Mechanism of chain termination in lipid peroxidation by carotenes: A theoretical study

Jian Jhih Guo, Ching Han Hu

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


The reaction mechanism of carotenes (CARs) in chain termination against lipid peroxidation was studied using density functional theory. In the presence of peroxide (ROO), the reaction barrier for its addition to CAR to form ROO-CAR is smaller than those for its hydrogen abstractions from CAR and linoleic acid (LAH), respectively. In contrast, the reaction barriers for the O2 additions of the carbon-centered radicals are ordered as ROO-CAR > CAR(-H) > LA. Thus, the chain-termination function of CAR is best demonstrated by trapping the addition radical and suppressing O2 addition. For either the ROO-CAR or CAR(-H) radicals, β-carotene has noticeably higher O2 addition barriers than those of their lycopene counterparts. The reaction barrier for the rearrangement of ROO-CAR into RO + epoxide is much smaller than that for the formation of cyclic ether and is comparable to that of O2 addition. Since RO has a stronger tendency toward hydrogen abstraction than ROO, the rearrangement of the addition adduct has to be recognized as an important factor while evaluating the chain-termination potency of a molecule. The overall reaction energy profile reveals that the protective function of CAR is mostly exhibited via formation of the addition adduct. Comparatively, β-carotene is a more potent antiradical agent than lycopene against peroxide-initiated lipid peroxidation.

Original languageEnglish
Pages (from-to)16948-16958
Number of pages11
JournalJournal of Physical Chemistry B
Issue number50
Publication statusPublished - 2010 Dec 23

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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