Comparative mechanisms and rates of free radical scavenging by carotenoid antioxidants

FEBS Letters

Rice-Evans, Catherine¹  Everett, Steven A.³  Skibsted, Leif H.²  Sampson, Julia¹  Mortensen, Alan² 

[1] International Antioxidant Research Centre, UMDS-Guy's Hospital, London SE1 9RT, UK;Department of Dairy and Food Science, Royal Veterinary and Agricultural University, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark;Gray Laboratory Cancer Research Trust, P.O. Box 100, Mount Vernon Hospital, Northwood, Middlesex HA6 2JR, UK

关键词: Carotenoid;    Thiyl radical;    Nitrogen dioxide radical;    Sulphonyl radical;    Pulse radiolysis;   

DOI  :  10.1016/S0014-5793(97)01355-0

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The comparative mechanisms and relative rates of nitrogen dioxide (NO₂ ^⋅), thiyl (RS^⋅) and sulphonyl (RSO₂ ^⋅) radical scavenging by the carotenoid antioxidants lycopene, lutein, zeaxanthin, astaxanthin and canthaxanthin have been determined by pulse radiolysis. All the carotenoids under study react with the NO₂ ^⋅ radical via electron transfer to generate the carotenoid radical cation (Car^⋅+). In marked contrast the glutathione and 2-mercaptoethanol thiyl radicals react via a radical addition process to generate carotenoid-thiyl radical adducts [RS-Car]^⋅. The RSO₂ ^⋅ radical undergoes both radical addition, [RSO₂-Car]^⋅ and electron abstraction, Car^⋅+. Both carotenoid adduct radicals and radical cations decay bimolecularly. Absolute rate constants for radical scavenging were in the order of ∼10⁷–10⁹ M⁻¹ s⁻¹ and follow the sequence HO(CH₂)₂S^⋅>RSO₂ ^⋅>GS^⋅>NO₂ ^⋅. Although there were some discernible trends in carotenoid reactivity for individual radicals, rate constants varied by no greater than a factor of 2.5. The mechanism and rate of scavenging is strongly dependent on the nature of the oxidising radical species but much less dependent on the carotenoid structure.

【 授权许可】

Unknown