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Differentiation between phenol- and amino-substances in voltammetry determination of synthetic antioxidants in oils

100%
Chýlková J., Šelešovská R., Machalíková J., Dušek L.
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EN
The paper describes a method of voltammetric determination of antioxidants in lubricating oils developed with the use of Linear Sweep Voltammetry (LSV) and Fast Scan Differential Pulse Voltammetry (FSDPV). Experimental conditions have been found for simultaneous determination of phenol-based antioxidants and amino-antioxidants: the phenols can be electrochemically oxidized using the polarisation of gold disc electrode (AuDE) in the potential range of 0–1400 mV in 0.2 M H2SO4 in the presence of ethanol and acetonitrile at the ratio of 3:1. Secondary aromatic amines can be determined directly in this supporting electrolyte; the presence of phenolic antioxidants does not interfere with this analysis. On the other hand, secondary aromatic amines interfere with the determination of phenolic substances; therefore, the amines present have to be eliminated in a suitable way. A procedure for masking the aromatic amines using their reaction with nitrous acid has been suggested and optimised. The nitrosamines thus formed can be used for sensitive and selective determination of amino-antioxidants by means of cathodic reduction on the hanging mercury drop electrode (HMDE) using Fast Scan Differential Pulse Voltammetry. The method was applied in analysis of real samples of lubricating oils. [...]
2
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New evidence for vascular interactions between aldosterone, angiotensin II and antioxidants in isolated smooth muscle cells of rats

88%
Popescu R., Bild W., Ciobica A., Bild V.
Open Medicine
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2012
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vol. 7
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issue 6
704-712
EN
Accumulating evidence suggests that the nongenomic cardiovascular actions of aldosterone are produced by varied cellular pathways and mediated by a multitude of messenger systems including the reactive oxygen and nitrogen species. Considering the involvement of the oxidative and nitrosative stress in the pathways leading to the activation of the angiotensin - aldosterone system, in the current study we tried to evaluate the functional interactions between aldosterone, angiotensin II and antioxidants in isolated vascular smooth muscle of aortic rings from rats. Our data provide additional arguments that the nongenomic actions of aldosterone on aortic smooth muscle cells of rats are a question of cross-talk and balance between its rapid vasoconstrictor and vasodilator effects, as result of the activation of reactive oxygen species in the first case and of nitrogen species in the second. In this way, it seems that at low ambient oxidative stress, aldosterone promotes nitric oxide (NO) production and vasodilatation, while in situations with increased oxidative stress the endothelial dysfunction and detrimental effects induced by vasoconstriction will prevail. Thus, aldosterone could be considered both “friend and foe”. This could be relevant for the ways in which aldosterone damages cardiovascular functions and could lead to significant therapeutic improvements.
3
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Comparison of pressurised fluid and ultrasonic extraction methods for analysis of plant antioxidants and their antioxidant capacity

88%
Dobiáš P., Pavlíková P., Adam M., Eisner A., Beňová B., Ventura K.
Open Chemistry
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2010
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vol. 8
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issue 1
87-95
EN
The analytical method based on the high-performance liquid chromatography coupled with UV detection (HPLC/UV) for determination of selected antioxidants (i.e., esculetin, scopoletin, 7-hydroxycoumarine, rutin, xanthotoxin, 5-methoxypsoralen and quercetin) in plant material was developed. Pressurised fluid extraction (PFE) and ultrasonic extraction (USE) methods for the isolation of these compounds from ten real plant samples were used. Both extraction methods were optimised and compared to each other. For the proposed HPLC/UV method the LOQ values (limit of quantification) in the range from 22.7 (xanthotoxin) to 97.2 ng mL−1 (rutin) were obtained. For all extracts the antioxidant capacity based on the reduction of free 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) was also determined. Results ranged from 82.04 to 94.43% of DPPH radical inhibition for PFE method and from 76.01 to 89.94% in the case of USE method. [...]
4
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Determination and correlation of physicochemical properties of aqueous extracts from edible portions of common tropical fruits

63%
Ejiako E. J., Ngozi V. E., Ebele M. S., Wirnkor V. A., Ehirim F.
World News of Natural Sciences
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2023
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vol. 47
104-114
EN
The quantity and quality of these constituent may not usually be the same under certain conditions, so fruits sold in Owerri where heavy pollutant abound were analysed, three samples of each water melon, Pawpaw, pineapple and orange fruits were bought from Owerri commercial centre and their juices extracted and stored in screw cap bottles prior to analysis. The physiochemical parameters revealed that fruits were of good quality but showed positive and negative significant relationship correlation ships such as pH-FW (0.958), pH-SG (-0.025), TS-MC (-0.999), TA-FW (-0.987). Vitamin C content ranged from 13.14 ± 0.39 mg/100g to 75.46 ±1.72 mg/100g for water melon and orange respectively. In conclusion, fruits studied showed good quality and a good source of vitamin C and mineral content. Such analysis needs to be carried out periodically to ensure quality and create awareness to the public.
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