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Major phenolic compounds from olive oil (ArOH-EVOO), oleuropein (Ole), tyrosol (Tyr), and p-coumaric acid (p-Cou), are known for their antioxidant and neuroprotective properties. We previously demonstrated that their combination could potentiate their antioxidant activity in vitro and in cellulo. To further our knowledge of their electron-transfer properties, Ole, Tyr, and p-Cou underwent a spectroelectrochemical study, performed either individually or in equimolar mixtures. Two mixtures (Mix and Mix-seq) were prepared in order to determine whether distinct molecules could arise from their simultaneous or sequential oxidation. The comparison of Liquid Chromatography–Electrospray Ionization–Tandem Mass Spectrometry (LC-ESI-MS2) profiles highlighted the presence of specific oxidized products found in the mixes. We hypothesized that they derived from the dimerization between Tyr and Ole or p-Cou, which have reacted either in their native or oxidized forms. Moreover, Ole regenerates when the Mix undergoes oxidation. Our study also showed significant neuroprotection by oxidized Ole and oxidized Mix against H2O2 toxicity on SK-N-SH cells, after 24 h of treatment with very low concentrations (1 and 5 nM). This suggests the putative relevant role of oxidized Ole products to protect or delay neuronal death.

DNA damage induced by free radicals is associated with mutation-based health impairment and cancers. The protective effect of five different extracts from an aquatic macrophyte, the alternate water-milfoil Myriophyllum alterniflorum DC (Haloragaceae), is investigated on the DNA disruption mediated by hydroxyl (HO • ) and hydroperoxyl (HOO • ) radicals, and their antioxidant activity on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals and O 2 •À . Indeed, M. alterniflorum is supposed to be a good candidate for DNA protection as this species was recently used in ecological surveys as a bioindicator of water quality because of its ability to cope with and to reflect the heavy-metal pollution through variations of antioxidant contents. Moreover, preliminary results indicated higher levels of scavengers specialized in reactive oxygen species reduction, than common medicinal plants. Acetone and ethanol extracts from vegetative parts limit significantly the oxidative damage of plasmid DNA induced by Fenton-reaction reactive oxygen species. The radical antioxidant activities of acetone and aqueous extracts are higher than those of other solvents:[DPPH] IC 50 = 2.4 ± 0.2 mg.ml -1 and [O 2•À ] AI 50 = 220.0 ± 14.1 μg.ml -1 , respectively. Protection towards free radicals is correlated with high contents of antioxidant compounds in acetone extracts [phenol compounds: 21.00 ± 0.69 mg gallic acid.g -1 DW (dry weight)] and aqueous extracts (flavonoids: 125.48 ± 1.26 mg rutin.g -1 DW). Myriophyllum alterniflorum can be regarded as a promising natural-product source of antigenotoxics and antioxidants and could be envisaged for therapeutic purposes.