RESUMO
In this work photo-electro-Fenton (PEF) processes using a dimensionally stable anode-gas diffusion electrode (DSA-GDE) system under light emission diodes (LED)-type radiation were used in the degradation of the angiotensin-II-receptor antagonists (ARA II), valsartan (VAL), and losartan (LOS), which are used in the treatment of hypertension diseases, and are considered among the emerging contaminants (ECs). Organic acids as citric, tartaric, and oxalic acids were used as complexing agents of iron ions in order to maintain the performance of the Fenton reaction at near-neutral pH value. The results show that at 3.42 mA/cm2 after 90 min of electro-Fenton (EF) treatment, degradation of 70% of VAL and 100% of LOS were observed. Total degradation of VAL and LOS was reached with a PEF process at the same time with mineralization of 30%. When citric and tartaric acids were used instead of oxalic acid, similar results were obtained, i.e., total degradation of both compounds, LOS and VAL, after 90 min of treatment. The degradation performance can be attributed to the increase of the initial dissolved iron in the system, facilitating the Fe3+/Fe2+ turnover in the catalytic photo-Fenton reaction and consequently, hydroxyl radical (â¢OH) production. In addition, the increased photo-activity of the complexes can be associated with their high capability to complex Fe3+ and to promote ligand-to-metal charge transfer, which is of key importance to feed Fe2+ to the Fenton process. The results show that the system evaluated was more efficient to eliminate sartan family compounds using LED lighting in comparison with traditional UV-A lamps used in this kind of work. Moreover, three transformation products of VAL degradation and two transformation products of LOS degradation were identified by high-resolution mass spectrometry (HRMS) using hybrid quadrupole-time-of-flight (QTOF) MS and, at the end of the PEF system, the several organic compounds accumulated and no mineralized were effectively treated in a subsequent aerobic biological system.
Assuntos
Eletrodos , Losartan/química , Valsartana/química , Poluentes Químicos da Água/química , Anti-Hipertensivos/química , Anti-Hipertensivos/metabolismo , Biodegradação Ambiental , Ácido Cítrico/química , Difusão , Peróxido de Hidrogênio/química , Concentração de Íons de Hidrogênio , Radical Hidroxila/química , Ferro/química , Iluminação/instrumentação , Iluminação/métodos , Losartan/metabolismo , Oxirredução , Tartaratos/química , Valsartana/metabolismo , Poluentes Químicos da Água/metabolismoRESUMO
DFT calculations suggest that O-monoacyl L-tartaric acids catalyze the asymmetric conjugate alkenylboration of enones through transition structures that are stabilized by hydrogen-bonding interactions. Formation of a five-membered acyloxyborane is proposed. The hydrogen of the free carboxy group derived from the catalyst interacts with the carbonyl group of the cyclic acyloxyborane, stabilizing the transition structure and reducing the flexibility of the system. Additional stabilizing nonclassical CH···O hydrogen-bond interactions seem to determine the observed enantioselectivity.
Assuntos
Boranos/síntese química , Cetonas/química , Tartaratos/química , Boranos/química , Catálise , Ligação de Hidrogênio , Conformação Molecular , EstereoisomerismoRESUMO
Tartaric acid (TA), a dicarboxylic acid, can act as a compatibiliser in starch/polyester blends. A mixture design was proposed to evaluate the effect of TA on the properties of starch/poly (butylene adipate co-terephthalate) (PBAT) blown films plasticised with glycerol. The interaction between the starch/PBAT and the TA has a positive effect on the tensile strength and puncture force. Additionally, greater proportions of TA increased Young's modulus. The starch+PBAT/TA and Gly/TA interactions contributed to a reduction in the water vapour permeability of the films. The inclusion of TA did not change the crystallinity of the samples. Formulations with intermediate proportions of TA (0.8 g/100 g) were shown to produce the best compatibilising effect. This was observed by DMA analysis as a consequence of the perfect equilibrium between the contributions of TA as a compatibiliser and in the acidolysis of starch, resulting in films with a tensile strength of 5.93 MPa, a possible alternative to non-biodegradable packaging.
Assuntos
Poliésteres/química , Amido/química , Tartaratos/química , Glicerol/química , Fenômenos Mecânicos , Permeabilidade , Temperatura , Volatilização , Água/químicaRESUMO
The Biginelli reaction is a multicomponent reaction involving the condensation between an aldehyde, a ß-ketoester, and urea or thiourea, in the presence of an acid catalyst, producing dihydropyrimidinones (DHPMs). Owing to their important pharmacological properties, the DHPMs have been studied by many authors. However, most of the methodologies used for the synthesis of these compounds require drastic reaction conditions. In the current study, we report an efficient and clean procedure for preparing DHPMs by the use of citric acid or tartaric acid as a promoter of the Biginelli synthesis in ethanol as solvent. In addition, we have evaluated the antioxidant capacity of the compounds synthesized by the 2,2-diphenyl-1-picrylhydrazyl radical scavenging assay and the thiobarbituric acid-reactive species test. Two compounds presented antioxidant activity and also reduced lipid peroxidation at concentrations of 200 and 300 µM. In summary, we report an environmentally friendly procedure for the preparation of DHPMs and demonstrate the antioxidant capacity of some of the compounds.
Assuntos
Antioxidantes/síntese química , Ácido Cítrico/química , Pirimidinonas/síntese química , Tartaratos/química , Animais , Antioxidantes/química , Antioxidantes/farmacologia , Etanol/química , Peroxidação de Lipídeos/efeitos dos fármacos , Pirimidinonas/química , Pirimidinonas/farmacologia , Ratos , Ratos Wistar , Solventes/químicaRESUMO
The influence of citric acid (CA), malic acid (MA) and tartaric acid (TA) in starch/poly (butylene adipate co-terephthalate) blown films was evaluated by examining the barrier, structural and mechanical properties of the films. These properties were analysed in different relative humidities. Greater concentrations of TA and CA (1.5 wt%) produced films with improved tensile strength (6.8±0.3 and 6.7±0.3 MPa, respectively), reduced water vapour permeability and a more homogeneous structure. The compatibilising effect of MA was less efficient, as shown in the scanning electron microscopy (SEM) images. Changes in the relative humidity (RH) affected the elongation of the films, which reached values of 5.7±0.5 at 33% RH and increased to 312.4±89.5% at 53% RH. The FT-IR spectra showed no additional reactions caused by the incorporation of the additives, and the observed results are attributed to the esterification reactions and/or hydrolysis of the starch, producing films with interesting properties. This process represents an alternative to the use of non-biodegradable materials.
Assuntos
Plásticos Biodegradáveis/química , Ácido Cítrico/química , Malatos/química , Poliésteres/química , Amido/química , Tartaratos/química , Plásticos Biodegradáveis/metabolismo , Ácido Cítrico/metabolismo , Malatos/metabolismo , Plastificantes/química , Plastificantes/metabolismo , Poliésteres/metabolismo , Amido/metabolismo , Tartaratos/metabolismoRESUMO
The partitioning pattern of bovine trypsinogen (TRPz) and alpha-chymotrypsinogen (ChTRPz) was investigated in a low impact aqueous two-phase system formed by polyethyleneglycol (PEG) and sodium tartrate (NaTart) pH 5.00. ChTRPz exhibited higher partition coefficients than TRPz did in all the assayed systems. The decrease in PEG molecular weight and the increase in tie line length were observed to displace the partitioning equilibrium of both proteins to the top phase, while phase volume ratios in the range 0.5-1.5 showed not to affect protein partitioning behaviour. Systems formed by PEG of molecular weight 600 with composition corresponding to a high tie line length (PEG 12.93%, w/w and NaTart 21.20%, w/w) are able to recover most of both zymogens in the polymer-enriched phase. A crucial role of PEG-protein interaction in the partitioning mechanism was evidenced by isothermal calorimetric titrations. The major content of highly exposed tryptophan rests, present in ChTRPz molecule, could be considered to be determinant of its higher partition coefficient due to a selective charge transfer interaction with PEG molecule. A satisfactory correlation between partition coefficient and protein surface hydrophobicity was observed in systems formed with PEGs of molecular weight above 4000, this finding being relevant in the design of an extraction process employing aqueous two-phase systems.
Assuntos
Quimotripsinogênio/química , Polietilenoglicóis/química , Tartaratos/química , Tripsinogênio/química , Animais , Bovinos , Quimotripsinogênio/isolamento & purificação , Concentração de Íons de Hidrogênio , Peso Molecular , Ligação Proteica , Temperatura , Termodinâmica , Tripsinogênio/isolamento & purificaçãoRESUMO
Chromatographic separation of the chiral drugs rolipram, bupivacaine and omeprazole on a tartardiamide-based stationary phase commercially named Kromasil CHI-TBB is shown in this work. The effect of temperature on the chromatographic separation of the chiral drugs using the Kromasil CHI-TBB stationary phase was determined quantitatively so as to contribute toward the design for the racemic mixtures of the named compound by using chiral columns. A decrease in the retention and selectivity factors was observed, when the column temperature increased. Van't Hoff plots provided the thermodynamic data. The variation of the thermodynamic parameters enthalpy and entropy are clearly negative meaning that the separation is enthalpy controlled.
Assuntos
Bupivacaína/isolamento & purificação , Cromatografia Líquida de Alta Pressão/métodos , Cromatografia por Troca Iônica/métodos , Omeprazol/isolamento & purificação , Rolipram/isolamento & purificação , Tartaratos/química , Algoritmos , Resinas de Troca Aniônica , Bupivacaína/química , Fenômenos Químicos , Físico-Química , Modelos Químicos , Estrutura Molecular , Omeprazol/química , Rolipram/química , Estereoisomerismo , Temperatura , TermodinâmicaRESUMO
The percolation leaching of the Cuban nickel tailings containing 0.34% Ni, 0.08% Co and 44.2% Fe was investigated by using tartaric and oxalic acids at different concentrations. About 70% Ni, 80% Co and 30% Fe were extracted after 5 days of leaching with the mixture of 0.15 mol/L tartaric acid and 0.05 mol/L oxalic acid at ambient temperature and normal pressure. Nickel and cobalt extraction of 80% as well as iron extraction of 50% were achieved from the pregnant solution by means of precipitation at 80 degrees C for 2h. The precipitation at ambient temperature led to a similar result after 16 days. Cobalt, nickel and iron oxalates were found in the precipitate by using the X-ray diffraction method. The regeneration of acids during the precipitation step made possible the reuse of the raffinate at the leaching step. Heating of the precipitate at 200 degrees C increased the metal concentration to 1.22% Ni and 0.33% Co, which can be fed in the existing nickel plant in Moa, Cuba. The magnetic processing of the leaching residues led to a non-magnetic product containing less than 20% Fe and a magnetic product containing more than 50% Fe.
Assuntos
Ácidos Carboxílicos/química , Magnetismo , Metais/química , Metais/isolamento & purificação , Níquel/química , Precipitação Química , Cuba , Concentração de Íons de Hidrogênio , Ácido Oxálico/química , Oxirredução , Sais/química , Soluções , Tartaratos/química , Temperatura , Fatores de TempoRESUMO
Vitellin (VT) is a lipoglycophosphoprotein stored inside the eggs of every oviparous organism during oogenesis. In the blood-sucking bug Rhodnius prolixus, VT is deposited inside growing oocytes together with two acid hydrolases: acid phosphatase (AP) and cathepsin D (CD). Egg fertilization triggers AP activity and VT proteolysis in vivo [Insect Biochem. Mol. Biol. 2002 (32) 847]. Here, we show that CD is the main protease targeting VT proteolysis during egg development. CD activity in total egg homogenates is blocked by the classical aspartyl protease inhibitor, pepstatin A. Surprisingly, AP inhibitors such as NaF, Na+/K+ tartrate, and inorganic phosphate also block VT proteolysis, whereas this effect is not observed when tyrosine phosphatase inhibitors such as vanadate and phenylarsine oxide or an inhibitor of alkaline phosphatases such as levamisole are used in a VT proteolysis assay. NaF concentrations that block isolated AP activity do not affect the activity of partially purified CD. Therefore, a specific repressor of VT proteolysis must be dephosphorylated by AP in vivo. In conclusion, these results demonstrate for the first time that acid hydrolases act cooperatively to promote yolk degradation during egg development in arthropods.
Assuntos
Catepsina D/metabolismo , Proteínas do Ovo/metabolismo , Fosfatase Ácida/antagonistas & inibidores , Fosfatase Ácida/química , Fosfatase Ácida/metabolismo , Fosfatase Alcalina/metabolismo , Animais , Catepsina D/química , Catepsinas/química , Eletroforese em Gel de Poliacrilamida , Concentração de Íons de Hidrogênio , Hidrolases/química , Insetos/metabolismo , Oócitos/metabolismo , Oogênese , Fosfoproteínas/química , Monoéster Fosfórico Hidrolases/química , Fosforilação , Proteínas Tirosina Fosfatases/química , Proteínas Tirosina Fosfatases/metabolismo , Rhodnius/metabolismo , Sódio/química , Tartaratos/química , Temperatura , Fatores de Tempo , Vitelinas/químicaRESUMO
A convenient method is described for the resolution of racemic Albuterol by selective crystallization of its di-p-toluoyl-D-tartrate salt. The separation resulted in a 38% yield of the (R)-enantiomer. Racemization of the (S)-enantiomer occurs in diluted H2SO4 at 100 degrees C in 80% yield. This racemic mixture was recycled to the diastereomer salt, in order to improve the overall yield. The (R)-Albuterol tartrate salt was decomposed in a sulfuric acid solution, and the (R)-Albuterol was isolated as its sulfate salt with 67% overall yield with 99.5% optical purity.