Otimização da esterificação de ácido hexanóico com n-butanol empregando lipase (Termomyces lanuginosus) imobilizada em gelatina

The application of Lipozyme (Termomyces lanuginosus) immobilized in gelatin gel in aliphatic ester synthesis was investigated taking the esterification of hexanoic acid with n-butanol as a model reaction. Conditions were optimized by factorial design and the highest conversion was obtained under the following conditions: molar ratio alcohol: acid of 2:1, reaction time of 48 h and biocatalyst weight of 7.0 g. Under these conditions the esterification yield was around 98 %. The operational stability of the immobilized lipase was assessed and results showed that after 12 batch runs, the enzyme showed no significant loss of activity.

Estudo do comportamento da lipase comercial Lipozyme RM IM em reações de esterificação para obtenção de biodiesel

The aim of this work was to study monoalkyl ester synthesis catalyzed by immobilized lipase Lipozyme RM IM via the esterification reaction. Yields of over 90% were obtained with butanol in esterification reactions with oleic acid. In the reactions with deodorizer distillates of vegetable oils and butanol, the conversion obtained was greater than 80% after 2.5 h. For the esterification reaction of palm fatty acid deodorizer distillate (PFAD) and butanol, seven reuse cycles of Lipozyme RM IM were carried out and the final conversion was 42% lower than the initial conversion.

Ésteres de cloropropanóis e de glicidol em alimentos

Chloropropanols are a well-known group of food processing contaminants. They are formed through the reaction between lipids and chlorides when submitted to thermal treatment, and can be found in free and bound form. Although free chloropropanols were identified around 30 years ago, the occurrence of bound forms, especially 3-MCPD, and glycidyl fatty acid esters, has only recently been reported in several food products. Dietary exposure to these ester-bound compounds has been considered a priority food safety issue since free forms can be potentially released through the action of gut lipases, representing a major toxicological concern.

Chemical constituents isolated from turnera subulata Sm. and electrochemical characterization of phaeophytin b

Turnera subulata Sm., known as "Chanana" or "flor-do-Guarujá" in Brazilian folklore, is a plant species belonging to the subfamily Turneroideae of family Passifloraceae, which is used for various medicinal purposes in Brazil. The phytochemical study conducted here led to the isolation and identification of ten compounds present in T. subulata: two mixtures of steroids, sitosterol and stigmasterol (nonglycosylated and glycosylated); a mixture of flavonoids, 5,7,4′-trihidroxiflavona-8-C-α-glucopyranoside and 5,7,3′,4′-tetrahidroxiflavona-8-C-α-glucopyranosidel; and four phaeophytins, phaeophytin purpurin-18-phytyl ester, a rare natural product, phaeophytin a , 13²-hydroxy-(13²-S)-phaeophytin a , and phaeophytin b Phaeophytin b exhibited electrochemical activity similar to that of phthalocyanines.

Optimization of chromatographic conditions and comparison of extraction efficiencies of four different methods for determination and quantification of pesticide content in bovine milk by UFLC-MS/MS

This paper describes the optimization of a multiresidue chromatographic analysis for the identification and quantification of 20 pesticides in bovine milk, including three carbamates, a carbamate oxime, six organophosphates, two strobilurins, a pyrethroid, an oxazolidinedione, an aryloxyphenoxypropionate acid/ester, a neonicotinoid, a dicarboximide, and three triazoles. The influences of different chromatographic columns and gradients were evaluated. Furthermore, four different extraction methods were evaluated; each utilized both different solvents, including ethyl acetate, methanol, and acetonitrile, and different workup steps. The best results were obtained by a modified QuEChERS method that lacked a workup step, and that included freezing the sample for 2 hours at -20 ºC. The results were satisfactory, yielding coefficients of variation of less than 20%, with the exception of the 50 µg L-1 sample of famoxadone, and recoveries between 70 and 120%, with the exception of acephate and bifenthrin; however, both analytes exhibited coefficients of variation of less than 20%.

ENZYMATIC RESOLUTION OF ANTIDEPRESSANT DRUG PRECURSORS IN AN UNDERGRADUATE LABORATORY

The use of biocatalysts in synthetic chemistry is a conventional methodology for preparing enantiomerically enriched compounds. Despite this fact, the number of experiments in chemical teaching laboratories that demonstrate the potential of enzymes in synthetic organic chemistry is limited. We describe a laboratory experiment in which students synthesized a chiral secondary alcohol that can be used in the preparation of antidepressant drugs. This experiment was conducted by individual students as part of a Drug Synthesis course held at the Pharmacy Faculty, Lisbon University. This laboratory experiment requires six laboratory periods, each lasting four hours. During the first four laboratory periods, students synthesized and characterized a racemic ester using nuclear magnetic resonance spectroscopy and gas chromatography. During the last two laboratory periods, they performed enzymatic hydrolysis resolution of the racemic ester using Candida antarctica lipase B to yield enantiomerically enriched secondary alcohol. Students successfully prepared the racemic ester with a 70%-81% overall yield in three steps. The enzymatic hydrolysis afforded (R)- secondary alcohol with good enantioselectivity (90%-95%) and reasonable yields (10%-19%). In these experiments, students were exposed to theoretical and practical concepts of aromatic acylation, ketone reduction, esterification, and enzymatic hydrolysis.

COMPOSIÇÃO QUÍMICA E TEMPERATURA DE CRISTALIZAÇÃO DE ÉSTERES OBTIDOS DE QUATRO ÓLEOS VEGETAIS EXTRAÍDOS DE SEMENTES DE PLANTAS DO CERRADO

The seed oils from four plants (Scheelea phalerata, Butia capitata, Syagrus romanzoffiana, Terminalia cattapa) found in Mato Grosso do Sul were extracted at good yields. Alkaline transesterification of these seed oils to esters using methanol and ethanol was studied and also produced good yields. Oleic acid (30.5/32.3%), lauric acid (30.7/32.9%) methyl and ethyl esters, were the main components of transesterification of the oils from Scheelea phalerata and Syagrus romanzoffiana. Lauric acid (42.2%), capric acid (15.9%) and caprylic acid (14.6%) methyl and ethyl esters were the main ester components of transesterification of the oil from Butia capitata. Oleic acid (37.8%), palmitic acid (33.5%) and linoleic acid (22.6%) methyl and ethyl esters were the main components of transesterification of oil from Terminalia catappa. Based on differential scanning calorimetry (DSC) studies, the first crystallization peak temperature of esters was observed. Esters derived from oils of the family Arecaceae (Scheelea phalerata, Butia capitata, Syagrus romanzoffiana) showed the lowest points of crystallization, despite having high levels of saturated fat. Esters of Terminalia cattapa oil, rich in unsaturated fat, showed the highest crystallization temperature. This difference in behavior is probably related to the high concentration of esters derived from lauric acid and palmitic acid.

HYDROLYTIC DEGRADATION BEHAVIOR OF PLLA NANOCOMPOSITES REINFORCED WITH MODIFIED CELLULOSE NANOCRYSTALS

Bionanocomposites derived from poly(L-Lactide) (PLLA) were reinforced with chemically modified cellulose nanocrystals (m-CNCs). The effects of these modified cellulose nanoparticles on the mechanical and hydrolytic degradation behavior of polylactide were studied. The m-CNCs were prepared by a method in which hydrolysis of cellulose chains is performed simultaneously with the esterification of hydroxyl groups to produce modified nanocrystals with ester groups. FTIR, elemental analysis, TEM, XRD and contact angle measurements were used to confirm and characterize the chemical modifications of the m-CNCs. These bionanocomposites gave considerably better mechanical properties than neat PLLA based on an approximately 100% increase in tensile strength. Due to the hydrophobic properties of the esterified nanocrystals incorporated into a polymer matrix, it was also demonstrated that a small amount of m-CNCs could lead to a remarkable decrease in the hydrolytic degradation rate of the biopolymer. In addition, the m-CNCs considerably delay the degradation of the nanocomposite by providing a physical barrier that prevents the permeation of water, which thus hinders the overall absorption of water into the matrix. The results obtained in this study show the nanocrystals can be used to reinforce polylactides and fine-tune their degradation rates in moist or physiological environments.

DERIVATIZACIÓN Y CARACTERIZACIÓN ESPECTROSCÓPICA DE UN BIOPOLÍMERO A BASE DE L -LISINA CON ANÁLOGOS DE LA D-BIOTINA: CO -POLI(L-LISINA)-GRAFT -(ε-N-[X-D -BIOTINIL]-L-LISINA)

We report the single-step derivatization reaction of a biopolymer based onL -lysine with D -biotin analogs:Co -poly(L -lysine)-graft-(ε-N -[X-D-biotinyl]-L -lysine) (PLL-X-Biotin). The valeric acid carboxylate of D -biotin is activated to an NHS ester for direct modification of amine groups in proteins and other macromolecules. NHS esters react by nucleophilic attack of an amine in the carbonyl group, releasing the NHS group, and forming a stable amide linkage. NHS-X-Biotin is the simplest biotinylation reagent commercially available. In contrast withD -biotin, it has a longer spacer arm off the valeric acid side chain allowing better binding potential for avidin or streptavidin probes. Derivatization of poly(L -lysine) (PLL) with NHS-X-Biotin led to a copolymer PLL-X-Biotin. UV-Visible, IR-FT and 1H NMR characteristics derived from synthesis are briefly discussed.

COMPOSIÇÃO QUÍMICA DAS CASCAS DAS RAÍZES E FLORES DEPoincianella pyramidalis (Fabaceae)

Chemical investigation of the MeOH extract of root barks of P. pyramidallis (Tul.) L. P. Queiroz resulted in the isolation of 3,3'-dimethylellagic acid and 3,3'-dimethylellagic acid-4'-O-β-D-xyloside. Lupeol, β-sitosterol/stigmasterol and the mixture of fatty acid methyl ester derivatives were also obtained. Chromatographic procedures of the MeOH extract of the flowers of this species led to obtain an unusual mixture of fatty alcohols, β-sitosterol/stigmasterol, α-amyrin, β-amyrin and methyl gallate. The structures of the isolates were established by spectral data analysis. This is the first occurrence of 3,3'-dimethylellagic acid, 3,3'-dimethylellagic acid-4'- O-β-D-xyloside and free fatty alcohols in the Fabaceae family.

The use of fluorescent probes to assess viability of the plant pathogenic bacterium Clavibacter michiganensis subsp. michiganensis by flow cytometry

Determination of the viability of bacteria by the conventional plating technique is a time-consuming process. Methods based on enzyme activity or membrane integrity are much faster and may be good alternatives. Assessment of the viability of suspensions of the plant pathogenic bacterium Clavibacter michiganensis subsp. michiganensis (Cmm) using the fluorescent probes Calcein acetoxy methyl ester (Calcein AM), carboxyfluorescein diacetate (cFDA), and propidium iodide (PI) in combination with flow cytometry was evaluated. Heat-treated and viable (non-treated) Cmm cells labeled with Calcein AM, cFDA, PI, or combinations of Calcein AM and cFDA with PI, could be distinguished based on their fluorescence intensity in flow cytometry analysis. Non-treated cells showed relatively high green fluorescence levels due to staining with either Calcein AM or cFDA, whereas damaged cells (heat-treated) showed high red fluorescence levels due to staining with PI. Flow cytometry also allowed a rapid quantification of viable Cmm cells labeled with Calcein AM or cFDA and heat-treated cells labeled with PI. Therefore, the application of flow cytometry in combination with fluorescent probes appears to be a promising technique for assessing viability of Cmm cells when cells are labeled with Calcein AM or the combination of Calcein AM with PI.

Comparative analysis of the trypanocidal activity and chemical properties of E-lychnophoric acid and its derivatives using theoretical calculations

E-Lychnophoric acid 1, its derivative ester 2 and alcohol 3 killed 100% of trypomastigote blood forms of Trypanosoma cruzi at the concentrations of 13.86, 5.68, and 6.48 µg/mL, respectively. Conformational distribution calculations (AM1) of 1, 2 and 3 gave minimum energies for the conformers a, b, c, and d, which differ from each other only in the cyclononene ring geometry. Calculations (DFT/BLYP/6-31G*) of geometry optimization and chemical properties were performed for conformers of 1, 2, and 3. The theoretical results were numerically compared to the trypanocidal activity. Calculated values of atomic charge, orbital population, and vibrational frequencies showed that the C-4-C-5 pi-endocyclic bond does not affect the trypanocidal activity of the studied compounds. Nevertheless, the structure of the group at C-4 strongly influences the activity. However, the theoretical results indicated that the intra-ring (C-1 and C-9) and pi-exocycle (C-8 and C-14) carbons of caryophyllene-type structures promote the trypanocidal activity of these compounds.

Production of biodiesel from babassu oil using methanol-ethanol blends

Maranhão state in Brazil presents a big potential for the cultivation of several oleaginous species, such as babassu, soybean, castor oil plant, etc... These vegetable oils can be transformed into biodiesel by the transesterification reaction in an alkaline medium, using methanol or ethanol. The biodiesel production from a blend of these alcohols is a way of adding the technical and economical advantages of methanol to the environmental advantages of ethanol. The optimized alcohol blend was observed to be a methanol/ethanol volume ratio of 80 % MeOH: 20 % EtOH. The ester content was of 98.70 %, a value higher than the target of the ANP, 96.5 % (m/m), and the biodiesel mass yield was of 95.32 %. This biodiesel fulfills the specifications of moisture, specific gravity, kinematic viscosity and percentages of free alcohols (methanol plus ethanol) and free glycerin.

O "jovem" Lukács: trágico, utópico e romântico?

Dada o caráter polêmico da trajetória intelectual do "Jovem" Lukács, sobretudo em relação às obras A alma e as formas e A teoria do romance, o objetivo central do presente artigo é delinear com largos traços a trajetória de Lukács em sua fase de juventude, tendo como base seus próprios textos e depoimentos, com vistas a problematizar certas atribuições feitas a esse importante período de sua produção intelectual.

Controle biológico da mancha-aquosa do melão por compostos bioativos produzidos por Bacillus spp.

A mancha-aquosa, causada por Acidovorax avenae subsp. citrulli (Aac) causa grandes prejuízos à cultura do melão. O controle dessa doença foi estudado in vivo, com microbiolização de sementes de melão Amarelo infectadas, com líquidos fermentados de Bacillus subtilis R14, B. megaterium pv. cerealis RAB7, B. pumilus C116 e Bacillus sp. MEN2, com e sem células bacterianas. O mecanismo de ação dos isolados foi estudado in vitro pelo método de difusão em ágar e os compostos bioativos parcialmente caracterizados por testes de hemólise e atividade surfactante. Nos testes in vivo, não houve diferença significativa entre os tratamentos com e sem células, indicando que o controle ocorreu devido à presença de compostos bioativos produzidos durante as fermentações. Todos os tratamentos diferiram da testemunha sem diferir entre si (P=0,05%). B. megaterium pv. cerealis RAB7 proporcionou redução da incidência (89,1%) e do índice de doença (92,7%), elevou o período de incubação da mancha-aquosa de 9,8 para 11,9 dias e reduziu a AACPD de 3,36 para 0,17. In vitro, todos isolados apresentaram antibiose contra Aac e os compostos bioativos foram parcialmente caracterizados como lipopeptídeos.