Abstract:
:Approaching living systems, aqueous solutions are appropriate to characterize antioxidants, whereas the frequently used standard 1,1-diphenyl-2-picrylhydrazyl (DPPH) is insoluble in water. Therefore, mixed water-ethanol solvents were investigated using the electron paramagnetic resonance (EPR) spectroscopy. Two forms of DPPH were identified: at higher ethanol ratios a quintet spectrum characteristic of solutions, and at lower ratios, a singlet spectrum typical for solid DPPH, were found. Mixed solvents with 0-50% (v/v) water reproduced the same antioxidant equivalent points well and the reaction rate between DPPH and the antioxidant may increase considerably with increasing water ratios, as demonstrated using vitamin E as an antioxidant. But at still higher water ratios (70-90% (v/v)) the antioxidant activities dropped, since a part of the DPPH in the aggregated form does not react sufficiently with the antioxidants. Characteristics of the most common antioxidants were determined in ethanol or its 50% (v/v) aqueous solution.
journal_name
Free Radic Resjournal_title
Free radical researchauthors
Stasko A,Brezová V,Biskupic S,Misík Vdoi
10.1080/10715760600930014subject
Has Abstractpub_date
2007-04-01 00:00:00pages
379-90issue
4eissn
1071-5762issn
1029-2470pii
773542917journal_volume
41pub_type
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