Hydrogen Abstraction From Lipids by Triplet States of Derivatized Benzophenone Photosensitizers

Abstract

Laser photolysis techniques have been used to characterize the reactivity of triplet state lipoidal benzophenone derivatives toward fatty acids and glycerides in benzene solution. The reactivities of benzophenone-4-heptyl-4'-pentanoic acid (BHPA) toward fatty acid compounds having different configurations of olefinic bonds have been determined. The rates of hydrogen abstraction are found to be lower when compared with similar measurements using benzophenone alone. However, the contribution of physical quenching of the triplet derivative by double bonds also appears to be slightly lower than that found with benzophenone itself. The hydrogen abstraction efficiencies of three other benzophenone derivatives toward linoleic acid in benzene have also been measured. For benzophenone incorporated into a fatty acid molecule, there is a limited relationship between structure and photoreactivity. Finally, these sensitizers have been incorporated into mixed SDS/linoleate micelles to determine the effects of molecular organization on photochemical behavior of the sensitizer and lipid.

Lycopene control of benzophenone-sensitized lipid peroxidation

“…This selectivity of BZP itself and lipoidal BZP derivatives has been already demonstrated toward series of pure, unsaturated fatty acids with rising number of double bonds in benzene solution [12,13].…”

“…A choice of benzophenone as the sensitizer in this study is led by its most known organic photochemistry reaction, H abstraction by its long lived triplet state (3BZP) [12][13][14][15][16][17]. Of course, photochemistry of benzophenone and BZP related compounds is very complex and depends in homogeneous solution on particular sol vent [18][19][20], or on particular BZP interactive com pound in the given solvent [21,22].…”

“…Among the other ways they can be created through a variety of external stresses [6], implying very commonly an external radi ation [10,11], which, in case of UV irradiation may include a special type of LP initiators, photosensitizes [4], in very different media [12][13][14].…”

New Photosafety Assessment Strategy Based on the Photochemical and Pharmacokinetic Properties of Both Parent Chemicals and Metabolites

“…In addition, enhanced superoxide generation could be observed after preincubation of FF with active rat hepatic S9 fractions compared with the denatured group. Benzophenones including FF and FA can elicit lipid peroxidation, a major mechanism of photoirritation, via type I photochemical reactions after photoexcitation (Markovic et al, 1990). In this context, FA might be a major contributor to FFinduced phototoxicity after metabolism of FF.…”

Radical-mediated dehydrogenation of bile acids by means of hydrogen atom transfer to triplet carbonyls

“…3), have been chosen because they can be efficiently generated upon selective UVA-excitation and have reactive nπ* electronic configuration. In fact, they are known to act as formal biradicals, mediating H-abstraction from allylic positions in polyunsaturated fatty acids 17,18 and cholesterol, 19,20 a key step in type I lipid peroxidation. In spite of the intensive efforts devoted to developing alcohol oxidation methodologies, the photochemical dehydrogenation for synthetic purposes remains almost unexplored, and the reported examples are essentially restricted to benzyl alcohols.…”