Polyphenols enhance total oxidant-scavenging capacities of human blood by binding to red blood cells

The present study offers a new look at the role of erythrocytes and of erythrocytes-polyphenol complexes as potent 'sinks' for reactive oxygen species. We hereby show that human erythrocytes have the capacity not only to carry oxygen, but also to bind avidly to their surfaces a large variety of polyphenol antioxidants, which endows upon such complexes enhanced total oxidant-scavenging capacities (TOSC). This was proven by using confocal microscopy, 2,2-diphenyl-1-picrylhydrazyl radical, Folin-Ciocalteu's reagent, cyclic voltammetry and chemiluminescence techniques. The results presented suggest that the true TOSC of blood is the sum of intracellular antioxidants of red blood cells and other blood cells (mainly due to catalase), the polyphenols bound to their surfaces and the antioxidant agents present in plasma. Since erythrocytes can avidly bind and rapidly remove circulating polyphenols, the rule of the thumb to quantify antioxidants in health and disease processes exclusively in plasma as customary in clinical settings, does not represent the true TOSC of whole blood. We also postulate that circulating erythrocytes and possibly also other blood cells might be constantly coated by polyphenols from supplemented nutrients, which act as antioxidant depots and can thus act as protectors against the harmful consequences of oxidative stress. Further studies are needed to determine the faith of polyphenols in the circulation and their sequestration in the spleen.