scholarly journals Effects of continuous UV-irradiation on the antioxidant activities of quercetin and rutin in solution in the presence of lecithin as the protective target

2011 ◽  
Vol 76 (7) ◽  
pp. 973-985 ◽  
Author(s):  
Dragan Cvetkovic ◽  
Dejan Markovic ◽  
Dragana Cvetkovic ◽  
Blaga Radovanovic
Keyword(s):  
Lipid Peroxidation ◽  
Uv Irradiation ◽  
Energy Input ◽  
Antioxidant Activities ◽  
Antioxidant Action ◽  
First Order ◽  
First Order Kinetics ◽  
Uv Photons ◽  
Uv C

The stabilities and antioxidant action of two selected flavonoids, quercetin and rutin, dissolved in methanol and water, toward continuous UV-irradiation from three different sub-ranges (UV-A, UV-B and UV-C) were studied. The flavonoids underwent degradation (bleaching) following first-order kinetics. The bleaching rates were highly dependent on the energy input of the involved UV-photons. The antioxidant activities of the two flavonoids on UV-induced lecithin lipid peroxidation were studied by the TBA-MDA test, and appeared to be also affected by the continuous UV irradiation. The energy input of the incident UV-photons again played a major governing role, but an impact of the flavonoids structures cannot be neglected.

scholarly journals Bleaching of chlorophylls by UV irradiation in vitro: The effects on chlorophyll organization in acetone and n-hexane

2008 ◽  
Vol 73 (3) ◽  
pp. 271-282 ◽  
Author(s):  
Jelena Zvezdanovic ◽  
Dejan Markovic
Keyword(s):  
Uv Irradiation ◽  
Photosynthetic Pigments ◽  
Energy Input ◽  
First Order ◽  
First Order Kinetics ◽  
Uv Photons ◽  
The Stability ◽  
Major Factors

The stability of chlorophylls toward UV irradiation was studied by Vis spectrophotometry in extracts containing mixtures of photosynthetic pigments in acetone and n-hexane. The chlorophylls underwent destruction (bleaching) obeying first-order kinetics. The bleaching was governed by three major factors: the energy input of the UV photons, the concentration of the chlorophylls and the polarity of the solvent, implying different molecular organizations of the chlorophylls in the two solvents.

scholarly journals UV-induced change in quercetin antioxidant activity toward benzophenone initiated lipid peroxidation

2012 ◽  
Vol 77 (11) ◽  
pp. 1571-1588 ◽  
Author(s):  
Jelena Zvezdanovic ◽  
Dejan Markovic ◽  
Dragan Cvetkovic ◽  
Jelena Stanojevic
Keyword(s):  
Lipid Peroxidation ◽  
Antioxidant Activity ◽  
Uv Irradiation ◽  
Energy Input ◽  
Incident Light ◽  
Methanol Solution ◽  
Suppression Effect ◽  
Peroxidation Processes ◽  
Uv Photons ◽  
Uv C

The aim of this work is to estimate the degradation and change in antioxidant activity of quercetin in the presence of two different mixtures of phospholipids in methanol solution, under continuous UV-irradiation from three different sub-ranges (UV-A, UV-B and UV-C), in the presence and in the absence of selected UV-absorbing photosensitizer, benzophenone. Quercetin is employed to control lipid peroxidation process generated by UV-irradiation, by absorbing part of the UV-incident light, or/and by scavenging the involved, created free radicals. The results show that quercetin undergoes to irreversible destruction, highly dependent on UV-photons energy input, more expressed in the presence than in the absence of benzophenone. In the same time quercetin expresses suppression effect on lipid peroxidation processes in UV-irradiated phospholipid mixtures in both cases - absence or presence of benzophenone (more or less effective, respectively). In UV-C-irradiated mixtures, benzophenone photosensitizing function is significantly reduced due to its strong absorption in the same UV-C spectral range, therefore affecting less antioxidant activity of the remained quercetin.

scholarly journals Irreversible UV-induced quercetin and rutin degradation in solution, studied by UV-spectrophotometry and HPLC chromatography

2012 ◽  
Vol 77 (3) ◽  
pp. 297-312 ◽  
Author(s):  
Jelena Zvezdanovic ◽  
Jelena Stanojevic ◽  
Dejan Markovic ◽  
Dragan Cvetkovic
Keyword(s):  
Rate Constants ◽  
Energy Input ◽  
Degradation Products ◽  
Formation Rate ◽  
Uv Spectrophotometry ◽  
First Order ◽  
First Order Kinetics ◽  
Uv Photons ◽  
Rutin Degradation ◽  
Uv C

Irreversible degradation of quercetin and rutin, dissolved in methanol and water, induced by continuous UV-irradiation from two different sub-ranges (UV-B and UV-C) has been studied in this work. The degradation of both flavonoids is related to formation of UV-induced degradation products: both processes follow first-order kinetics. The degradation and products formation rate constants are both dependent on the involved UV-photons energy input in both solvents.

scholarly journals Stability of carotenoids toward UV-irradiation in hexane solution

2008 ◽  
Vol 73 (1) ◽  
pp. 15-27 ◽  
Author(s):  
Dragan Cvetkovic ◽  
Dejan Markovic
Keyword(s):  
Free Radical ◽  
Uv Irradiation ◽  
First Order ◽  
Chemical Structures ◽  
First Order Kinetics ◽  
Uv C ◽  
Hexane Solution

The stabilities of four selected carotenoids dissolved in hexane, two carotenes and two xanthophylls, toward UV-irradiation of three different ranges (UV-A, UV-B and UV-C) were studied in this work. The carotenoids underwent bleaching via a probable free radical mediated mechanism following first-order kinetics. The bleaching rates were highly dependent on the input of the involved photons and, although not consistently, on the chemical structures of the investigated compounds. For the two xanthophylls, a possible role of oxygen associated with their bleaching cannot be neglected.

scholarly journals A marginal contribution of selected carotenoids to the supression of UV-irradiation-induced lecithin peroxidation in hexane solution

2007 ◽  
Vol 72 (3) ◽  
pp. 235-250 ◽  
Author(s):  
Dragan Cvetkovic ◽  
Dejan Markovic
Keyword(s):  
Lipid Peroxidation ◽  
Free Radicals ◽  
Uv Irradiation ◽  
Marginal Contribution ◽  
Lipid Peroxidation Process ◽  
Uv Photons ◽  
Uv C ◽  
Hexane Solution

The aim of this work was to study the anticipated antioxidant role of four selected carotenoids in mixtures with lecithin lipoidal compounds in hexane solution, under continuous UV-irradiation in three different ranges (UV-A, UV-B and UV-C). Two carotenes (b-carotene and licopene) and two xantophylls (lutein and neoxanthin) were employed to control the lipid peroxidation process generated by UV-irradiation, by scavenging the involved free radicals. The results show that while carotenoids undergo a substantial, structural dependent destruction (bleaching), which is highly dependent on energy of the UV-photons, their contribution to the expected suppression of lecithin peroxidation is of marginal importance, not exceeding a maximum of 20%. The marginal antioxidant behaviour has been attributed to a highly unordered hexane solution, where the scavenging action of the carotenoids becomes less competitive.

scholarly journals UV-effects on antioxidant activity of selected carotenoids in the presence of lecithin estimated by DPPH test

2008 ◽  
Vol 73 (11) ◽  
pp. 1051-1061 ◽  
Author(s):  
Dragan Cvetkovic ◽  
Dejan Markovic
Keyword(s):  
Antioxidant Activity ◽  
Ultraviolet Radiation ◽  
Energy Input ◽  
High Energy ◽  
Antioxidant Action ◽  
Dpph Radical ◽  
Dpph Test ◽  
Uv Photons

The effects of ultraviolet radiation (UV) on the antioxidant action of three selected carotenoids (?-carotene, lycopene and lutein) in the presence of a lipoidal lecithin mixture were studied by the DPPH (1,1-diphenyl-2-picrylhydrazyl) test. The test is based on the measurement of the decrease of the free DPPH radical absorbance at 517 nm caused by the antioxidant action of carotenoids, which appeared to be strongly affected by UV-action. The high-energy input of the involved UV-photons plays a major governing role.

scholarly journals Separation of Ag and Cu from Their Aqueous Thiosulfate Complexes by UV-C Irradiation

Metals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1178 ◽  
Author(s):  
Han ◽  
Wang ◽  
Zou ◽  
Shi
Keyword(s):  
Silver Sulfide ◽  
Recovery Ratio ◽  
Silver Recovery ◽  
First Order ◽  
First Order Kinetics ◽  
Recycle Ratio ◽  
Copper Component ◽  
Phase And Chemical Composition ◽  
Thiosulfate Leaching ◽  
Uv C

In recent years, there has been renewed interest in the use of thiosulfate as a substitute for cyanide in silver leaching. Copper thiosulfate leaching without ammonia was applied to extract silver from silver sulfide, resulting in the production of Ag–Cu polymetallic thiosulfate complexes in solutions. It is necessary to separate Ag–Cu polymetallic thiosulfate complexes with the purposes of silver recovery and copper recycling. In this paper, the feasibility study on the use of UV-C irradiation to separate Ag–Cu polymetallic thiosulfate complexes was investigated based on the different photosensitivity of silver and copper. First, a kinetic study on the photolysis of silver and copper thiosulfate complexes by UV-C was investigated, indicating that the reactions follow first-order kinetics. The rate constant reactions were calculated, and it decreased with solution concentrations. On the other hand, the photoproducts of the silver and copper thiosulfate complexes were characterized by XRD and XPS in order to confirm the phase and chemical composition. It indicated that the silver photoproducts are Ag2S, S, Ag and the copper photoproducts are Cu2S, CuS, CuO, Cu, S. Finally, the four-step continuous separation of Ag–Cu polymetallic thiosulfate complexes by UV-C irradiation was investigated. The silver component was recovered with the accumulated recovery ratio of 97%, and the copper component was recycled with the accumulated recycle ratio of 51%, which made it possible for silver recovery and copper recycling.

Decolourization of Methylene Blue by Persulfate

2013 ◽  
Vol 634-638 ◽  
pp. 76-80
Author(s):  
Wei Hu ◽  
Shen Xin Li ◽  
Cheng Duan Wang
Keyword(s):  
Methylene Blue ◽  
Ionic Strength ◽  
Uv Irradiation ◽  
Reaction Temperature ◽  
Uv Light ◽  
Kinetics Model ◽  
Dye Wastewater ◽  
First Order ◽  
First Order Kinetics ◽  
Pseudo First Order

The decolourization of dye wastewater by persulfate was studied using methylene blue as a model dye wastewater. Effects of several parameters, such as dose of oxidant, ionic strength, pH, temperature and UV irradiation, were investigated in detail. The results showed that the decolourization reaction of methylene blue by persulfate could be fitted to a pseudo-first order kinetics model. In addition, when the oxidant amount used is 2 times of methylene blue, pH 3.43 and reaction temperature for 60°C, after uv light under the irradiation of 20 min, methylene blue decolorization rate can reach more than 98%. The results are useful for the treatment of dye wastewater.

Decolourization of Kiscolon Scarlet 2KN by Persulfate

2013 ◽  
Vol 864-867 ◽  
pp. 256-260
Author(s):  
Wei Hu ◽  
Shen Xin Li ◽  
Wang Ying ◽  
Cheng Duan Wang
Keyword(s):  
Uv Irradiation ◽  
Reaction Temperature ◽  
Kinetics Model ◽  
Dye Wastewater ◽  
First Order ◽  
Decolorization Rate ◽  
First Order Kinetics ◽  
Pseudo First Order

The decolourization of dye wastewater by persulfate was studied using kiscolon scarlet2KN as a model dye wastewater. Effects of several parameters, such as dose of oxidant, pH, temperature and UV irradiation, were investigated in detail. The results showed that the decolourization reaction of kiscolon scarlet2KN by persulfate could be fitted to a pseudo-first order kinetics model. In addition, when the oxidant amount used is 70 times of kiscolon scarlet2KN, pH 5.71 and reaction temperature for 70°C, kiscolon scarlet2KN decolorization rate can reach more than 98%. The results are useful for the treatment of dye wastewater.Keywords:Kiscolon scarlet 2KN, Decolourization, Persulfate

scholarly journals Photocatalytic removal of cefazolin from aqueous solution by AC prepared from mango seed+ZnO under UV irradiation

2018 ◽  
Vol 20 (2) ◽  
pp. 399-407 ◽  
Keyword(s):  
Activated Carbon ◽  
Kinetic Model ◽  
Uv Irradiation ◽  
Advanced Oxidation ◽  
Beam Radiation ◽  
Initial Concentration ◽  
First Order ◽  
First Order Kinetics ◽  
Pseudo First Order ◽  
Mango Seed

Presence of antibiotics in the environment specially in aqueous environments is considered a major warning about health and environment. Thus, this study aims the efficiency of coupled process of Activated Carbon (AC) prepared from mango seed+ZnO under UV irradiation as an advanced oxidation process in removing cefazolin antibiotic from aqueous solutions. This experimental study was carried out in a discontinuous reaction chamber with volume of one liter. In this process, the effect of initial pH parameters of the environment (3– 9), initial concentration of cefazolin (20 – 200 mg/L), concentration of modified, photocatalyzer (20 – 100 mg/L) and reaction time (10 – 60 min) were studied. The pilot used consisted of a low pressure mercury lamp with a 55-watt beam radiation power inside the steel chamber. The kinetic of the process was studied based on pseudo first order kinetics. Results showed that the highest removal efficiency of cefazolin antibiotics in the reaction of UV/AC + ZnO, at optimal conditions of pH= 3, contact time of 60 min, initial concentration of 100 mg/L and modified photocatalyzer of 0.1 g/L was equal to 96%. The kinetic model determined for the process followed kinetic model of pseudo- first order kinetics with high correlation of (R2 = 0.99). Results of present study revealed that photocatalyzer process of nanoparticles oxidation on synthetic activated carbon can be effectively used as an advanced oxidation reaction to remove cefazolin and similar pollutants.

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