QSAR STUDIES ON UREA AND THIOUREA DERIVATIVES. RELATIONSHIP BETWEEN DESCRIPTORS LOG P, π, MR AND MV AND ANTIBACTERIAL ACTIVITY IN Staphylococcus aureus, Klebsiella pneumoniae AND Escherichia coli

In this work the structural requirements of both urea and thiourea derivatives were evaluated for optimal antibacterial activity on Staphylococcus aureus, Klebsiella pneumoniae and Escherichia coli, using several organic compounds (VI-X) as chemical tools. In order to delineate the structural chemical requirements of studied compounds, the descriptors Log P, π MR and MV were calculated. The results showed that bacterial growth of the studied microorganisms, in presence of IV and VI compounds was inhibited at low concentrations in comparison with I-III, V and VII-X. Other results indicate that Log P increase in II-V, VIII compounds and decrease in the VI-X substances in comparison with I thiourea-derivative. In addition, other data indicate that the π values are lower in the II-X substances in comparison with I compound. Other data showed an increase in both MR and MV values in the I-V and VIII compounds and a decrease in the VI, VII, IX and X substances. In conclusion, the results found indicate that substituents involved in the chemical structure of both urea and thiourea derivatives increase the lipophilicity and changes in the functional groups decrease the LogP. Therefore, this phenomenon can affect the antibacterial activity on Staphylococcus aureus, Klebsiella pneumoniae and Escherichia coli. In addition the results indicate that steric impediment, the molecular mechanism, conformational preferences and internal rotation of different compounds could affect the antibacterial effect of studied compounds.