title: Photophysical and photobiological behavior of antimalarial drugs in aqueous solutions.
abstract: This article describes the results of a combined photophysical and photobiological study aimed at understanding the phototoxicity mechanism of the antimalarial drugs quinine (Q), quinacrine (QC) and mefloquine (MQ). Photophysical experiments were carried out in aqueous solutions by stationary and time-resolved fluorimetry and by laser flash photolysis to obtain information on the various decay pathways of the excited states of the drugs and on transient species formed on irradiation. The results obtained showed that fluorescence and intersystem crossing account for all the adsorbed quanta for Q and MQ (quantum yield of about 0.1 and 0.9, respectively) and only for 24% in the case of QC, which has a negligible fluorescence quantum yield (0.001). Laser flash photolysis experiments evidenced, for QC and MQ, the occurrence of photoionization processes leading to the formation of the radical cations of the drugs. The effects of tryptophan and histidine on the excited states and transient species of the three drugs were also investigated. In parallel, the photoactivity of the antimalarial drugs was investigated under UV irradiation on various biological targets through a series of in vitro assays in the presence and in the absence of oxygen. Phototoxicity on 3T3 cultured fibroblasts and lipid photoperoxidation were observed for all the drugs. The photodamage produced by the drugs was also evaluated on proteins by measuring the photosensitized cross-linking of spectrin. The combined approaches were proven to be useful for understanding the mechanism of phototoxicity induced by the antimalarial drugs.
authors.affiliation: Laboratorio di Chimica Fisica, Dipartimento di Chimica, Università di Perugia, Perugia, Italy. aloisi@unipg.it
authors.forename: Gian Gaetano
authors.initials: GG
authors.lastname: Aloisi
authors.forename: Arianna
authors.initials: A
authors.lastname: Barbafina
authors.forename: Marcella
authors.initials: M
authors.lastname: Canton
authors.forename: Francesco
authors.initials: F
authors.lastname: Dall'Acqua
authors.forename: Fausto
authors.initials: F
authors.lastname: Elisei
authors.forename: Laura
authors.initials: L
authors.lastname: Facciolo
authors.forename: Loredana
authors.initials: L
authors.lastname: Latterini
authors.forename: Giampietro
authors.initials: G
authors.lastname: Viola
mesh_terms: D016475:3T3 Cells / Q000187:drug effects / Q000528:radiation effects; D000818:Animals; D000962:Antimalarials / Q000737:chemistry* / Q000528:radiation effects / Q000633:toxicity; D002470:Cell Survival; D004249:DNA Damage; D005609:Free Radicals; D006639:Histidine / Q000737:chemistry; D007834:Lasers; D015767:Mefloquine / Q000737:chemistry* / Q000528:radiation effects / Q000633:toxicity; D008563:Membrane Lipids / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry; D051379:Mice; D018462:Photobiology; D010777:Photochemistry; D010782:Photolysis; D011796:Quinacrine / Q000737:chemistry* / Q000528:radiation effects / Q000633:toxicity; D011803:Quinine / Q000737:chemistry* / Q000528:radiation effects / Q000633:toxicity; D013050:Spectrometry, Fluorescence; D014364:Tryptophan / Q000737:chemistry; D014466:Ultraviolet Rays
chemical_list: D000962:Antimalarials; D005609:Free Radicals; D008563:Membrane Lipids; D008565:Membrane Proteins; D006639:Histidine; D014364:Tryptophan; D011803:Quinine; D011796:Quinacrine; D015767:Mefloquine