LC-MS/MS-based phytochemical characterization and bioactivity evaluation of Hypericum calycinum: Antioxidant, enzyme Inhibitory, and in silico approaches

Hypericum calycinum L. (Hypericaceae) is a medicinal plant used in Turkish traditional medicine, yet its phytochemical profile and associated biological activities remain comparatively undercharacterised. In this study, the ethyl acetate (EA), methanol, and water extracts of the aerial parts of H. calycinum were prepared and evaluated for their total phenolic content (TPC), total flavonoid content (TFC), antioxidant properties, and enzyme inhibitory activities against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), tyrosinase, α-amylase, and α-glucosidase. Chemical component profiling was carried out by UPLC-QToF MS in negative ion mode (ESI-), tentatively identifying over 90 phytoconstituents belonging to the classes of hydroxycinnamic and hydroxybenzoic acids, flavonoids, condensed and hydrolysable tannins, xanthones, and acylphloroglucinols. The water extract showed the highest TPC (89.34 mg GAE/g) and the strongest radical scavenging and reducing power activities. The highest α-amylase inhibitory activity was observed for the ethyl acetate (0.99 mmol ACAE/g). Molecular docking of the major phytochemicals against the five target enzymes revealed consistently favorable binding energies for caffeoylquinic acid isomers, chlorogenic acid, quercitrin, hyperoside, and myricetin 3-(2″-galloylglucoside). Collectively, these findings provide a detailed phytochemical and pharmacological characterization of H. calycinum and highlight its potential as a source of multitarget bioactive compounds relevant to neurodegenerative, metabolic, and pigmentation-related disorders.