Involvement of type I and type II mechanisms in the linoleic acid peroxidation photosensitized by tiaprofenic acid

Francisco Boscá, Miguel A. Miranda, Isabel M. Morera, Abdelouahid Samadi

Research output: Contribution to journalArticlepeer-review

20 Citations (Scopus)

Abstract

Analysis of the photomixtures resulting from irradiation of aqueous solutions of linoleic acid sensitized by tiaprofenic acid (TPA) or its major photoproduct (DTPA) by HPLC has shown the formation of all the four possible conjugated dienic hydroperoxides. According to laser flash photolysis experiments the rate constants for hydrogen abstraction from linoleic acid by the excited triplet states of TPA and DTPA are 2x105 and 3.2x105 M-1 s-1, respectively. These data, together with the known rate constants for oxygen quenching of triplet (D)TPA and for the reaction of singlet oxygen with linoleic acid, show that the mechanism is mixed type I/type II. Finally, typical radical scavengers such as BHA and singlet oxygen quenchers such as DABCO and sodium azide are efficient quenchers of the triplet excited state of DTPA. This shows the risk of assigning mechanisms based on indirect 'evidences' using 'specific' additives. (C) 2000 Elsevier Science B.V. All rights reserved.

Original languageEnglish
Pages (from-to)1-5
Number of pages5
JournalJournal of Photochemistry and Photobiology B: Biology
Volume58
Issue number1
DOIs
Publication statusPublished - 2000
Externally publishedYes

Keywords

  • Benzophenone
  • Benzoylthiophene
  • Hydroperoxides
  • Ketyl radical
  • Linoleic acid
  • Photochemistry
  • Photoperoxidation
  • Photoxicity
  • Singlet oxygen
  • Triplet

ASJC Scopus subject areas

  • Radiation
  • Radiological and Ultrasound Technology
  • Biophysics
  • Radiology Nuclear Medicine and imaging

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