The potential pitfalls of using 1,1-diphenyl-2-picrylhydrazyl to characterize antioxidants in mixed water solvents.

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.

Monomerization of photosensitizers by ultrasound irradiation in surfactant micellar solutions.

The absorption and fluorescence properties of pheophorbide-a, Sodium salt of pheophorbide-a and its long chain (C20H39) ester (Pheophytine) were investigated in air-saturated micellar aqueous solutions before and after ultrasound irradiation (48 kHz, 10 min). The absorption spectra changed depending on the surfactant; cetyltrimethyl ammonium bromide (CTAB) or sodium dodecyl sulfate concentrations. The formation of different molecular species in various micellar solutions was estimated from the analysis of the absorption spectra.

Free radical intermediates in sonodynamic therapy.

Current understanding of the mechanism of sonodynamic action (i.e. the ultrasound-dependent enhancement of the cytotoxic action of certain drugs--sonosensitizers) with potential applications for cancer therapy is presented.

EPR spectroscopy of free radical intermediates of antiarrhythmic-antihypoxic drug stobadine, a pyridoindole derivative.

Mechanisms of antioxidant action of stobadine, a pyridoindole derivative with cardioprotective and antihypoxic properties, has been probed using EPR spectroscopy. Oxidation of stobadine by PbO2/tBuOOH in benzene results in the formation of nitroxide radical observable directly by EPR spectroscopy at room temperature, indicating conversion of indolic amino group to the corresponding nitroxide.

Effects of cysteamine and cystamine on the sonochemical accumulation of hydrogen peroxide--implications for their mechanisms of action in ultrasound-exposed cells.

Based on the observed cytoprotective effect of the intracellularly permeable radical scavenger cysteamine (+NH3CH2CH2SH) in cells exposed to ultrasound and the lack of protection by its oxidized cell-nonpermeable form, cystamine (+NH3CH2CH2S-SCH2CH2NH3+), it was suggested that inertial cavitation (the growth of small gas bubbles present in the liquid exposed to ultrasound and their subsequent violent collapse) and associated free radical production may occur intracellularly (Radiat. Res. 89:369; 1982).