Quality Evaluation of Commercial Products Marketed as Thymus vulgaris L. Essential Oil According to European Pharmacopoeia 10.0 Criteria

Abstract

Essential oils are mixtures of complex secondary metabolites with variable chemical compositions that determine their therapeutic effects. Thyme oil, obtained from the fresh or dried leaves and flowers of Thymus spp. through steam distillation, is widely used in food, pharmacy, and perfumery-cosmetics due to its antimicrobial, antitussive, and antioxidant properties. Ensuring the quality of essential oils is important for public health, as globally encountered deviations from the established standards pose a risk to consumers. This study evaluated the quality of 12 different Thymus vulgaris L. essential oil (TVEO) samples from pharmacies and various sources on the Turkish market, focusing on their adherence to the European Pharmacopoeia (EP) 10.0. Following primary assessments of appearance, solubility, relative density and refractive index; high-performance thin-layer chromatography (HPTLC) and gas chromatography-mass spectrometry (GC-MS) analyses were performed for each TVEO sample to profile their phytochemical composition. Results revealed that none of the samples met all the criteria specified in EP 10.0. The mean proportion of EP criteria fulfilled per sample is 46.9% for pharmacy-sourced samples and 41.9% for non-pharmacy-sourced samples. The findings of this study suggest that future quality control analysis for TVEO samples on the Turkish market should integrate comprehensive chemical profiling with advanced analytical strategies.