Biomedical subjects

A Cifuentes

Publications and source records attributed to A Cifuentes.

At least 19 recordsLinked to original sources

PubMed2006

Subcritical water extraction of nutraceuticals with antioxidant activity from oregano. Chemical and functional characterization.

In the present work, oregano leaves (Origanum vulgare L.) are explored as natural source of nutraceuticals with antioxidant activity. To do this, subcritical water extraction (SWE), a new environmentally friendly technique, is employed as extraction procedure and HPLC coupled to DAD is used for the chemical characterization of the extracts. Moreover, the radical scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH) method and the determination of the total phenolic content (measured with the Folin test) are applied to evaluate the antioxidant activity of the extracts. The extraction of antioxidants from oregano leaves by SWE is studied considering different temperatures (25, 50, 100, 150 and 200 degrees C) to investigate the selectivity of the process. The highest antioxidant activity is observed for the extract obtained at the highest temperature, 200 degrees C (EC(50) equal to 10 microg/ml). Moreover, the extraction yield was also the highest (54% dry weight) at these extraction conditions. The total phenolic content showed no differences among the different extracts, concluding that the amount of phenolic compounds extracted was similar but the type and structure of the phenolics was different, providing in this way different antioxidant activity. Some compounds could be tentatively identified, proposing some probable chemical structures for some of them, such as flavanones, dihydroflavonols, favonols and flavones.

Antioxidants↗

PubMed2005

Liquid separation techniques coupled with mass spectrometry for chiral analysis of pharmaceuticals compounds and their metabolites in biological fluids.

Determination of the chiral composition of drugs is nowadays a key step in order to determine purity, activity, bioavailability, biodegradation, etc., of pharmaceuticals. In this article, works published for the last 5 years on the analysis of chiral drugs by liquid separation techniques coupled with mass spectrometry are reviewed. Namely, chiral analysis of pharmaceuticals including, e.g., antiinflammatories, antihypertensives, relaxants, etc., by liquid chromatography-mass spectrometry and capillary electrophoresis-mass spectrometry are included. The importance and interest of the analysis of the enantiomers of the active compound and its metabolites in different biological fluids (plasma, urine, cerebrospinal fluid, etc.) are also discussed.

Animals↗

PubMed2005

Capillary electrophoresis of glutathione to monitor oxidative stress and response to antioxidant treatments in an animal model.

Glutathione plays a central role in metabolism and antioxidant defence. Several factors can influence the analytical efficiency and rapidity of the quantitative determination of glutathione. Procedures in sample pre-treatment have been compared in order to minimize analytical errors. Capillary electrophoresis has been chosen as a more adequate technique for obtaining a rapid and simple method for glutathione and glutathione disulfide determination in the blood and liver of the rat. The methods, once optimised, have been validated and applied for monitoring the oxidative stress in an animal model, such as the rat made diabetic by streptozotocin injection, when the animals are treated with antioxidants and compared with the corresponding controls.

Animals↗

PubMed2004

Pesticide analysis by capillary electrophoresis.

In this work, a critical and updated revision of the current situation of the analysis of pesticides by Capillary Electrophoresis (CE) is presented. The review has been written in two main sections. The first one presents a thorough revision of the various offline and on-line sample preconcentration procedures that have been used in conjunction with CE to analyze these compounds. The second part reviews the various detection strategies (i.e., UV, LIF, MS, and electrochemical) and CE modes that have been applied to the analysis of pesticides. Future trends that can be expected from this hot research area are also discussed.

Chromatography, Micellar Electrokinetic Capillary↗

PubMed2002

Fast and sensitive capillary electrophoresis method to quantitatively monitor ibuprofen enantiomers released from polymeric drug delivery systems.

In this work, the capability of two polymeric drug delivery systems (DDS) containing racemic ibuprofen (IBU) for controlled release of IBU in different media was studied carrying out assays in-vitro. To quantitatively monitor the release of R(-)- and S(+)-IBU, a fast, sensitive and inexpensive capillary electrophoresis (CE) method was developed. To do this, different chiral selectors, temperatures, buffer compositions and pHs were tested. This new CE method uses bare silica columns together with a buffer containing 6% Dextrin in a 150 mM sodium tetraborate buffer at pH 9. Baseline separations of R(-)- and S(+)-IBU were achieved in less than 5 min at 20 degrees C. By using this method, both enantiomers can be determined at concentrations as low as 1 microg/ml, allowing the detection of enantiomeric percentages of 0.5% of R(-)-IBU in the presence of 99.5% of the optical antipode. Moreover, the method shows a high reproducibility for the same day and different days. The usefulness of this method to quantitatively monitor the release of R(-)- and S(+)-IBU from two different polymeric DDS is demonstrated. It is shown that the release rate of IBU depends on the spacer of the side residue used in the polymeric device. Also, it is demonstrated that the release of both enantiomers is enzymatically activated in rat plasma.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2002

Monitoring ibuprofen enantiomers released from polymeric systems.

Two methacrylic derivatives of ibuprofen (N-[4-[2-(4-isobutylphenyl)propionyloxy]phenyl] methacrylamide (MAI) and 2-[(4-isobutylphenyl)propionyloxy]ethyl methacrylate (MEI)) were used together with 2-hydroxyethyl methacrylate (HEMA) to synthesize four polymeric materials: two hydrophobic homopolymers, PMAI and PMEI, and two hydrophilic copolymers containing 70% (w/w) HEMA, MAI-HEMA 30 and MEI-HEMA 30. The enantiomeric determination of R- and S-IBU released from these four systems has been carried out by capillary electrophoresis. Release of R- and S-IBU was monitored during in vitro assays done at 37 degrees C at pH 7.4 and 10 in buffered solutions and rat plasma. There is a hydrolytical activation in plasma and at pH 10 compared to pH 7.4; moreover, the release rate from the copolymers is much higher than from the homopolymers as a consequence of the greater hydrophilic character. A slight excess of the S-enantiomer of IBU is observed in all the experiments, being more relevant at higher release rates, i.e. copolymers at pH 10.

Animals↗

PubMed2001

Modulated release of cyclosporine from soluble vinyl pyrrolidone--hydroxyethyl methacrylate copolymer hydrogels. A correlation of 'in vitro' and 'in vivo' experiments.

Soluble, uncrosslinked and high molecular weight copolymers of vinylpyrrolidone, VP, with 2-hydroxyethyl methacrylate, HEMA, prepared by free radical copolymerization, are proposed as supports for the modulated release of the immunosuppressor cyclosporine. Two copolymeric systems with copolymer compositions f(VP)=0.52 (namely VP--HEMA 60--40) and 0.42 (VP--HEMA 40--60) have been prepared and tested in vitro and in vivo using rats as animal model. Micellar electrokinetic capillary chromatography, MEKC, has been used for the simultaneous detection of the polymer reabsorption and the drug release for the in vitro experiments. The composition and microstructural distribution of the copolymer system controls the solubilization rate which modulates the in vitro release of the drug (with time profiles from a few days to several weeks for the VP--HEMA 60--40 and 40--60, respectively) and the in vivo response that correlates with the previous in vitro results: the more hydrophobic implant (VP--HEMA 40--60) reverts the immune response more slowly (2--4 weeks) compared to the more hydrophilic one (VP--HEMA 60--40, 1--2 weeks).

Animals↗

PubMed2001

Fast determination of procyanidins and other phenolic compounds in food samples by micellar electrokinetic chromatography using acidic buffers.

Procyanidins are phenolic oligomers, mainly composed of (+)-catechin and (-)-epicatechin units that exhibit certain sensorial and physiological properties of interest (e.g., astringency and bitterness of food, antioxidant activity, etc.). This paper shows the development of a micellar electrokinetic chromatography (MEKC) method for the separation of three procyanidin dimers (B1, B2, and B3), their monomers ((+)-catechin and (-)-epicatechin), and the cis- and trans-forms of p-coumaric acid. Separation conditions are optimized in terms of buffer pH, SDS concentration, and washing routine between injections. The best results in terms of peak resolution and reproducibility between separations were obtained with a MEKC running buffer at pH 5 with 100 mM SDS and a washing routine that includes a rinse step with 0.1 M sodium hydroxide. Using this new MEKC method it is possible to separate in less than 5 min the seven substances. More interestingly, it is demonstrated that the low pH used in this MEKC method allows one to obtain clean electropherograms when samples are injected. The method is shown to be reproducible between different days with relative standard deviation (RSD) values lower than 1% for migration times and lower than 7% for peak areas (3 days, 24 injections). The usefulness of this procedure to determine these compounds in effluents from food processing (i.e., soaking water from lentils, white beans and black beans) and in food by-products (i.e., almond peels) considered as potential procyanidin sources is demonstrated. To our knowledge, this is the first report of separation and determination of procyanidins in food samples done by capillary electrophoresis.

Biflavonoids↗

PubMed2001

Isolation of antioxidant compounds from orange juice by using countercurrent supercritical fluid extraction (CC-SFE).

Antioxidants from orange juice are isolated by the use of countercurrent supercritical fluid extraction (CC-SFE) and characterized by reversed-phase liquid chromatography (RPLC) coupled to mass spectrometry (MS) and diode-array detection (DAD). A pilot-scale SFE plant equipped with a packed column has been employed for countercurrent extraction and fractionation of raw orange juice with carbon dioxide. Several experiments have been performed in order to study the effect of the countercurrent conditions on the content of antioxidative compounds. In this study, the main variable that has been considered is the solvent-to-feed ratio (S/F) because it plays an essential role in the extraction efficiency. The values tested covered a wide range of sample and solvent (CO(2)) flow rates. In each experimental run, two different extracted fractions and the residual nonextracted juice were obtained and characterized. Different flavonoids have been identified in the fractions obtained after CC-SFE. The possibility of using this process for antioxidant compounds enrichment is discussed.

Antioxidants↗

PubMed2001

New analytical techniques in food science.

In this review, some of the latest analytical techniques that are being used for the study and characterization of food are examined. This work intends to provide an updated overview (including works published up to June 1999) on the principal applications of such techniques together with their main advantages and drawbacks in food analysis. Some future developments of these systems and their foreseeable application in food characterization are also discussed. The reviewed techniques are those based on spectroscopic, biological, separation, and electrochemical procedures. Moreover, some relevant facts on new systems for sample preparation and on-line couplings are also given.

Chemistry Techniques, Analytical↗

PubMed2000

Controlled release of cyclosporine from VP-HEMA copolymer systems of adjustable resorption monitorized by MEKC.

Soluble, uncrosslinked and high molecular weight copolymers of vinylpyrrolidone, VP, with 2-hydroxyethyl methacrylate, HEMA, prepared by free radical copolymerization, are proposed as supports for the modulated release of drugs, taking cyclosporine as a model system. The copolymerization parameters described as reactivity ratios, rVP = 0.08 and rHEMA = 7.97, indicate that the copolymer systems prepared at high conversion have two main components with a microstructural arrangement which depends on the average composition, i.e., an initial HEMA-rich copolymer and a final PVP homopolymer or VP-rich copolymer. This microstructural distribution controls the resorption rate of the polymeric support and therefore the release process of cyclosporine which is demonstrated experimentally by the application of a modern technique known as micellar electrokinetic capillary chromatography (MEKC).

Chromatography, Micellar Electrokinetic Capillary↗

PubMed2000

Combined use of supercritical fluid extraction, micellar electrokinetic chromatography, and reverse phase high performance liquid chromatography for the analysis of antioxidants from rosemary (Rosmarinus officinalis L.).

Antioxidants from rosemary were determined by the combined use of supercritical fluid extraction (SFE) prior to reverse-phase high-performance liquid chromatography (RP-HPLC) or micellar electrokinetic chromatography (MEKC). The separation of antioxidants found in the SFE fractions was achieved by using a new MEKC method and a published HPLC procedure, both with diode array detection. The characterization of the different antioxidants was further done by HPLC-mass spectrometry. Advantages and drawbacks of HPLC and MEKC for analyzing the antioxidants found in the different extracts are discussed. From the results it is concluded that HPLC renders higher peak area and is better in its reproducibility than MEKC; both techniques provide similar analysis time reproducibility. The main advantage of MEKC is its much higher separation speed, which is demonstrated to be useful for the quick adjustment of SFE conditions, allowing rosemary fractions of higher antioxidative power to be obtained quickly. Moreover, the possibilities of this approach for following the degradation of antioxidants are discussed.

Antioxidants↗

PubMed2000

Dobutamine restores intestinal mucosal blood flow in a porcine model of intra-abdominal hyperpressure.

OBJECTIVE: To assess the effects of dopamine and dobutamine administration on the systemic and mesenteric (macro- and microvascular) circulatory disturbances induced by intra-abdominal hyperpressure. DESIGN: Prospective, randomized study. SETTING: Animal research laboratory in a university hospital. SUBJECTS: Twenty-five pigs of either gender, weighing 30-35 kg. INTERVENTIONS: Animals were anesthetized, and their lungs were mechanically ventilated. Pulmonary artery flotation and carotid artery catheters were inserted for hemodynamic monitoring and blood sampling. A perivascular flow probe was placed around the superior mesenteric artery, and a laser Doppler probe was positioned in the lumen of the ileum to measure arterial and intestinal mucosal blood flows, respectively. CO2 was insufflated into the peritoneal cavity to reach an intra-abdominal pressure of 15 mm Hg, and 60 mins later, animals received dopamine (5 microg/kg/min; n = 10), dobutamine (5 microg/kg/min; n = 10), or saline (n = 5) for 30 mins. MEASUREMENTS AND MAIN RESULTS: Peritoneal CO2 insufflation induced significant increases in heart rate, arterial pressure, and systemic vascular resistance with concomitant decreases in cardiac output and superior mesenteric arterial and intestinal mucosal blood flows. Although dobutamine infusion reversed the decrease in cardiac output, it failed to restore superior mesenteric artery blood flow; however, intestinal mucosal blood flow returned to baseline levels. Dopamine also attenuated the decrease in cardiac output, but it had no beneficial effect on splanchnic hemodynamic variables. CONCLUSIONS: Low-dose infusion of dobutamine, but not dopamine, corrects the intestinal mucosal perfusion impairment induced by moderate increases in intra-abdominal pressure.

Abdomen↗

PubMed2000

Prokaryotic diversity in Zostera noltii-colonized marine sediments.

The diversity of microorganisms present in a sediment colonized by the phanerogam Zostera noltii has been analyzed. Microbial DNA was extracted and used for constructing two 16S rDNA clone libraries for Bacteria and Archaea. Bacterial diversity was very high in these samples, since 57 different sequences were found among the 60 clones analyzed. Eight major lineages of the Domain Bacteria were represented in the library. The most frequently retrieved bacterial group (36% of the clones) was delta-Proteobacteria related to sulfate-reducing bacteria. The second most abundant group (27%) was gamma-Proteobacteria, including five clones closely related to S-oxidizing endosymbionts. The archaeal clone library included members of Crenarchaeota and Euryarchaeota, with nine different sequences among the 15 analyzed clones, indicating less diversity when compared to the Bacteria organisms. None of these sequences was closely related to cultured Archaea organisms.

Archaea↗

PubMed2000

Recombinant growth hormone delivery systems based on vinylpyrrolidone-hydroxyethyl methacrylate copolymer matrices: monitoring optimization by capillary zone electrophoresis.

Experimental conditions for the fabrication of two new polymeric devices (i.e. films and slabs) useful for the controlled release of recombinant growth hormone (GH) are given. The release rate is controlled by the resorption profile of the vinylpyrrolidone-hydroxyethyl methacrylate (VP-HEMA) tested systems which is related to the copolymer composition. The suitability of capillary electrophoresis (CE) for following the complete preparation of the different VP-HEMA devices is shown. Moreover, CE allows simultaneous monitoring of the controlled release of GH and dissolved polymer during in vitro experiments. From these results, guidelines are given for the fabrication of polymeric devices containing protein as active drug as well as for the correct selection of conditions during in vitro experiments.

Biocompatible Materials↗

PubMed1999

Capillary isoelectric focusing of erythropoietin glycoforms and its comparison with flat-bed isoelectric focusing and capillary zone electrophoresis.

The influence of several operation conditions on separation of recombinant human erythropoietin glycoforms by capillary isoelectric focusing (cIEF) is explored. From this study it is deduced that in order to separate several glycoforms of erythropoietin, urea has to be added to sample, which should not be completely depleted of the excipients used in its formulation. On-line desalting does not provide separation enhancement for samples with high content of salt. Better resolution is obtained using a mixture of a broad and a narrow pH-range carrier ampholytes than with either one used separately. Under the experimental conditions, focusing voltages of 25 kV improve separation compared to lower and higher electric fields. Focusing times shorter than the time necessary for electric current to reach a minimum provide similar separations than longer focusing times at which a minimum value of the current has already been achieved. The optimized method allows the separation and quantitation in 12 min of at least seven bands containing glycoforms of recombinant erythropoietin with apparent isoelectric points in the range 3.78-4.69. Compared to flat-bed isoelectric focusing, cIEF provides better separation of bands of glycoforms in a shorter time, and allows quantitative determination. Capillary zone electrophoresis (CZE) gives rise to resolution of erythropoietin glycoforms similar to that obtained by cIEF. Although CZE requires a longer analysis time, its reproducibility in terms of peak area of glycoforms is better than in cIEF.

Animals↗

PubMed1999

Evaluation of ischemic injury during liver procurement from non-heart-beating donors.

UNLABELLED: The aim of this study was to assess liver viability after different periods of cardiac arrest and the predictive value of two markers of ischemia-reperfusion injury. METHODS: A pig liver transplantation model of non-heart-beating donors was studied. Four donor groups were designed; three groups were submitted to different periods of cardiac arrest (20, 30 and 40 min), and the fourth group served as the control group (without cardiac arrest). In the non-heart-beating donor groups, normothermic recirculation was established 30 min prior to total body cooling. Aminotransferase, alpha-glutathione-S-transferase, and hyaluronic acid determinations as well as liver biopsies, were serially performed. RESULTS: Although hepatocellular function could be preserved after 40 min of cardiac arrest, histological lesions at 5 days were considered irreversible due to the presence of a necrotic biliary tract. An overall significant relationship was found between the time period of cardiac arrest (20, 30 or 40 min) and the levels of hyaluronic acid (p = 0.004) or alpha-glutathione-S-transferase (p = 0.01) obtained during liver procurement and transplantation. CONCLUSIONS: The period of cardiac arrest is the determinant factor of liver viability after liver transplantation from non-heart-beating donors. As early markers of endothelial or hepatocellular damage, hyaluronic acid or alpha-glutathione-S-transferase levels may help to evaluate the ischemic injury of a potential donor.

Alanine Transaminase↗

PubMed1998

Use of detergents and high contents of organic solvents for simultaneous quantitation of ionic and nonionic drugs by electrokinetic chromatography.

Buffers containing high percentages of organic solvents, typically 50% of acetonitrile and/or methanol, together with sodium dodecyl sulfate (SDS) are employed for the separation and quantitation by electrokinetic chromatography (EKC) of analytes found in a nasal spray. Solutes consist of benzalkonium chloride, a family of highly positive compounds, and 2-phenylethanol and beclomethasone dipropionate, which are electrically neutral and poorly soluble in aqueous buffers. It is observed that the effect of both concentration of SDS and temperature on the separation depends on the organic solvent used and the solute nature. It is also observed that SDS-solute interaction for neutral and cationic compounds are weaker in the presence of high contents of acetonitrile than in methanol. Concentration of SDS, temperature, and organic solvent nature and content, allow one to modify the selectivity of the separation when neutral and ionic species have to be simultaneously determined. The optimization of EKC conditions enables the analysis of compounds in less than 5 min. A one-step sample treatment consisting of centrifugation of the nasal spray solved in acetonitrile, together with the referenced optimum separation conditions enable the reproducible quantitation of the analytes. Relative standard deviation values of inter-day migration times lower than 2.45% are obtained (R.S.D.n = 12), while R.S.D.n = 12 values for inter-day peak areas were lower than 6.32%.

Administration, Intranasal↗