Electron-Spin-Resonance Studies of DPPH Solutions

Abstract

The effects of impurities on the ESR of DPPH in various solutions were studied. The broad quintet spectrum usually obtained with DPPH solutions becomes well resolved after dissolved gases are removed. Addition of tertiary hydroperoxides to DPPH solutions gives a triplet spectrum, which further splits into 17 lines after subsequent degassing in the case of t-butyl hydroperoxide. From an analysis of this spectrum, a determination was made of the spin-density distribution of the unpaired electron in a species electronically analogous to biphenylaminium ion. An aerated DPPH solution of xylene loses its paramagnetic nature in time, but regeneration of the quintet ESR spectrum of DPPH is observed if this solution is mixed with the so-called lophine-x compound solution kept in the dark, and then irradiated by sunlight. The interpretation of this phenomenon is that the lophine-x compound, when irradiated by sunlight, has an odd electron which shifts onto the nonparamagnetic DPPH—O2 reaction product regenerating DPPH as a result. This is, therefore, a radical transfer reaction and is one of the few chemical reactions giving evidence for the radical nature of the lopine-x compound when photochemically excited.

Radioprotection of thymine and calf thymus DNA by an azo compound: mechanism of action followed by DPPH radical quenching & ROS depletion in WI 38 lung fibroblast cells

“…Owing to the presence of an odd electron, DPPH shows a strong absorption band at 517 nm. This gradually decreases if the odd electron pairs up in the presence of a radical scavenger, which was followed during the course of the experiment [21,22,23]. There are not many studies that indicate interaction of an azo compound with DPPH, not to mention any that aims to establish an application where an azo compound by virtue of its attribute of quenching DPPH might become biologically useful [32].…”

“…The EPR signal of DPPH was used to monitor the free radical scavenging activity of HPIA [21,22,23,42,43,44]. Figure 7, shows for the same initial concentration of DPPH, increasing concentrations of HPIA lead to gradual decrease in its EPR response suggesting that with an increase in concentration of HPIA, a substantial amount of DPPH radical was no more present.…”

“…Thymine and calf thymus DNA were used as biological targets in model studies where they were irradiated in the absence and presence of HPIA by 60 Co γ-rays in de-aerated (Ar saturated) and N 2 O saturated medium. To establish the mechanism by which radio-protection by HPIA is possible, radical scavenging experiments were designed and performed in the presence of the stable radical DPPH [21,22,23]. To further establish if radio-protection of a biological target was due to scavenging of free radicals within cells, 2‛,7‛-dichlorofluorescin diacetate (DCF-DA) ROS depletion assay was performed on WI-38 lung fibroblast cells [24,25,26,27,28].…”

Detection of L-band electron paramagnetic resonance in the DPPH molecule using impedance measurements

“…As a stable and well-characterized solid radical source, DPPH is the most popular reference sample with Landé g-factor of 2.0036. 22 The intensity of EPR signals depends on the number of radicals for a freshly prepared sample and can be determined by weighing the DPPH sample. DPPH exhibits a single response line in X-band with a small linewidth $1.5-4.7 Oe due to the presence of only one unpaired spin per 41 atoms.…”

Non-reductive Scavenging of 1,1-Diphenyl-2-picrylhydrazyl (DPPH) by Peroxyradical: A Useful Method for Quantitative Analysis of Peroxyradical

“…1. Besides DPPH-scavenging by reductive hydrogen transfer between various donors and DPPH, non-reductive DPPH-decomposing and -scavenging were found to be induced by reacting with tertiary hydroperoxides 6) and by radical-binding at the para position in the phenyl rings of DPPH, 7) respectively.…”