A density functional theory study for the role of end groups on the antioxidative potency of carotenoids

Role of carotenoid end groups on their chainbreaking potency against lipid peroxidation was explored using density functional theory. Hydrogen abstraction and addition of the peroxide and O₂ of the resultant radicals were investigated. The protective potency of CARs is exhibited by their faster reactions with the peroxide radical than fatty acid, and by the much reduced reactivity of the initiated radical toward O₂. 3,3'-Dihydroxyisorenieratene (DHIR), which consists of hydroxyaryl (3-hydroxy-φ) end groups, is by far the most efficient chain-breaking antioxidant. The quinone form of DHIR is also an effective antioxidant. 4-Oxo functional group in β-ring enhances the antioxidative potency of carotenoids, while 3-hydroxyl functional group in β-ring does not have a noticeable effect.