Natural Phenolic Antioxidants from Micromeria aybalae: Solvent-Dependent Composition and Bioactivity

Micromeria aybalae H.Duman & Dirmenci is a recently described endemic Lamiaceae species from southwestern Türkiye whose non-volatile phytochemistry and biological properties remain largely unexplored. This study comparatively evaluated ethyl acetate, methanol, and water extracts of its aerial parts for phenolic composition, antioxidant capacity, and enzyme inhibitory activity. Targeted Targeted liquid chromatography–tandem mass spectrometry (LC–MS/MS) screening of 31 phenolics detected 23 compounds, with rosmarinic acid as the predominant constituent, reaching 19,650.23 µg/g extract in the water extract. The water extract also showed the highest extraction yield (11.14%), total phenolic content (71.62 mg gallic acid equivalents (GAE)/g extract), and activities in the phosphomolybdenum, 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), cupric reducing antioxidant capacity (CUPRAC), and ferric reducing antioxidant power (FRAP) assays. In contrast, the methanol extract exhibited the highest total flavonoid content (17.73 mg RE/g extract) and the strongest tyrosinase and α-amylase inhibitory activities. Verbascoside was markedly enriched in the ethyl acetate extract (1288.60 µg/g extract), which also displayed the greatest metal-chelating activity. These findings provide the first comprehensive phenolic and bioactivity profile of M. aybalae and highlight extraction-condition-dependent differences in phenolic composition and in vitro activities, establishing a foundation for future investigations of this endemic species.