Background: The exact mechanism(s) of atherosclerosis in humans remains elusive, but one theory
hypothesizes that this deleterious process results from the oxidative modification of low-density lipoprotein
(LDL). Research suggests that foods rich in dietary phenolic compounds with antioxidant activity can mitigate the
extent of LDL oxidation in vivo. With regard to the different classes of flavonoids, there appears to be a structurefunction
relationship between the various moieties/constituents attached to the flavonoids’ three ring system and
their impact at retarding LDL oxidation.
Methods: This article summarizes the findings to date of both in vitro and in vivo studies using foods or phenolic
extracts isolated from foodstuffs at inhibiting the incidence of LDL oxidation. Three bases: SCOPUS, Web Science,
and PubMed were used for search.
Results: An often used method for the determination of antioxidant properties of natural phenolic compounds is
the LDL oxidation assay. LDLs are isolated from human plasma and their oxidation is induced by Cu2+ ions or
2,2′-azobis(2-methylpropionamidine) dihydrochloride (AAPH). The sample is incubated with a phenolic extract
or individual/isolated phenolic compounds. LDL oxidation is then monitored by various chemical methods (e.g.,
measurement of the generation of conjugated dienes and trienes). This technique confirmed the antioxidant properties
of several extracts as obtained from plant material (e.g., grapes, berries, orange, grapefruit, coffee, tea,
chocolate, olives, nuts) as well as the individual phenolic compounds (e.g., luteolinidin, apigenidin, caffeic acid,
chlorogenic acid, catechin, quercetin, rutin). Several studies in vivo confirmed protective effects of phenolic compounds
against LDL oxidation. They covered the healthy subjects with hyperlipidaemia, overweight, obesity,
metabolic syndrome, heavy smokers, patients receiving haemodialysis, patients with peripheral vascular disease,
and subjects at high cardiovascular risk. The studies comprise individuals of all ages, and the number of participants
in the different experiments varied widely.
Conclusion: Properly designed double-blind, placebo-controlled randomised clinical trials offer stronger evidence
as to the impact of dietary phenolics consumption at retarding LDL oxidation. More such clinical trials are
needed to strengthen the hypothesis that foods rich in dietary phenolic compounds with antioxidant activity can
mitigate the extent of LDL oxidation in vivo.