PubMed Health⌕ Search

Biomedical subjects

L A Martínez

Publications and source records attributed to L A Martínez.

6 recordsLinked to original sources
PubMed2001

Mechanism of lipid peroxidation photosensitized by tiaprofenic acid: product studies using linoleic acid and 1,4-cyclohexadienes as model substrates.

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-dienecarboxylic acid (CHDCA) have also been used as models for LA since they also have double allylic systems. Coirradiation 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.

Carboxylic Acids↗
PubMed1998

Effect of the microenvironment on the efficiency of singlet oxygen (O2(1 delta g)) production by photosensitizing anti-inflammatory drugs.

The influence of the medium on the quantum yields of singlet oxygen (O2(1 delta g)) production (phi delta) by a series of photosensitizing non-steroidal anti-inflammatory drugs (NSAID) derived from 2-arylpropionic acid (APA) has been investigated. Four-component oil-in-water and water-in-oil microemulsions, based on anionic and cationic surfactants, have been employed as the simplest models to mimic more complex biological environments. phi delta values have been determined by monitoring the singlet oxygen (1O2) luminescence at 1270 nm upon continuous excitation of the drugs under air-equilibrated conditions. Results indicate that phi delta values are highly affected by the medium, being higher in microheterogeneous systems than in (homogeneous) solution. Some of the anti-inflammatory derivatives are very efficient 1O2 sensitizers: e.g., values of apparent phi delta as high as 0.86 (+/- 0.04) and 0.70 (+/- 0.03) have been found for tiaprofenic acid and suprofen, respectively. The location of the drugs in the interfacial region of the microemulsions combined with their high phi delta values suggest that type II reactions may play a significant role in the overall photodynamic process in more complex organized media, such as biological membranes.

Absorption↗
PubMed1992

Inhibition of nonenzymic lipid peroxidation by benzylisoquinoline alkaloids.

A group of benzylisoquinoline alkaloids, including five simple benzylisoquinolines, three phtalideisoquinolines, six aporphines, three protoberberines, and two benzophenanthridines, have been studied as inhibitors of lipid peroxidation stimulated by Fe2+/cysteine in rat liver microsomal fractions. Protopapaverine, apomorphine, laudanosoline, tetrahydroberberine, isoboldine, bulbocapnine, boldine, anonaine, glaucine, and stepholidine showed antiperoxidative effects, and structure-activity relationships were established. In simple benzylisoquinolines, the presence of phenolic hydroxyls or similar reactive groups is necessary for inhibition of peroxidation, while in aporphines and protoberberines nonhydroxylated compounds can exert antiperoxidative effects. The phtalideisoquinolines and benzophenanthridines tested were inactive.

Alkaloids↗