Thymus vulgaris and Thymus serpyllum: extraction, distillation, and encapsulation strategies, phytochemical composition and bioactivity

In recent years, Thymus vulgaris and Thymus serpyllum essential oils and polyphenolic extracts have attracted considerable attention as sources of bioactive compounds with health-related biological effects. This review aims to provide a comprehensive and comparative evaluation of these two species, focusing on extraction and distillation strategies, phytochemical composition, biological activities, and encapsulation approaches. The influence of chemotype, geographical origin, environmental conditions, and extraction methodology on the composition of essential oils and extracts of both species was critically evaluated. Both species are characterized by the presence of monoterpenes (thymol and carvacrol) and polyphenolic compounds (rosmarinic acid and flavonoids), although their relative abundance varies depending on multiple factors. Reported biological activities, including antioxidant, antimicrobial, anti-inflammatory, cytotoxic, and anticarcinogenic effects, were evaluated with emphasis on the limitations of cross-study comparison and the distinction between essential oils, extracts, and isolated compounds. Encapsulation strategies were highlighted as promising approaches for improving stability, bioavailability, and biological activity of Thymus vulgaris and Thymus serpyllum essential oils, extracts, and individual compounds. This review provides a solid basis for the interpretation of existing findings and indicates directions for future research requiring further pharmacological and toxicological validation.