How distillation alters bioactivity: Comparative phytochemical and biological evaluation of three Lamiaceae species (Origanum sipyleum, Thymus sipyleus, and Sideritis phrygia) before and after distillation

In the current study chemical profiles and the biological activities of three different plant species (Origanum sipyleum, Thymus sipyleus, and Sideritis phrygia) of the Lamiaceae family native to Turkey were explored considering different approaches leading to extracts with different composition. We adopted for each plant extraction with methanol (Total Methanol), water infusion (W), supercritical CO2 extract (SCO2), essential oil (EO). Furthermore, the residues remaining after hydrodistillation and supercritical CO2 extraction were subsequently extracted with methanol, yielding the Spent HD and Spent SCO2 extracts for each plant species. To evaluate possible bioactivities several assays were performed. Antioxidant capacities were measured with multiple in vitro assays (ABTS, DPPH, FRAP, CUPRAC, PBD, and metal chelating ability (MCA), along with total phenolic content. Enzyme inhibitory activities of the obtained extracts were evaluated against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), tyrosinase, amylase, and glucosidase, important enzymes involved in metabolic and degenerative disorders like diabetes, neurodegenerative and skin disorders. Methanol and water extracts generally exhibited the highest total phenolic content, along with the greatest antioxidant capacities. Among the remaining extracts, the spent fractions (especially spent SCO₂) also demonstrated notable antioxidant activity. Beneath them the extracts spent (especially spent SCO2) were the most active. The different extraction procedures lead to different chemical composition with limited extraction of phytoconstituents in the SCO2 and larger presence of phenolics in the other extracts. Salvianolic acid B, rosmarinic acid and kaempferol-hexoside-derivate were the main components in the total methanol extracts of O. sipyleum, T. sipyleus and S. phrygia, respectively. In same order, the main components were alloaromadendrene, valencene and spathulenol in their EOs. The results indicate that the plant materials after HD and SCO2 are still rich in bioactive compounds and they can be used to extract bioactive compounds. The obtained extracts present different potential bioactivities and can be the starting point to design multidirectional health-promoting products for applications in pharmaceutical and nutraceutical areas.