of reaction. The Nef reaction occurred without racemization of the stereogenic center generated in the conjugate addition step.
  • 4-(hidroximetil)-benzenossulfonato de potássio: metabólito inédito isolado da alga marinha Bostrychia tenella (Rhodomelaceae, ceramiales) Artigo

    Felício, Rafael de; Debonsi, Hosana Maria; Yokoya, Nair Sumie

    Resumo em Inglês:

    Chemical investigation of the dichloromethane/methanol extract of the marine alga Bostrychia tenella has led to the isolation of two aromatic compounds, the new sulfate metabolite potassium 4-(hydroxymethyl)-benzenosulfonate (1) and the compound 1-methoxyphenethyl alcohol (2), described previously as a synthetic product. Their structures were determined by spectroscopic methods including NMR, MS, IR and by comparison with literature data.
  • Aplicação da química quântica computacional no estudo de processos químicos envolvidos em espectrometria de massas Revisão

    Vessecchi, Ricardo; Galembeck, Sérgio E.; Lopes, Norberto P.; Nascimento, Paulo G. B. D.; Crotti, Antônio E. M.

    Resumo em Inglês:

    The field of application of mass spectrometry (MS) has increased considerably due to the development of ionization techniques. Other factors that have stimulated the use of MS are the tandem mass spectrometry (MS/MS) and sequential mass spectrometry (MSn) techniques. However, the interpretation of the MS/MS and MSn data may lead to speculative conclusions. Thus, various quantum chemical methods have been applied for obtaining high quality thermochemical data in gas phase. In this review, we show some applications of computational quantum chemistry to understand the formation and fragmentation of gaseous ions of organic compounds in a MS analysis.
  • Sínteses totais das crocacinas A, C e D: novos antibióticos isolados de Chondromyces crocatus e Chondromyces pediculatus Revisão

    Oliveira, Luciana G. de; Dias, Luiz C.; Rosso, Giovanni B.

    Resumo em Inglês:

    This review describes the endeavors that led to the total synthesis of a novel class of antibiotic compounds: the crocacins A-D. Other aspects such as isolation, structural elucidation as well as the biological activities are also presented.
  • Catalisadores contendo carbenos n-heterocíclicos como ligantes: propriedades, sínteses, aplicações e comparação com outros ligantes Revisão

    Pastre, Julio Cezar; Correia, Carlos Roque Duarte

    Resumo em Inglês:

    N-heterocyclic carbenes (NHCs) have become of considerable importance in modern organometallic chemistry and homogeneous catalysis. There are several advantages in the use NHCs over their phosphorus analogues, which explains the enormous development of NHC ligands in the field of organometallic catalysis in the past few years. In this article, we present an overview of the importance of the catalysts containing NHC ligands, their synthesis, some pertinent synthetic applications, and a brief comparison with other catalysts.
  • Natural occurrence, biological activities and synthesis of eight-, nine-, and eleven-membered ring lactones

    Ferraz, Helena M. C.; Bombonato, Fernanda I.; Sano, Myrian K.; Longo Jr., Luiz S.

    Resumo em Inglês:

    The natural occurrence, biological activities and synthetic approaches to natural eight-, nine-, and eleven-membered lactones is reviewed. These medium ring lactones are grouped according to ring size, and their syntheses are discussed. The structures of some natural products early identified as medium-ring lactones were revised after total synthesis.
  • Determination of moisture content and water activity in algae and fish by thermoanalytical techniques

    Silva, Vilma Mota da; Silva, Luciana Almeida; Andrade, Jailson B. de; Veloso, Márcia C. da Cunha; Santos, Gislaine Vieira

    Resumo em Inglês:

    The water content in seafoods is very important since it affects their sensorial quality, microbiological stability, physical characteristics and shelf life. In this study, thermoanalytical techniques were employed to develop a simple and accurate method to determine water content (moisture) by thermogravimetry (TG) and water activity from moisture content values and freezing point depression using differential scanning calorimetry (DSC). The precision of the results suggests that TG is a suitable technique to determine moisture content in biological samples. The average water content values for fish samples of Lutjanus synagris and Ocyurus chrysurus species were 76.4 ± 5.7% and 63.3 ± 3.9%, respectively, while that of Ulva lactuca marine algae species was 76.0 ± 4.4%. The method presented here was also successfully applied to determine water activity in two species of fish and six species of marine algae collected in the Atlantic coastal waters of Bahia, in Brazil. Water activity determined in fish samples ranged from 0.946 - 0.960 and was consistent with values reported in the literature, i.e., 0.9 - 1.0. The water activity values determined in marine algae samples lay within the interval of 0.974 - 0.979.
  • Métodos simples de formação de monocristal de substância orgânica para estudo estrutural por difração de raios X Nota Técnica

    Cunha, Silvio

    Resumo em Inglês:

    This work presents three operationally simple laboratory protocols for monocrystal growth of small-molecule organic compounds, which have been applied with success in the last ten years for the formation of single crystals for X-ray structural studies. In addition, five structure hints were formulated as general guidelines for selecting a small-molecule organic compound as a candidate for monocrystal growth: molecular weight >200 D, melting point >100 ºC, two or more aromatic rings in the structure, at least two sites for intermolecular hydrogen bond formation, and a halogen or other heavy atom in the structure.
  • A convenient method for lecithin purification from fresh eggs

    Maximiano, Flavio A.; Silva, Marcia A. da; Daghastanli, Katia R. P.; Araujo, Pedro S. de; Chaimovich, Hernan; Cuccovia, Iolanda M.

    Resumo em Inglês:

    The increasing demand for fatty acid-free lecithin required modifications in existing purification methods. In this technical note we describe a purification procedure with the following steps: a) homogenization and extraction of yolks obtained from fresh eggs with acetone, b) solubilization with ethanol and solvent elimination and c) repeated solubilization/precipitation with petroleum ether/acetone. This crude extract was chromatographed on neutral alumina, which was exhaustively washed with chloroform before elution with chloroform:methanol, allowing the sequential separation of fatty acids and lecithin. Chromatographic behavior and mass spectra of the product are presented. This fast procedure yields fatty acid-free lecithin at a competitive cost.
  • I2: uma molécula didática Educação

    Sala, Oswaldo

    Resumo em Inglês:

    Iodine vapor is a very suitable substance to learn about molecular energy levels and transitions, and to introduce spectroscopic techniques. As a diatomic molecule its spectra are relatively simple and allow straightforward treatment of the data leading to the potential energy curves and to quantum mechanics concepts. The overtone bands, in the resonance Raman scattering, and the band progressions, in the electronic spectra, play an important role in the calculation of the Morse potential curves for the fundamental and excited electronic state. A weaker chemical bond in the electronic excited state, compared to the fundamental state, is evidenced by the increase in the equilibrium interatomic distance. The resonance Raman scattering of I2 is highlighted due to its importance for obtaining the anharmonicity constant in the fundamental electronic state.
  • A linguagem química e o ensino da química orgânica Educação

    Roque, Nídia Franca; Silva, José Luis P. B.

    Resumo em Inglês:

    The importance of chemical language and specifically of molecular models and their representations in the development of chemistry is discussed. Structural formulas are projections of molecular models used as a specific language by chemists. The meaningful learning of chemistry requires knowledge of this language. The use of these analogical symbols without the necessary understanding engenders difficulties for the learning of chemistry.
  • Do isolamento à síntese da convolutamidina A Educação

    Silva, Rosângela B.; Torres, José C.; Garden, Simon J.; Violante, Flavio de Almeida; Rezende, Michelle J. C.; Silva, Bárbara V. da; Pinto, Angelo C.

    Resumo em Inglês:

    Convolutamydine A is a member of a family of oxindole alkaloids isolated from the Floridian marine bryozan Amathia convoluta in 8.6x10-6 % yield. This compound is interesting as it has been described in the literature to have significant pharmacological activity. When bioactive substances are isolated in low yields, such as in the case of convolutamydine A, the use of synthetic organic chemistry to prepare larger quantities of these substances is necessary. This paper describes the isolation, structural characterization and synthesis of convolutamydine A, using readily available reagents and reaction conditions that may be applied in any organic chemistry undergraduate laboratory course.
  • O fabrico e uso da pólvora no Brasil colonial: o papel de alpoim na primeira metade do século XVIII Assuntos Gerais

    Piva, Teresa C. C.; Filgueiras, Carlos A. L.

    Resumo em Inglês:

    Gunpowder played a significant role in colonial Brazil. This reached a climax in the eighteenth century, when the country's large gold output enticed the greed of many. The French invasion of Rio de Janeiro in 1711 made the city's defense even more pressing to the metropolis. Brigadier Alpoim symbolized this reaction. He was a leading Luso-Brazilian engineer of that century, whose multiple activities set him apart in colonial life. These activities included a pioneer role in teaching the manufacture and use of gunpowder, about which he wrote extensively during the first half of the eighteenth century. His work is thus among the first to treat chemical technology in the colony at such an early age.
  • A síntese dos sesquiterpenos baquenolidas Assuntos Gerais

    Brocksom, Timothy John; Brocksom, Ursula; Constantino, Maurício G.

    Resumo em Inglês:

    The bakkenolide group of sesquiterpenes has been a focal point of synthetic efforts amongst several research laboratories all linked to our common origins at the Chemistry Institute at the State University in São Paulo. In this review we would like to present a historical perspective of this research, with unpublished background information, and a definitive retrosynthetic analysis of these molecules. This chemistry spans the time period from 1972 to 2006, and traces the initial steps with Prof. Dr. Helena Ferraz to the present day.
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