Lauric acid conjugated ureido derivatives of 2-(4-aminopiperidin-4-yl)acetic acid (β3,3-Pip): Overcoming resistance and outperforming standard antibacterials

The imperative for the expeditious development of novel antibiotics stems from the escalating resistance trends witnessed against conventional antibiotic agents. The present study delineates the synthesis, characterization, and antibacterial efficacy of β,β-disubstituted-β-amino acid derivatives, specifically those capped with lauric acid at the N-terminus through amide and urea bonds, LA-β 3,3 -Pip-PEA, 1 ; LA-β 3,3 -Pip(G)-PEA, 2 ; LA U -β 3,3 -Pip-PEA, 3 ; and LA U -β 3,3 -Pip(G)-PEA, 4 . Against E. coli , S. aureus, and E. faecalis LA U -β 3,3 -Pip-PEA, 3 exhibited robust antibacterial activity having a low minimum inhibitory concentration (MIC) of 0.5 μg/mL. It also showed a remarkable MIC of 8 μg/mL and 16 μg/mL against MRSA and MDR E. coli respectively outperforming amoxicillin, cefpodoxime, and 10 other standard antibiotics. It also synergized with antibiotics like Ciprofloxacin, Streptomycin, and Ampicillin. Mechanistic insights revealed membrane disruption in E. coli and S. aureus upon treatment with compound 3 . Compound 3 maintained complete cell viability across observed cell lines; AML12, RAW 264.7, and HEK-293 at concentrations of 1 μg/mL and 10 μg/mL. Demonstrating notable stability, compound 3 resisted trypsin degradation and maintained antibacterial efficacy across diverse temperatures and pH conditions. Concentration-dependent reductions in swimming and swarming movements associated with E. coli flagella showed compound 3 's potential against biofilm development at both MIC and sub-MIC concentrations. Notably, after minimal exposure, compound 3 exhibited a 4-h Post-Antibiotic Effect (PAE) i.e. halting bacterial growth. Compound 3 also demonstrated DNA binding at 64 μg/mL, retarding bacterial DNA movement in agarose gel electrophoresis. In a mouse wound infection model, compound 3 outperformed mupirocin, sterilizing 7 logs CFU of S. aureus in just 2 days, achieving full wound closure by Day 6, and early cessation of pus, showcasing its superior therapeutic efficacy.