The gastric digestion of food containing oxidizable lipids and iron catalysts for peroxide decomposition such as (met)myoglobin from muscle meat can be accompanied by an extensive formation of potentially toxic lipid hydroperoxides. An early protective action by dietary antioxidants in the gastro-intestinal tract is plausible, especially for poorly bioavailable antioxidants such as polyphenols. Hence, the ability of antioxidants to inhibit lipid peroxidation initiated by dietary iron in mildly acidic emulsions is a valuable and general model. In this work, the ability of some ubiquitous dietary antioxidants representative of the main antioxidant classes (alpha-tocopherol, the flavonol quercetin, beta-carotene) to inhibit the metmyoglobin-induced peroxidation of linoleic acid is investigated by UV-visible spectroscopy and HPLC in mildly acidic emulsions. The phenolic antioxidants quercetin and alpha-tocopherol come up as the most efficient peroxidation inhibitors. Inhibition by quercetin essentially proceeds in the aqueous phase via a fast reduction of an unidentified activated iron species (with a partially degraded heme) produced by reaction of metmyoglobin with the lipid hydroperoxides. This reaction is faster by, at least, a factor 40 than the reduction of ferrylmyoglobin (independently prepared by reacting metmyoglobin with hydrogen peroxide) by quercetin. By contrast, alpha-tocopherol mainly acts in the lipid phase by reducing the propagating lipid peroxyl radicals. The poorer inhibition afforded by beta-carotene may be related to both its slower reaction with the lipid peroxyl radicals and its competitive degradation by autoxidation and/or photo-oxidation.

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This study was aimed at assessing the DNA damage protective activity of different types of extracts (aqueous, methanolic and acetonic) using an in vitro DNA nicking assay. Several parameters were optimized using the pUC18 plasmid, especially FeSO4, EDTA, solvent concentrations and incubation time. Special attention has been paid to removing the protective and damaging effect of the solvent and FeSO4 respectively, as well as to identifying the relevant positive and negative controls. For each solvent, the optimal conditions were determined: (i) for aqueous extracts, 0.33 mM of FeSO4 and 0.62 mM of EDTA were incubated for 20 min at 37 °C; (ii) for acetone extracts, 1.16% solvent were incubated for 15 min at 37 °C with 1.3 mM of FeSO4 and 2.5 mM of EDTA and (iii) for methanol extracts, 0.16% solvent, were incubated for 1.5 h at 37 °C with 0.33 mM of FeSO4 and 0.62 mM of EDTA. Using the optimized conditions, the DNA damage protective activity of aqueous, methanolic and acetonic extracts of an Amazonian palm berry (Oenocarpus bataua) and green tea (Camellia sinensis) was assessed. Aqueous and acetonic Oenocarpus bataua extracts were protective against DNA damage, whereas aqueous, methanolic and acetonic extracts of Camellia sinensis extracts induced DNA damage.

The ripening ability of a fruit is acquired on the tree and defines its postharvest changes. Control of the physiological age at harvest can minimise the variability observed under natural conditions and guarantee fruit batches whose postharvest changes will be relatively homogeneous.