Desenvolvimento e validação de um método analítico por espectrofotometria UV para quantificação de carvedilol

This paper reports the development and validation of a new analytical method using UV spectrophotometry to quantify carvedilol (CRV) in hydrophilic matrices and raw material. This method was shown to be linear, accurate, precise, robust and to have adequate limits of quantification and detection (LQ and LD, respectively), allowing its use in the dissolution test of hydrophilic matrices. The content of CRV determined through this method was compared with two previously validated methods based on the reference techniques of High Performance Liquid Chromatography (HPLC) and Potentiometric Titrations (PT). ANOVA confirmed the equivalence of these methods, showing no significant differences.

Optimization of solvent mixtures for extraction from bark of Schinus terebinthifolius by a statistical mixture-design technique and development of a UV-Vis spectrophotometric method for analysis of total polyphenols in the extract

A statistical mixture-design technique was used to study the effects of different solvents and their mixtures on the yield, total polyphenol content, and antioxidant capacity of the crude extracts from the bark of Schinus terebinthifolius Raddi (Anacardiaceae). The experimental results and their response-surface models showed that ternary mixtures with equal portions of all the three solvents (water, ethanol and acetone) were better than the binary mixtures in generating crude extracts with the highest yield (22.04 ± 0.48%), total polyphenol content (29.39 ± 0.39%), and antioxidant capacity (6.38 ± 0.21). An analytical method was developed and validated for the determination of total polyphenols in the extracts. Optimal conditions for the various parameters in this analytical method, namely, the time for the chromophoric reaction to stabilize, wavelength of the absorption maxima to be monitored, the reference standard and the concentration of sodium carbonate were determined to be 5 min, 780 nm, pyrogallol, and 14.06% w v-1, respectively. UV-Vis spectrophotometric monitoring of the reaction under these conditions proved the method to be linear, specific, precise, accurate, reproducible, robust, and easy to perform.

Análise dos produtos de degradação do esfenvalerato por SBSE/CLAE-UV/DAD utilizando planejamento fatorial fracionário

A simple procedure based on stir bar sorptive extraction and high-performance liquid chromatography-ultraviolet/photodiode array detection (SBSE/LC-UV/PAD) to determine intermediates and by-products of esfenvalerate is described. The influence of organic modifier, ionic strength, extraction time, temperature and pH were simultaneously evaluated by using a factorial experimental design. The utilization of different organic solvents and desorption times were also investigated to establish the optimal conditions for SBSE liquid desorption. Among the ten different peaks (intermediates and by-products) detected after degradation of esfenvalerate, eight (including 3-phenoxybenzoic acid and 3-phenoxybenzaldehyde) were successfully extracted by SBSE under the optimized conditions.

Synthesis and evaluation of octocrylene-inspired compounds for UV-filter activity

Octocrylene (2-ethylhexyl 2-cyano-3,3-diphenyl-2-propenoate) is present in several sunscreens and is known to work synergistically with UV filters. We prepared eight octocrylene-related compounds to test their photoprotective activities by measuring diffuse transmittance. The compounds had varied photoprotection profiles, with Sun Protection Factors (SPF) ranging from 1 to 5 and UVA Protection Factors (UVAPF) ranging from 1 to 8. Compounds 4, 5, and 7 showed the best protection against UVB sunrays, while compounds 5, 6, and 7 presented the best results for protection from UVA, so compound 7 had the most balanced protection overall. Results for compounds 4, 8, and 9 are reported for the first time in the literature.

UV determination of epinephrine, uric acid, and acetaminophen in pharmaceutical formulations and some human body fluids using multivariate calibration

In this work, a spectrophotometric methodology was applied in order to determine epinephrine (EP), uric acid (UA), and acetaminophen (AC) in pharmaceutical formulations and spiked human serum, plasma, and urine by using a multivariate approach. Multivariate calibration methods such as partial least squares (PLS) methods and its derivates were used to obtain a model for simultaneous determination of EP, UA and AC with good figures of merit and mixture design was in the range of 1.8 - 35.3, 1.7 - 16.8, and 1.5 - 12.1 µg mL-1. The 2nd derivate PLS showed recoveries of 95.3 - 103.3, 93.3 - 104.0, and 94.0 - 105.5 µg mL-1 for EP, UA, and AC, respectively.

Simultaneous determination of four phenolic compounds in extracts of aerial parts of Ipomoea pes-caprae (L.) R. Br. (Convolvulaceae) by HPLC-UV

Among other applications, Ipomoea pes-caprae is popularly used to treat jellyfish stings, supporting the development of a product for dermatological use. Hydroethanolic spray-dried extract was chosen for the further development of phytomedicines, and a stability-indicative HPLC-UV method was developed and validated for the determination of isoquercitrin and isochlorogenic acids A, B and C. The method was developed using a C18 column (250 x 4.6 mm, 5 µm) with an acetonitrile:water mobile phase at pH 3.0 in a gradient run. The four constituents and other unidentified components of the extract were appropriately resolved without interference of degradation products after stress tests (acid, alkali, neutral, oxidant, photolysis). The method showed linearity in the isoquercitrin concentration range from 5.0-50.0 µg mL-1, with adequate precision (RSD% < 2.5% for the intra- and inter-day studies), accuracy (recovery of 100.0 ± 2.0%), and robustness. Both the herbal drug and spray-dried extract of I. pes-caprae were subjected to stability studies in accelerated and long-term conditions over four months. The samples maintained their characteristics and marker contents (< 10% of variation).

CHARACTERIZING THE MECHANISM OF QUETIAPINE DISTRIBUTION IN LIPID-CORE NANOCAPSULES PSEUDO-PHASES USING A VALIDATED LC/UV METHOD

Quetiapine is an atypical antipsychotic used to treat schizophrenia. However, despite great interest for its chronic therapeutic use, quetiapine has some important side effects such as weight gain induction. The development of a quetiapine nanocarrier can potentially target the drug into central nervous system, resulting in a reduction of systemic side effects and improved patient treatment. In the present work, a simple liquid chromatography/ultraviolet detection (LC/UV) analytical method was developed and validated for quantification of total quetiapine content in lipid core nanocapsules as well as for determination of incorporation efficiency. An algorithm proposed by Oliveira et al. (2012) was applied to characterize the distribution of quetiapine in the pseudo-phases of the nanocarrier, leading to a better understanding of the quetiapine nanoparticles produced. The analytical methodology developed was specific, linear in the range of 0.5 to 100 µg mL−1 (r2 > 0,99), and accurate and precise (R.S.D < ±5%). The absolute recovery of quetiapine from the nanoparticles was approximately 98% with an incorporation efficiency of approximately 96%. The results indicated that quetiapine was present in a type III distribution according to the algorithm, and was mainly located in the core of the nanoparticle because of its logD in the formulation pH (6.86 ± 0.4).

MCR-ALS APLICADO NO MONITORAMENTO QUANTITATIVO DO PROCESSO DE ELETRODEGRADAÇÃO DA ATRAZINA USANDO ESPECTROS UV: RESULTADOS COMPARATIVOS COM HPLC-DAD COMO UM MÉTODO DE REFERÊNCIA

Electrodegradation of atrazine in water was performed using homemade (PA and PB) and purchased (PC) boron-doped diamond anodes. The degradation was monitored off-line by analyzing total organic carbon and high performance liquid chromatography with diode array detector (HPLC-DAD) and at-line by UV spectroscopy. The spectra were recorded every 2 min. The rank deficiency problem was resolved by assembling an augmented column-wise matrix. HPLC was employed to separate the original and byproducts degradation components. Aiming the same goal, multivariate curve resolution - alternating least squares (MCR-ALS) was applied to resolve the UV spectroscopic data. Comparison between HPLC and MCR-ALS separations is presented. By using MCR-ALS the spectra of atrazine and two byproducts were successfully resolved and the resulted concentration profiles properly represented the system studied. The ALS explained variance (R2) for PA, PB and PC was equal to 99.99% for all of them and the lack of fit for PA, PB and PC were 0.39, 0.34 and 0.54 respectively. The correlation (R) between the recovered and pure spectra were calculate for each electrodegradation, validating the MCR-ALS results. The average R was equal to 0.997. The spectral and concentration profiles described with this new approach are in agreement with HPLC-DAD results. The proposed method is an alternative to classical analyses for monitoring of the degradation process, mainly due to the simplicity, fast results and economy.

Efeito da irradiação UV-C no controle da podridão parda (Monilinia fructicola) e da podridão mole (Rhizopus stolonifer) em pós-colheita de pêssegos

Este trabalho teve por objetivo avaliar o efeito da irradiação UV-C no controle in vitro de Monilinia fructicola e Rhizopus stolonifer e no controle das doenças causadas por estes fungos em pêssegos inoculados com ferimento. No experimento in vitro, avaliou-se o crescimento micelial dos fungos em meio BDA após a exposição nas doses de UV-C de 0, 0,26, 0,52, 1,04, 3,13, 5,22, 10,44, 15,66, e 31,32 kJ.m-2 num equipamento com quatro lâmpadas com taxa de fluência de 1,74 mW.cm-2. Nos experimentos in vivo, os frutos foram tratados com irradiação UV-C de forma protetora e curativa. No tratamento protetor, os frutos foram expostos a 1,04 kJ.m-2 por 1 min. e foram inoculados imediatamente após e 16, 24 e 40 h após. No tratamento curativo, os frutos foram inoculados, incubados e irradiados com doses de UV-C de 0, 1,04, 5,22, 10,44, 15,66 e 31,32 kJ.m². Avaliou-se a incidência das doenças e a severidade da podridão parda. No experimento in vitro, apenas as doses aplicadas durante 1 e 10 min. de exposição reduziram o crescimento micelial de M. fructicola enquanto que a aplicação da luz UV-C entre 10-15 minutos reduziu o crescimento micelial de R. stolonifer e a dose aplicada durante 30 minutos inibiu completamente o crescimento micelial deste fungo. Não houve efeito protetor da luz UV-C no controle das doenças. Não houve controle curativo da podridão parda. A irradiação UV-C foi eficiente no controle curativo da podridão mole e o tempo de exposição de 10 min. foi o que apresentou melhor resultado.

Análise do teor de cocaína em amostras apreendidas pela polícia utilizando-se a técnica de cromatografia liquida de alta eficiência com detector UV-Vis

A técnica de CLAE com detecção UV-Vis foi empregada na análise do teor de cocaína em amostras apreendidas de cocaína e crack. Uma fase móvel de acetonitrila/água (95:5v/v) possibilitou um sinal de pico para a cocaína em 3,5 minutos. O sinal espectrofotométrico otimizado foi obtido em um comprimento de onda de 224 nm. A curva analítica de 1,0 a 40,0 ppm para cocaína foi obtida, exibindo um coeficiente de correlação linear de 0,9989, com limites de detecção e quantificação de 0,75 e 3,78 ppm, respectivamente. Esta metodologia foi aplicada na dosagem de amostras confiscadas de cocaína e crack no Laboratório de Polícia Científica de Ribeirão Preto-SP.

Hidrotermia e radiação UV-C no controle de patógenos de manga e melão

As doenças de pós-colheita são, em geral, de difícil controle e são responsáveis por perdas significativas de manga (Mangifera indica L.) e melão (Cucumis melo L.) no Brasil. Os principais patógenos pós-colheita do melão são Alternaria alternata, Fusarium pallidoroseum e Myrothecium roridum, enquanto que na manga são Colletotrichum gloeosporioides e Lasiodiplodia theobromae. O objetivo deste trabalho foi avaliar a sensibilidade dos propágulos destes patógenos aos tratamentos de hidrotermia e de radiação UV-C. Suspensões de conídios e discos de micélio de cada patógeno foram submetidos aos tratamentos de hidrotermia a 50, 55 e 58 ºC por 15 e 30 s e de radiação UV-C nas doses de 0,330 kJ m-2, 0,660 kJ m-2 e 1,320 kJ m-2. Após os tratamentos e incubação por 72 e 48 h, foram avaliados o número de unidades formadoras de colônias (UFCs) e o crescimento micelial dos patógenos, respectivamente. Os tratamentos apresentaram eficiência distinta entre os propágulos e os patógenos. O controle de UFCs e do crescimento micelial de C. gloeosporioides e L. theobromae foi superior a 88 % com água aquecida a 55 ºC ou 58 ºC, independente do tempo de tratamento. Para os mesmos patógenos, a maior dose de radiação, 1,320 kJ m-2, controlou acima de 96 % das UFCs. Entretanto, o controle do crescimento micelial destes patógenos com radiação UV-C foi inferior quando comparado ao uso de água aquecida a 55 ºC ou 58 ºC. O controle de UFCs de A. alternata, M. roridum e F. pallidoroseum foi superior com os tratamentos de água aquecida a 55 ºC por 30 s, 58 ºC por 15 s e 30 s e com as doses de radiação de 0,660 kJ m-2 e 1,320 kJ m-2. O controle do crescimento micelial de A. alternata e de M. roridum foi inferior com as doses de radiação e com a temperatura de 50 ºC quando comparados aos demais tratamentos. Na redução do crescimento micelial de F. pallidoroseum, os tratamentos a 58 ºC ou as doses de 0,660 kJ m-2 e 1,320 kJ m-2 foram mais eficiêntes, com controle superior a 88 %. Água aquecida a 58 ºC por 15 s controlou UFCs e o crescimento micelial dos patógenos testados.

Regulation of the expression of NADP-malic enzyme by UV-B, red and far-red light in maize seedlings

The induction of nicotinamide adenine dinucleotide phosphate-malic enzyme (NADP-ME) in etiolated maize (Zea mays) seedlings by UV-B and UV-A radiation, and different levels of photosynthetically active radiation (PAR, 400-700 nm) was investigated by measuring changes in activity, protein quantity and RNA levels as a function of intensity and duration of exposure to the different radiations. Under low levels of PAR, exposure to UV-B radiation but not UV-A radiation for 6 to 24 h caused a marked increase in the enzyme levels similar to that observed under high PAR in the absence of UV-B. UV-B treatment of green leaves following a 12-h dark period also caused an increase in NADP-ME expression. Exposure to UV-B radiation for only 5 min resulted in a rapid increase of the enzyme, followed by a more gradual rise with longer exposure up to 6 h. Low levels of red light for 5 min or 6 h were also effective in inducing NADP-ME activity equivalent to that obtained with UV-B radiation. A 5-min exposure to far-red light following UV-B or red light treatment reversed the induction of NADP-ME, and this effect could be eliminated by further treatment with UV-B or red light. These results indicate that physiological levels of UV-B radiation can have a positive effect on the induction of this photosynthetic enzyme. The reducing power and pyruvate generated by the activity of NADP-ME may be used for respiration, in cellular repair processes and as substrates for fatty acid synthesis required for membrane repair.

An HPLC-UV method for the measurement of permeability of marker drugs in the Caco-2 cell assay

The Caco-2 cell line has been used as a model to predict the in vitro permeability of the human intestinal barrier. The predictive potential of the assay relies on an appropriate in-house validation of the method. The objective of the present study was to develop a single HPLC-UV method for the identification and quantitation of marker drugs and to determine the suitability of the Caco-2 cell permeability assay. A simple chromatographic method was developed for the simultaneous determination of both passively (propranolol, carbamazepine, acyclovir, and hydrochlorothiazide) and actively transported drugs (vinblastine and verapamil). Separation was achieved on a C18 column with step-gradient elution (acetonitrile and aqueous solution of ammonium acetate, pH 3.0) at a flow rate of 1.0 mL/min and UV detection at 275 nm during the total run time of 35 min. The method was validated and found to be specific, linear, precise, and accurate. This chromatographic system can be readily used on a routine basis and its utilization can be extended to other permeability models. The results obtained in the Caco-2 bi-directional transport experiments confirmed the validity of the assay, given that high and low permeability profiles were identified, and P-glycoprotein functionality was established.

STABILITY OF OILS HEATED BY MICROWAVE: UV - SPECTROPHOTOMETRIC EVALUATION

The effects of microwave heating on the oxidative stability of refined canola, corn and soybean oils were determined by absorptivity in the UV spectrum and by chemical analysis (peroxide and acid values). Samples were heated in a microwave oven (800 W, 2,450 MHz) for 0 to 36 min. Microwave heating produced oxidative degradation in the three oils. Absorptivity at 232 and 270 nm increased gradually with an increase in microwave exposure time (0-36 min) for canola, corn and soybean oils. Values of absorptivity at 232 nm increased from 4.812, 3.568 and 4.183 to 10.579, 12.874 and 15.950 after 36 min of heating canola, corn and soybean oil, respectively. The absorptivity at 232nm, due to the formation of conjugated dienes, was a good index for measuring the degradation of microwaved samples. UV scanning (220 - 320 nm) detected alterations in the spectrum of microwaved samples. Acid value also increased within 36 min of heating for all oils. Peroxide value showed a significant difference (P<0.05) in the initial stage of heating (0-6 min) for all oils. After this period it could not be correlated with absorptivity at 232 nm, due to the instability of hydroperoxides at high temperatures.