The present work studied and compared the capacity of four important
olive oil polyphenolic 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 H2O2. 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 H2O2 at 40 and 80 microM, with the order of activity being 3,4-DHPEA-EDA>3,4-DHPEA-EA>
hydroxytyrosol=
oleuropein. At 20, 10, and 5 microM, 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 microM increased the stability of erythrocytes. The addition of phenolic compounds at 20 and 10 microM 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 5 microM. 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.