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

doi:10.1016/S1011-1344(00)00102-0

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 journal › Article › peer-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 language	English
Pages (from-to)	1-5
Number of pages	5
Journal	Journal of Photochemistry and Photobiology B: Biology
Volume	58
Issue number	1
DOIs	https://doi.org/10.1016/S1011-1344(00)00102-0
Publication status	Published - 2000
Externally published	Yes

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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10.1016/S1011-1344(00)00102-0

Cite this

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title = "Involvement of type I and type II mechanisms in the linoleic acid peroxidation photosensitized by tiaprofenic acid",

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.",

keywords = "Benzophenone, Benzoylthiophene, Hydroperoxides, Ketyl radical, Linoleic acid, Photochemistry, Photoperoxidation, Photoxicity, Singlet oxygen, Triplet",

author = "Francisco Bosc{\'a} and Miranda, {Miguel A.} and Morera, {Isabel M.} and Abdelouahid Samadi",

note = "Funding Information: Financial support from Generalitat Valenciana (grant GV.DOC98-VS-24-2) and European Union (grant BMH-4-97-2590) is gratefully acknowledged.",

year = "2000",

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language = "English",

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T1 - Involvement of type I and type II mechanisms in the linoleic acid peroxidation photosensitized by tiaprofenic acid

AU - Boscá, Francisco

AU - Miranda, Miguel A.

AU - Morera, Isabel M.

AU - Samadi, Abdelouahid

N1 - Funding Information: Financial support from Generalitat Valenciana (grant GV.DOC98-VS-24-2) and European Union (grant BMH-4-97-2590) is gratefully acknowledged.

PY - 2000

Y1 - 2000

N2 - 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.

AB - 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.

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KW - Triplet

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

Abstract

Keywords

ASJC Scopus subject areas

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