Phytochemical Characterization and Biological Activity of Stachys pinardii Extracts

The study investigated how solvent choice affects the extraction of bioactive phytochemicals from Stachys pinardii. Methanol and aqueous extracts of aerial parts were obtained using ultrasound-assisted extraction and analyzed for phytochemical content, antioxidant capacity, and enzyme inhibition. The methanol extract showed higher total phenolic (52.56 mg GAEs/g) and flavonoid contents (18.19 mg REs/g) than the aqueous extract (15.62 mg GAEs/g and 8.25 mg REs/g). Liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) analysis identified verbascoside and chlorogenic acid as major compounds in methanol, while aqueous extract was richer in caffeic acid and hydroxycinnamic derivatives. Despite lower phenolic content, the aqueous extract demonstrated stronger antioxidant activity across 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), cupric ion reducing antioxidant capacity (CUPRAC), and ferric reducing antioxidant power (FRAP) assays, with lower IC₅₀/EC₅₀ values. It also exhibited superior enzyme inhibitory effects, particularly against α-amylase (2.52 mg/mL) and α-glucosidase (1.58 mg/mL), although its inhibitory activity remained lower than that of the standard acarbose. Overall, solvent polarity significantly influences both phytochemical composition and biological activity. The aqueous extract, despite its lower total quantified phenolic content, shows promising multifunctional bioactivity. Further studies should focus on bioactivity-guided fractionation and mechanistic insights into individual compounds.