A comparative study of the effects of oleuropein and its dialdehydic form (oleacein) on human neutrophil oxidative burst

Polyphenols extracted from extra virgin olive oil are known to play a role in preventing atherosclerotic damage by inhibiting LDL oxidation. Olive phenolics include phenolic alcohols (hydroxytyrosol), secoiridoids (oleuropein) and its dialdehydic forms (oleacein) [1]. Oleuropein is well known to possess antioxidant activity but little is known about oleacein activity. Taking into account, that neutrophils are suggested to be implicated in vascular and heart diseases [2], we analysed the effect of oleuropein and oleacein on neutrophil oxidative burst after receptor-mediated (N- formyl-methionyl-leucyl-phenylalanine; f-MLP) and non-receptor-mediated (phorbol-12-myristate-13-acetate; PMA) stimulation. We also performed cell free assays in order to determined the scavenger potential of tested compounds on selected reactive oxygen species (ROS). The comparison of inhibition of ROS production showed that oleacein strongly inhibits the oxidative burst in human neutrophil, in comparison with oleuropein. The cell free experiments demonstrated that oleacein is a strong HClO scavenger, which may be connected with the presence of dialdehydic groups. These results indicate that oleacein down-regulated the PMN responsiveness and may contribute to the protective effect of extra virgin olive oil against vascular and heart diseases.

Table 1

ROS	Oleuropein [IC50;µM]	Oleacein [IC50;µM]
f-MLP induced	11.9	1.6
PMA induced	>20	3.8
O2 –	21.1	17.1
H2O2	>50	>50
HClO	NA	1.5

References: 1. Ervili, M, et al. (2002) Eur J Lipid Sci Technol 104: 602–613.

2. Ernst, E, et al. (1987) JAMA 257: 2318–2324.