Evaluation of the antibacterial activity of (R)-(+)-Limonene against strains of Enterococcus faecium isolated from food: an in vitro and in silico study

Microbial resistance demands new effective drugs, and phytotherapy emerges as an alternative by using medicinal plants to prevent and treat diseases. Thus, the present study aimed to evaluate the antimicrobial activity of (R)-(+)-Limonene against E. faecium strains isolated from food and its mechanism of action by molecular docking with the EfDAP enzyme. The Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) techniques were performed by microdilution in 96-well plates, while the Minimum Inhibitory Adhesion Concentration (MIAC) was evaluated in test tubes. In addition, the association with antimicrobials was analysed by disc diffusion, and the molecular docking test was performed with AutoDock 4.2 software. The results showed MIC90 of 1000 μg/mL and MBC at ratios of 1:1 and 2:1, characterising bactericidal action. Regarding anti-adhesive activity, (R)-(+)-Limonene inhibited biofilm formation up to a ratio of 1:8. Regarding association with antimicrobials, it showed synergism with Gentamicin, Tetracycline, Ciprofloxacin, Amoxicillin, and Ceftriaxone. In addition, molecular interactions based on van der Waals forces and alkyl bonds with EfDAP were identified. These results indicate that the bioactive compounds present in essential oils and their derivatives have the potential to act as inhibitors of microorganisms, highlighting the need for further studies to evaluate their efficacy and possible therapeutic applications.