title: Photophysics and photochemistry of aflatoxins B1 and B2.
abstract: Aflatoxins are mycotoxins produced by fungi of the genus Aspergillus, which is widely spread in the tropics and subtropics. To date, aflatoxin phototoxicity has been recognized, but the mechanism responsible for this phototoxicity has not been fully characterized. In the present paper, nanosecond laser flash photolysis studies allowed us to elucidate the photochemical processes undergone by two mycotoxins, namely aflatoxin B(1) and B(2), upon UV irradiation. In brief, photolysis (308 nm) of the aflatoxins leads to intersystem crossing, giving rise to their triplet excited state. The triplet state can readily be quenched by indole and hydroquinone, and also by molecular oxygen yielding singlet oxygen (singlet oxygen quantum yields of 0.51 and 0.59 were found for aflatoxin B(1) and B(2), respectively). In addition, our data indicate the ability of the two aflatoxins to photoionize upon 248 nm excitation. The photoionization quantum yield for aflatoxin B(1) and B(2) have been estimated to be 0.11 and 0.29, respectively.
authors.affiliation: Department of Chemistry and Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada. jcnetto@:ufrrj.br
authors.forename: J C
authors.initials: JC
authors.lastname: Netto-Ferreira
authors.forename: B
authors.initials: B
authors.lastname: Heyne
authors.forename: J C
authors.initials: JC
authors.lastname: Scaiano
mesh_terms: D016604:Aflatoxin B1 / Q000737:chemistry* / Q000633:toxicity; D000348:Aflatoxins / Q000737:chemistry* / Q000633:toxicity; D001230:Aspergillus / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D006873:Hydroquinones / Q000737:chemistry; D007211:Indoles / Q000737:chemistry; D007834:Lasers; D010777:Photochemistry; D010782:Photolysis; D011789:Quantum Theory; D026082:Singlet Oxygen / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D000348:Aflatoxins; D006873:Hydroquinones; D007211:Indoles; D026082:Singlet Oxygen; C029753:aflatoxin B2; C030374:indole; D016604:Aflatoxin B1; C031927:hydroquinone