scholarly journals Effect of UV Irradiation and Temperature on Free Radical Properties in Dehydrocholic and Ursodeoxycholic Acids: An EPR Study

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Małgorzata Dołowy ◽  
Paweł Ramos ◽  
Barbara Pilawa
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Free Radicals ◽  
Bile Acid ◽  
Free Radical ◽  
Bile Acids ◽  
Uv Irradiation ◽  
Thermal Method ◽  
Paramagnetic Resonance ◽  
Thermal Sterilization ◽  
Electron Paramagnetic

The effect of UV irradiation and temperature on the formation and properties of free radicals in two pharmaceutical important bile acids, such as dehydrocholic (DH) and ursodeoxycholic acids (UDC), was examined. Electron paramagnetic resonance (EPR) spectroscopy was applied to determine the paramagnetic character of UV irradiated and thermally sterilized drugs. Thermal and UV irradiation sterilizations of both compounds were carried out at different conditions according to pharmaceutical norms. The performed EPR measurements of UV irradiated and thermally sterilized DH and UDC samples proved the existence of the complex free radical systems in examined bile acids. Significant influence of UV irradiation in comparison with applied thermal sterilization on free radical concentrations in DH and UDC samples was observed. The results pointed out that thermal method is most suitable for bile acid sterilization. Therefore, this kind of sterilization should be applied in practice.

Quantitative Electron Paramagnetic Resonance: The Importance of Matching the Q-Factor of Standards and Samples

2001 ◽  
Vol 55 (10) ◽  
pp. 1375-1381 ◽  
Author(s):  
Richard L. Blakley ◽  
Dwight D. Henry ◽  
Walter T. Morgan ◽  
William L. Clapp ◽  
Carr J. Smith ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Free Radicals ◽  
Free Radical ◽  
Spin Trapping ◽  
Microwave Energy ◽  
Q Factor ◽  
Paramagnetic Resonance ◽  
Tert Butyl ◽  
Electron Paramagnetic ◽  
Stable Free Radicals

Electron paramagnetic resonance (EPR) quantification of free radicals from different samples facilitates comparison of free radical concentrations. Stable free radicals, such as 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), in a suitable solvent (e.g., benzene) can be used as a quantification standard. Free radicals found in samples can be shorter lived than radicals in prepared standards and require stabilizing spin-trapping agents such as N-tert-butyl-α-phenylnitrone (PBN) in an appropriate solvent (e.g., benzene). Analysis in our laboratory showed that free radicals from spin-trapped samples quantified against a standard of TEMPO in benzene displayed large differences among identical samples measured on either a Micro-Now 8300, Micro-Now 8400, or Bruker EMX EPR instrument. The Bruker instrument reported that the typical TEMPO in benzene standard had a Q-factor of ∼4400 while the Q-factor of our PBN-containing samples was ∼2500. (The Q-factor is inversely proportional to the amount of dissipated microwave energy in an EPR cavity.) By placing the TEMPO standard in a PBN/benzene solvent matrix we were able to match the Q-factor of our standards and samples, resulting in each of the three EPR instruments giving the same quantified free radical yields for the samples. This result points out the importance of matching the Q-factor between samples and standards for any quantitative EPR measurement.

Observations on the in situ detection of free radicals in leaves using electron paramagnetic resonance spectrometry

1992 ◽  
Vol 70 (1) ◽  
pp. 192-199 ◽  
Author(s):  
Victor C. Runeckles ◽  
Manivalde Vaartnou
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Free Radicals ◽  
Free Radical ◽  
Poa Pratensis ◽  
Leaf Tissue ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic Resonance Spectrometry ◽  
Intact Leaf ◽  
Electron Paramagnetic

To follow in situ changes in free radicals in leaves subjected to changes in the composition of the surrounding air, a system has been developed for obtaining X-band (9 GHz) electron paramagnetic resonance (EPR) spectra of intact leaf tissue over extended periods. Studies with radish (Raphanus sativus), bluegrass (Poa pratensis), and ryegrass (Lolium perenne) leaves in darkness or illuminated with 650 nm, 710 nm, or white light in the spectrometer cavity readily reveal the photosynthetic signals I and II, and signals attributable to Mn2+ and Fe3+. Detached pieces of leaf cannot be used after about 1 h in the cavity because of the appearance of a large EPR signal resulting from excision. However, attached leaves of the grasses can be maintained in a fully functioning state in the cavity for several days, or can be withdrawn and replaced at will. Plants grown in high photon influx densities were found to reveal a large free radical signal, related to photoinhibition, that masks the typical photosynthetic signals but that can usually be eliminated by subjecting the tissue to 9 GHz microwave radiation. Signal changes in response to changes in the composition of the air stream can be directly tracked over extended periods, provided that no major changes occur in the underlying Mn2+ or Fe3+ signals. Preliminary studies with the air pollutants, sulphur dioxide, and ozone have demonstrated the potential of the system for revealing changes in the photosynthetic and other EPR signals resulting from the uptake of such phytotoxic gases. Key words: free radical, electron paramagnetic resonance spectrometry, intact leaf tissue, photosystem, air pollution, stress.

scholarly journals Effect of UV Irradiation on Interactions ofα-Lipoic Acid with Free Radicals

2013 ◽  
Vol 2013 ◽  
pp. 1-5
Author(s):  
Paweł Ramos ◽  
Piotr Pepliński ◽  
Barbara Pilawa
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Free Radicals ◽  
Uv Irradiation ◽  
Lipoic Acid ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Antioxidant Properties ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Pharmacological Substance ◽  
Electron Paramagnetic

Changes of antioxidant properties ofα-lipoic acid (LA) after UV irradiation were studied. LA is the typical drug used in diabetic neuropathy. Quenching of free radicals is an important factor of therapy by using this substance.α-Lipoic acid is exposed to UV irradiation during the storage. The aim of our studies was to examine the effect of UV irradiation on the interactions of LA with free radicals. Theα-lipoic acid was irradiated by UVA 315–400 nm light during 10 to 110 minutes by intervals of 10 minutes. The electron paramagnetic resonance spectroscopy was used as the experimental technique. The antioxidant properties of LA were spectroscopically confirmed. The strong effect of UV irradiation on interactions ofα-lipoic acid with free radicals was observed. It was pointed out that interactions of LA with free radicals decrease after its exposition on UV. The interactions of LA with free radicals were higher after the sample irradiation during 10 minutes than for the samples irradiated longer (20–110 minutes). The results are important for problems connected with photomedicine; they pointed out thatα-lipoic acid should not be stored on UV exposition. Application of electron paramagnetic resonance spectroscopy to characterize interactions of pharmacological substance with free radicals was confirmed.

Electron paramagnetic resonance spectroscopy of stable free radicals in the liver compared with ultrastructural and functional damage in a rat model of alcohol- and iron-overload

1993 ◽  
Vol 84 (3) ◽  
pp. 339-348 ◽  
Author(s):  
Graham P. Butcher ◽  
Nigel Deighton ◽  
Roger M. Batt ◽  
Boliang Ding ◽  
Susan Haywood ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Free Radicals ◽  
Free Radical ◽  
Iron Overload ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Significant Difference ◽  
Electron Paramagnetic ◽  
Radical Signal

1. Electron paramagnetic resonance spectroscopy was used to study free-radical signals in freeze-clamped frozen liver tissue from rats after a 1 year period of dietary supplementation with alcohol, iron, or alcohol and iron. In alcohol-fed, iron-fed and alcohol- and iron-fed animals, mild histological damage was seen on light microscopy and evidence of mitochondrial and nuclear injury was identified by electron microscopy. 2. Subcellular fractionation studies showed an increase in the activity of the peroxisomal marker catalase (P <0.01) in alcohol-fed rats compared with controls, but a fall of 82% (P <0.001) in alcohol- and iron-fed animals. The activity of the mitochondrial marker succinate dehydrogenase rose by 7% (not significant) in alcohol-fed animals and by 17% (not significant) in iron-fed animals, but fell by 94% (P <0.001) in alcohol- and iron-fed animals, suggesting serious impairment of mitochondrial function. 3. Iron overload was substantial in the iron-fed animals and there was an excellent correlation between liver iron concentration and iron-derived signals by electron paramagnetic resonance spectroscopy (P <0.001). A clear free-radical signal of g = 2.003–2.005 was detected in all liver samples, but there was no significant difference in the magnitude of this signal in any study group. 4. The absence of any increase in the stable free-radical signal, even in the presence of considerable hepatic damage, does not support the hypothesis that free radicals mediate alcoholic liver disease in this animal model, although the results cannot be taken as proof against this hypothesis.

Investigation of Antioxidant Activity of Pomegranate Juices by Means of Electron Paramagnetic Resonance and UV-Vis Spectroscopy

2015 ◽  
Vol 98 (4) ◽  
pp. 866-870 ◽  
Author(s):  
Violetta Kozik ◽  
Krystyna Jarzembek ◽  
Agnieszka Jędrzejowska ◽  
Andrzej Bąk ◽  
Justyna Polak ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Free Radical ◽  
Epr Spectroscopy ◽  
Antioxidant Properties ◽  
Free Radical Scavenger ◽  
Pomegranate Juice ◽  
Radical Scavenger ◽  
Paramagnetic Resonance ◽  
Vis Spectroscopy ◽  
Electron Paramagnetic

Abstract Pomegranate fruit (Punica granatum L.) is a source of numerous phenolic compounds, and it contains flavonoids such as anthocyanins, anthocyanidins, cyanidins, catechins and other complexes of flavonoids, ellagitannins, and hydrolyzed tannins. Pomegranate juice shows antioxidant, antiproliferative, and anti-atherosclerotic properties. The antioxidant capacity (TEAC) of the pomegranate juices was measured using electron paramagnetic resonance (EPR) spectroscopy and 1,1-diphenyl-2-picrylhydrazyl (DPPH•) as a source of free radicals, and the total phenolic (TP) content was measured using UV-Vis spectroscopy. All the examined pomegranate juices exhibited relatively high antioxidant properties. The TEAC values determined by means of EPR spectroscopy using Trolox (TE) as a free radical scavenger were in the range of 463.12 to 1911.91 μmol TE/100 mL juice. The TP content measured by the Folin-Ciocalteu method, using gallic acid (GA) as a free radical scavenger, widely varied in the investigated pomegranate juice samples and ranged from 1673.62 to 5263.87 mg GA/1 L juice. The strongest antioxidant properties were observed with the fresh pomegranate juices obtained from the fruits originating from Israel, Lebanon, and Azerbaijan. Correlation analysis of numerical data obtained by means of EPR spectroscopy (TEAC) and UV-Vis spectroscopy (TP) gave correlation coefficient (r) = 0.90 and determination coefficient (r2) = 0.81 (P &lt;0.05).

Sign in / Sign up

Export Citation Format

Share Document