Thyme Beyond Its Traditional Culinary Use: Bioactive Constituents as Potential Modulators of the Gut Microbiome

Abstract Thyme, particularly Thymus vulgaris L., is a widely used culinary spice and a source of compounds with diverse reported pharmacological activities. This Review examines how thyme extracts, essential oils, and their major constituents, including characteristic monoterpenes, sesquiterpenes, triterpenes, phenolic acids, and flavonoids, interact with the gut microbiome. On the basis of structure–activity relationships, we evaluate how these constituents influence gut microbial composition and function and summarize the implicated mechanisms. Thyme preparations and individual compounds can influence intestinal availability, microbial transformation, and target selectivity, while microbiota-dependent and -independent pathways may contribute to changes in intestinal barrier function, metabolite profiles, and related signaling pathways. Interactions among multiple constituents may produce additive or synergistic effects, suggesting potential advantages of multicomponent thyme preparations, whereas studies of individual compounds can facilitate the target identification and mechanistic analysis. Future research should systematically address gaps in causal validation, formulation standardization, and human evidence to consolidate the translational foundations.