Design, Synthesis, and Biological Evaluation of Tetrahydropyridine Analogues as Potent Antibiofilm Agents against <i>S. aureus</i> : In Vitro and In Silico Studies

An ecofriendly approach has been developed for the highly efficient atom-economical one-pot multicomponent synthesis of substituted tetrahydropyridine scaffolds as potent antibiofilm agents via using 1,2,4,5-Benzenetetracarboxylic acid (H₄BTCA) as a novel, mild organocatalyst. This is the first-ever report on the use of 1,2,4,5-Benzenetetracarboxylic acid (H₄BTCA) as a catalyst in organic synthesis. This protocol's appealing features include column chromatography-free purification, resulting in high-purity products and compatibility with a broad range of substrates. Moreover, this method afforded good results to excellent yields (i.e., 86-93%) of compounds (<b>4a</b>-<b>4r</b>). The biological utility of the tetrahydropyridine derivatives as antibiofilm agents has been demonstrated. The synthesized compounds were screened against <i>Staphylococcus aureus</i> and <i>P. aeruginosa</i> with in vitro and in silico approaches. It is noteworthy to mention that some of the tetrahydropyridine derivatives exhibited potent antibiofilm activity with minimum or no toxicity in the in vitro study. On the basis of antibiofilm activity, 3 compounds (<b>4k</b>, <b>4l</b>, and <b>4n</b>) were formulated into nanoparticles (<b>4k</b> NPs, 4l NPs, <b>4n</b> NPs) have shown appreciable antibiofilm activity with a maximum disruption, 87.74 ± 2.26%, shown by 4l NPs and toxicity further reduced below 2% when the compound was loaded into nanoparticles. The docking studies of the active 3 compounds (<b>4k</b>, <b>4l</b>, and <b>4n</b>) have been tested against different biofilm target proteins like sarA, crtM, fnbA, PBP2, clfA, clfB, AgrA, and AgrC associated with the <i>S. aureus</i> biofilm. Our in silico study results demonstrate the high affinity of the molecules with lower (more negative) docking scores ranging from ∼-10 to -6 kcal/mol. The highest affinities were observed with <b>4k</b> and <b>4b</b> against the 1n67 protein (clumping factor protein) compared to other studied antibiofilm-related proteins.