A comparison of antioxidant activities of oleuropein and its dialdehydic derivative from olive oil, oleacein

Phenolic compounds from virgin olive oil are known to play an antioxidant role in preventing biomolecule damage. One of the most abundant components of olive oil is an oleuropein derivative named oleacein (dialdehydic form of decarboxymethyl elenolic acid linked to hydroxytyrosol; 3,4-DHPEA-EDA). The aim of the study was to establish the antioxidant activity of oleacein for an array of reactive oxygen (superoxide anion, O 2 - ; hydrogen peroxide, H2O2; hypochlorous acid, HOCl) and nitrogen species (nitric oxide, NO; peroxynitrite, ONOO−) formation, using in vitro non-cellular systems, as well as cellular screening systems (human neutrophil oxidative burst, monocytes’ nitric oxide production). We used a well-known antioxidant, oleuropein, as a reference compound. in proved to be stronger in the reduction of formyl-met-leu-phenylalanine (f-MLP) and phorbol–myristate–acetate (PMA)-induced oxidative bursts in neutrophils (IC50 = 1.8 μM, IC50 = 1.5 μM, respectively) and myeloperoxidase release (IC50 = 8.8 μM) than was oleuropein (IC50 = 2.4 μM, IC50 = 16.0 μM, IC50 = 30.7 μM, respectively). Both compounds were stronger scavengers of O 2 - than H2O2. Oleuropein did not scavenge HOCl as opposed to oleacein (IC50 = 1.5 μM). Both compounds, in a concentration range 1–10 μM, significantly decreased nitrogen species formation in cell-free systems and by lipopolysaccharide (LPS)-stimulated monocytes.