Hydroxyl radical induced oxidation of theophylline in water: a kinetic and mechanistic study

2014 ◽  
Vol 12 (30) ◽  
pp. 5611-5620 ◽  
Author(s):  
M. M. Sunil Paul ◽  
U. K. Aravind ◽  
G. Pramod ◽  
A. Saha ◽  
C. T. Aravindakumar
Keyword(s):  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Active Compound ◽  
Hydrogen Abstraction ◽  
Mechanistic Study ◽  
Pharmaceutically Active Compound

Evidence is reported for the addition and hydrogen abstraction reactions of hydroxyl radicals with an important pharmaceutically active compound, theophylline.

Pharmaceutically Active Compounds Degradation Using Doped TiO2 Functionalized Zeolite Photocatalyst

2018 ◽  
Vol 69 (1) ◽  
pp. 34-37 ◽  
Author(s):  
Monica Ihos ◽  
Corneliu Bogatu ◽  
Carmen Lazau ◽  
Florica Manea ◽  
Rodica Pode
Keyword(s):  
Organic Carbon ◽  
Active Compound ◽  
Uv Spectra ◽  
Pharmaceutically Active Compounds ◽  
Mineralization Process ◽  
Active Compounds ◽  
Spectra Analysis ◽  
Doped Tio2 ◽  
Toc Removal ◽  
Pharmaceutically Active Compound

The aim of this study was the investigation of photocatalytic degradation of pharmaceutically active compounds using doped TiO2 functionalized zeolite photocatalyst. Diclofenac (DCF), a non-steroidal anti-inflammatory drug, that represents a biorefractory micropollutant, was chosen as model of pharmaceutically active compound. The photocatalyst was Z-TiO2-Ag. The concentration of DCF in the working solutions was 10 mg/L,50 mg/L,100 mg/L and 200 mg/L and of photocatalyst 1 g/L in any experiments. The process was monitored by recording the UV spectra of the treated solutions and total organic carbon (TOC) determination. The UV spectra analysis and TOC removal proved that along the advanced degradation of DCF also a mineralization process occurred. The carried out research provided useful information envisaging the treatment of pharmaceutical effluents by photocatalysis.

Enhancement of hydroxyl radical generation by phenols and their reaction intermediates during ozonation

1998 ◽  
Vol 38 (6) ◽  
pp. 147-154 ◽  
Author(s):  
Hideo Utsumi ◽  
Sang-Kuk Han ◽  
Kazuhiro Ichikawa
Keyword(s):  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Spin Trapping ◽  
Active Species ◽  
Generation Rate ◽  
Peak Height Ratio ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Phenol Derivatives ◽  
Semiquinone Radicals

Generation of hydroxyl radicals, one of the major active species in ozonation of water was directly observed with a spin-trapping/electron spin resonance (ESR) technique using 5,5-dimethyl-1-pyrrolineN-oxide (DMPO) as a spin-trapping reagent. Hydroxyl radical were trapped with DMPO as a stable radical, DMPO-OH. Eighty μM of ozone produced 1.08 X 10-6M of DMPO-OH, indicating that 1.4% of •OH is trapped with DMPO. Generation rate of DMPO-OH was determined by ESR/stopped-flow measurement. Phenol derivatives increased the amount and generation rate of DMPO-OH, indicating that phenol derivatives enhance •OH generation during ozonation of water. Ozonation of 2,3-, 2,5-, 2,6-dichlorophenol gave an ESR spectra of triplet lines whose peak height ratio were 1:2:1. ESR parameters of the triplet lines agreed with those of the corresponding dichloro-psemiquinone radical. Ozonation of 2,4,5- and 2,4,6-trichlorophenol gave the same spectra as those of 2,5- and 2,6-dichlorophenol, respectively, indicating that a chlorine group in p-position is substituted with a hydroxy group during ozonation. Amounts of the radical increased in an ozone-concentration dependent manner and were inhibited by addition of hydroxyl radical scavengers. These results suggest that p-semiquinone radicals are generated from the chlorophenols by hydroxyl radicals during ozonation. The p-semiquinone radicals were at least partly responsible for enhancements of DMPO-OH generation.

scholarly journals Involvement of a local Fenton reaction in the reciprocal modulation by O2 of the glucagon-dependent activation of the phosphoenolpyruvate carboxykinase gene and the insulin-dependent activation of the glucokinase gene in rat hepatocytes

1998 ◽  
Vol 335 (2) ◽  
pp. 425-432 ◽  
Author(s):  
Thomas KIETZMANN ◽  
Torsten PORWOL ◽  
Karl ZIEROLD ◽  
Kurt JUNGERMANN ◽  
Helmut ACKER
Keyword(s):  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
Fenton Reaction ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Gene Activation ◽  
Three Dimensional ◽  
Rat Hepatocytes ◽  
Confocal Laser ◽  
Radical Scavenger ◽  
Insulin Dependent

H2O2 mimicked the action of periportal pO2 in the modulation by O2 of the glucagon-dependent activation of the phosphoenolpyruvate carboxykinase (PCK) gene and the insulin-dependent activation of the glucokinase (GK) gene. H2O2 can be converted in the presence of Fe2+ in a Fenton reaction into hydroxyl anions and hydroxyl radicals (•OH). The hydroxyl radicals are highly reactive and might interfere locally with transcription factors. It was the aim of the present study to investigate the role of and to localize such a Fenton reaction. Hepatocytes cultured for 24 h were treated under conditions mimicking periportal or perivenous pO2 with glucagon or insulin plus the iron chelator desferrioxamine (DSF) or the hydroxyl radical scavenger dimethylthiourea (DMTU) to inhibit the Fenton reaction. PCK mRNA was induced by glucagon maximally under conditions of periportal pO2 and half-maximally under venous pO2. GK mRNA was induced by insulin with reciprocal modulation by O2. DSF and DMTU reduced the induction of PCK mRNA to about half-maximal and increased the induction of GK mRNA to maximal under both O2 tensions. Hydroxyl radical formation was maximal under arterial pO2. Perivenous pO2, DSF and DMTU each decreased the formation of •OH to about 70% of control. The Fenton reaction could be localized in a perinuclear space by confocal laser microscopy and three-dimensional reconstruction techniques. In the same compartment, iron could be detected by electron-probe X-ray microanalysis. Thus a local Fenton reaction is involved in the O2 signalling, which modulated the glucagon- and insulin-dependent PCK gene and GK gene activation.

scholarly journals On the Nature of Hydrodynamic Cavitation Process and Its Application for the Removal of Water Pollutants

2019 ◽  
Vol 12 ◽  
pp. 117862211988048 ◽  
Author(s):  
Erick R Bandala ◽  
Oscar M Rodriguez-Narvaez
Keyword(s):  
Hydroxyl Radical ◽  
Hydroxyl Radicals ◽  
High Energy ◽  
Optimal Operation ◽  
Hydrodynamic Cavitation ◽  
Radical Scavenger ◽  
Process Conditions ◽  
Cavitation Process ◽  
Operation Conditions ◽  
Hydroxyl Radical Scavenger

Cavitation is considered a high energy demanding process for water treatment. For this study, we used a simple experimental setup to generate cavitation at a low pressure (low energy) and test it for hydroxyl radical production using a well-known chemical probe as a hydroxyl radical scavenger. The conditions for generating the cavitation process (eg, pressure, flow velocity, temperature, and other significant variables) were used to degrade model contaminants, an azo dye and an antibiotic. The amount of hydroxyl radicals generated by the system was estimated using N,N-dimethyl-p-nitrosoaniline (pNDA) as hydroxyl radical scavenger. The capability of hydrodynamic cavitation (HC) to degrade contaminants was assessed using Congo red (CR) and sulfamethoxazole (SMX) as model contaminants. Different chemical models were analyzed using UV-visible spectrophotometry (for pNDA and CR) and high-performance liquid chromatography (HPLC) (for SMX) after HC treatment under different process conditions (ie, pressure of 13.7 and 10.3 kPa, and flow rates of 0.14 to 3.6 × 10−4 m3/s). No pNDA bleaching was observed for any of the reaction conditions tested after 60 minutes of treatment, which suggests that there was no hydroxyl radical generation during the process. However, 50% degradation of CR and 25% degradation of SMX were observed under the same process conditions, comparable with previously reported results. These results suggest that the process is most likely thermally based rather than radically based, and therefore, it can degrade organic pollutants even if no hydroxyl radicals are produced. Hydrodynamic cavitation, either alone or coupled with other advanced water technologies, has been identified as a promising technology for removing organic contaminants entering the water cycle; however, more research is still needed to determine the specific mechanisms involved in the process and the optimal operation conditions for the system.

Myocardial alterations due to free-radical generation

1984 ◽  
Vol 246 (6) ◽  
pp. H776-H783 ◽  
Author(s):  
K. P. Burton ◽  
J. M. McCord ◽  
G. Ghai
Keyword(s):  
Endothelial Cells ◽  
Free Radicals ◽  
Hydroxyl Radical ◽  
Cardiac Myocytes ◽  
Hydroxyl Radicals ◽  
Vascular Endothelial Cells ◽  
Tissue Injury ◽  
Myocardial Damage ◽  
Vascular Endothelial ◽  
Radical Generation

Oxygen-derived free radicals have been proposed as general mediators of tissue injury in a variety of disease states. Recent interest has focused on the possibility that free radicals may be involved in ischemic myocardial damage. However, the exact types of damage that result from myocardial exposure to free radicals remains to be established. The purpose of this study was to evaluate the effects of superoxide and hydroxyl radicals on myocardial structure and function in an isolated perfused rabbit interventricular septal preparation. Superoxide was generated by adding purine (2.3 mM) and xanthine oxidase (0.01 U/ml) to the physiological solutions perfusing the septa. Hydroxyl radical generation was catalyzed by the addition of 2.4 microM Fe3+-loaded transferrin to the system. Exposure of normal septa to superoxide-generating solutions resulted in the development of structural alterations in the vascular endothelium including the development of vacuoles. Membranous cellular debris was evident in the extracellular space and within the vessels. Cardiac myocytes showed evidence of mild alterations. Exposure of septa to solutions capable of generating hydroxyl radicals resulted in more extensive and severe damage. Vascular endothelial cells showed evidence of vacuoles or blebs and edema. Severe swelling of mitochondria was evident in cardiac myocytes and vascular endothelial cells. In addition, myocytes often showed blebbing of the basement membrane. Normal septa exposed to superoxide showed no significant decrease in developed tension, whereas hydroxyl radical exposure resulted in a significant decrease in myocardial function.(ABSTRACT TRUNCATED AT 250 WORDS)

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