Chemical Profiling and Antioxidant Capacity Assessment of Three Endemic Thymus Species Distributed in Bulgaria

Abstract

The genus Thymus, a member of the Lamiaceae family, encompasses species renowned for their medicinal properties. This study aimed to determine the metabolite composition and free radical scavenging potential of three endangered species with restricted distribution in Bulgaria: T. perinicus (Velen.) Jalas, T. jalasaianus Stoyanov & Marinov, and one endemic to the Balkans – T. aznavourii Velen., all fall under the section Hyphodromi. Non-polar (chloroform and diethyl ether) and polar (methanol) extracts were prepared from the studied species. GC/MS and HPTLC analyses were applied to identify the metabolites. Antioxidant capacity was assessed using the DPPH test, while the Folin-Ciocalteu colourimetric assay measured total phenolic content (TPC). Chromatographic analyses revealed a rich array of primary and secondary metabolites, some known for their health-promoting properties. HPTLC identified compounds such as rosmarinic acid, lupeol, uvaol, ursolic, and oleanolic acids, while GC/MS detected terpenes like thymol, caryophyllene, cis–β-farnesene, and germacrene D, as well as phenolic acids such as 4-hydroxybenzoic, 4-hydroxycinnamic, vanillic, and caffeic acids, alongside fatty acids, fatty alcohols, and saccharides. Methanol extracts exhibited significant antiradical activity (IC50 < 50 µg/mL), with TPC values ranging from 7.44 to 17.97 mg GAE/g extract, aligning with DPPH assay findings. This study represents the first report on the chemical composition of extracts with varying polarity from T. jalasaianus and T. aznavourii. It offers valuable insights into the phytochemistry of these Thymus species, highlighting their potential applications across diverse industries and the need for their conservation.