Anwar El-Shahawy is a associate professor in Assiut University
Comparative DFT calculations have been studied for Paracetamol (PA) and its analogue Phenacetin (PH) to verify their electronic resemblance. DFT studies concluded that PA and PH have lower energy predominant trans conformers with respect to the cis-conformers. From TD-DFT studies, the electronic transition energies between the ground state and singlet excited states for the two conformers have been done. The metabolized product of PA or PH i.e., m-PA in the liver of the human being is N-acetylimidoquinone. The electron affinity, Ea, of metabolized Paracetamol (m-PA) is sufficient to interact with the nucleic acid bases in the liver. As long as the m-PA product is produced in the liver and the electron transfer energy, Eet, between m-PA and nucleic acid bases has very small energy value with guanine, i.e., 0.382 eV, from the nucleus of the cell in the liver producing a spontaneous electron transfer from the nucleus to m-PA, it produced cationic nucleus leading to the carcinogenic behavior of the cell in the liver. The presence of glutathione in the liver prevents the formation of m-PA via proton transfer avoiding the carcinogenic effect of PA and PH. Repetitive usage of PA or PH drug consume the glutathione in the liver permitting the interaction between m-PA and guanine in the liver. Addition of N-acetylcysteine (NAC), N-acetylmethionine (NAM) or N-acetylglucoseamine (NAGA) prevents the formation of m-PA i.e., cancer effect. Therefore PA and PH can be used as safe drugs after mixing with the pharmacological dose of N-acetylcysteine, N-acetylmethionine or N-Acetylglucoseamine.