Honey flavonoids as protection agents against oxidative damage to human red blood cells

Honey phenol extracts separated on the base of their hydrophobicity were evaluated for the antioxidant content and for the ability to inhibit oxidative damage induced by radical species generated in the water phase or in the membrane of human erythrocytes. The water and ether fractions obtained from crude methanol extract of honey exhibited a phenolic content of 5.33 and 2.62 mg caffeic acid equivalents/100 g honey, respectively. These values correlate well with those of total antioxidant power, as assessed by FRAP assay (37.67 vs. 10.65 μmol/100 g honey). Flavonoid contents were 2.57 and 1.64 mg catechin equivalents/100 g honey for ether and water fractions, respectively. Although both honey fractions protect erythrocytes against 2,2′-azobis(2-amidinopropane)dihydrochloride-induced lysis, only the ether fraction was found to be active in inhibiting hemolysis but not methemoglobin and ferrylhemoglobin formation caused by H2O2. In addition, the ether fraction prevents tert-butylhydroperoxide-induced lipid peroxidation in whole erythrocytes and in isolated membranes. The significant antioxidant effect against damages induced by both water-soluble and hydrophobic exogenous oxidants suggests that the ether fraction, owing to its lipophilic character, can interact with red blood cell membrane, and the protective effect can be associated with the binding of the flavonoids to the membrane. On the other hand, the water fraction is more hydrophilic than ether fraction and it acts only from the outside of the membrane by scavenging the radicals before they attack the erythrocyte membrane.