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1.
Biomed Chromatogr ; 34(1): e4712, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31633799

RESUMO

Coffee and tea are the most widely consumed beverages worldwide. However, the consumer may be unaware of the exact amount of methyl xanthine (MX, i.e. caffeine [C], theobromine [TB] and theophylline [TH]) consumed, as most of the products do not list the proper amounts. This may lead to serious risks including cardiovascular, kidney and stimulant effects. The aim of the study was to determine the MX amount in ready-to-use beverages (coffee and tea) collected from various outlets in the city of Al-Khobar, Saudi Arabia. Forty different samples of espresso, black coffee and red tea were collected. A fast, reliable and efficient UHPLC-DAD method was developed and validated for MX determination. Total lipids were extracted and fractionated in order to determine glycolipids, phospholipids and neutral lipids. The r2 value for the method was 0.980-0.988 in a linearity range of 0.5-200 ppm. The range for MX (C [0.02-2.39 mg/ml], TB [0.00-0.10 mg/ml] and TH [0.00-0.004 mg/ml]) and total lipids was 1-5 g. The amount of glycolipids (3.1 g) was higher among the lipid fractions followed by phospholipids (1.8 g) and neutral lipids (0.25 g). In general, espresso beverages (20-30 ml) contained high amounts of MX whereas black coffee beverages contained high amount of lipids. Most of the beverages expressed C, TB, TH, lipids or their fractions; however, the product with high amounts of MX and lipids at the same time was espresso (brands Chemistry and Wogard). Although the MX and lipid levels in these beverages well below the allowed limits, care must still be taken, especially when using the beverages with high serving volumes (200-250 ml) or coffee prepared via the filter method i.e. black coffee, using a high temperature for a longer time.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Café/química , Chá/química , Xantinas , Culinária , Temperatura Alta , Lipídeos/análise , Reprodutibilidade dos Testes , Arábia Saudita , Xantinas/análise , Xantinas/química , Xantinas/isolamento & purificação
2.
Food Res Int ; 114: 20-29, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30361017

RESUMO

Cocoa shell (CS) is a co-product of the cocoa industry used mainly as fuel for boilers but with secondary applications as fertilizer and in animal feed. Although it is known that this material is rich in flavanols and alkaloids, to date, a study has not been conducted that has quantitatively identified these compounds in CS. Thus, the aim of this work was to characterize CS in terms of its composition, regarding catechin, epicatechin, procyanidin B2, caffeine and theobromine, and to evaluate the extraction kinetics of the total flavanols using pressurized liquid extraction (PLE) with absolute ethanol. For the determination of the extraction kinetic data, the DMAC method was used, while each compound was quantified using a UPLC-MS/MS analysis. The major compounds found were theobromine and epicatechin (mean values of 9.89 and 3.5 mg/g CS, respectively). PLE proved to be quite effective; the flavanols extraction yield was enhanced by increasing the temperature and extraction time however, high extraction times and temperatures degraded the procyanidins B2. Peleg's model applied to extraction data description provided a reasonable agreement with the experimental results, which allows their application in modeling and optimization of solid-liquid extraction of the total flavanols from cocoa bean shell.


Assuntos
Antioxidantes/isolamento & purificação , Cacau/química , Flavonoides/isolamento & purificação , Extração Líquido-Líquido/métodos , Sementes/química , Xantinas/isolamento & purificação , Antioxidantes/análise , Antioxidantes/química , Cromatografia Líquida de Alta Pressão , Etanol/química , Flavonoides/análise , Flavonoides/química , Resíduos Industriais , Cinética , Espectrometria de Massas em Tandem , Termogravimetria , Xantinas/análise , Xantinas/química
3.
PLoS One ; 12(2): e0171872, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28231253

RESUMO

Phytoplankton, with an estimated 30 000 to 1 000 000 species clustered in 12 phyla, presents a high taxonomic and ecophysiological diversity, reflected by the complex distribution of pigments among the different algal classes. High performance liquid chromatography is the gold standard method for qualitative and quantitative analysis of phytoplankton pigments in seawater and culture samples, but only a few pigments can be used as robust chemotaxonomic markers. A major challenge is thus to identify new ones, characteristic of a strain, species, class or taxon that cannot be currently identified on the basis of its pigment signature. Using an optimized extraction process coupled to a HPLC de-replication strategy, we examined the pigment composition of 37 microalgae strains, representative of the broad taxonomic diversity of marine and freshwater species (excluding cyanobacteria). For each species, the major pigments already described were unambiguously identified. We also observed the presence of several minor unidentified pigments in each chromatogram. The global analysis of pigment compositions revealed a total of 124 pigments, including 98 pigments or derivatives unidentified using the standards. Absorption spectra indicated that 35 corresponded to chlorophyll/porphyrin derivatives, 57 to carotenoids and six to derivatives having both spectral signatures. Sixty-one of these unidentified or new carotenoids and porphyrin derivatives were characteristic of particular strains or species, indicating their possible use as highly specific chemotaxonomic markers capable of identifying one strain out of the 37 selected. We developed a graphical analysis using Gephi software to give a clear representation of pigment communities among the various phytoplankton strains, and to reveal strain-characteristic and shared pigments. This made it possible to reconstruct the taxonomic evolution of microalgae classes, on the basis of the conservation, loss, and/or appearance of pigments.


Assuntos
Carotenoides/análise , Microalgas/química , Pigmentos Biológicos/análise , Porfirinas/análise , Carotenoides/isolamento & purificação , Cromatografia Líquida de Alta Pressão , Água Doce/análise , Microalgas/classificação , Pigmentos Biológicos/isolamento & purificação , Porfirinas/isolamento & purificação , Água do Mar/análise , Xantinas/análise , Xantinas/isolamento & purificação
4.
Metab Eng ; 38: 191-203, 2016 11.
Artigo em Inglês | MEDLINE | ID: mdl-27519552

RESUMO

Engineered microbial biosynthesis of plant natural products can support manufacturing of complex bioactive molecules and enable discovery of non-naturally occurring derivatives. Purine alkaloids, including caffeine (coffee), theophylline (antiasthma drug), theobromine (chocolate), and other methylxanthines, play a significant role in pharmacology and food chemistry. Here, we engineered the eukaryotic microbial host Saccharomyces cerevisiae for the de novo biosynthesis of methylxanthines. We constructed a xanthine-to-xanthosine conversion pathway in native yeast central metabolism to increase endogenous purine flux for the production of 7-methylxanthine, a key intermediate in caffeine biosynthesis. Yeast strains were further engineered to produce caffeine through expression of several enzymes from the coffee plant. By expressing combinations of different N-methyltransferases, we were able to demonstrate re-direction of flux to an alternate pathway and develop strains that support the production of diverse methylxanthines. We achieved production of 270µg/L, 61µg/L, and 3700µg/L of caffeine, theophylline, and 3-methylxanthine, respectively, in 0.3-L bench-scale batch fermentations. The constructed strains provide an early platform for de novo production of methylxanthines and with further development will advance the discovery and synthesis of xanthine derivatives.


Assuntos
Técnicas de Cultura Celular por Lotes/métodos , Vias Biossintéticas/genética , Cafeína/biossíntese , Coffea/fisiologia , Engenharia Metabólica/métodos , Saccharomyces cerevisiae/fisiologia , Xantinas/metabolismo , Cafeína/isolamento & purificação , Redes e Vias Metabólicas/genética , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Xantinas/isolamento & purificação
5.
Phytochemistry ; 119: 51-61, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26429632

RESUMO

The present study focuses on development of phytochemical methods for quality assessment of two West-African Cochlospermum species (Cochlospermum planchonii and Cochlospermum tinctorium) traditionally used for malaria treatment in Burkina Faso. Antimalarial activity of preparations from dried rhizomes (decoction) was tested against the chloroquine-sensitive Plasmodium strain 3D7 using the histidine-rich protein II (HRP2) drug susceptibility assay and compared with extract preparations using organic solvents of different polarity. Two main apocarotenoids were isolated from rhizomes of C. planchonii and unambiguously identified as dihydrocochloxanthine and cochloxanthine by spectroscopic methods. Comparative HPLC analyses of thirty-nine (39) samples from markets and from collections in natural habitats of both species showed a high variability in the accumulation of cochloxanthines and related carotenoids which were proven to be characteristic for rhizomes of both species and generally absent in leaves. Furthermore, content of total phenolics and antioxidant activities (DPPH and FRAP) as well as haemolytic activity of various extracts was tested. The HPLC method presented here was validated and provides a good separation of both compounds including 10 minor carotenoids. Extracts from both species and pure cochloxanthine offered pronounced antioxidant activities and weak haemolytic activity while, in contrast, dihydrocochloxanthine had a strong haemolytic effect at the highest concentration analysed. However, cochloxanthine as well as dihydrocochloxanthine showed erythroprotective effects against the haemolytic activity of the reference saponin. Moderate antiplasmodial activity between 16 and 63 µg/ml were observed with all tested extracts, and lower IC50 values were obtained with pure dihydrocochloxanthine (IC50=6.9 µg/ml), cochloxanthine (IC50=6.8 µg/ml), the DCM fraction (IC50=2.4 µg/ml) and the ethyl acetate fraction (IC50=11.5µg/ml) derived from a methanolic extract of C. planchonii. This study shows a major variability of carotenoid content and antiplasmodial activity of both C. planchonii and C. tinctorium. The high haemolytic activity of dihydrocochloxanthine (at 100 µg/ml) should be considered as a selection criterion for choosing species phenotypes for treatment.


Assuntos
Antimaláricos , Bixaceae/química , Medicina Tradicional Africana , Xantinas/isolamento & purificação , Xantinas/farmacologia , Antimaláricos/química , Antimaláricos/isolamento & purificação , Antimaláricos/farmacologia , Burkina Faso , Malária/tratamento farmacológico , Estrutura Molecular , Folhas de Planta/química , Plasmodium falciparum/efeitos dos fármacos , Proteínas/química , Proteínas/isolamento & purificação , Proteínas/farmacologia , Xantinas/química
6.
Biomed Chromatogr ; 29(1): 1-20, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-25381720

RESUMO

In recent years demands on the amount of information that can be obtained from the analysis of a single sample have increased. For time and economic reasons it is necessary to examine at the same time larger number of compounds, and compounds from different groups. This can best be seen in such areas as clinical analysis. In many diseases, the best results for patients are obtained when treatment fits the individual characteristics of the patient. Dosage monitoring is important at the beginning of therapy and in the full process of treatment. In the treatment of many diseases biogenic amines (dopamine, serotonin) and methylxanthines (theophylline, theobromine, caffeine) play an important role. They are used as drugs separately or in combination with others to support and strengthen the action of other drugs - for example, the combination of caffeine and paracetamol. Vitamin supplementation may be also an integral part of the treatment process. Specification of complete sample preparation parameters for extraction of the above compounds from biological matrices has been reviewed. Particular attention was given to the preparation stage and extraction methods. This review provides universal guidance on establishing a common procedures across laboratories to facilitate the preparation and analysis of all discussed compounds.


Assuntos
Ácido Ascórbico/isolamento & purificação , Aminas Biogênicas/isolamento & purificação , Fracionamento Químico/métodos , Complexo Vitamínico B/isolamento & purificação , Xantinas/isolamento & purificação , Ácido Ascórbico/análise , Ácido Ascórbico/química , Aminas Biogênicas/análise , Aminas Biogênicas/química , Humanos , Modelos Moleculares , Complexo Vitamínico B/análise , Complexo Vitamínico B/química , Xantinas/análise , Xantinas/química
7.
J Sep Sci ; 37(5): 536-42, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24347554

RESUMO

Hydrophilic interaction LC was investigated in hydro-organic and nonaqueous elution modes on a titania column by using a set of N-methyl xanthines as neutral polar probes. To get information regarding the mechanisms that are behind the discrimination of these analytes in hydrophilic interaction, we focused our study on the type and amount of organic modifier as a critical yet rarely explored mobile phase parameter. Several alcohols such as methanol, ethanol, and isopropanol were studied as substitutes to acetonitrile in hydro-organic elution mode. Compared to silica, the investigation of the eluotropic series of these alcohols on titania highlighted a different implication in the retention mechanism of the xanthine derivatives. At low amounts of protic solvents, the adsorption mainly characterized the retention of analytes on bare silica; whereas mixed interactions including adsorption and ligand exchange were identified on native titania. To investigate the peculiar behavior of alcohols on the metal oxide, methanol, ethanol, and ethylene glycol were tested in replacement of water in polar-organic elution mode. Distinctive effects on the chromatographic retention and selectivity of xanthines were noticed for the dihydric alcohol, which was found to be a stronger eluting component than water on titania.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Compostos Orgânicos/química , Xantinas/isolamento & purificação , Cromatografia Líquida de Alta Pressão/instrumentação , Solventes/química , Xantinas/química
8.
Vopr Pitan ; 82(6): 19-23, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24741952

RESUMO

The main goal of this study is to describe the scientific basis of the beneficial effects of E.L.I.S. using, intended to improve motor coordination and muscular memory, optimizing the neuronal circuits throughout the entire body, involved in learning and doing sports. These effects, combined with the synergic action presented by these extracts (E.L.I.S.) when administered together with compounds of xanthine structure, also lead to improved blood circulation and glucose consumption optimizing the cellular metabolism, the production of neurotransmitters and the cognitive capacity and, therefore, the cerebral activity is reinforced in general both in the short term and the long-term after administering them orally. 285 references of scientific literature relating to the E.L.I.S. are submitted on the basis of requests from olympics2014@memorysecret.net and olympics.sochi@ memorysecret.net.


Assuntos
Desempenho Atlético , Indóis/farmacologia , Extratos Vegetais/farmacologia , Plantas Medicinais/química , Medicina Esportiva , Xantinas/farmacologia , Humanos , Indóis/isolamento & purificação , Extratos Vegetais/isolamento & purificação , Xantinas/isolamento & purificação
9.
Proc Natl Acad Sci U S A ; 110(1): E99-107, 2013 Jan 02.
Artigo em Inglês | MEDLINE | ID: mdl-23248299

RESUMO

Biosynthetic pathways of secondary metabolites from fungi are currently subject to an intense effort to elucidate the genetic basis for these compounds due to their large potential within pharmaceutics and synthetic biochemistry. The preferred method is methodical gene deletions to identify supporting enzymes for key synthases one cluster at a time. In this study, we design and apply a DNA expression array for Aspergillus nidulans in combination with legacy data to form a comprehensive gene expression compendium. We apply a guilt-by-association-based analysis to predict the extent of the biosynthetic clusters for the 58 synthases active in our set of experimental conditions. A comparison with legacy data shows the method to be accurate in 13 of 16 known clusters and nearly accurate for the remaining 3 clusters. Furthermore, we apply a data clustering approach, which identifies cross-chemistry between physically separate gene clusters (superclusters), and validate this both with legacy data and experimentally by prediction and verification of a supercluster consisting of the synthase AN1242 and the prenyltransferase AN11080, as well as identification of the product compound nidulanin A. We have used A. nidulans for our method development and validation due to the wealth of available biochemical data, but the method can be applied to any fungus with a sequenced and assembled genome, thus supporting further secondary metabolite pathway elucidation in the fungal kingdom.


Assuntos
Aspergillus nidulans/genética , Vias Biossintéticas/genética , Perfilação da Expressão Gênica/métodos , Regulação Fúngica da Expressão Gênica/genética , Metaboloma/genética , Família Multigênica/genética , Análise por Conglomerados , Análise em Microsséries/métodos , Policetídeo Sintases/genética , Espectrometria de Massas em Tandem , Xantinas/química , Xantinas/isolamento & purificação
10.
Fitoterapia ; 82(6): 818-26, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21600272

RESUMO

This study analyzed the plasma lipid profile, glucose levels and fat deposits in male rats treated with aqueous extract of gross yerba mate, commercial yerba mate or water. Yerba mate treatment did not change body weight gain and lipid profile. The consumption of gross yerba mate significantly increased blood glucose (6.6 mmol/L) as compared to the water (4.8 mmol/L) and commercial group (5.2 mmol/L) and decreased epididymal and intra-abdominal deposits (10.1mg/g and 23.7 mg/g of weight) as compared to the water (15.4 mg/g and 36.9 mg/g of weight) and commercial group (12.5mg/g and 28 mg/g of weight). The results suggest that gross yerba mate reduces fat more efficiently but produces a greater increase in blood glucose when compared to commercial yerba mate and water groups.


Assuntos
Tecido Adiposo/efeitos dos fármacos , Glicemia/efeitos dos fármacos , Ilex paraguariensis/química , Polifenóis/farmacologia , Saponinas/farmacologia , Xantinas/farmacologia , Tecido Adiposo/metabolismo , Animais , Glicemia/metabolismo , Peso Corporal/efeitos dos fármacos , Epididimo/metabolismo , Gordura Intra-Abdominal/efeitos dos fármacos , Masculino , Componentes Aéreos da Planta/química , Extratos Vegetais/química , Extratos Vegetais/farmacologia , Polifenóis/química , Polifenóis/isolamento & purificação , Distribuição Aleatória , Ratos , Ratos Wistar , Saponinas/química , Saponinas/isolamento & purificação , Xantinas/química , Xantinas/isolamento & purificação
11.
J Chromatogr A ; 1217(9): 1496-500, 2010 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-20079499

RESUMO

Monolithic capillary columns based on zirconia were prepared directly from zirconium alkoxide. They were also prepared coating a classical silica based monolithic column with zirconium butoxide. Using the gradual evolution of the theophylline/caffeine separation factor, it was found that successive zirconia coatings produced the progressive fading of surface silanols replaced by Zr-OH groups. The behavior of a silica monolith coated four times with zirconium butoxide was very similar to that of a pure zirconia monolith. The dramatic change in xanthine separation factor observed with zirconia stationary phases and the theophylline and caffeine probe solutes was used to develop a complete separation of xanthines on zirconia stationary phase in less than 6 min. The three dimethylxanthine isomers, theophylline, theobromine and paraxanthine, are very difficult to separate in RPLC with classical C18 stationary phases. The three isomers were easily separated in HILIC mode on a zirconia based stationary phase.


Assuntos
Cromatografia Líquida/instrumentação , Xantinas/isolamento & purificação , Zircônio/química , Cafeína/isolamento & purificação , Concentração de Íons de Hidrogênio , Microscopia Eletrônica de Varredura , Concentração Osmolar , Dióxido de Silício/química , Teofilina/isolamento & purificação , Água/química , Xantinas/química
12.
J Sep Sci ; 32(7): 1002-10, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19266552

RESUMO

In this paper, the simultaneous separation of several polyphenols such as (+)-catechin, (-)-epicatechin, (-)-epigallocatechin, theophylline, caffeine in green and black teas by capillary electrochromatography (CEC) was developed. Several experimental parameters such as stationary phase type, mobile phase composition, buffer and pH, inner diameter of the columns, sample injection, were evaluated to obtain the complete separation of the analysed compounds. Baseline resolution of the studied polyphenols was achieved within 30 min by using a capillary column (id 100 microm) packed with bidentate C(18) particles for 24.5 cm and a mobile phase composed of 5 mM ammonium acetate buffer pH 4 with H(2)O/ACN (80:20, v/v). The applied voltage and the temperature were set at 30 kV and 20 degrees C. Precision, detection and quantification limits, linearity, and accuracy were investigated. A good linearity (R(2) > 0.9992) was achieved over a concentration working range of 2-100 microg/mL for all the analytes. LOD and LOQ were 1 and 2 microg/mL, respectively, for all studied compounds. The CEC method was applied to the analysis of those polyphenols in green and black tea samples after an extraction procedure. Good recovery data from accuracy studies ranged between 90% and 112% for all analytes.


Assuntos
Eletrocromatografia Capilar/métodos , Catequina/isolamento & purificação , Chá/química , Xantinas/isolamento & purificação , Concentração de Íons de Hidrogênio , Modelos Lineares , Estrutura Molecular
13.
J Chromatogr A ; 1214(1-2): 183-6, 2008 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-19010481

RESUMO

Titania monoliths inside capillary columns were prepared from a mixture of titanium propoxide, hydrochloric acid, formamide and water. Several synthesis parameters such as hydrolysis ratio, porogen type, precursor concentration, and drying step have been identified and controlled in order to obtain a macroporous titania monolith, efficient for liquid chromatography, inside a silica capillary. Pure titania monolith with a 10 times higher permeability as compared to a classical packed column was produced, and was able to separate a xanthine test mixture in the LC mode. Even if direct observations with scanning electron microscopy cannot be performed in wet conditions, the homogenous structure of the monolith was demonstrated by the plate height observed during chromatographic separation of xanthines in hydrophilic interaction liquid chromatography.


Assuntos
Cromatografia Líquida/métodos , Titânio/química , Microscopia Eletrônica de Varredura , Permeabilidade , Transição de Fase , Porosidade , Propriedades de Superfície , Xantinas/isolamento & purificação
14.
Planta Med ; 74(10): 1276-9, 2008 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-18622908

RESUMO

The dried seeds of XANTHIUM STRUMARIUM (Asteraceae) are used after thorough stir-frying as an ingredient in traditional Chinese medicines for relieving allergy. Two new compounds, xanthialdehyde ( 2) and (-)-xanthienopyran ( 7), as well as 26 known compounds were isolated in the present study. The structures of the isolates were elucidated by spectroscopic methods. Among them, compound 7 exhibited significant selective inhibition of superoxide anion generation by human neutrophils induced by formyl- L-methionyl- L-leucyl- L-phenylalanine, with an IC50 value of 1.72 microg/mL.


Assuntos
Aldeídos/isolamento & purificação , Neutrófilos/efeitos dos fármacos , Piranos/farmacologia , Superóxidos/metabolismo , Xantinas/isolamento & purificação , Xantinas/farmacologia , Xanthium/química , Aldeídos/química , Antineoplásicos Fitogênicos/isolamento & purificação , Linhagem Celular Tumoral , Medicamentos de Ervas Chinesas/química , Humanos , Concentração Inibidora 50 , Estrutura Molecular , Neutrófilos/metabolismo , Piranos/química , Piranos/isolamento & purificação , Sementes/química , Xantinas/química
15.
J Chromatogr A ; 1160(1-2): 150-9, 2007 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-17537447

RESUMO

In the last decade, silica monolithic capillaries have focused more and more attention on miniaturized separation techniques like capillary electrochromatography (CEC), nano-liquid chromatography (nano-LC) and chip electrochromatography owing to their unique chromatographic properties and their simplified preparation compared with packed columns. They are synthesized according to a sol-gel multi-step process that includes, after a gelation step at 40 degrees C leading to the formation of the macropores network and the silica skeleton, a post-gelation step (hydrothermal treatment at 120 degrees C in basic medium) that allows to tailor the mesopores and finally a calcination or a washing step to remove remaining polymers. In order to reduce the synthesis time, the number of synthesis steps and above all the temperature synthesis, to adapt the synthesis of such silica monoliths in polymeric microsystem devices, we extensively studied the influence of the hydrothermal treatment and its duration on textural (pore size distribution) and chromatographic properties (retention, efficiency) of in situ-synthesized capillary monoliths in nano-LC and CEC. This study was performed on pure silica and octyl chains grafted silica monoliths. Untreated monoliths show small pores (<6 nm), whereas hydrothermally treated monoliths exhibit medium and large mesopores (8-17 nm). It was demonstrated that the hydrothermal treatment at 120 degrees C was not necessary for pure silica monolithic capillaries dedicated to normal phase liquid chromatography or hydrophilic interaction liquid chromatography (HILIC) and electrochromatography: the suppression of the hydrothermal treatment did not impair efficiencies in CEC and in nano-LC but contributed to increase in retention factors. Minimal plate heights of ca. 5 microm in CEC and 6 microm in nano-LC were obtained with or without hydrothermal treatment with bare silica. In the same way, the hydrothermal treatment was not necessary for grafted silica monoliths only dedicated to CEC. However, the results clearly indicate that the hydrothermal treatment becomes essential before grafting in order to preserve the efficiency of the monolithic silica capillaries dedicated to nano-LC: in this particular case, the suppression of the hydrothermal treatment leads approximately to a loss of a factor two in efficiency.


Assuntos
Eletrocromatografia Capilar/métodos , Nanotecnologia/métodos , Dióxido de Silício/química , Temperatura Ambiente , Água , Adsorção , Nitrogênio , Compostos de Fenilureia/isolamento & purificação , Hidrocarbonetos Policíclicos Aromáticos/isolamento & purificação , Porosidade , Xantinas/isolamento & purificação
16.
Electrophoresis ; 27(20): 3971-80, 2006 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-16983639

RESUMO

Silica monolithic capillaries (SMCs) were synthesized by a sol-gel process. First, a simplification of the synthesis was proposed by replacing the calcination and the drying steps which can have tremendous effects on chromatographic and physical properties, by a single water or methanol 2 h washing step. The efficiency of such a washing step was demonstrated and the comparison of the chromatographic and electrochromatographic properties between calcined and washed SMCs has shown that such a modification did not impair retention, efficiency, and stability of the monolith. This simplified procedure was carried out to synthesize SMCs with two different skeleton sizes. These capillaries were evaluated in electrochromatography and present high efficiencies (H = 5 microm) at least equal to the best ones reported in the literature. Furthermore, the influence of the skeleton size on the EOF of the second kind (EOF-2) was investigated with unmodified SMCs used under various experimental conditions including electrical field strength and buffer concentration. The ionic strength of the mobile phase and the applied electrical field that enable this EOF-2 were related to the size of the skeleton which was tuned by the synthesis conditions.


Assuntos
Eletrocromatografia Capilar/métodos , Eletrocromatografia Capilar/instrumentação , Eletro-Osmose , Polietilenoglicóis , Sílica Gel , Dióxido de Silício/síntese química , Dióxido de Silício/química , Solventes , Xantinas/isolamento & purificação
17.
Mutat Res ; 605(1-2): 22-9, 2006 Jun 16.
Artigo em Inglês | MEDLINE | ID: mdl-16678474

RESUMO

The roots of Rubia tinctorum L. have a long tradition of being used in dyeing processes of textiles from centuries ago until the present time. The colouring principles belong to the class of hydroxyanthraquinones. Concern arose because several of these compounds were recognised as mutagenic in vitro and even carcinogenic in rodents. To assess the possible risk to humans caused by coloured textiles, mutagenicity was investigated with two madder root samples of different origin (Iran and Bhutan) along the entire dyeing process from root extracts to the dyed wool. The Salmonella/microsome test (Ames assay) with the strains TA98, TA100 and TA1537 was used. Significant mutagenic effects could be detected in madder root extracts and also in the final product, the dyed wool. Madder root from Iran showed considerably higher mutagenic responses than samples from Bhutan. Analytical investigations of the extracts by HPLC showed the presence of a spectrum of anthraquinones typical for madder root. Three mutagenic compounds, lucidine, rubiadine and purpuroxanthine, together with the non-mutagenic alizarine could be detected. The mutagenic response of the different samples was positively correlated with the concentration of the mutagenic anthraquinones, and with lucidine in particular. Based on these investigations a risk to dye-house workers and users of textiles dyed with R. tinctorum must be anticipated.


Assuntos
Corantes/toxicidade , Mutagênicos/toxicidade , Raízes de Plantas/química , Rubia/química , Indústria Têxtil/ética , Animais , Antraquinonas/isolamento & purificação , Antraquinonas/farmacologia , Antraquinonas/toxicidade , Cromatografia Líquida de Alta Pressão , Corantes/isolamento & purificação , Compostos Heterocíclicos de 4 ou mais Anéis/isolamento & purificação , Compostos Heterocíclicos de 4 ou mais Anéis/toxicidade , Humanos , Testes de Mutagenicidade , Mutagênicos/isolamento & purificação , Extratos Vegetais/química , Quinolinas/isolamento & purificação , Quinolinas/toxicidade , Salmonella/efeitos dos fármacos , Salmonella/genética , Salmonella/crescimento & desenvolvimento , , Xantinas/isolamento & purificação , Xantinas/toxicidade
18.
J Chromatogr A ; 1114(2): 216-23, 2006 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-16616927

RESUMO

A organically modified molecularly imprinted silica (MIS), selective for methylxanthines, was prepared using a simple sol-gel procedure. Caffeine was used as template; 3-aminopropyltrimethoxysilane (APTMS) as functional monomer and tetraethyl orthosilicate (TEOS) as reticulating agent. The material was packed on solid-phase extraction (SPE) cartridges and evaluated with aqueous test samples, natural water and human urine; a quantitative method for methylxanthines in water, using SPE cartridges packed with the MIS coupled with HPLC-UV was developed. The MIS was highly specific for methylxanthines, with an imprinting factor of (20.5+/-1.9). The analytical method resulted in detection limits of 85 microgL(-1) for theobromine, 44 microgL(-1) for theophylline and 53 microgL(-1) for caffeine.


Assuntos
Siloxanas/química , Xantinas/isolamento & purificação , Cromatografia Líquida de Alta Pressão/métodos , Transição de Fase , Sensibilidade e Especificidade , Espectrofotometria Infravermelho , Raios Ultravioleta , Xantinas/urina
19.
Chem Pharm Bull (Tokyo) ; 54(1): 111-3, 2006 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-16394561

RESUMO

Further study of the methanol extract of the stem bark of Allanblackia monticola STANER L.C. resulted in the isolation of a new prenylated xanthenedione, designated allanxanthone C, together with the five known xanthones, garciniafuran, tovophyllin A, rubraxanthone, norcowanin and mangostin and one saponin, stigmasterol-3-O-beta-D-glucopyranoside. The structure of the new compound was established by detailed spectroscopic analysis to be 1,2-dihydro-3,6,8-trihydroxy-1,1,7-tri(3-methylbut-2-enyl)xanthen-2,9-dione (3-hydroxyapetalinone C). The methanol extract and pure compounds were tested on two strains of Plasmodium falciparum, F32 (chloroquine sensitive) and FcM29 (chloroquine resistant). The IC50 values obtained ranged from 0.6 to 8.9 microg/ml. Their cytotoxicity was estimated on human melanoma cells (A375) and the cytotoxicity/antiplasmodial ratio was found to be between 15.45 and 30.46. The antimicrobial activities against a range of microorganisms of the crude extract and some of these compounds are also reported.


Assuntos
Antimaláricos/química , Antimaláricos/farmacologia , Clusiaceae/química , Xantinas/química , Xantinas/farmacologia , Xantonas/química , Xantonas/farmacologia , Animais , Anti-Infecciosos/farmacologia , Antimaláricos/isolamento & purificação , Candida tropicalis/efeitos dos fármacos , Linhagem Celular Tumoral , Resistência a Medicamentos , Humanos , Espectroscopia de Ressonância Magnética , Melanoma/tratamento farmacológico , Testes de Sensibilidade Microbiana , Casca de Planta/química , Caules de Planta/química , Plasmodium falciparum/efeitos dos fármacos , Prenilação de Proteína , Espectrometria de Massas por Ionização por Electrospray , Espectrofotometria Infravermelho , Espectrofotometria Ultravioleta , Staphylococcus aureus/efeitos dos fármacos , Xantinas/isolamento & purificação
20.
Chem Pharm Bull (Tokyo) ; 54(1): 126-8, 2006 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-16394566

RESUMO

Two new xanthones, 1,5,6-trihydroxy-3-methoxy-4-(3-hydroxyl-3-methylbutyl)xanthone (1) and 1,5-dihydroxy-3-methoxy-6',6'-dimethyl-2H-pyrano(2',3':6,7)-4-(3-methylbut-2-enyl)xanthone (2), have been isolated together with six known xanthones: 1,3,5-trihydroxy-6',6'-dimethyl-2H-pyrano(2',3':6,7)xanthone (3), dulxanthone A (4), 1,5,6-trihydroxy-3,7-dimethoxyxanthone (5), 1,7-dihydroxyxanthone (6), 1,3,5-trihydroxy-6-methoxyxanthone (7), 1,3,6,7-tetrahydroxyxanthone (8), from the stems of Garcinia cowa (Guttiferae).


Assuntos
Garcinia/química , Xantinas/química , Xantonas/química , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Conformação Molecular , Extratos Vegetais/química , Caules de Planta/química , Solventes , Espectrometria de Massas por Ionização por Electrospray , Espectrofotometria Infravermelho , Espectrofotometria Ultravioleta , Xantinas/isolamento & purificação , Xantonas/isolamento & purificação
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