Ultrasonic extraction methods enhance the antimicrobial activity of plant extracts against foodborne pathogens

The search for biological alternatives has grown in contemporary society, driving the development of natural products with technological potential against different contaminants. In the food sector, plant extracts with antimicrobial action represent a promising alternative to reduce the use of synthetic preservatives. Thus, this study aimed to evaluate the antimicrobial potential of extracts of Bidens pilosa, Baccharis trimera and Anadenanthera colubrina against eight bacterial strains. The extracts were obtained using 20% ethanol by three methods: ultrasonic bath (1 h), blender (10 min) and sonicator (10 min). The resulting material was lyophilized for 72 h and reconstituted in 20% DMSO to obtain 1 mg/mL solutions. The bacterial concentration used was 10⁸ CFU/mL, and the plating was performed by swab. 10 μL of each extract was applied on paper discs on the plates, and DMSO 20% and the extractor solution were used as controls. All experiments were performed in triplicate and analyzed by ANOVA followed by Tukey's test (p ≤ 0.05). The controls showed no antimicrobial activity. Among the extracts evaluated, B. pilosa (ultrasonic bath and sonicator) showed the highest inhibition halos against Escherichia coli (23.4 and 24.0 mm) and Klebsiella pneumoniae (18.2 and 19.7 mm). A. colubrina, on the other hand, showed better performance against Pseudomonas aeruginosa and Bacillus cereus (20.3–21.6 mm), in addition to expressive results against Staphylococcus aureus and Salmonella enteritidis (23.4 and 23.8 mm). Extracts obtained by ultrasonic bath and sonicator showed greater efficiency, possibly due to cavitation phenomena that promote the release of bioactive compounds during extraction. These compounds may interact with bacterial membranes, causing disruption and inhibiting microbial growth. It is concluded that the studied extracts, especially those obtained by ultrasound-assisted methods, demonstrated relevant antimicrobial activity and promising potential for application in animal-derived food products, contributing to the inhibition of spoilage and pathogenic microorganisms, extending shelf life, and ensuring greater microbiological safety. Future studies should be conducted in real food matrices for validation under practical conditions, and phenolic and antioxidant profiling may elucidate the relationship between chemical composition and observed activity.