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1.
Nutrients ; 11(9)2019 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-31450771

RESUMO

Emerging data suggest that intravenous ascorbic acid (AA) may be beneficial in patients with sepsis. Clinicians require data on stability of diluted AA for safe administration. We evaluated the stability of AA diluted in normal saline (NS) or 5% dextrose in water (D5W) solutions over 14 days at 25 °C and at 4 °C, protected from light, using concentrations of 37 mg/mL and 77 mg/mL (Sandoz) and 40 mg/mL and 92 mg/mL (Mylan). We also assessed stability of a 40 mg/mL solution (Mylan) at 25 °C exposed to light for 75 h. Concentrations were measured using liquid chromatographic separation with ultraviolet light detection on days 0, 0.33, 1, 1.33, 2, 3, 4, 7, 10 and 14. By day 14, solutions at 4 °C retained >97.72% of the initial concentration; at 25 °C, solutions retained >88.02% of the initial concentration, but visual changes were evident after day 2. Multiple linear regression demonstrated that study day and temperature (p < 0.001) but not solution type (p = 0.519), concentration (p = 0.677) or manufacturer (p = 0.808) were associated with the percentage remaining. At 75 h, degradation rates were similar in solutions protected from vs. exposed to light. In conclusion, AA solutions are stable for at least 14 days at 4 °C, with protection from light.


Assuntos
Ácido Ascórbico/química , Sepse/tratamento farmacológico , Ácido Ascórbico/administração & dosagem , Ácido Ascórbico/efeitos da radiação , Composição de Medicamentos , Embalagem de Medicamentos , Estabilidade de Medicamentos , Armazenamento de Medicamentos , Glucose/química , Humanos , Infusões Intravenosas , Luz , Fotólise , Solução Salina/química , Sepse/diagnóstico , Temperatura , Fatores de Tempo
2.
Bioorg Med Chem ; 27(19): 115046, 2019 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-31422010

RESUMO

When a neutral solution of thymidine and ascorbic acid was irradiated with UV light of wavelength longer than 300 nm in the presence of salicylic acid as a photosensitizer, six product peaks appeared in an HPLC chromatogram in addition to small amounts of thymidine dimers. The six products were identified as three pairs of diastereomers of 5-(2-deoxy-2-l-ascorbyl)-5,6-dihydrothymidine, 5-(2-l-ascorbyl)-5,6-dihydrothymidine, and 5,6-dihydrothymidine. These results suggest that novel DNA damage may be generated by ascorbic acid with salicylic acid induced by sunlight.


Assuntos
Ácido Ascórbico/química , Fármacos Fotossensibilizantes/química , Ácido Salicílico/química , Timidina/química , Ácido Ascórbico/efeitos da radiação , Cinética , Fármacos Fotossensibilizantes/efeitos da radiação , Dímeros de Pirimidina/síntese química , Ácido Salicílico/efeitos da radiação , Timidina/efeitos da radiação , Raios Ultravioleta
3.
Carbohydr Polym ; 216: 217-223, 2019 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-31047060

RESUMO

This study determines storage stability and release of encapsulated ascorbyl palmitate in normal and high amylose maize starch by pasting and spray drying. The amount of ascorbyl palmitate released was analysed in the stored samples (dark cupboard, and under UV light at a temperature of 40 °C for 12 weeks) and their antioxidant activity determined. Storage of encapsulated ascorbyl palmitate at 40 °C under both dark and UV light conditions did not affect the amount release and the ability to scavenge the free radical (ABTS+). However, the antioxidant activity of free ascorbyl palmitate exponentially decreased at 40 °C under UV light condition. The analysed residues after α-amylase digestion of encapsulated ascorbyl palmitate showed some endothermic peaks, suggesting that amylose-lipids complexes formed were resistant to α-amylase digestion. Encapsulation of ascorbyl palmitate in maize starch may improve its storage stability under light (UV) conditions.


Assuntos
Amilose/química , Ácido Ascórbico/análogos & derivados , Portadores de Fármacos/química , Sequestradores de Radicais Livres/química , Zea mays/química , Ácido Ascórbico/química , Ácido Ascórbico/efeitos da radiação , Liberação Controlada de Fármacos , Estabilidade de Medicamentos , Sequestradores de Radicais Livres/efeitos da radiação , Hidrólise , Temperatura , Raios Ultravioleta , alfa-Amilases/química
4.
Sci Rep ; 8(1): 13822, 2018 09 14.
Artigo em Inglês | MEDLINE | ID: mdl-30218013

RESUMO

DMSO, glycerol, and ascorbic acid (AA) are used in pharmaceuticals and known to display radioprotective effects. The present study investigates radioprotective properties of novel glyceryl glucoside, ascorbic acid 2-glucoside, glyceryl ascorbate, and palmitoyl ascorbic acid 2-glucoside (PA). Gamma-rays or high-LET carbon-ions were irradiated in the presence of tested chemicals. Lambda DNA damage, cell survival, and micronuclei formation of CHO cells were analyzed to evaluate radioprotective properties. Radiation-induced Lambda DNA damage was reduced with chemical pre-treatment in a concentration-dependent manner. This confirmed tested chemicals were radical scavengers. For gamma-irradiation, enhanced cell survival and reduction of micronuclei formation were observed for all chemicals. For carbon-ion irradiation, DMSO, glycerol, and PA displayed radioprotection for cell survival. Based on cell survival curves, protection levels by PA were confirmed and comparable between gamma-rays and high-LET carbon-ions. Micronuclei formation was only decreased with AA and a high concentration of glycerol treatment, and not decreased with PA treatment. This suggests that mechanisms of protection against high-LET carbon-ions by PA can differ from normal radical scavenging effects that protect DNA from damage.


Assuntos
Ácido Ascórbico/análogos & derivados , Dano ao DNA/efeitos dos fármacos , DNA/efeitos dos fármacos , Animais , Ácido Ascórbico/farmacologia , Ácido Ascórbico/efeitos da radiação , Células CHO/efeitos da radiação , Sobrevivência Celular/efeitos dos fármacos , Cricetulus , Reparo do DNA/efeitos dos fármacos , Raios gama/efeitos adversos , Glucosídeos/farmacologia , Glicerídeos/farmacologia , Radioterapia com Íons Pesados/efeitos adversos , Íons/farmacologia , Transferência Linear de Energia/fisiologia , Lipoilação , Substâncias Protetoras/farmacologia , Protetores contra Radiação/metabolismo , Protetores contra Radiação/farmacologia
5.
Phys Med Biol ; 63(6): 06NT01, 2018 03 12.
Artigo em Inglês | MEDLINE | ID: mdl-29528035

RESUMO

Recent developments in radiation therapy aimed at more precise dose delivery along with higher dose gradients (dose painting) and more efficient dose delivery with higher dose rates e.g. flattening filter free (FFF) irradiation. Magnetic-resonance-imaging based polymer gel dosimetry offers 3D information for precise dose delivery techniques. Many of the proposed polymer gels have been reported to exhibit a dose response, measured as relaxation rate ΔR2(D), which is dose rate dependent. A lack of or a reduced dose-rate sensitivity is very important for dosimetric accuracy, especially with regard to the increasing clinical use of FFF irradiation protocols with LINACs at high dose rates. Some commonly used polymer gels are based on Methacrylic-Acid-Gel-Initiated-by-Copper (MAGIC). Here, we report on the dose sensitivity (ΔR2/ΔD) of MAGIC-type gels with different oxygen scavenger concentration for their specific dependence on the applied dose rate in order to improve the dosimetric performance, especially for high dose rates. A preclinical x-ray machine ('Yxlon', E = 200 kV) was used for irradiation to cover a range of dose rates from low [Formula: see text] min = 0.6 Gy min-1 to high [Formula: see text] max = 18 Gy min-1. The dose response was evaluated using R2-imaging of the gel on a human high-field (7T) MR-scanner. The results indicate that all of the investigated dose rates had an impact on the dose response in polymer gel dosimeters, being strongest in the high dose region and less effective for low dose levels. The absolute dose rate dependence [Formula: see text] of the dose response in MAGIC-type gel is significantly reduced using higher concentrations of oxygen scavenger at the expense of reduced dose sensitivity. For quantitative dose evaluations the relative dose rate dependence of a polymer gel, normalized to its sensitivity is important. Based on this normalized sensitivity the dose rate sensitivity was reduced distinctly using an increased oxygen scavenger concentration with reference to standard MAGIC-type gel formulation at high dose rate levels. The proposed gel composition with high oxygen scavenger concentration exhibits a larger linear active dose response and might be used especially in FFF-radiation applications and preclinical dosimetry at high dose rates. We propose in general to use high dose rates for calibration and evaluation as the change in relative dose sensitivity is reduced at higher dose rates in all of the investigated gel types.


Assuntos
Ácido Ascórbico/química , Sulfato de Cobre/química , Sequestradores de Radicais Livres/química , Gelatina/química , Hidroquinonas/química , Imageamento por Ressonância Magnética/métodos , Metacrilatos/química , Oxigênio/química , Polímeros/química , Radiometria/métodos , Ácido Ascórbico/efeitos da radiação , Calibragem , Sulfato de Cobre/efeitos da radiação , Gelatina/efeitos da radiação , Humanos , Hidroquinonas/efeitos da radiação , Metacrilatos/efeitos da radiação , Polímeros/efeitos da radiação , Dosagem Radioterapêutica , Planejamento da Radioterapia Assistida por Computador
6.
J Sci Food Agric ; 97(3): 984-990, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27246969

RESUMO

BACKGROUND: Thermal processing causes a number of undesirable changes in physicochemical and bioactive properties of tomato products. Microwave (MW) technology is an emergent thermal industrial process that offers a rapid and uniform heating, high energy efficiency and high overall quality of the final product. The main quality changes of tomato puree after pasteurization at 96 ± 2 °C for 35 s, provided by a semi-industrial continuous microwave oven (MWP) under different doses (low power/long time to high power/short time) or by conventional method (CP) were studied. RESULTS: All heat treatments reduced colour quality, total antioxidant capacity and vitamin C, with a greater reduction in CP than in MWP. On the other hand, use of an MWP, in particular high power/short time (1900 W/180 s, 2700 W/160 s and 3150 W/150 s) enhanced the viscosity and lycopene extraction and decreased the enzyme residual activity better than with CP samples. For tomato puree, polygalacturonase was the more thermo-resistant enzyme, and could be used as an indicator of pasteurization efficiency. CONCLUSION: MWP was an excellent pasteurization technique that provided tomato puree with improved nutritional quality, reducing process times compared to the standard pasteurization process. © 2016 Society of Chemical Industry.


Assuntos
Hidrolases de Éster Carboxílico/metabolismo , Irradiação de Alimentos , Qualidade dos Alimentos , Frutas/química , Proteínas de Plantas/metabolismo , Poligalacturonase/metabolismo , Solanum lycopersicum/química , Antioxidantes/análise , Antioxidantes/efeitos da radiação , Ácido Ascórbico/análise , Ácido Ascórbico/efeitos da radiação , Hidrolases de Éster Carboxílico/química , Hidrolases de Éster Carboxílico/efeitos da radiação , Carotenoides/análise , Carotenoides/efeitos da radiação , Fenômenos Químicos , Relação Dose-Resposta à Radiação , Estabilidade Enzimática/efeitos da radiação , Manipulação de Alimentos , Irradiação de Alimentos/efeitos adversos , Frutas/enzimologia , Frutas/efeitos da radiação , Temperatura Alta/efeitos adversos , Humanos , Licopeno , Solanum lycopersicum/enzimologia , Solanum lycopersicum/efeitos da radiação , Fenômenos Mecânicos , Micro-Ondas/efeitos adversos , Valor Nutritivo , Pasteurização/métodos , Pigmentos Biológicos/análise , Pigmentos Biológicos/efeitos da radiação , Proteínas de Plantas/química , Proteínas de Plantas/efeitos da radiação , Poligalacturonase/química , Poligalacturonase/efeitos da radiação , Viscosidade/efeitos da radiação
7.
PLoS One ; 8(12): e84474, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24367665

RESUMO

Understanding how the fruit microclimate affects ascorbate (AsA) biosynthesis, oxidation and recycling is a great challenge in improving fruit nutritional quality. For this purpose, tomatoes at breaker stage were harvested and placed in controlled environment conditions at different temperatures (12, 17, 23, 27 and 31 °C) and irradiance regimes (darkness or 150 µmol m(-2) s(-1)). Fruit pericarp tissue was used to assay ascorbate, glutathione, enzymes related to oxidative stress and the AsA/glutathione cycle and follow the expression of genes coding for 5 enzymes of the AsA biosynthesis pathway (GME, VTC2, GPP, L-GalDH, GLDH). The AsA pool size in pericarp tissue was significantly higher under light at temperatures below 27 °C. In addition, light promoted glutathione accumulation at low and high temperatures. At 12 °C, increased AsA content was correlated with the enhanced expression of all genes of the biosynthesis pathway studied, combined with higher DHAR and MDHAR activities and increased enzymatic activities related to oxidative stress (CAT and APX). In contrast, at 31 °C, MDHAR and GR activities were significantly reduced under light indicating that enzymes of the AsA/glutathione cycle may limit AsA recycling and pool size in fruit pericarp, despite enhanced expression of genes coding for AsA biosynthesis enzymes. In conclusion, this study confirms the important role of fruit microclimate in the regulation of fruit pericarp AsA content, as under oxidative conditions (12 °C, light) total fruit pericarp AsA content increased up to 71%. Moreover, it reveals that light and temperature interact to regulate both AsA biosynthesis gene expression in tomato fruits and AsA oxidation and recycling.


Assuntos
Ácido Ascórbico/biossíntese , Ácido Ascórbico/metabolismo , Regulação da Expressão Gênica de Plantas/efeitos da radiação , Temperatura Alta , Luz , Solanum lycopersicum/genética , Solanum lycopersicum/metabolismo , Ácido Ascórbico/efeitos da radiação , Frutas/genética , Frutas/metabolismo , Frutas/efeitos da radiação , Regulação da Expressão Gênica de Plantas/genética , Glutationa/metabolismo , Solanum lycopersicum/efeitos da radiação , Oxirredução/efeitos da radiação , RNA Mensageiro/genética , RNA Mensageiro/metabolismo
8.
Gen Physiol Biophys ; 32(2): 173-7, 2013 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-23479451

RESUMO

We have studied interaction of well known antioxidant L-ascorbic acid with magnetic nanoparticles containing insoluble Fe(III) in their core. In analogy with ferritin, mobilization of iron in the form of water soluble Fe(II) was observed, especially pronounced at higher temperatures. In the presence of hydrogen peroxide cytotoxic hydroxyl radicals are produced. These results suggest possible harmful effects of widely used magnetic nanoparticles as a MRI contrast agents in combination with overload of organism with ascorbic acid in some specific conditions, like fever of patient. On the other hand combination of magnetic nanoparticles and ascorbic acid may be used for a cancer therapy using alternating magnetic field for the release of Fe(II) via Néel relaxation of magnetic moment of used nanoparticles. We have further found that lipoic acid is an efficient antioxidant scavenging hydroxyl radicals produced by Fenton reaction from Fe(II).


Assuntos
Antioxidantes/química , Ácido Ascórbico/química , Nanopartículas de Magnetita/química , Antioxidantes/análise , Antioxidantes/efeitos da radiação , Ácido Ascórbico/análise , Ácido Ascórbico/efeitos da radiação , Campos Eletromagnéticos , Nanopartículas de Magnetita/análise , Nanopartículas de Magnetita/efeitos da radiação , Nanopartículas de Magnetita/uso terapêutico , Doses de Radiação , Temperatura
9.
Int J Radiat Biol ; 89(6): 411-5, 2013 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-23362934

RESUMO

PURPOSE: The aim of this work was to investigate the protective role of ascorbic acid on irradiation-induced modification of casein. MATERIALS AND METHODS: Casein stock solutions were irradiated with increasing doses 2-10 kGy using (60)Co Gamma rays at a dose rate D• = 136.73 Gy/min at room temperature. The total viable microorganism content of cow milk casein was evaluated by Plate Count Agar (PCA) incubation for 48 h at 37°C. Sodium dodecylsulfate gel electrophoresis (SDS-PAGE) and Matrix-Assisted Laser Desorption-Ionization Time-of-Flight mass spectrometry (MALDI-TOF-MS) analysis were used to evaluate the effect of gamma irradiation on casein integrity. RESULTS: Gamma irradiation reduced the bacterial contamination of casein solutions at a lower irradiation dose when performed in the presence of ascorbic acid. The irradiation treatment of casein in the absence of ascorbic acid with a dose of 4 kGy could reduce 99% of the original amount of bacterial colonies. However, in the presence of ascorbic acid the irradiation treatment of casein with a dose lower than 2 kGy could reduce 99% of the original amount of bacterial colonies which suggested that the irradiation dose lower than 2 kGy achieved almost the entire decontamination result. SDS-PAGE and MALDI-TOF-MS analysis showed that ascorbic acid protected cow milk casein from degradation and subsequent aggregation probably by scavenging oxygen and protein radicals produced by the irradiation. CONCLUSIONS: It is demonstrated that the combination of gamma irradiation and ascorbic acid produce additive effects, providing acceptable hygienic quality of cow milk casein and protects caseins against Reactive Oxygen Species (ROS) generated, during the irradiation process.


Assuntos
Ácido Ascórbico/química , Fenômenos Fisiológicos Bacterianos/efeitos da radiação , Caseínas/química , Caseínas/efeitos da radiação , Leite/química , Leite/microbiologia , Esterilização/métodos , Animais , Ácido Ascórbico/efeitos da radiação , Bovinos , Descontaminação/métodos , Aditivos Alimentares/química , Aditivos Alimentares/efeitos da radiação , Raios gama , Doses de Radiação , Protetores contra Radiação/química
10.
Molecules ; 18(1): 574-87, 2013 Jan 04.
Artigo em Inglês | MEDLINE | ID: mdl-23292326

RESUMO

The catechin (-)-epigallocatechin-3-gallate (EGCG) exhibits high antioxidant activity and it has been reported to provide protection of the skin against damage induced by solar UV radiation. However, EGCG is highly unstable under sunlight. The present study aimed to compare the effectiveness of the co-antioxidant agents vitamin E, butylated hydroxytoluene, vitamin C and a-lipoic acid for their potential to protect the catechin from photochemical degradation. Model creams (oil-in-water emulsions) containing EGCG (1%, w/w) alone or combined with equimolar concentrations of co-antioxidant were exposed to a solar simulator at an irradiance corresponding to natural sunlight. Photodegradation was evaluated by HPLC-UV and HPLC-ESI-MS/MS. Addition of the co-antioxidants vitamin C and a-lipoic acid to the formulation significantly reduced the light-induced decomposition of EGCG from 76.9 ± 4.6% to 20.4 ± 2.7% and 12.6 ± 1.6%, respectively. Conversely, butylated hydroxytoluene had no effect (EGCG loss, 78.1 ± 4.6%) and vitamin E enhanced the EGCG photolysis to 84.5 ± 3.4%. The functional stability of the catechin in the creams exposed to the solar simulator was also evaluated by measuring the in vitro antioxidant activity. Following irradiation, the reduction of the EGCG formulation antioxidant power was lower (21.8%) than the extent of degradation (76.9%), suggesting the formation of photoproducts with antioxidant properties. The influence of the examined co-antioxidants on the functional stability of the catechin under simulated sunlight paralleled that measured for the EGCG photodecomposition, a-lipoic acid exerting the greatest stabilising effect (antioxidant activity decrease, 1.4%). These results demonstrated that a-lipoic acid is an effective co-antioxidant agent for the stabilization of EGCG in dermatological products for skin photoprotection.


Assuntos
Antioxidantes/química , Catequina/análogos & derivados , Luz , Creme para a Pele/efeitos da radiação , Ácido Tióctico/química , Antioxidantes/efeitos da radiação , Ácido Ascórbico/química , Ácido Ascórbico/efeitos da radiação , Compostos de Bifenilo/química , Hidroxitolueno Butilado/química , Hidroxitolueno Butilado/efeitos da radiação , Catequina/química , Catequina/efeitos da radiação , Química Farmacêutica , Cromatografia Líquida de Alta Pressão , Estabilidade de Medicamentos , Emulsões/química , Emulsões/efeitos da radiação , Radicais Livres/química , Oxirredução , Fotólise , Picratos/química , Creme para a Pele/química , Espectrometria de Massas por Ionização por Electrospray , Espectrometria de Massas em Tandem , Ácido Tióctico/efeitos da radiação , Vitamina E/química , Vitamina E/efeitos da radiação
11.
Phys Med Biol ; 56(22): 7273-86, 2011 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-22037790

RESUMO

This study evaluates the dosimetric performance of the polymer gel dosimeter 'Methacrylic and Ascorbic acid in Gelatin, initiated by Copper' and its suitability for quality assurance and analysis of I-131-targeted radionuclide therapy dosimetry. Four batches of gel were manufactured in-house and sets of calibration vials and phantoms were created containing different concentrations of I-131-doped gel. Multiple dose measurements were made up to 700 h post preparation and compared to equivalent Monte Carlo simulations. In addition to uniformly filled phantoms the cross-dose distribution from a hot insert to a surrounding phantom was measured. In this example comparisons were made with both Monte Carlo and a clinical scintigraphic dosimetry method. Dose-response curves generated from the calibration data followed a sigmoid function. The gels appeared to be stable over many weeks of internal irradiation with a delay in gel response observed at 29 h post preparation. This was attributed to chemical inhibitors and slow reaction rates of long-chain radical species. For this reason, phantom measurements were only made after 190 h of irradiation. For uniformly filled phantoms of I-131 the accuracy of dose measurements agreed to within 10% when compared to Monte Carlo simulations. A radial cross-dose distribution measured using the gel dosimeter compared well to that calculated with Monte Carlo. Small inhomogeneities were observed in the dosimeter attributed to non-uniform mixing of monomer during preparation. However, they were not detrimental to this study where the quantitative accuracy and spatial resolution of polymer gel dosimetry were far superior to that calculated using scintigraphy. The difference between Monte Carlo and gel measurements was of the order of a few cGy, whilst with the scintigraphic method differences of up to 8 Gy were observed. A manipulation technique is also presented which allows 3D scintigraphic dosimetry measurements to be compared to polymer gel dosimetry measurements without generating misleading errors due to the limited spatial resolution.


Assuntos
Géis/efeitos da radiação , Método de Monte Carlo , Imagens de Fantasmas , Radiometria/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Ácido Ascórbico/química , Ácido Ascórbico/efeitos da radiação , Calibragem , Géis/química , Metacrilatos/química , Metacrilatos/efeitos da radiação , Dosagem Radioterapêutica
12.
AAPS PharmSciTech ; 12(3): 917-23, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21735345

RESUMO

The kinetics of photolysis of ascorbic acid in cream formulations on UV irradiation has been studied using a specific spectrophotometric method with a reproducibility of ± 5%. The apparent first-order rate constants (k(obs)) for the photolysis of ascorbic acid in creams have been determined. The photoproducts formed in the cream formulations include dehydroascorbic acid and 2,3-diketogulonic acid. The photolysis of ascorbic acid appears to be affected by the concentration of active ingredient, pH, and viscosity of the medium and formulation characteristics. The study indicates that the ionized state and redox potentials of ascorbic acid are important factors in the photostability of the vitamin in cream formulations. The viscosity of the humectant present in the creams appears to influence the photostability of ascorbic acid. The results show that the physical stability of the creams is an important factor in the stabilization of the vitamin. In the cream formulations stored in the dark, ascorbic acid undergoes aerobic oxidation and the degradation is affected by similar factors as indicated in the photolysis reactions. The rate of oxidative degradation in the dark is about seventy times slower than that observed in the presence of light.


Assuntos
Ácido Ascórbico/análise , Ácido Ascórbico/efeitos da radiação , Espectrofotometria Ultravioleta/métodos , Vitaminas/efeitos da radiação , Ácido 2,3-Dicetogulônico/análise , Ácido Desidroascórbico/análise , Estabilidade de Medicamentos , Emulsões/química , Excipientes/química , Oxirredução , Fotólise , Raios Ultravioleta , Viscosidade , Vitaminas/análise
13.
J Food Sci ; 76(2): H62-71, 2011 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21535769

RESUMO

UNLABELLED: Ultraviolet radiation induced degradation of ascorbic acid in a model apple juice system and in apple juice was studied using a collimated beam batch UV reactor. In the model system, ascorbic acid degradation was more rapid at higher dose levels and the reaction accelerated with increasing exposure time. Ascorbic acid degradation significantly (P < 0.05) increased as the pH was raised from 2.4 to 5.5, although no difference was observed between 2.4 and 3.3. Increasing malic acid concentration between 0.1 and 1%, increased ascorbic acid degradation (P < 0.05) although there was no difference between 0.5 and 1.0%. Solution absorbance, varied by addition of tannic acid, decreased ascorbic acid degradation with increasing concentration due to absorption of UV radiation. Fructose at levels found in apple juice significantly increased ascorbic acid degradation while glucose and sucrose did not. Factors identified that accelerate ascorbic acid degradation may at least partially explain why ascorbic acid degradation occurred more rapidly in UV-treated apple juice than in the 0.5% malic acid model system. Ascorbic acid degradation continued after UV treatments during dark storage. Storage decreases were faster at higher initial UV dose levels and higher storage temperature. PRACTICAL APPLICATION: The present study shows the effect of UV processing on ascorbic acid, a key vitamin found in many fruit juices. Process developers and researchers can use this study as a model for designing experiments to identify factors that influence the stability of vitamin C and other bioactive compounds during UV processing.


Assuntos
Ácido Ascórbico/efeitos da radiação , Bebidas/efeitos da radiação , Manipulação de Alimentos/métodos , Malus/química , Malus/efeitos da radiação , Raios Ultravioleta , Ácido Ascórbico/química , Conservação de Alimentos , Frutose/metabolismo , Glucose/metabolismo , Concentração de Íons de Hidrogênio , Cinética , Malatos/metabolismo , Modelos Biológicos , Sacarose/metabolismo
14.
Ultrason Sonochem ; 18(5): 988-96, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21273112

RESUMO

This work is focused on the optimization of reaction parameters for the synthesis of ascorbyl palmitate catalyzed by Candida antarctica lipase in different organic solvents under ultrasound irradiation. The sequential strategy of experimental design proved to be useful in determining the optimal conditions for reaction conversion in tert-butanol system using Novozym 435 as catalyst. The optimum production was achieved at 70°C, ascorbic acid to palmitic acid molar ratio of 1:9, enzyme concentration of 5 wt% at 3h of reaction, resulting in an ascorbyl palmitate conversion of about 27%. Reaction kinetics for ascorbyl palmitate production in ultrasound device showed that satisfactory reaction conversions (∼26%) could be achieved in short reaction times (2h). The empirical kinetic model proposed is able to satisfactorily represent and predict the experimental data.


Assuntos
Ácido Ascórbico/análogos & derivados , Lipase/química , Lipase/efeitos da radiação , Modelos Químicos , Sonicação/métodos , Ácido Ascórbico/síntese química , Ácido Ascórbico/efeitos da radiação , Simulação por Computador , Cinética , Doses de Radiação
15.
J Food Sci ; 75(3): C263-7, 2010 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-20492277

RESUMO

Under certain conditions, benzene can form in beverages containing benzoic and ascorbic acids. The American Beverage Assn. (ABA) has published guidelines to help manufacturers mitigate benzene formation in beverages. These guidelines recommend accelerated testing conditions to test product formulations, because exposure to ultraviolet (UV) light and elevated temperature over the shelf life of the beverage may result in benzene formation in products containing benzoic and ascorbic acids. In this study, the effects of UVA exposure on benzene formation were determined. Benzene formation was examined for samples contained in UV stabilized and non-UV stabilized packaging. Additionally, the usefulness of accelerated thermal testing to simulate end of shelf-life benzene formation was evaluated for samples containing either benzoic or ascorbic acid, or both. The 24 h studies showed that under intense UVA light benzene levels increased by as much as 53% in model solutions stored in non-UV stabilized bottles, whereas the use of UV stabilized polyethylene terephthalate bottles reduced benzene formation by about 13% relative to the non-UV stabilized bottles. Similar trends were observed for the 7 d study. Retail beverages and positive and negative controls were used to study the accelerated thermal testing conditions. The amount of benzene found in the positive controls and cranberry juice suggests that testing at 40 degrees C for 14 d may more reliably simulate end of shelf-life benzene formation in beverages. Except for cranberry juice, retail beverages were not found to contain detectable amounts of benzene (<0.05 ng/g) at the end of their shelf lives.


Assuntos
Ácido Ascórbico/química , Benzeno/análise , Benzoatos/química , Bebidas/análise , Análise de Alimentos/métodos , Contaminação de Alimentos/prevenção & controle , Ácido Ascórbico/efeitos da radiação , Benzoatos/efeitos da radiação , Bebidas/efeitos da radiação , Embalagem de Alimentos , Indústria de Processamento de Alimentos/métodos , Frutas/química , Cromatografia Gasosa-Espectrometria de Massas , Temperatura Alta/efeitos adversos , Modelos Químicos , Fenóis/química , Polietilenotereftalatos/química , Fatores de Tempo , Triazóis/química , Raios Ultravioleta/efeitos adversos , Vaccinium macrocarpon/química
16.
Med Phys ; 37(1): 183-8, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20175480

RESUMO

PURPOSE: Polymer-based gel dosimeter (MAGIC type) is a preferable phantom material for PET range verification of proton beam therapy. However, improvement in elemental tissue equivalency (specifically O/C ratio) is very desirable to ensure realistic time-activity measurements. METHODS: Glucose and urea was added to the original MAGIC formulation to adjust the O/C ratio. The dose responses of the new formulations were tested with MRI transverse relaxation rate (R2) measurements. RESULTS: The new ingredients improved not only the elemental composition but also the sensitivity of the MAGIC gel. The O/C ratios of our new gels agree with that of soft tissue within 1%. The slopes of dose response curves were 1.6-2.7 times larger with glucose. The melting point also increased by 5 degrees C. Further addition of urea resulted in a similar slope but with an increased intercept and a decreased melting point. CONCLUSIONS: Our improved MAGIC gel formulations have higher sensitivity and better elemental tissue equivalency for 3D dosimetry applications involving nuclear reactions.


Assuntos
Ácido Ascórbico/química , Ácido Ascórbico/efeitos da radiação , Materiais Biomiméticos/química , Materiais Biomiméticos/efeitos da radiação , Sulfato de Cobre/química , Sulfato de Cobre/efeitos da radiação , Gelatina/química , Gelatina/efeitos da radiação , Hidroquinonas/química , Hidroquinonas/efeitos da radiação , Metacrilatos/química , Metacrilatos/efeitos da radiação , Polímeros/química , Polímeros/efeitos da radiação , Radiometria/métodos , Relação Dose-Resposta à Radiação , Prótons , Doses de Radiação , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
17.
J Hazard Mater ; 178(1-3): 152-6, 2010 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-20138426

RESUMO

A novel photodegradable polyvinyl chloride (PVC)-vitamin C (VC)-TiO(2) nano-composite film was prepared by embedding VC modified nano-TiO(2) photocatalyst into the commercial PVC plastic. The solid-phase photocatalytic degradation behavior of PVC-VC-TiO(2) nano-composite film under UV light irradiation was investigated and compared with those of the PVC-TiO(2) film and the pure PVC film, with the aid of UV-Vis spectroscopy, scanning electron microscopy (SEM), weight loss monitoring, and X-ray diffraction spectra (XRD). The results show that PVC-VC-TiO(2) nano-composite film has a high photocatalytic activity; the photocatalytic degradation rate of it is two times higher than that of PVC-TiO(2) film and fifteen times higher than that of pure PVC film. The optimal mass ratio of VC to TiO(2) is found to be 0.5. The mechanism of enhancing photocatalytic activity is attributed to the formation of a Ti(IV)-VC charge-transfer complex with five-member chelate ring structure and a rapid photogenerated charge separation is thus achieved.


Assuntos
Ácido Ascórbico/química , Cloreto de Polivinila/química , Titânio/química , Ácido Ascórbico/efeitos da radiação , Catálise , Microscopia Eletrônica de Varredura , Nanotecnologia , Fotoquímica , Cloreto de Polivinila/efeitos da radiação , Espectrofotometria Ultravioleta , Titânio/efeitos da radiação , Raios Ultravioleta , Difração de Raios X
18.
Free Radic Biol Med ; 48(8): 1002-12, 2010 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-20100566

RESUMO

Multivitamin preparation (MVP) is part of total parenteral nutrition given to premature infants. Photoactivated MVP carries an important load in peroxides, but their cellular effects have not yet been determined. We hypothesized that these peroxides may elicit a DNA-damage response. We found that photoactivation of MVP and the resulting peroxide production were time-dependent and required the simultaneous presence of ascorbic acid and riboflavin. Cells treated with photoactivated MVP showed strongly stimulated poly(ADP-ribosyl)ation, an early DNA-damage response in mammals. Poly(ADP-ribosyl)ation stimulation was dependent on the presence of ascorbic acid and riboflavin in the photoactivated MVP. It did not occur in the presence of a specific PARP inhibitor nor in mouse fibroblasts deficient in PARP-1. Photoactivated MVP was able to induce single- and double-strand breaks in DNA, with a predominance of single-stand breaks. The presence of double-strand breaks was further confirmed using a 53PB1 focus analysis. Finally, photoactivated MVP was shown to be toxic to human cells and induced caspase-independent cell death. These results suggest that photoactivated MVP carries an important toxic load able to damage DNA and induce cell death. This study also emphasizes the importance of protecting MVP solution from light before use in preterm infants.


Assuntos
Dano ao DNA , Peróxidos/toxicidade , Poli Adenosina Difosfato Ribose/metabolismo , Vitaminas/efeitos da radiação , Animais , Ácido Ascórbico/efeitos da radiação , Morte Celular/efeitos dos fármacos , Células Cultivadas , Fibroblastos/efeitos dos fármacos , Humanos , Luz , Camundongos , Nutrição Parenteral Total/efeitos adversos , Poli(ADP-Ribose) Polimerase-1 , Poli(ADP-Ribose) Polimerases/deficiência , Poli(ADP-Ribose) Polimerases/metabolismo , Riboflavina/efeitos da radiação
19.
J Biophotonics ; 3(1-2): 82-8, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-19681037

RESUMO

Carotenoids beta-carotene, lutein, lycopene and others are well-known powerful antioxidants acting as an effective neutralizer of free radicals produced in the human organism as a result of the influence of stress factors, such as UV irradiation. The protective effect of antioxidants is used in cosmetic products to increase the skin protection against the destructive action of free radicals and for the stabilization of formulations against oxidation. In the skin, the different antioxidant substances form protection chains to avoid their destruction by the interaction with the free radicals. Similar effects have to be expected also in topically applied formulations. In the present study the influence of different mixtures of antioxidants (beta-carotene, vitamins C and E) on the stability of antioxidants in formulations used for skin treatment was investigated. The measurements were carried out by using non-invasive resonance Raman spectroscopy for the detection of the carotenoid concentration in the cosmetic formulations.


Assuntos
Antioxidantes/química , Cosméticos/química , Análise Espectral Raman/métodos , Antioxidantes/efeitos da radiação , Ácido Ascórbico/química , Ácido Ascórbico/efeitos da radiação , Carotenoides/química , Carotenoides/efeitos da radiação , Cosméticos/efeitos da radiação , Radicais Livres/química , Humanos , Cinética , Análise Espectral Raman/instrumentação , Raios Ultravioleta , Vitamina E/química , Vitamina E/efeitos da radiação , beta Caroteno/química , beta Caroteno/efeitos da radiação
20.
J Food Sci ; 74(5): C370-4, 2009 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-19646029

RESUMO

The viability of broccoli seeds and functional properties, such as ascorbic acid, carotenoid, chlorophyll, and total phenol contents, of broccoli sprouts grown from irradiated seeds were evaluated. The seeds were irradiated using electron beam and gamma ray at doses up to 8 kGy. High germination percentages (>90%) were observed in seeds irradiated at < or =4 kGy, but the yield ratio and sprout length decreased with increased irradiation dose. Irradiation at > or =6 kGy resulted in curling of the sprout roots. Germinated seeds contained higher amounts of nutrients than raw seeds but the nutritional quality of sprouts decreased during postharvest storage. Radiation treatment hampered the growth of irradiated seeds resulting in underdeveloped sprouts with decreased ascorbic acid, carotenoid, and chlorophyll contents. In addition, the decrease in functional content of sprouts was more substantial in samples grown from high-dose (5 kGy) irradiated seeds than that of the low-dose (1 kGy) treated ones. Seed irradiation did not negatively affect the total phenol content of sprouts. In general, electron beam and gamma irradiation of broccoli seeds showed similar effects on the viability and functional properties of sprouts.


Assuntos
Brassica/efeitos da radiação , Manipulação de Alimentos/métodos , Irradiação de Alimentos/métodos , Germinação/efeitos da radiação , Sementes/efeitos da radiação , Ácido Ascórbico/efeitos da radiação , Brassica/fisiologia , Carotenoides/efeitos da radiação , Sobrevivência Celular/fisiologia , Sobrevivência Celular/efeitos da radiação , Clorofila/efeitos da radiação , Relação Dose-Resposta à Radiação , Germinação/fisiologia , Valor Nutritivo , Fenóis/efeitos da radiação , Sementes/fisiologia
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