Nitrogen (N) is essential for plant survival, growth, and crop production. In agriculture, it has been recognized as the single most vital nutrient for increasing crop yields across the globe. The use of N fertilizers is essential to maintain agricultural productivity, which is essential to provide sustenance to the human population. Urea is the most worldwide nitrogen fertilizer used; however, its enzymatic hydrolysis leads to losses through ammonia volatilization causing economic and environmental problems. To prevent this loss, urease inhibitors have been used. Among the new inhibitors synthesized by our research group, the Schiff bases have excelled results. In this work two substances, a Schiff base (3B4) and its amine derivative (3B4a), were synthesized (Scheme 1) and their in vitro antiureolytic activities were also determined. Additionally, the interactions of these substances with the urease enzyme was studied by using a molecular docking approach. The 3B4 and 3B4a were prepared with 72% and 76% yields, respectively. The in vitro antiureolytic activity of 3B4 and 3B4a (22.62 ± 6.87 and 24.16 ± 9.56, respectively) showed that both substances inhibited the urease in the same level to the positive control hydroxyurea (HU) (23.45 ± 11.95). However, it is important to mention that, differently from 3B4a, the imine 3B4 is unstable in presence of water and this can restrict the use of 3B4 as additive in N fertilizer. The molecular docking studies for 3B4 and 3B4a showed that the orientation of the hydroxyl group 3-OHPh of 3B4 and 4-OHPh of 3B4a plays an important role in the biding orientation of such subtances with the 2 nickel atoms of the urease catalytic site. Furthermore, the complex urease-3B4a showed to be more stable than complex urease-3B4, in part, due to an additional hydrogen bonding interaction between His593 with amine group and two hydrogen bonds involving hydroxyl group and the residues Ala436, Arg439 and Asp633. As a conclusion, this work have disclosed substances 3B4 and 3B4a as promising urease inhibitors, particularly amine 3B4a that is as potent as 3B4 and it is stable in aqueous medium - an important requirement for potential urease with agriculture interests.

Highlights

►Urea is the most used nitrogen (N) fertilizer in the world. ►Up to 70% of urea is lost due to ammonia volatilization due to the enzymatic action of urease. ►Both urease inhibitors, prepared in excellent yields, showed as potent as the positive control, hydroxyurea. ► The amine 3B4a is the most promising urease inhibitor