Vanadate and chromate reduction in the presence of biocomponents like saccharides and L-ascorbic acid is demonstrated to generate V(IV) and Cr(III) species, respectively. The incipiently formed V(IV) and Cr(III) species are demonstrated to cause single strand and plasmid DNA nicking, lipid pcroxidation and cytotoxicity in isolated rat hepatocytes. The V(IV) complexes depleted the levels of non-enzymatic antioxidants like L-ascorbic acid and glutathione and parallelly increased the levels of enzymatic antioxidants like glutathione reductase, glutathione S-transferase, glutathione peroxidase, superoxide dismutase and catalases. However, the Cr(III) species did not have any significant effect on the antioxidant enzymes. Thus the reducing and complexing abilities of biogenic ligands and the corresponding effects of the V(IV) and Cr(III) species generated from vanadate and chromate reduction, respectively, may lead to a better understanding of the toxic effects of the corresponding metal ions. © 1997 Elsevier Science S.A.