Abstract: In present study, molecular modelling analyses based on molecular mechanics, semi-empirical (PM3) and DFT (at B3LYP/6-31G* level) calculations have been carried out to obtain information on relative toxicity of UDF and its metabolites. The results of the analyses show that UDF and its metabolites have LUMO-HOMO energy differences of the order of 4.1 to 4.2 eV so that the compounds would all be moderately inert kinetically. The molecular surfaces of UDF and NDUDF are found to abound in neutral green and electron-deficient blue regions so that they can be subject to lyophilic and nucleophilic attacks. The latter attack can be due to glutathione and nucleobases in DNA so that the two compounds may induce cellular toxicity due to glutathione depletion and DNA damage due to oxidation of nucleobases in DNA. The other two metaboltes UDFM1 and UDFM3 abound in electron-rich red and yellow regions so that they are more likely to be subject to electrophilic attacks and may very well act as antioxidants.