Antimicrobial Peptides from Herbal Plants: A Critical Review of Antimicrobial, Antibiofilm, and Quorum Sensing-Related Activities Against Antimicrobial Resistance

Antimicrobial resistance (AMR) is a rising worldwide health issue that has increased the need for alternative approaches to managing bacterial infections. Plant-derived antimicrobial peptides (PAMPs) are promising bioactive molecules because of their structural diversity and multifunctional antimicrobial, antibiofilm, and anti-virulence activities. This review examines the potential of PAMPs from medicinal and herbal plants to interfere with bacterial quorum sensing (QS) and QS-associated virulence and to combat biofilm-associated infections caused by antimicrobial-resistant pathogens. It summarizes the major PAMP families and their direct antimicrobial mechanisms, including disruption of bacterial membranes, altered membrane permeability, and interference with extracellular polymeric substances. Particular attention is given to QS-related mechanisms, including interference with signal production and recognition, suppression of virulence factor expression, and modulation of biofilm development and extracellular polymeric substance formation. Evidence from clinically relevant pathogens, particularly Pseudomonas aeruginosa, is discussed to distinguish experimentally demonstrated QS inhibition from reductions in QS-associated phenotypes and QS-independent antibiofilm effects. The review also highlights the potential of PAMPs as complementary agents in combination with conventional antibiotics. Despite their promise, the therapeutic application of PAMPs remains limited by incomplete peptide characterization, insufficient validation of molecular targets, and challenges associated with stability, safety, delivery, and in vivo efficacy. Future research should prioritize the identification of individual active peptides, rigorous experimental validation of QS-dependent and QS-independent mechanisms, and the evaluation of efficacy against multidrug-resistant pathogens. Integrating peptide engineering, computational approaches, and in vivo studies may facilitate the development of PAMPs as anti-virulence agents, antibiofilm therapeutics, and antibiotic adjuvants for managing drug-resistant infections.