Background: Thiourea is a classical urease inhibitor which is usually used as a positive
control, and many N,N'-disubstituted thioureas have been determined as urease inhibitors. However,
due to steric hindrance, N,N'-disubstituted thiourea motif could not bind urease as thiourea. On
the contrary, N-monosubstituted thiourea with a tiny thiourea motif could theoretically bind into
the active pocket as thiourea.
Objective: A series of N-monosubstituted aroylthioureas were designed and synthesized for evaluation
as urease inhibitors.
Methods: Urease inhibition was determined by the indophenol method and IC50 values were calculated
using computerized linear regression analysis of quantal log dose-probit functions. The kinetic
parameters were estimated via surface plasmon resonance (SPR) and by nonlinear regression
analysis based on the mixed type inhibition model derived from Michaelis-Menten kinetics.
Results: Compounds b2, b11, and b19 reversibly inhibited urease with a mixed mechanism, and
showed excellent potency against both cell-free urease and urease in the intact cell, with IC50 values
being 90- to 450-fold and 5- to 50-fold lower than the positive control acetohydroxamic acid,
respectively. The most potent compound b11 showed an IC50 value of 0.060 ± 0.004μM against
cell-free urease, which bound to urea binding site with a very low KD value (0.420±0.003nM) and a
very long residence time (6.7 min). Compound b11 was also demonstrated to have very low cytotoxicity
to mammalian cells.
Conclusion: The results revealed that N-monosubstituted aroylthioureas bound to the active site of
urease as expected, and represent a new class of urease inhibitors for the development of potential
therapeutics against infections caused by urease-containing pathogens.