Kinetic study of the quenching reaction of singlet oxygen by carotenoids and food extracts in solution. Development of a singlet oxygen absorption capacity (SOAC) assay method.
A kinetic study of the quenching reaction of singlet oxygen (1O2) with eight kinds of carotenoids and α-tocopherol was performed in ethanol/chloroform/D2O (50:50:1, v/v/v) solution at 35 °C. The overall rate constants, kQ (=kq+kr, physical quenching+chemical reaction), for the reaction of carotenoids with 1O2 were measured, using the competition reaction method, where endoperoxide was used as a singlet oxygen generator, 2,5-diphenyl-3,4-benzofuran (DPBF) as an UV-vis absorption prove, and α-tocopherol as a standard compound. The rate constants, kQ (S) and kQ (t1/2), were determined by analyzing the first-order rate constant (S) and the half-life (t1/2) of the decay curve of DPBF with carotenoids, respectively, showing good accordance with each other. Similar measurements were performed for tomato and carrot extracts. From the results, a new assay method that can quantify the singlet oxygen absorption capacity (SOAC) of antioxidants, including carotenoids, α-tocopherol, and vegetable extracts, has been proposed.
Ouchi
Aya
A
Department of Chemistry, Faculty of Science, Ehime University, Matsuyama 790-8577, Japan.
Aizawa
Koichi
K
Iwasaki
Yuko
Y
Inakuma
Takahiro
T
Terao
Junji
J
Nagaoka
Shin-ichi
S
Mukai
Kazuo
K
D000975:Antioxidants / Q000032:analysis / Q000737:chemistry; D002338:Carotenoids / Q000737:chemistry*; D018552:Daucus carota / Q000737:chemistry; D005504:Food Analysis / Q000379:methods*; D016166:Free Radical Scavengers / Q000032:analysis / Q000737:chemistry*; D005638:Fruit / Q000737:chemistry; D007700:Kinetics; D018551:Solanum lycopersicum / Q000737:chemistry; D010936:Plant Extracts / Q000737:chemistry*; D018517:Plant Roots / Q000737:chemistry; D026082:Singlet Oxygen / Q000737:chemistry*
D000975:Antioxidants; D016166:Free Radical Scavengers; D010936:Plant Extracts; D026082:Singlet Oxygen; D002338:Carotenoids