Phytochemical profile and multi-target biological activities of <i>Sideritis lanata</i> water extract: antioxidant, enzyme inhibition, and anti-inflammatory potential

<i>Sideritis lanata</i> ("mountain tea") is widely consumed; however, its water-extractable chemotype and associated biological activities remain underdefined. In this study, an ultrasound-assisted aqueous extract was characterized to link chemical composition with biological function. The extract exhibited a moderate phenolic load, with a total phenolic content (TPC) of 22.27 mg gallic acid equivalents per gram (GAEs/g) and a total flavonoid content (TFC) of 7.50 mg rutin equivalents per gram (REs/g). Phenolic profiling by liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) revealed a phenolic-acid-dominated signature, mainly hydroxycinnamic acids led by chlorogenic acid (691 µg/g), followed by caffeic acid (231 µg/g), <i>p</i>-coumaric acid (211 µg/g), and ferulic acid (50.4 µg/g), together with abundant hydroxybenzoic acids such as 3- and 4-hydroxybenzoic acids (188 and 183 µg/g, respectively). Antioxidant activity, evaluated using six complementary assays, was moderate and assay-dependent, with stronger metal-chelating activity (IC₅₀ = 1.31 mg/mL) and ferric reducing antioxidant power (FRAP; EC₅₀ = 1.38 mg/mL), followed by phosphomolybdenum (EC₅₀ = 2.03 mg/mL), and weaker cupric reducing antioxidant capacity (CUPRAC; EC₅₀ = 3.10 mg/mL), ABTS (IC₅₀ = 3.64 mg/mL), and DPPH (IC₅₀ = 5.13 mg/mL). The extract inhibited acetyl- and butyrylcholinesterase and tyrosinase with comparable potency (2.69, 2.53, and 2.64 mg/mL, respectively), while weaker inhibition was observed for α-glucosidase (10.63 mg/mL) and α-amylase (19.93 mg/mL). In A549 lung carcinoma cells, viability decreased concentration-dependently; at the half-maximal inhibitory concentration (IC₅₀), tumor necrosis factor-alpha (TNF-α) increased to 26.73 ng/mL, whereas transforming growth factor-beta (TGF-β) and interleukin-1 beta (IL-1β) decreased to 9.4 and 10.83 pg/mL, respectively, while at ½ × IC₅₀ TNF-α was 1.3 ng/mL and TGF-β reached 46.6 pg/mL. Overall, this hydroxycinnamate- and hydroxybenzoate-rich aqueous extract exhibits moderate, target-selective antioxidant and enzyme-inhibitory activities together with dose-dependent immunomodulatory effects.