Ma. Laura Vicente’s scientific contributions

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Publications (1)


Use of EPR and ENDOR spectroscopy in conjunction with the spin trapping technique to study the high-temperature oxidative degradation of fatty acid methyl esters †
  • Article

February 1998

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12 Reads

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12 Citations

Journal of the Chemical Society Perkin Transactions 2

Ma. Laura Vicente

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Christopher C. Rowlands

Free radicals produced during the autoxidation of unsaturated edible oils are extremely short-lived, but are able to react with spin traps to produce adducts with sufficient stability for spectroscopic characterisation at (near) cooking temperatures (353–443 K). EPR spectra have shown that the model esters methyl oleate, linoleate and linolenate each formed three distinct radical adducts with N-tert-butyl-α-phenylnitrone (PBN). These adducts have been further characterised by obtaining spectra under conditions of limited oxygen availability and in the presence of α-tocopherol; two of these adducts corresponded to peroxyl and alkyl radical adducts of PBN, whereas the other was an alkyl adduct of 2-methyl-2-nitrosopropane (MNP), which was formed as a result of decomposition of the PBN peroxyl radical adduct. The origins of the various 1H hyperfine splittings have been determined by using selectively and fully deuterated PBN and selectively deuterated oleate and some of their magnitudes have been confirmed by ENDOR spectroscopy. The results obtained clearly confirm the high temperature oxidation of fatty acid esters to proceed via a different mechanism from that observed at low temperature, and point to significant differences in oxidation mechanisms of monounsaturated fatty acid esters relative to polyunsaturated.

Citations (1)


... The coupling constants obtained were consistent with those reported for 2-methyl-2-nitrosopropane (MNP), i.e. 14.8-14.9 G ( 14 N) and 2.1 G ( 1 H) (Vicente, Empis, Deighton, Glidewell, Goodman & Rowlands, 1998;Merkx et al., 2021), rather than with those for alkyl-PBN adducts, i.e. 14.7 G ( 14 N) and 3.26 G ( 1 H), found in fatty acid methyl esters oxidized in the presence of PBN (Vicente et al., 1998). Through ESR and ENDOR analyses, it has been found that MNP is a decomposition product of the highly unstable peroxyl-PBN spin adducts, whose 14 N and 1 H hyperfine splitting constants were 13.7 G and 2.0 G, respectively. ...

Reference:

ESR spin trapping for in situ detection of radicals involved in the early stages of lipid oxidation of dried microencapsulated oils
Use of EPR and ENDOR spectroscopy in conjunction with the spin trapping technique to study the high-temperature oxidative degradation of fatty acid methyl esters †
  • Citing Article
  • February 1998

Journal of the Chemical Society Perkin Transactions 2