In vitro diffusion of plant phenolics through the skin: A review update.

OBJECTIVE: Excessive skin exposure to deleterious environmental variables results in inflammation as well as molecular and cellular impairments that compromise its functionality, aesthetic qualities, and overall well-being. The implementation of topical administration of antioxidants and other compounds as a method for preventing or reversing damage is a rational approach. Numerous phenolic compounds derived from plants have demonstrated capabilities such as scavenging free radicals and promoting tissue healing. However, the primary obstacle lies in effectively delivering these compounds to the specific place on the skin, and accurately forecasting their diffusion through the skin can assist in determining the most effective tactics. Hence, this article provides a comprehensive analysis of recent literature pertaining to the in vitro skin diffusion characteristics of plant phenolics. The aim is to gain a deeper understanding of their behaviour when present in various forms such as solutions, suspensions, and formulations. METHOD: The data on plant extracts and isolated plant phenolic compounds in vitro skin diffusion assays published over the last six years were compiled and discussed. RESULTS: Even though the gold standard Franz diffusion cell is the most commonly used in the assessment of in vitro plant phenolic skin diffusion profiles, a plethora of skin models and assay conditions are reported for a variety of compounds and extracts in different vehicles. CONCLUSION: The presence of numerous models and vehicles poses a challenge in creating correlations among the existing data on plant phenolic compounds. However, it is possible to draw some general conclusions regarding molecular, vehicle, and skin characteristics based on the gathered information.

OBJECTIF: Une exposition excessive de la peau a des variables environnementales délétères entraîne une inflammation ainsi que des déficiences moléculaires et cellulaires qui compromettent sa fonctionnalité, ses qualités esthétiques et son bien­être général. La mise en œuvre de l'administration topique d'antioxydants et d'autres composés comme méthode de prévention ou d'inversion des dommages est une approche rationnelle. De nombreux composés phénoliques dérivés de plantes ont démontré des capacités telles que l'élimination des radicaux libres et la promotion de la cicatrisation des tissus. Cependant, le principal obstacle réside dans l'administration efficace de ces composés à un endroit spécifique de la peau, et une prévision précise de leur diffusion a travers la peau peut aider à déterminer les tactiques les plus efficaces. Par conséquent, cet article fournit une analyse complète de la littérature récente concernant les caractéristiques de diffusion cutanée in vitro des composés phénoliques végétaux. L'objectif est de mieux comprendre leur comportement lorsqu'ils sont présents sous diverses formes telles que solutions, suspensions et formulations. MÉTHODES: Les données sur les extraits de plantes et les composés phénoliques végétaux isolés in vitro par diffusion cutanée, publiées au cours des six dernières années, ont été compilées et discutées. RÉSULTATS: Même si la cellule de diffusion Franz de référence est la plus couramment utilisée dans l'évaluation des profils de diffusion cutanée phénoliques végétales in vitro, une pléthore de modelés de peau et de conditions d'analyse sont rapportées pour une variété de composés et d'extraits dans différents véhicules. CONCLUSION: La présence de nombreux modèles et véhicules pose un défi dans la création de corrélations entre les données existantes sur les composés phénoliques végétaux. Cependant, il est possible de tirer des conclusions générales concernant les caractéristiques moléculaires du véhicule et de la peau sur la base des informations recueillies.

Controlled crosslinking of trimethylolpropane trimethacrylate for preparation of organic monolithic columns for capillary liquid chromatography.

Organic monolithic columns based on single crosslinking of trimethylolpropane trimethacrylate (TRIM) monomer were prepared in a single step by living/controlled free-radical polymerization. Full optimization of the preparation, such as using different percentages of TRIM and different amounts of radical promoter as well as various porogen solvents were explored. The resulting monolithic columns were characterized by scanning electronic microscopy and nitrogen sorption for structure morphology studies and surface area measurements, respectively. Using capillary liquid chromatography, 150 µm i.d. columns were applied to separate a mixture of small hydrophobic molecules. The results indicated that column performance is highly sensitive to the type and the amount of porogen solvents used in the polymerization mixture composition. Good resolution factors and methylene selectivity were obtained, indicating the promising potential of this material for capillary liquid chromatography separations.

Polyphenol profile by UHPLC-MS/MS, anti-glycation, antioxidant and cytotoxic activities of several samples of propolis from the northeastern semi-arid region of Brazil.

CONTEXT: Propolis has promising biological activities. Propolis samples from the Northeast of Bahia, Brazil - sample A from Ribeira do Pombal and B, from Tucano - were investigated, with new information regarding their biological activities. OBJECTIVE: This paper describes the chemical profile, antioxidant, anti-glycation and cytotoxic activities of these propolis samples. MATERIAL AND METHODS: Ethanol extracts of these propolis samples (EEP) and their fractions were analyzed to determine total phenolic content (TPC); antioxidant capacity through DPPH•, FRAP and lipid peroxidation; anti-glycation activity, by an in vitro glucose (10 mg/mL) bovine serum albumine (1 mg/mL) assay, during 7 d; cytotoxic activity on cancer (SF295, HCT-116, OVCAR-8, MDA-MB435, MX-1, MCF7, HL60, JURKAT, MOLT-4, K562, PC3, DU145) and normal cell lines (V79) at 0.04-25 µg/mL concentrations, for 72 h. The determination of primary phenols by ultra high-pressure liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS) and volatile organic compounds content by gas chromatography-mass spectrometry (GC-MS) were also performed. RESULTS: The EEP polar fractions exhibited up to 90% protection against lipid peroxidation. The IC50 value for anti-glycation activity of EEP was between 16.5 and 19.2 µg/mL, close to aminoguanidine (IC50 = 7.7 µg/mL). The use of UHPLC-MS/MS and GC-MS allowed the identification of 12 bioactive phenols in the EEP and 24 volatile compounds, all already reported. CONCLUSIONS: The samples present good antioxidant/anti-glycation/cytotoxic activities and a plethora of biologically active compounds. These results suggest a potential role of propolis in targeting ageing and diseases associated with oxidative and carbonylic stress, aggregating value to them.

Improvement in Liquid Chromatographic Performance of Organic Polymer Monolithic Capillary Columns with Controlled Free-Radical Polymerization.

Capillary columns containing butyl or lauryl methacrylate monoliths were prepared using two different free-radical polymerization methods: conventional free-radical polymerization and controlled/living free-radical polymerization, both initiated thermally, and these methods were compared for the first time. Both monolith morphology and chromatographic efficiency were compared for the synthesized stationary phases using scanning electronic microscopy (SEM) and capillary liquid chromatography, respectively. Columns prepared using controlled method gave better chromatographic performance for both monomers tested. The lauryl-based monolith showed 7-fold improvement in chromatographic efficiency with a plate count of 42,000 plates/m (corrected for dead volume) for a non-retained compound. Columns fabricated using controlled polymerization appeared more homogenous radially with fused small globular morphologies, evaluated by SEM, and lower column permeability. The columns were compared with respect to resolving power of a series of alkylbenzenes under isocratic and gradient elution conditions.

High-performance liquid chromatographic analysis of biogenic amines in pharmaceutical products containing Citrus aurantium.

A reverse-phase (RP)-HPLC method is reported for determining L-tyrosine, p-octopamine, synephrine, tyramine and hordenine as chemical markers of the species Citrus aurantium in raw material, dry extracts and phytotherapeutic herbal formulations. Using RP-HPLC with diode array detection (DAD) and gradient elution, the amines were determined in 12 different products from different Brazilian states labelled as containing C. aurantium. The presence of the amines was confirmed by mass spectrometry using electrospray ionisation (ESI-MS/MS). This RP-HPLC method allowed the separation of the amines from complex mixtures containing caffeine, ephedrine, salicin and other raw materials (e.g. Garcinia camboja, Phaseolus vulgaris, Caralluma fimbriata, Cassia nomane, Ephedra sp. and Cordia ecalyculata). The method proved useful and selective for inspecting herbal medicines containing p-synephrine and structural analogues. The herbal products analysed had a p-synephrine content ranging from 0.005 to 4.0% (w/w).

Nano-liquid chromatography in pharmaceutical and biomedical research.

Miniaturized separation techniques have emerged as environmentally friendly alternatives to available separation methods. Nano-liquid chromatography (nano-LC), microchip devices and nano-capillary electrophoresis are miniaturized methods that minimize reagent consumption and waste generation. Furthermore, the low levels of analytes, especially in biological samples, promote the search for more highly sensitive techniques; coupled to mass spectrometry, nano-LC has great potential to become an indispensable tool for routine analysis of biomolecules. This short review presents the fundamental aspects of nano-LC analytical instrumentation, discussing practical considerations and the primary differences between miniaturized and conventional instrumentation. Some theoretical aspects are discussed to better explain both the potential and the principal limitations of nano-LC. Recent pharmaceutical and biomedical applications of this separation technique are also presented to indicate the satisfactory performance for complex matrices, especially for proteomic analysis, that is obtained with nano-LC.

New silica gel-based monolithic column for nano-liquid chromatography, used in the HILIC mode.

This paper describes the synthesis and chromatographic and morphologic characterization of two monolithic silica nano-columns (50 µm i.d.) prepared by sol-gel processes, using hydrophilic interaction (HILIC) mode separations to evaluate their performance. Two types of monoliths were prepared by varying the precursors (tetraethoxysilane or a tetraethoxysilane-methyltrimethoxysilane mixture) and by changing the type of catalyst (urea and acetic acid or ammonium hydroxide). The monoliths were characterized by scanning electron microscopy, thermogravimetric analysis, infrared spectroscopy and nitrogen adsorption-desorption isotherms. The columns were tested for the separation of several mixtures, with the organically modified silica (ormosil) column successfully separating two challenging mixtures using HILIC conditions.

Anion separations for liquid chromatography using propylpyridinium silica as the stationary phase.

This work describes the characterization and potential applications of a silica-based anion-exchange phase prepared by a two-step modification process that incorporates a propylpyridinium group. The effects of pH and eluent concentration on anion separation were examined using 150 mm × 3.9 mm HPLC columns packed with the new phase. The mobile phase pH values ranged from 3.8 to 6.6 using phthalic acid/Tris solutions. The best separation was achieved using 2.5 mmol L(-1) phthalate/2.4 mmol L(-1) Tris solution at pH 4.2 as mobile phase with non-suppressed conductivity detection. The new stationary phase was used for the separation of some inorganic and organic anions showing good resolution. The stability of the silica-based anion exchange phase was also evaluated. Analytical curves, for concentrations ranging from 0.25 to 10 mg L(-1) for the inorganic anions chloride, nitrite, bromide and nitrate, showed good linear correlations (r>0.998). The method was tested with certified rainwater samples. The measured and certified values were in good agreement, indicating that the new phase holds significant promise for the analysis of these anions in environmental samples.

Molecularly imprinted silica as a selective SPE sorbent for triazine herbicides.

A molecularly imprinted organically modified silica was prepared through a simple sol-gel procedure and evaluated as a specific sorbent for SPE of triazine herbicides. The material proved to be highly selective for the template molecule, atrazine, as well as for other structurally related species such as simazine and propazine. The performance of this material was shown to be comparable with commercial acrylate-based molecularly imprinted polymers. The molecularly imprinted silica was applied for the determination of trace levels of the target triazine analytes in sugar cane juice (locally called "garapa").

Application of genetic algorithm for selection of variables for the BLLS method applied to determination of pesticides and metabolites in wine.

A variable selection methodology based on genetic algorithm (GA) was applied in a bilinear least squares model (BLLS) with second-order advantage, in three distinct situations, for determination by HPLC-DAD of the pesticides carbaryl (CBL), methyl thiophanate (TIO), simazin (SIM) and dimethoate (DMT) and the metabolite phthalimide (PTA) in wine. The chromatographic separation was carried out using an isocratic elution with 50:50 (v/v) acetonitrile:water as mobile phase. Preprocessing methods were performed for correcting the chromatographic time shifts, baseline variation and background. The optimization by GA provided a significant reduction of the errors, where for SIM and PTA a decrease of three times the value obtained using all variables, and an improvement in the distribution of them, reducing the observed bias in the results were observed. Comparing the RMSEP of the optimized model with the uncertainty estimates of the reference values it is observed that GA can be a very useful tool in second-order models.

Determination of pesticides and metabolites in wine by high performance liquid chromatography and second-order calibration methods.

The models parallel factor analysis (PARAFAC) and the recently introduced bilinear least squares (BLLS) were applied to develop second-order calibration methods to high performance liquid chromatography with diode array detection (HPLC-DAD) data, where overlap of interferences with the compounds of interest was observed, making the determination and resolution of the analytes possible. In this work, the simultaneous determination of five pesticides and two metabolites in wine samples by HPLC-DAD was performed, using the second-order advantage. The results of two chromatographic methods were compared, involving either isocratic or gradient elution. An appropriate preprocessing method was necessary to correct the effects of time shifts, baseline variations and background. BLLS presented results that were of the same quality as PARAFAC in five cases, but in two other situations only PARAFAC enabled analyte quantitation. Relative errors of prediction lower than 10% for all compounds were obtained, indicating that the methodology employing HLPC-DAD and second-order calibration can handle complex analytical systems.

Preparation of stationary phases for reversed-phase high-performance liquid chromatography using thermal treatments at high temperature.

Batches of poly(methyloctylsiloxane) (PMOS)-loaded silica were prepared by deposition from a solution of PMOS into the pores of HPLC silica. Portions of PMOS-loaded silica were subjected to a thermal treatment at 100 degrees C for 24h (condition 1) in a tube furnace under a nitrogen atmosphere. After that, the material was heated for 4h at higher temperatures (150-400 degrees C) (condition 2). Heating at higher temperatures produces polymer bilayers. Non-immobilized and thermally treated stationary phases were characterized by percent carbon, (29)Si cross-polarization magic angle spinning nuclear magnetic resonance spectroscopy and reversed-phase chromatographic performance. The results show that thermal treatment between 150 and 300 degrees C accelerates the immobilization process, possibly due to some bond breaking of the polysiloxane, with formation of strong linkages to the surface of the support, resulting in more complete coverage of the silica. The chromatographic results show an improvement of efficiency with the increase of the temperature of condition 2 up to 300 degrees C and an increase in the resolution of the components, mainly for the phase heated at 300 degrees C. Such results demonstrate that a two-step thermal treatment (100 degrees C then 150-300 degrees C) produces stationary phases with good properties for use in reversed-phase high-performance liquid chromatography.

Validation of chromatographic methods: evaluation of detection and quantification limits in the determination of impurities in omeprazole.

To guarantee that an analytical procedure gives reliable, exact and interpretable information about a sample, it must be validated. Two ambiguous parameters are detection limit and quantification limit. The determination of these limits is still of great concern and there are still a variety of procedures described in the current literature. The fundamental objective of the present work is to apply the different recommendations suggested by official guidelines for the quantitative determination of omeprazole and its impurities (omeprazole sulphone and 5-hydroxy-omeprazole) in capsules and tablets using high performance liquid chromatography with UV detection. The importance of calibration linearity in the context of the quantification limit is considered, since one of the approaches, the estimated concentrations of this limit, are deduced from the regression line. The values of the detection limit and the quantification limit obtained show that, in chromatographic analyses, the best method is that based on the use of the parameters obtained from the analytical curve, which are statistically reliable. It was shown that smaller values of the detection limit and the quantification limit were obtained by the visual approach and by the method using the signal-to-noise ratio. However, these values may reflect a subjective evaluation, prone to error and large variations. This was confirmed by showing that these methods result in values that fall outside the linear range of the method.

Self-immobilization and/or thermal treatment for preparing silica-poly(methyloctylsiloxane) stationary phases.

Batches of poly(methyloctylsiloxane) (PMOS)-loaded silica were prepared by the deposition of PMOS, into the pores of HPLC silica. Portions of PMOS-loaded silica were allowed to remain at ambient temperature, without further treatment for 2, 9, 20, 31, 51, 105 and 184 days after preparation to undergo self-immobilization (irreversible adsorption of a layer of polymer on silica at ambient temperature in the absence of initiators). Other portions were subjected to a thermal treatment (100 degrees C for 4h) after 1, 2, 5, 7, 9, 15, 20, 25, 70, 111 and 184 days. Self-immobilized and thermally treated samples were characterized by % C, 29Si cross-polarization magic angle spinning (CP/MAS) NMR spectroscopy and reversed-phase column performance. The results show that thermal immobilization accelerates the distribution and rearrangement of the polymer on the silica surface. However, from the time that a monolayer has been formed by self-immobilization (approximately 100 days for PMOS on Kromasil silica), the thermal treatment does not alter this configuration and, thus, does not change the resulting chromatographic parameters.

Self-immobilization of poly(methyloctylsiloxane) on high-performance liquid chromatographic silica.

Poly(methyloctylsiloxane) (PMOS) was deposited on HPLC silica by a solvent evaporation procedure and this material was then extracted, using a good solvent for the PMOS, after different time periods, to remove unretained liquid polymer. Solvent extraction data reveal changes which occur at ambient temperature as a function of the time interval between particle loading and extraction. The quantity of PMOS remaining on the silica after extraction, as determined by elemental analysis for carbon, is attributed to strongly adsorbed polymer. This phenomenon is termed self-immobilization. Solid-state 29Si NMR spectra indicate the formation of a silicon species with a different chemical shift than the original PMOS. These new signals are attributed to a combination of different adsorbed and chemically bonded groups.

Chromatographic evaluation of self-immobilized stationary phases for reversed-phase liquid chromatography.

The preparation of stationary phases for HPLC using polymers deposited on silica usually includes an immobilization step involving cross-linking by free radicals induced by ionizing radiation or by other radical initiators. The present paper reports changes which occur at ambient temperature in the character of poly(methyloctylsiloxane) deposited on porous silica particles as a function of the time interval between particle loading and column packing. Column performance and retention factors increase with time and these changes are attributed to rearrangement (self-assembly) which result in "self-immobilization" of the polymer molecules on the silica surface.

Poly(alkylmethylsiloxanes) thermally immobilized on silica as stationary phases for high-performance liquid chromatography.

Poly(methyloctylsiloxane) (PMOS) and poly(methyloctadecylsiloxane) (PMODS) were sorbed onto porous HPLC silica and thermally immobilized, in the absence of radical initiators, at temperatures in the range of 80 to 180 degrees C. Following extraction of non-immobilized polymer the materials were packed into columns and their chromatographic properties evaluated. The shorter chain (PMOS) stationary phase showed good HPLC characteristics after thermal immobilizations up to 120 degrees C while the longer chain (PMODS) phase gave satisfactory HPLC phases following thermal immobilizations at 80 and 100 degrees C. Stability evaluation for the PMOS and PMODS columns immobilized at 100 degrees C required 250 ml of pH 8.5 mobile phase at 60 degrees C to significantly decrease efficiency, suggesting a long useful life time at neutral pH and ambient temperature.