New N-acyl Thiourea Derivatives: Synthesis, Standardized Quantification Method and In Vitro Evaluation of Potential Biological Activities

Abstract

New N-acyl thiourea derivatives with heterocyclic rings have been synthesized by first obtaining isothiocyanate, which further reacted with a heterocyclic amine, characterized by (FT-IR, NMR spectroscopy and FT-ICR) and tested for their in vitro antimicrobial, anti-biofilm and antioxidant activities to obtain a drug candidate in a lead-optimization process. From the tested compounds, those bearing benzothiazole (<b>1b</b>) and 6-methylpyridine (<b>1d</b>) moieties revealed anti-biofilm activity against <i>E. coli</i> ATCC 25922 at MBIC values of 625 µg/mL. Compound <b>1d</b> exhibited the highest antioxidant capacity (~43%) in the in vitro assay using 1,1-diphenyl-2-picrylhydrazyl (DPPH). Considering the in vitro results, the highest anti-biofilm and antioxidant activities were obtained for compound <b>1d</b>. Therefore, a reversed-phase high-performance liquid chromatography (RP-HPLC) method has been optimized and validated for the quantitative determination of compound <b>1d</b>. The detection and quantitation limits were 0.0174 μg/mL and 0.0521 μg/mL, respectively. The R² correlation coefficient of the LOQ and linearity curves were greater than 0.99, over the concentration range of 0.05 μg/mL-40 μg/mL. The precision and accuracy of the analytical method were within 98-102%, confirming that the method is suitable for the quantitative determination of compound <b>1d</b> in routine quality control analyses. Evaluating the results, the promising potential of the new N-acyl thiourea derivatives bearing 6-methylpyridine moiety will be further investigated for developing agents with anti-biofilm and antioxidant activities.