INVESTIGADORES
BORSARELLI Claudio Dario
artículos
Título:
Singlet Oxygen Quenching Ability of Carotenoids in a Reverse Micelle Membrane Mimetic System
Autor/es:
M. A. MONTENEGRO; M. A. NAZARENO; E. N. DURANTINI; C. D. BORSARELLI
Revista:
PHOTOCHEMISTRY AND PHOTOBIOLOGY
Editorial:
American Society for Photobiology
Referencias:
Año: 2002 vol. 75 p. 353 - 362
ISSN:
0031-8655
Resumen:
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The influence of the medium
heterogeneity upon the bimolecular rate constants for the physical quenching, kq, and chemical quenching, kr, of singlet molecular
oxygen O2(1Dg) by 7 natural and 3 synthetic
carotenoids with different substituent patterns was studied in a reverse
micelle system of sodium bis(2-ethylhexyl)sulfosuccinate (AOT), hexane, and
water. Since O2(1Dg)
was generated inside the water pools of the reverse micelles by
photosensitization of the water-soluble dye rose bengal (RB), and the carotenoids
are mainly located in the external hexane pseudophase, the quenching process
was interpreted using a pseudophase model for the partition of O2(1Dg) between the water pools and the organic
pseudophases. The kq
values were mainly dependent on the extent of the double-bond conjugation of
the carotenoids, as demonstrated by a good empirical relationship between log(kq,) and the energy E(S) of the longest wavelength
transition p®p* of the carotenoids.
In contrast, the kr values were almost
independent on the extent of the double-bond conjugated system and about four
orders of magnitude lower than kq.
However, in all cases, carotenoid photobleaching was observed with the
formation of various oxidation products depending on the photosensitization
time. Chromatographic and spectroscopic product analysis for the reaction
products of b-carotene with O2(1Dg) indicated the formation of the b-carotene-5,8-endoperoxide as primary oxidation
product.
