TY - JOUR
T1 - Mechanism of lipid peroxidation photosensitized by tiaprofenic acid
T2 - Product studies using linoleic acid and 1,4-Cyclohexadienes as model substrates
AU - Samadi, Abdelouahid
AU - Martínez, Luis A.
AU - Miranda, Miguel A.
AU - Morera, Isabel M.
PY - 2001/4/1
Y1 - 2001/4/1
N2 - A careful study of the linoleic acid hydroperoxide (LOOH) profile obtained upon peroxidation of linoleic acid (LA) photosensitized by tiaprofenic acid (TPA) and analogous ketones has been undertaken to distinguish between type-I and type-II photoperoxidation mechanisms. 1,4-Cyclohexadiene and 1,2-dimethylcyclohexa-2,5-diene-carboxylic acid (CHDCA) have also been used as models for LA since they also have double allylic systems. Coir-radiation of LA with TPA and decarboxytiaprofenic acid (DTPA) in acetonitrile and micellar media produced significant amounts of conjugated dienic LOOH. The cis,trans to trans,trans ratio depended on the irradiation time; thus, this parameter is an ambiguous tool for mechanistic assignment. An interesting finding was the decrease of the LOOH level after long irradiation times in mixtures photooxidized by DTPA, which is attributed to quenching of the DTPA triplet by the generated dienic LOOH. High-performance liquid chromatography analyses confirmed that the main pathway operating in photodynamic lipid peroxidation sensitized by (D)TPA is a type-I mechanism. However, product studies using CHDCA have clearly shown that a type-II mechanism is also operating and might contribute to the overall photooxidation process in a significant way.
AB - A careful study of the linoleic acid hydroperoxide (LOOH) profile obtained upon peroxidation of linoleic acid (LA) photosensitized by tiaprofenic acid (TPA) and analogous ketones has been undertaken to distinguish between type-I and type-II photoperoxidation mechanisms. 1,4-Cyclohexadiene and 1,2-dimethylcyclohexa-2,5-diene-carboxylic acid (CHDCA) have also been used as models for LA since they also have double allylic systems. Coir-radiation of LA with TPA and decarboxytiaprofenic acid (DTPA) in acetonitrile and micellar media produced significant amounts of conjugated dienic LOOH. The cis,trans to trans,trans ratio depended on the irradiation time; thus, this parameter is an ambiguous tool for mechanistic assignment. An interesting finding was the decrease of the LOOH level after long irradiation times in mixtures photooxidized by DTPA, which is attributed to quenching of the DTPA triplet by the generated dienic LOOH. High-performance liquid chromatography analyses confirmed that the main pathway operating in photodynamic lipid peroxidation sensitized by (D)TPA is a type-I mechanism. However, product studies using CHDCA have clearly shown that a type-II mechanism is also operating and might contribute to the overall photooxidation process in a significant way.
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U2 - 10.1562/0031-8655(2001)073<0359:MOLPPB>2.0.CO;2
DO - 10.1562/0031-8655(2001)073<0359:MOLPPB>2.0.CO;2
M3 - Article
C2 - 11332030
AN - SCOPUS:0035324314
SN - 0031-8655
VL - 73
SP - 359
EP - 365
JO - Photochemistry and Photobiology
JF - Photochemistry and Photobiology
IS - 4
ER -