E. Oliveros et al., QUENCHING OF SINGLET OXYGEN (1-DELTA-G) BY CAROTENOID DERIVATIVES - KINETIC-ANALYSIS BY NEAR-INFRARED LUMINESCENCE, New journal of chemistry, 18(4), 1994, pp. 535-539
We have evaluated the efficiency of singlet oxygen (O2 (1DELTA(g)) que
nching by a series of carotenoid derivatives. The rate constants of si
nglet oxygen quenching (k(q)) have been determined by monitoring the n
ear-infrared (1 270 nm) luminescence of singlet oxygen, produced by ph
otosensitization upon continuous excitation of the sensitizer. The kin
etic analysis of the results shows that, with values of k(q) higher th
an 10(10) L mol-1 s-1. rhodoxanthin, zeaxanthin and lutein in benzene
quench singlet oxygen almost as efficiently as beta, beta-carotene and
canthaxanthin. Substituents on the ring systems of the carotenoids (h
ydroxyl, phenylseleno, oxime or sulfate groups) seem to have little in
fluence on the quenching rate constants. In fact, the potential increa
se of k(q) resulting from favorable electronic factors may be compensa
ted by aggregation effects due to a decrease of solubility of the caro
tenoid.