The effects of derivatives of the nitroxide tempol on UVA-mediated in vitro lipid and protein oxidation.
Derivatives of tetramethylpiperidines are extensively employed in polymers to prevent photooxidation, and their stabilizing effect is attributed to the activity of the nitroxide radical derived from the parent amine. In this study, we examined the photoprotective effect of a commercial polymer photostabilizer, HALS-1, its corresponding nitroxide, bis(2,2,6,6-tetramethyl-piperidine-1-oxyl-4-yl)sebacate (TINO), and two derivatives of the piperidine nitroxide TEMPOL, 2,2,6,6-tetramethyl-piperidin-4-acetyloxy-1-oxyl (TEMP2) and 2,2,6,6-tetramethyl-piperidin-4-octanoyloxy-1-oxyl (TEMP8) synthesized by us, in liposomes exposed to ultraviolet A (UVA) radiation. For comparison, the UVA-absorber, 4-tert-butyl-4'-methoxydibenzoylmethane (Parsol 1789) used in many suncream formulations, was also included. The nitroxide TINO resulted extremely efficient at inhibiting aldehydic breakdown products deriving from 30 min exposure of liposomes to UVA and the protection was dose-dependent (10-100 microM). The corresponding amine HALS-1 was the least efficient while protection increased in the order: TEMP2 < Parsol 1789 < TEMP 8. HALS-1, TINO, and the two TEMPOL derivatives were also tested in a simple protein system consisting of bovine serum albumin (BSA) exposed to UVA. In this case, these compounds did not inhibit nor enhance UVA-mediated protein carbonyl formation in BSA. The differences in protection between the compounds are discussed in relation to their chemical reactivity, UVA-absorbing capacities, and their molecular structure. Overall, the results obtained envisage the potential use of nitroxide compounds as topical antioxidants.
Damiani
Elisabetta
E
Dipartimento di Scienze dei Materiali e della Terra, Università di Ancona, Ancona, Italy. liz@unian.it
Castagna
Riccardo
R
Greci
Lucedio
L
D000818:Animals; D001565:Benzoates / Q000494:pharmacology; D002417:Cattle; D047188:Chalcones; D003497:Cyclic N-Oxides / Q000494:pharmacology*; D003652:Decanoic Acids / Q000494:pharmacology; D004357:Drug Synergism; D005609:Free Radicals; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D008081:Liposomes; D009589:Nitrogen Oxides / Q000494:pharmacology*; D010084:Oxidation-Reduction; D010880:Piperidines / Q000494:pharmacology; D011427:Propiophenones; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D012710:Serum Albumin, Bovine / Q000187:drug effects / Q000528:radiation effects; D013113:Spin Labels; D014466:Ultraviolet Rays
D001565:Benzoates; D047188:Chalcones; D003497:Cyclic N-Oxides; D003652:Decanoic Acids; D005609:Free Radicals; D008055:Lipids; D008081:Liposomes; D009589:Nitrogen Oxides; D010880:Piperidines; D011427:Propiophenones; D011506:Proteins; D011837:Radiation-Protective Agents; D013113:Spin Labels; D012710:Serum Albumin, Bovine; C083752:Tinuvin 770; C049935:avobenzone; C001803:tempol