Chemical Profiling and Antimicrobial Prospective of Commercial Essential Oils from Selected Lamiaceae Genera

Essential oils (EOs) of Lamiaceae family have been reported to possess antimicrobial properties. However, commercial preparations of EOs are often of variable quality and inconsistent efficacy due to adulteration and chemotypic variation. This study comprehensively profiled six retail Lamiaceae EOs (Origanum vulgare, O. vulgare subsp. hirtum, Thymus vulgaris, Lavandula angustifolia, Salvia officinalis, and Melissa officinalis) available in Türkiye using GC-MS, complemented by principal component analysis (PCA) and hierarchical cluster analysis (HCA) to discern chemotypic relationships. Antimicrobial and anti-biofilm activities were evaluated against standard bacterial and fungal strains via disc diffusion, broth microdilution, and crystal violet assays. GC-MS and chemometric analyses resolved three distinct chemotypes: phenol-rich (carvacrol/thymol, 49.7-78.2%), ester/alcohol-rich (linalool/linalyl acetate, ~74%), and ketonic/aldehydic-rich (thujone/camphor or citral, 38-54%). Phenol-dominant EOs exhibited potent broad-spectrum activity, with MIC values as low as 0.19% v/v against Enterococcus faecalis and 0.78% v/v against Candida albicans, often surpassing reference antibiotics against Gram-positive and fungal pathogens. In contrast, non-phenolic EOs showed selective or reduced bioactivity, and Pseudomonas aeruginosa remained highly resistant across all samples. These findings confirm that retail Lamiaceae EOs retain authentic phytochemical profiles that emphasize their robust, constituent-dependent antimicrobial efficacy, supporting their therapeutic reliability for consumers when quality is assured.