Antioxidant activity of resveratrol and alcohol-free wine polyphenols related to LDL oxidation and polyunsaturated fatty acids

Wine polyphenols were examined for their capacity to protect the lipid and protein moieties of porcine low density lipoproteins (LDL) during oxidation. The efficiency of resveratrol (3, 4'; 5, trihydroxystilbene) and defined flavonoids was compared to that of a wine extract (WE) containing 0.5 g/g proanthocyanidols. The efficiency of resveratrol for protecting polyunsaturated fatty acids (PUFA) was higher than that of flavonoids in copper-induced oxidation and lower in AAPH (radical initiator)induced oxidation. The LDL receptor activity was evaluated by now cytometry using LDL labeled with fluorescein isothiocyanate (FITC) and Chinese hamster ovary cells (CHO-K-1). The incubation of CHO-K-1 with FITC-LDL oxidized for 16 h reduced the proportion of fluorescent cells from 97% to 4%. At a concentration of 40 mu M, resveratrol and flavonoids completely restored the uptake of copper-oxidized LDL and AAPH-oxidized LDL respectively. Total fluorescence could also be obtained with 20 mg/L of WE with both oxidation systems. These data are consistent with previous findings relative to the formation of degradative products from PUFA. They confirm that resveratrol was more effective than flavonoids as a chelator of copper and less effective as a free-radical scavenger. Moreover, they show that WE, which contained monomeric and oligomeric forms of flavonoids and phenolic acids, protected LDL by both mechanisms.