Powerful protective role of 3,4-dihydroxyphenylethanol-elenolic acid dialdehyde against erythrocyte oxidative-Lnduced hemolysis

The present work studied and compared the capacity of four important olive oil polyphenols compounds, oleuropein, hydroxytyrosol, and the oleuropein aglycones 3,4-dihydroxyphenylethanol-elenolic acid (3,4-DHPEA-EA) and 3,4-dihydroxyphenylethanol-elenolic acid dialdehyde (3,4-DHPEA-EDA), to protect red blood cells (RBCs) from oxidative hemolysis induced by the physiological initiator H ₂O ₂. The amount of hemolysis was evaluated spectrophotometrically. The compounds were also tested in the presence and absence of the naturally occurring antioxidant ascorbic acid. All compounds were revealed to significantly protect RBCs from oxidative hemolysis induced by H ₂O ₂ at 40 and 80 μM, with the order of activity being 3,4-DHPEA-EDA > 3,4-DHPEAEA > hydroxytyrosol = oleuropein. At 20, 10, and 5 μM, only 3,4-DHPEA-EDA showed a significant protection against the oxidative injury. In the presence of ascorbic acid at physiological concentration, the addition of individual compounds at 40 μM increased the stability of erythrocytes. The addition of phenolic compounds at 20 and 10 μM did not produce further protection when compared with the protection given by ascorbic acid alone, except for 3,4-DHPEA-EDA. This compound was shown to produce further protection even at 5μM. In summary, 3,4-DHPEA-EDA plays an important protective role against reactive oxygen species-induced oxidative injury in RBCs, and this effect is more potent than the one evidenced by hydroxytyrosol or oleuropein.