Thermal decomposition of 3-(1,4-epidioxy-4-methyl-1,4-dihydro-1-naphthyl)propionic acid () has been used to measure both the physical and chemical quenching rate constants of 1O2 (kQ and kR, respectively) by water-soluble 8,8′-diapocarotenoids such as crocin () and its derivatives (,). The value of kQ was found to be slightly lower than the diffusion controlled rate constant in all the solvents examined, whereas kR showed strong dependence on the medium, going from ca. 108 in H2O to 106 M−1s−1 in DMF and DMSO. These findings suggest that both energy- and electron-transfer mechanisms are involved in the quenching of O2 (1Δg) by crocinoids.
Singlet oxygen reactions in aqueous solution. Physical and chemical quenching rate constants of crocin and related carotenoids / P. Manitto, G. Speranza, D. Monti, P. Gramatica. - In: TETRAHEDRON LETTERS. - ISSN 0040-4039. - 28:36(1987), pp. 4221-4224.
Singlet oxygen reactions in aqueous solution. Physical and chemical quenching rate constants of crocin and related carotenoids
P. Manitto;G. Speranza;
1987
Abstract
Thermal decomposition of 3-(1,4-epidioxy-4-methyl-1,4-dihydro-1-naphthyl)propionic acid () has been used to measure both the physical and chemical quenching rate constants of 1O2 (kQ and kR, respectively) by water-soluble 8,8′-diapocarotenoids such as crocin () and its derivatives (,). The value of kQ was found to be slightly lower than the diffusion controlled rate constant in all the solvents examined, whereas kR showed strong dependence on the medium, going from ca. 108 in H2O to 106 M−1s−1 in DMF and DMSO. These findings suggest that both energy- and electron-transfer mechanisms are involved in the quenching of O2 (1Δg) by crocinoids.
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