The use of multi-frequency EPR techniques to identify the radicals produced in irradiated beta-blockers
(2004) Free Radical Research — Vol. 38, n° 1, p. 59-66 (2004)
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- Abstract
- The identification of radicals trapped in irradiated drugs can be very intricate. A multi-frequency electron paramagnetic resonance (EPR) study is proposed to resolve this problem. The Q-band (ca. 34 GHz) comparison with X-band (ca. 9 GHz) did not show significant differences for the four beta-blockers studied (atenolol, esmolol, nadolol and propranolol). The use of a higher frequency (285 GHz) was required. It enabled us to determine the g -tensor values of the radicals present in atenolol and esmolol, respectively, g(1) = 2.0086, g(2) = 2.0059 and g(3) = 2.0021 and g(1) = 2.0066, g(2) = 2.0044 and g(3) = 2.0021. The latter was assigned as a phenoxyl radical, which can not be the case for the former. Therefore, radicals produced in esmolol may result from a more complex mechanism than the abstraction followed by the diffusion of an H atom inside the solid. In addition, two molecules as similar as atenolol and esmolol hydrochloride do not contain the same radicals after irradiation. These two conclusions drawn from the EPR results on beta-blockers show clearly the importance of continuing the investigations on radiolytic mechanisms in solid-state drugs.
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Engalytcheff, A., Kolberg, M., Barra, A.-L., Andersson, K. K., & Tilquin, B. (2004). The use of multi-frequency EPR techniques to identify the radicals produced in irradiated beta-blockers. Free Radical Research, 38(1), 59-66. https://doi.org/10.1080/1071576310001634672 (Original work published 2004)