Design, Synthesis And Evaluation Of Hydroxamic Acids As Urease Inhibitors

There are more than half of people in the world having infected Helicobacter pylori(Hp), and the infected population is even up to 80 percent in some underdeveloped countries as shown in epidemiologic study. People infected with Hp are vulnerable to get other diseases, such as pyelonephritis, urolithiasis, urinary tract infections, gastritis, gastric ulcer, gastric cancer and so on, owing to the strong inhibition on Hp survival caused by urease inhibitor. Therefore, approaches depended on urease inhibition have been currently considered as front line treatment for infections caused by urease-producing bacteria.A series of hydroxamic acid urease inhibitors have been designed and synthesized by employing molecular fusion technology, according to the important effect of three-ring flavonoid skeleton on improving the activity of urease inhibitors. The fact that hydroxamic acid can form a firm compound via binding nickel ions in urease activity center, can provide the possibility for urease inhibitors synthesis. The structure of synthesized compounds was characterized by modern analysis methods and their activity on urease was also tested. The results show that most of synthesized compounds have some inhibiting effects on urease. To our excitement, four kinds of synthesized compounds exhibit similar urease inhibition activity to acetohydroxamic acid(IC50=17.0 μM), however, compounds c22(IC50=1.2 μM)and c24(IC50=1.1 μM)possess higher activity than acetohydroxamic acid with exceeding over 10 times. The enzyme kinetics, molecular docking and plasma protein binding rate of compounds c22 and c24 were also discussed. The results demonstrate that the urease inhibiting type of compounds c22 and c24 belongs to the mixed and reversible inhibition. The kinetic constant Ki and Ki′ of compound c22 are 1.08 μmol?L-1 and 0.95 μmol?L-1, respectively. However, the two kinetic constant Ki and Ki′ of compound c24 are slightly lower compared to c22 that reach to 0.92 μmol?L-1 and 0.81 μmol?L-1. It displays that c22 and c24 are easy to integrate with urease.Based on molecular docking, the binding mode between urease and c22 exhibits a little different compared with c24.The urease inhibition on Hp urease of compound c22 is achieved mainly by combing C(O)NHOH with the amino acid residues, while the compound c24 realize its activity via binding C(O)NHOH to the amino acid residues and two Ni ion in urease active center. In addition, the test on protein binding rate was carried out by combining compound c22 with human plasma and rabbit, respectively, and the corresponding rates are 52.8 % and 45.2 %. By conducting the similar test, the relevant protein binding rate of compound c24 are 37.4 % and 43.8 %. Therefore, the protein binding rate of compound c22 and c24 have no obvious species diversity, and the moderate binding rate is benificial for compounds to develop their pharmacological effect.