Determinação potenciométrica em fluxo de cloreto de cetilpiridinio em desinfectantes bucais

The work describes a new procedure for cetylpyridinium chloride determination in oral disinfectants, based on a flow-injection system with potentiometric detection. The determination was based on the measurement of picrate concentration decrease as result of ion-pair reaction with the analyte present in the injected sample. In the optimised set-up the sample injection volume was kept at 400 µL and merged downstream with the reagent solution containing 1,0 x10-5 mol/L of picrate adjusted to pH 5.0 with citrate/citric acid buffer. The flow rate was fixed at 8 mL/min and the reactor length at 40 cm. The proposed procedure enables the determination of cetylpyridinium in the analytical range of 5,0x10-6 – 7,5x10-5 mol/L at a sampling rate of 60/h. The results for real samples had a precision better than 3% and were comparable to the labelled values

Sequential injection system for the spectrophotometric determination of reducing sugars in wines

A sequential injection system for the spectrophotometric determination of reducing sugars in wines is described. The methodology is based on the formation of a coloured complex produced by the reaction of copper (I) with 2,9-dimethyl-1,10-phenanthroline (neocuproine), after reduction of copper (II) to copper (I) by reducing sugars. In the present SI system, a dialysis unit was incorporated not only to allow the sample dilution, but also to minimise the interference of some coloured compounds. In this way, direct sample introduction into the system was possible, without any previous treatment of the wine samples. The proposed method can be applied to the determination of reducing sugars in two concentration ranges: from 2 to 25 g l 1 (table wines) and from 20 to 140 g l 1 (Port wines). To perform determinations in these two ranges, the manifold configuration remained the same; just a few operational parameters were changed in the controlling software. A sampling-rate of 14–18 samples per hour was obtained with good repeatability for ten consecutive injections of wine samples (relative standard deviations (RSD) B2.1%). The results obtained from 19 wine samples were comparable to those obtained by the reference method.info:eu-repo/semantics/publishedVersio

Synthesis and in vitro α-glucosidase inhibitory activity of polyhydroxylated 2-styrylchromones

2-Styrylchromones (2-SC) are a small class of naturally-occurring oxygen-containing heterocycles. Although they are scarce in nature, a large number of 2-SC derivatives has been synthesized and their biological activ ity evaluated, namely as antiallergic, anti-inflammatory, antimicrobial, antioxidant and antitumor agents [l]. As far as we know, the antidiabetic activity of 2-SC is still unexplored. With this rational in mind, a series of 12 polyhydroxylated derivatives of 2-SC (1) were synthethized and used as inhibitors of the carbohydrate hydrolyzing enzyme a-glucosidase. This enzyme catalyzes the final step of the digestive process of starch and break down oligosaccharides to monosaccharides being one of the most currently used therapeutic approaches to decrease postprandial hyperglycemia and consequently to control type 2 diabetes mellitus [2]. The synthesis of polyhydroxylated 2-SC involves a multi-step strategy starting with the condensation of the appropriate 2'-hydroxyacetophenones with cinnamic acid derivatives, base-promoted Baker- Yenkataraman rearrangement of the esters formed, cyclodehydration and finnaly cleavage of the protecting groups to afford the desired polyhydroxylated 2-SC (3]. The in vitro assay to evaluate the inhibitory activity of the compounds under study and the positive control, acarbose, against a-glucosidase was performed by monitoring the hydrolysis of the substrate p-nitrophenyl glucopyranoside into the product p-nitrophenol at 405 nm. In addition, the study of the inhibition type was carried out through nonlinear regression Michaelis-Menton enzymatic kinetics and the corresponding Lineweaver-Burk plot [4].This work received financial support from the European Union (FEDER funds POCI/01 /0145/FEDER/007265) and National Funds (FCT/MEC, Fundayiio para a Ciencia e Tecnologia and Ministerio da Educação e Ciência) under the Partnership Agreement PT2020 UID/ AGR/00690/2013; UID/QUI/50006/2013; UID/QUI/00062/2019, and "Programa Operacional Competitividade e Intemacionalizayiio" (COMPETE) (POCI-01-0145-FEDER-029241), and under the framework of QREN (NORTE-01-0145-FEDER-000024).info:eu-repo/semantics/publishedVersio

Inhibition of the carbohydrate-hydrolyzing enzymes α-amylase and α-glucosidase by hydroxylated xanthones

Xanthones are oxygen-containing heterocyclic compounds that exhibit a wide range of biological and pharmacological properties. Some natural and synthetic derivatives have been identified for their antidiabetic profile, mainly as α-glucosidase inhibitors. However, studies concerning the inhibition of both carbohydrate-hydrolyzing enzymes α-amylase and α-glucosidase are scarce. Thus, in order to identify some of these dual-target antidiabetic agents, a series of new synthetic xanthones were evaluated together with their commercial parents mangiferin (4), α-mangostin (5) and γ-mangostin (6). The results showed that xanthones exhibited a systematic stronger inhibition against α-glucosidase rather than for α-amylase. Derivatives 2c, 3a and 3b, bearing one catechol moiety, were the most active inhibitors of α-amylase, while xanthones 2c, 3b and 3c were the most active against α-glucosidase activity, with IC50 values lower than 10 μM. These findings suggest that the substitution pattern of the xanthone scaffold modulated the inhibitory activity of these compounds, and some structure–activity relationships could be established for both assays. In addition, the type of inhibition was also studied, and the results indicate a competitive type of inhibition for α-amylase activity by xanthones 2c, 3b, 3c and γ-mangostin (6). On the other hand, non-competitive inhibition mechanisms can be ascribed for all xanthones 1–6 against α-glucosidase. The present work can open a promising area of research based on the design of novel xanthone derivatives, based on natural ones, for targeting key enzymes involved in glucose metabolism and therefore in the management of type 2 diabetes mellitus.The work was supported by UIBD/00690/2020 and UIDB/50006/2020 with funding from FCT/MCTES through national funds, and by EXPL/MED-QUI/0815/2021, with funding from FCT. Carina Proença acknowledges funding from FCT and MCTES through national funds and COMPETE, grant number PTDC/MED-QUI/29243/2017 -POCI-01-0145-FEDER-029243. Marisa Freitas acknowledges her contract under the Scientific Employment Stimulus - Individual Call (CEEC Individual) 2020.04126.CEECIND/CP1596/CT0006.info:eu-repo/semantics/publishedVersio

2-Styrylchromones as inhibitors of α-amylase and α-glucosidase enzymes for the management of type 2 diabetes mellitus

alpha-amylase and alpha-glucosidase are key enzymes implicated in carbohydrate digestion and their inhibition has been suggested as a powerful approach for regulating blood glucose levels. The present work describes for the first time their inhibition by a group of twelve hydroxylated 2-styrylchromones (2-SC). Our findings revealed that 2-SC display strong systematic inhibition of alpha-glucosidase rather than alpha-amylase activity. The number and position of the hydroxy groups in the chromone moiety further modulate the inhibitory profile of the studied compounds, and the derivatives bearing one catechol unit are efficient inhibitors of both enzymes. Enzyme kinetic studies indicate that all active compounds act as competitive inhibitors of alpha-amylase while most of them behave as non-competitive inhibitors of alpha-glucosidase. The results are promising and pave the way to further deciphering the potential of this class of compounds as a suitable alternative for the management of type 2 diabetes and its complications.This work received support from national funds (FCT/ MCTES, Fundação para a Ciência e Tecnologia and Ministério da Ciência, Tecnologia e Ensino Superior) through the projects of CIMO (UIDB/00690/2020 and), SusTEC (LA/P/0007/2021) and REQUIMTE (UIDB/50006/2020 and UIDP/50006/2020). This work also received financial support from the project EXPL/MED-QUI/ 0815/2021, with funding from FCT/MCTES through national funds, and “Programa Operacional Competitividade e Internacionalização” (COMPETE). Open access funding provided by FCT|FCCN (b-on).info:eu-repo/semantics/publishedVersio

Monosegemented flow potentiometric titration for the determination of chloride in milk and wine

An automated flow potentiometric titration procedure for the determination of chloride in milk and wine exploiting the monosegmented flow approach is described. The flow network was designed based on a six-way solenoid valve, controlled by a microcomputer running software written in VisualBasic 3.0, allowing selection of the titration conditions. An Ag2S tubular electrode selective for Cl- and a conventional Ag/AgCl electrode were employed as indicator and reference, respectively. An algorithm based on the potential difference between two subsequent titrant additions was developed, allowing to reach the end point in less than 10 attempts, with a precision better than 1.0%. The proposed system was evaluated by determining chloride in milk and wine, using a standard AgNO3 solution as titrant. Accuracy was ascertained by comparing the results with those obtained using the AOAC procedure. No significant difference at a 95% confidence level was observed.Este trabalho descreve um procedimento automático em fluxo monossegmentado para titulação potenciométrica aplicado à determinação de cloreto em leite e vinho. O sistema de fluxo foi desenvolvido com base em uma válvula solenóide de 6 vias, controlada por um microcomputador através de um programa escrito em VisualBasic 3.0. Um eletrodo indicador tubular de Ag2S seletivo a Cl- e um eletrodo de referência convencional de Ag/AgCl foram empregados. Um algoritmo baseado na diferença de potencial entre duas adições subsequentes de titulante foi desenvolvido, possibilitando a determinação do ponto final da titulação em, no máximo, 10 tentativas, com uma precisão melhor que 1,0%. O sistema proposto foi avaliado pela determinação de cloreto em leite e vinho, usando uma solução padrão de AgNO3 como titulante. A exatidão foi avaliada comparando-se os resultados com aqueles obtidos pelo método da AOAC, não sendo encontradas diferenças significativas ao nível de confiança de 95%.259264Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Ecotoxicological aspects related to the presence of pharmaceuticals in the aquatic environment

Pharmaceuticals are biologically active and persistent substances which have been recognized as a continuing threat to environmental stability. Chronic ecotoxicity data as well as information on the current distribution levels in different environmental compartments continue to be sparse and are focused on those therapeutic classes that are more frequently prescribed and consumed. Nevertheless, they indicate the negative impact that these chemical contaminants may have on living organisms, ecosystems and ultimately, public health. This article reviews the different contamination sources as well as fate and both acute and chronic effects on non-target organisms. An extensive review of existing data in the form of tables, encompassing many therapeutic classes is presented

Physical–chemical parameters and validation of a colorimetric method for deoxycholic and ursodeoxycholic acids: kit reagent and optical sensor

AbstractThe simple and low cost β-cyclodextrin (β-CD)–phenolphthalein (PHP) inclusion complex was used for both the study of physical–chemical parameters and validation of analytical procedures for deoxycholic acid (DCA) and ursodeoxycholic acid (UDCA) determinations in different formulations. The usefulness of this inclusion complex is proposed either in the form of kit reagent and as an original optical sensor for DCA and UDCA. The results showed that temperature had a negative effect on the equilibrium constant resulting in high negative values of enthalpy and positive values of entropy. The half-life values for DCA and UDCA measurements were 68.71 and 294.71 days, respectively. The method was validated showing limits of detection and quantification of 4.92×10−5molL−1 and 1.64×10−4molL−1 for DCA, 1.14×10−5molL−1 and 3.79×10−5molL−1 for UDCA, respectively. The developed optical sensor also showed response linearity, ease of implementation and potential application in fast screening tasks even out of the laboratory

Gran method for end point anticipation in monosegmented flow titration

An automatic potentiometric monosegmented flow titration procedure based on Gran linearisation approach has been developed. The controlling program can estimate the end point of the titration after the addition of three or four aliquots of titrant. Alternatively, the end point can be determined by the second derivative procedure. In this case, additional volumes of titrant are added until the vicinity of the end point and three points before and after the stoichiometric point are used for end point calculation. The performance of the system was assessed by the determination of chloride in isotonic beverages and parenteral solutions. The system employs a tubular Ag2S/AgCl indicator electrode. A typical titration, performed according to the IUPAC definition, requires only 60 mL of sample and about the same volume of titrant (AgNO3) solution. A complete titration can be carried out in 1 - 5 min. The accuracy and precision (relative standard deviation of ten replicates) are 2% and 1% for the Gran and 1% and 0.5% for the Gran/derivative end point determination procedures, respectively. The proposed system reduces the time to perform a titration, ensuring low sample and reagent consumption, and full automatic sampling and titrant addition in a calibration-free titration protocol.Este trabalho descreve o uso do método de linearização de Gran em titulações em fluxo monossegmentado com detecção potenciométrica. O programa de controle pode estimar o ponto final após a adição de três ou quatro alíquotas de titulante. Alternativamente, o ponto final da titulação pode ser determinado pelo método da segunda derivada. Neste caso, alíquotas adicionais de titulante são adicionadas até a proximidade do ponto final e três pontos antes e após o ponto estequiométrico são usados para o cálculo de ponto final. O desempenho do sistema foi avaliado pela determinação de cloreto em soluções isotônicas e parenterais. O sistema emprega um eletrodo indicador tubular de Ag2S/AgCl. Uma titulação típica, realizada de acordo com a definição IUPAC, requer apenas 60 mL de amostra e aproximadamente o mesmo volume de titulante (AgNO3). Uma titulação completa pode ser realizada entre 1 e 5 min. Foram obtidas exatidão e precisão (desvio padrão relativo de 10 replicatas) de 2% e 1% para o método de Gran e 1% e 0,5% para o método de Gran associado ao método da segunda derivada, respectivamente. O sistema proposto reduz o tempo para realizar uma titulação, com baixo consumo de amostra e reagente, além de possibilitar uma amostragem automática completa e adição de titulante sem a necessidade de uma etapa de calibração.111115Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

A study towards drug discovery for the management of type 2 diabetes: Mellitus through inhibition of the carbohydrate-hydrolyzing enzymes α-amylase and α-glucosidase by chalcone derivatives

The inhibition of carbohydrate-hydrolyzing enzymes, α-amylase and α-glucosidase, is one of the major therapeutic strategies for the treatment of type 2 diabetes mellitus. Chalcones have been recognized for their multiple biological activities, including antidiabetic properties, through unclear mechanisms. In the present work, a panel of chalcones bearing hydroxy, methoxy, methyl, nitro, chloro, fluoro and bromo substituents were evaluated against α-amylase and α-glucosidase activities, most of them for the first time. The results showed that the substitution patterns and the type of substituents of chalcones influence their inhibitory activity. The presence of hydroxy groups at C-2’- and C-4’ of the A ring and at C-3 and C-4 of the B ring favors the intended effect. Chalcones holding nitro groups and chloro substituents, together with a hydroxy group in the chalcone scaffold, showed strong inhibition of the α-glucosidase activity. The present study provides related scaffolds that may serve as the basis for the design and synthesis of new structures in order to obtain the ideal antidiabetic chalcone.This work received financial support from the European Union (FEDER funds POCI/01/0145/FEDER/007265) and National Funds (FCT/MEC, Fundação para a Ciência e Tecnologia and Ministério da Educação e Ciência) under the Partnership Agreement PT2020 UID/QUI/50006/2013, and “Programa Operacional Competitividade e Internacionalização” (COMPETE) (POCI-01-0145-FEDER-029241). Thanks are due to University of Aveiro, Instituto Politécnico de Bragança, FCT/ MEC for the financial support to the QOPNA (FCT UID/QUI/ 00062/2013) and CIMO (UID/AGR/00690/2013) research Units through national funds and where applicable co-financed by the FEDER, within the PT2020 Partnership Agreement, and also to the Portuguese NMR Network. Sónia Rocha acknowledges FCT the financial support for the PhD grant (PD/BD/ 145169/2019), in the ambit of “QREN – POPH – Tipologia 4.1 – Formação Avançada”, co-sponsored by Fundo Social Europeu (FSE) and by national funds of Ministério da Ciência, Tecnologia e Ensino Superior (MCTES).info:eu-repo/semantics/publishedVersio