One electron reduction of vanadate(V) to vanadyl(IV) occurs in the presence of biocomponents, such as, saccharides and L-ascorbic acid under physiological conditions. The vanadyl(IV) complexes thus generated have been demonstrated to introduce nicks in pUC18 DNA in the absence or in the presence of hydrogen peroxide and also exhibit lipid peroxidation in isolated rat hepatocytes. Thus the reducing and complexing abilities of these molecules may help in understanding the in vivo reduction and the resultant toxicity to cells incubated with vanadate(V).