Vol. 5, Issue 1, Part A (2023)

Urea is an organic compound with the chemical formula CO(NH₂)₂. It is similar to thiourea of formula CS(NH₂)₂, except that the oxygen atom is replaced by a sulfur atom. It has been shown that urea and thiourea, have derivatives such as: Enolurea, hydroxyurea, hydroxyhiourea, enolthiourea.
Indeed, since the discovery of these different compounds, the results of in vitro tests have shown the capacity of each of them to participate in the antioxidant defence of the body by trapping free radicals.
In the present work, a comparative study of the antioxidant properties of urea, enolurea, thiourea, 1-hydroxyurea, hydroxythiourea and enolthiourea was carried out by DFT method M06-2X/6-311++G (d, p).
The results of the various calculations allowed to:
•    Identify the oxygen atoms of the O-H groups, O-H⁹, O-H⁷ and O-H⁸, as the most important sites for the manifestation of the antioxidant activity of hydroxythiourea, hydroxyurea, enolthiourea and Enolurea respectively. 
•    It was found that thiourea and hydroxythiourea are the most antioxidant of the six molecules.
•    to note that the replacement of the oxygen atom by that of sulfur considerably modifies the antioxidant properties of the urea molecule to note that the mechanism passing by the elimination of atomic hydrogen by homolytic rupture of bond (HAT), as the most probable for the trapping of a radical by each of the molecules.