Multifunctional properties of wintergreen (Gaultheria procumbens) essential oil. Antimicrobial, antibiofilm, and insecticidal effects

This study investigated the antimicrobial, antibiofilm, and insecticidal properties of wintergreen (Gaultheria procumbens L.) essential oil (GPEO). The EO was chemically characterized by GC–MS, confirming methyl salicylate as the predominant compound (99.3%). Its antimicrobial activity was evaluated against a panel of Gram-positive and Gram-negative bacteria, as well as Candida spp., using disc diffusion and broth microdilution assays. GPEO exhibited moderate to strong antimicrobial effects, with the highest inhibition zones recorded for Staphylococcus aureus (15.67 mm) and Listeria monocytogenes (14.67 mm). MIC50 values ranged from 0.34 mg/mL for Yersinia enterocolitica to 6.75 mg/mL for L. monocytogenes. In situ assays on pear, peach, Hokkaido pumpkin, and parsley confirmed that GPEO inhibited microbial growth in a dose-dependent manner, with the strongest effects observed at 500 μL/L, achieving up to 94.33% inhibition on parsley against E. coli. Antibiofilm assays demonstrated significant activity against biofilm-forming Salmonella enterica, with MBIC50 and MBIC90 values of 2.56 and 2.71 mg/mL, respectively. MALDI-TOF MS spectral analyses revealed distinct differences between planktonic and surface-attached cells, with spectral heterogeneity increasing over time and depending on the growth surface. In addition, insecticidal testing against Callosobruchus maculatus adults showed complete mortality at 50%–100% GPEO, whereas partial effects were observed at 25% (80% mortality). These results highlight the strong antimicrobial, antibiofilm, and insecticidal potential of GPEO, supporting its application as a natural preservative and bioactive agent in food safety and pest management.