title: Singlet molecular oxygen generation and quenching by the antiglaucoma ophthalmic drugs, Timolol and Pindolol.
abstract: The dye sensitized photooxidation in water (pH 6), of the pharmaceutical topical antiglaucoma drugs, Timolol and Pindolol, which act as beta-adrenergic receptor antagonists, were studied by means of static and time-resolved spectroscopic methods and polarographic determinations. O2(1delta(g))-mediated photooxidation of Timolol and Pindolol takes place with quantum efficiencies of 0.035 and 0.16, respectively, which raises concern about the possible daylight-mediated photodamaging of the drugs, in the presence of sensitizing agents. Pindolol behaves kinetically as a typical indole derivative, for which the intermediacy of a polar complex is proposed. Solvent effects on the kinetics of photooxidation suggests that the same mechanism could operate for the case of Timolol. Upon direct ultraviolet-light irradiation Timolol and Pindolol generate O2(1delta(g)), with quantum yields of 0.027 and 0.11 respectively. The former comprises three desirable properties for an external-use ocular drug: a reduced efficiency of O2(1delta(g)) photooxidation, a relatively high power as O2(1delta(g)) physical deactivator and a relatively low propensity to O2(1delta(g)) generation upon direct light irradiation.
authors.affiliation: Dto. de Qca, y Fca. Univ. Nac de Rio Cuarto., (5800) Rio Cuarto., Argentina. scriado@exa.unrc.edu.ar
authors.forename: Susana
authors.initials: S
authors.lastname: Criado
authors.forename: Daniel
authors.initials: D
authors.lastname: Mártire
authors.forename: Patricia
authors.initials: P
authors.lastname: Allegretti
authors.forename: Jorge
authors.initials: J
authors.lastname: Furlong
authors.forename: Sonia G
authors.initials: SG
authors.lastname: Bertolotti
authors.forename: Eduardo
authors.initials: E
authors.lastname: La Falce
authors.forename: Norman A
authors.initials: NA
authors.lastname: García
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000737:chemistry / Q000528:radiation effects*; D000818:Animals; D005901:Glaucoma / Q000188:drug therapy; D006801:Humans; D007700:Kinetics; D008027:Light; D010782:Photolysis; D017319:Photosensitizing Agents; D010869:Pindolol / Q000737:chemistry* / Q000528:radiation effects; D026082:Singlet Oxygen / Q000737:chemistry*; D013999:Timolol / Q000737:chemistry / Q000528:radiation effects*
chemical_list: D000319:Adrenergic beta-Antagonists; D017319:Photosensitizing Agents; D026082:Singlet Oxygen; D013999:Timolol; D010869:Pindolol