Singlet Oxygen Quenching Abilities of Carotenoids

✍ Scribed by Baltschun, Dietmar ;Beutner, Stefan ;Briviba, Karlis ;Martin, Hans-Dieter ;Paust, Joachim ;Peters, Manfred ;Röver, Stephan ;Sies, Helmut ;Stahl, Wilhelm ;Steigel, Alois ;Stenhorst, Frank

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 773 KB
• Volume: 1997
• Category: Article
• ISSN: 0947-3440
• DOI: 10.1002/jlac.199719970913

✦ Synopsis

Abstract

The bimolecular rate constants k~q~ for quenching of singlet oxygen (^1^Δ~g~ state) by 26 different natural and novel synthetic carotenoids were determined at 37 °C in a mixture of chloroform and ethanol. The steady‐state technique used involves the generation of ^1^O~2~ by thermal decomposition of disodium 3,3′‐naphtalene‐1,4‐diyl‐dipropionate endoperoxide (NDPO~2~) and the detection of its luminescence intensity at 1270 nm. Excitation energies (π,π*, 1^1^Ag → 1^1^B~u~) and absorption maxima (430–590 nm) vary in the broadest range. Deeply coloured blue carotenoids are also included in the studies for the first time. An empirical correlation between the π,π* (1^1^A~g~ → 1^1^B~u~) excitation energy and carotenoid structure (effective chain length N~eff~) was found: E(S) = 12642 cm^−1^ + 92027 cm^−1^ × 1/N~eff~. The quenching ability of the investigated carotenoids depends on the excitation energy of their transition at long wavelengths in a characteristic way showing as limiting factors either the thermal Arrhenius activation or the diffusion‐controlled rate. This dependence and the suspected relationship between singlet E(S) and triplet E(T) energies, respectively, are discussed.