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Fourier transform infrared spectroscopy evaluation of low density lipoprotein oxidation in the presence of quercetin, catechin, and α‐tocopherol
Author(s) -
Lam Henry S.,
Proctor Andrew,
Nyalala John,
Morris Manford D.,
Smith W. Grady
Publication year - 2005
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/s11745-005-1417-x
Subject(s) - chemistry , quercetin , catechin , antioxidant , fourier transform infrared spectroscopy , apolipoprotein b , low density lipoprotein , biochemistry , chromatography , organic chemistry , polyphenol , cholesterol , physics , quantum mechanics
We investigated the changes in human LDL primary and secondary lipid oxidation products and modification of the apolipoprotein B‐100 (apoB‐100) secondary structures during Cu 2+ ‐mediated oxidation by FTIR spectroscopy in the presence of catechin, quercetin, and α‐tocopherol at physiological concentrations. Catechin‐ and quercetin‐containing samples had slower rates and longer lag phases for conjugated diene hydroperoxide (CD) formation than α‐tocopherol‐containing samples; however, all antioxidant‐treated LDL samples generated similar CD levels ( P <0.05). A lower maximum (98.4 nmol/mg LDL protein) of carbonyl compounds was produced in the quercetin‐ and catechin‐treated samples than in α‐tocopherol samples. Modification of the apoB‐100 secondary structures corresponded closely to the formation of carbonyls and was hampered by the presence of antioxidants. Physiological concentrations of catechin and quercetin offered similar levels of protection against modification by carbonyls of the apoB‐100 at advanced stages (carbonyls ∼96.0 nmol/mg LDL protein) but not at the intermediate stages (carbonyls ∼58.0 nmol/mg LDL protein) of LDL oxidation probably owing to differences in the protein‐binding mechanisms of catechin and quercetin. Relationships between peroxide formation, carbonyl products, and LDL protein denaturation were shown by the FTIR approach. The FTIR technique provided a simple new tool for a comprehensive evaluation of antioxidant performance in protecting LDL during in vitro oxidation.