The "double-faced" effect of VC-12 on free-radical-induced haemolysis of human erythrocytes: antioxidant and prooxidant.

Vitamin C is a popular antioxidant; however, its water solubility limits its function in the lipid environment. As a result, the antioxidative properties of its lipophilic derivatives have aroused research attention, especially L-ascorbyl-6-laurate (VC-12). We have investigated the effect of a high concentration of VC-12 on 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced haemolysis of human erythrocytes. The findings indicated that VC-12 was capable of protecting erythrocytes against AAPH-induced haemolysis when its concentration was below 60 microM. With an increase in the concentration of VC-12 and a decrease in the concentration of AAPH, VC-12 promoted haemolysis remarkably, the mechanism of which has been proposed as VC-12-mediated peroxidation. When the concentration of VC-12 was increased to above 150 microM, VC-12 promoted haemolysis by its function as a surfactant, to unbalance the osmotic pressure within and outside erythrocytes. High concentrations of VC-12 may have generated radicals via autooxidation, resulting in eventual haemolysis. Therefore, the double-faced effect of VC-12 on haemolysis of human erythrocytes was due to its concentration. This information may be useful for the safe use of lipophilic vitamin C.