# Species-Specific Metabolite Profiles and Biological Activities of Bulgarian Thymus Species from Section Hyphodromi

## TL;DR

This study explores the unique chemical and biological properties of eight Bulgarian Thymus species, highlighting their antioxidant and enzyme-inhibiting potential.

## Contribution

The paper presents first-time data on the phytochemical and biological activity profiles of rare and endemic Bulgarian Thymus species.

## Key findings

- MeOH extracts showed high levels of phenolic acids and strong antioxidant activity in T. jalasianus and T. atticus.
- Et2O extracts were rich in triterpenic acids and monoterpenes, especially in T. zygioides and T. leucotrichus.
- Only T. zygioides and T. leucotrichus exhibited moderate acetylcholinesterase-inhibitory activity.

## Abstract

This study investigates the phytochemical composition and biological activity of eight Thymus species distributed in Bulgaria, with a focus on taxa from section Hyphodromi. High-performance liquid chromatography (HPLC) and gas chromatography–mass spectrometry (GC–MS) were used to characterize the methanolic (MeOH) and diethyl ether (Et2O) extracts, respectively. MeOH extracts revealed high concentrations of phenolic acids, particularly rosmarinic acid, salicylic acid, and flavonoid glycosides, with T. atticus, T. jalasianus, and T. leucotrichus showing the most diverse profiles. Et2O extracts were dominated by triterpenic acids (ursolic and oleanolic) and monoterpenes such as thymol and carvacrol, especially in T. zygioides and T. leucotrichus. All MeOH extracts exhibited significant antioxidant activity in the DPPH assay (IC50 < 50 µg/mL), with T. jalasianus and T. atticus demonstrating the strongest effects. Radical scavenging potential generally followed the trend of total phenolic content. Moderate acetylcholinesterase-inhibitory activity was observed only in T. zygioides and T. leucotrichus. The study reports for the first time data on the biological activity and metabolic composition of extracts from endemic and rare species and from the species of Bulgarian origin. The results provide new data on the phytochemical composition and in vitro antioxidant and acetylcholinesterase-inhibitory activities of selected Thymus species, contributing to the characterization of their overall in vitro biochemical profiles.