Chemical Composition of Thymus Species from Bulgarian Flora

The present study investigated the chemical composition of the main components of five commonly occurring Thymus species in Bulgaria: T. sibthorpii Benth., T. pulegioides L., T. glabrescens Willd. (syn. T. odoratissimus Mill.), T. callieri Borbas ex Velen. (syn. T. roegneri K. Koch), and T. zygioides Griseb. The phytochemical profiling of the Thymus species was performed using GC-MS for the analysis of essential oils and HPLC for the identification and quantification of phenolic compounds in the ethanolic extracts. Linalool was the dominant essential oil constituent in T. sibthorpii (48.17%), T. pulegioides (50.96%), and T. callieri (38.08%) while thymol prevailed in T. glabrescens (35.35%). A novel chemotype was observed in T. zygioides. The HPLC analysis confirmed rosmarinic acid as the major phenolic acid across all species. Rutin was the predominant flavonoid in four species whereas T. sibthorpii exhibited a remarkably high concentration of (+)-catechin. Overall, the high chemical diversity within the Thymus genus was confirmed. Due to the variability of compounds among plant species, the findings of the present study suggest that, along with essential oils, phenolic components may also contribute to the chemotaxonomic classification of the Thymus genus and influence the pharmacological activity of the species, which requires further study.