Comparative assessment of green extraction routes and chitosan nanoparticles of Salvia hispanica L. seed extracts as antimicrobial agents against Klebsiella pneumoniae

Abstract Antimicrobial resistance (AMR) is a fast-rising global health issue that requires the urgent discovery of new antimicrobial compounds. Plant extracts, including those from Salvia hispanica L. seeds, have shown great antibacterial and free-radical scavenging capacities. When formulated with nanoparticles, the extracts can enhance biological activity and provide a future alternative to conventional antibiotics. The current study aims to determine the antimicrobial activities of chia seed (Salvia hispanica L.) dry extract against multidrug-resistant (MDR) Klebsiella pneumoniae ATCC 700,603 bacterial strains, assess the enhancement of these activities upon its incorporation into nanoparticles, and investigate its synergistic interactions with conventional antibiotic (Amoxicillin) against Klebsiella pneumoniae ATCC 700,603.Chia seed extraction was performed using different solvents, including cold hexane, Soxhlet hexane, eutectic, and ethanol. Chitosan nanoparticles were loaded with extracts, and the loaded nanoparticles were characterized using UV spectroscopy, Fourier transform infrared spectroscopy (FTIR), and Zeta potential. Antibacterial activity was quantified by the minimum inhibitory concentration (MIC) against Klebsiella pneumoniae . Synergistic effects with antibiotics were analyzed using the checkerboard microdilution assay. Extraction efficiency varied significantly with method, with the deep eutectic solvent (DES) yielding the highest percentage recovery (44.6 ± 0.9%), while Soxhlet extraction produced the greatest absolute oil mass (15.446 g). Residual re-extraction confirmed significant differences among methods, with DES leaving the highest recoverable residues. Nanoparticle characterization revealed that Soxhlet-derived nanoparticles were the smallest (190.9 ± 2.9 nm), whereas DES-loaded systems exhibited larger size, higher polydispersity, and lower surface charge, indicating reduced stability. Antibacterial testing demonstrated that crude extracts varied in efficacy, with ethanolic cold-hexane extract showing the strongest activity (MIC 1.00 ± 0.10 mg/mL), while eutectic extracts were less active. Nanoencapsulation enhanced antibacterial performance, particularly for DES extracts, which improved markedly (MIC 0.50 ± 0.02 mg/mL), whereas most nanoparticle formulations converged around ~ 2 mg/mL. Comparative analysis showed up to 20–25-fold improvement in activity after encapsulation for weaker extracts, while highly active extracts showed limited or reduced benefit. Checkerboard assays indicated predominantly additive interactions with amoxicillin for both crude extracts and nanoparticles (FICI ~ 0.59–1.02), although antagonism was observed for ethanolic cold-hexane extract and empty nanoparticles. Overall, extraction method and nanoencapsulation significantly influenced both physicochemical properties and antibacterial performance. The study highlights the potential of extracts of chia seeds as antimicrobial agents, with improved activity when formulated into nanoparticles. The synergistic action of the extract when combined with antibiotics provides a potential solution to the problem of antibiotic resistance. Further research is needed to explore clinical applications and optimize nanoparticle-based drug delivery systems.