Grape and grape seed extract capacities at protecting LDL against oxidation generated by Cu2+, AAPH or SIN-1 and at decreasing superoxide THP-1 cell production. A comparison to other extracts or compounds.

A large body of evidence supports the key role of oxidized low-density lipoprotein in atherosclerosis. The aim of this study was to compare the capacity of natural polyphenols (PP) from Vitis vinifera and Olea europea at protecting LDL against oxidation brought about by Cu2+, oxygen-centered radical-generating AAPH, or peroxynitrite-generating SIN-1 in vitro systems, or at impairing superoxide production in promonocyte cells (THP-1) conveniently differentiated into adherent macrophages. PP were either from the whole grape (fraction A) containing mainly procyanidins, (epi)-catechin and anthocyanins, or from grape seed extracts (fractions B and C) consisting of tannins and procyanidin oligomers with a higher content in B than in C, or from a grape skin extract (fraction D) consisting mainly of anthocyanins, or from a hydrosoluble olive mill wastewater PP extract (fraction E) containing hydroxytyrosol and oleuropein. Chlorogenic acid (F) and catechin (G) were taken as archetypes of PP preventing oxidation partly as copper scavenger and as radical scavenger only, respectively. All grape fractions were efficient towards Cu2+ system (equally or more efficient than F), whereas they were rather poorly efficient towards AAPH and SIN-1 (less efficient than G but as efficient as F). Among the PP fractions, B was the most effective at protecting LDL in the SIN-1 system and at impairing THP-1 superoxide production. Taken together, these data suggest that the PP fraction from grape seed rich in procyanidins achieves the best compromise between the direct and indirect (i.e. cell-mediated) types of action in protecting LDL against oxidation, strengthening the need for improving the knowledge of its bioavailability in humans.

Synergistic antioxidative properties of phenolics from natural origin toward low-density lipoproteins depend on the oxidation system.

Using an approach in line with that of a previous report, we assessed the antioxidant activity of several natural, polyphenol- or tocotrienol-rich mixtures: extracts from Elaesis Guineensis oil (A) and Vitis vinifera (B), a Coffea robusta powder (C), and extracts from Olea europea mill wastewaters (D), Solanum melongena (E), and Lycopersicon esculentum (F). The copper- and 2-2'-azobis(2-amidinopropane) hydrochloride (AAPH)-oxidation systems were used in the presence of low-density lipoprotein. For comparison, antioxidant activities of chlorogenic acid and catechin, as archetypes of molecules highly efficient with the copper- and the AAPH-oxidation system, respectively, were assessed. The aim was to establish the occurrence of synergistic antioxidant actions among some of these natural mixtures. On a molar basis, the highest specific antioxidant activities (SAA) were found for B, chlorogenic acid, and C in the copper system, and for A, catechin, and B in the AAPH system. On a mass basis, the highest SAA were found, respectively, for chlorogenic acid, B, and catechin, and for catechin, chlorogenic acid, and B. These results show that large discrepancies take place in the evaluations between the two systems. B and C exhibited a synergistic antioxidant efficiency, in the presence or absence of A, but only with the copper system. This was also true for the two types of A+B+C mixture that were tested. It is thought that this association might provide an ideal combination, incorporating both the radical scavenger and the transition-metal ion chelation properties of B and C.