Abstract
Origanum sipyleum and Sideritis pisidica are endemic Turkish Lamiaceae species with previously reported phytochemistry and bioactivities, but matched-condition comparisons remain limited. This study aimed to compare aqueous extracts prepared by ultrasound-assisted extraction (5 g/100 mL water, 40 kHz, 360 W nominal ultrasonic power, 3 h, approximately 40 °C). A previously established 28-compound panel was analyzed by LC–MS/MS, alongside total phenolic and flavonoid contents, six antioxidant assays, and five enzyme-inhibitory assays. Eighteen and 19 phenolic compounds were detected in O. sipyleum and S. pisidica, respectively. Protocatechuic acid predominated in O. sipyleum (2334.15 µg/g extract), whereas chlorogenic acid predominated in S. pisidica (3525.31 µg/g extract). O. sipyleum exhibited significantly higher total phenolic and flavonoid contents and greater radical-scavenging and reducing activities, while phosphomolybdenum and ferrous-ion chelating activities were statistically comparable. Butyrylcholinesterase and α-amylase inhibitor-equivalent activities were statistically comparable between the species, whereas S. pisidica exhibited higher acetylcholinesterase-inhibitory (3.14 versus 2.94 mg galantamine equivalents/g extract) and tyrosinase-inhibitory activities (23.90 versus 21.01 mg kojic acid equivalents/g extract). O. sipyleum also displayed α-glucosidase inhibition (319.56 mg acarbose equivalents/g extract), while no inhibition was detected for S. pisidica within 0.1–5.0 mg/mL. This comparison identifies contrasting targeted phenolic profiles and assay-dependent in vitro responses without establishing compound-level causality.