title: The use of multi-frequency EPR techniques to identify the radicals produced in irradiated beta-blockers.
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, g1 = 2.0086, g2 = 2.0059 and g3 = 2.0021 and g1 = 2.0066, g2 = 2.0044 and g3 = 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.
authors.affiliation: Laboratory of Chemical and Physicochemical Analysis of Drugs (CHAM), UCL, Avenue Mounier, 72.30, B. 1200 Bruxelles, Belgium. alix.engalytcheff@cham.ucl.ac.be
authors.forename: Alix
authors.initials: A
authors.lastname: Engalytcheff
authors.forename: Matthias
authors.initials: M
authors.lastname: Kolberg
authors.forename: Anne-Laure
authors.initials: AL
authors.lastname: Barra
authors.forename: K Kristoffer
authors.initials: KK
authors.lastname: Andersson
authors.forename: Bernard
authors.initials: B
authors.lastname: Tilquin
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000528:radiation effects*; D001262:Atenolol / Q000528:radiation effects; D004578:Electron Spin Resonance Spectroscopy / Q000295:instrumentation / Q000379:methods*; D005609:Free Radicals / Q000032:analysis*; D009248:Nadolol / Q000528:radiation effects; D011412:Propanolamines / Q000528:radiation effects; D011433:Propranolol / Q000528:radiation effects; D013696:Temperature
chemical_list: D000319:Adrenergic beta-Antagonists; D005609:Free Radicals; D011412:Propanolamines; D009248:Nadolol; D001262:Atenolol; D011433:Propranolol; C036604:esmolol