Making vitamin C lipophilic enhances its protective effect against free radical induced peroxidation of low density lipoprotein.

The peroxidation of human low density lipoprotein (LDL) was initiated by water-soluble initiator 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH) and copper and inhibited by vitamin C (VC) and its lipophillic derivatives ascorbyl-6-caprylate (VC-8), 6-laurate (VC-12) and 6-palmitate (VC-16), respectively. The peroxidation was monitored by oxygen uptake, by decay of alpha-tocopherol and by formation of lipid oxidation products. Kinetic analysis of the antioxidation process demonstrates that the VCs can work synergistically with endogenous antioxidants (vitamin E, ubiquinol-10, beta-carotene etc.) in LDL to suppress the peroxidation and that the synergistic effect of the lipophilic VCs is appreciably higher than that of their lipophobic parent molecule. It is also shown that VC and especially the lipophilic VCs, are much more effective in inhibition of copper-induced than AAPH-induced LDL peroxidation.