Phytochemical Phenolic Profile, Cholinesterase and α-Glucosidase Inhibitory Activities Rationalized by Molecular Docking, and Antioxidant Capacity of Hibiscus sabdariffa

This study aimed to evaluate the antioxidant, anticholinesterase, and α-glucosidase (AG) inhibitory activities of the ethanolic leaf extract, characterize its phenolic composition, and investigate the interactions of the major identified phytochemicals with the target enzymes through molecular docking analysis. The phenolic profile was determined by LC–MS/MS, antioxidant activity was assessed using DPPH and ABTS radical scavenging assays, enzyme inhibitory activities against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and AG were evaluated in vitro, and molecular docking was performed to examine ligand–enzyme interactions. Among the analyzed compounds, quercetin, myricetin, fumaric acid, vanillic acid, 4-hydroxybenzoic acid, and salicylic acid were identified as the predominant phenolics in the leaf extract. The extract exhibited DPPH and ABTS radical scavenging activities of approximately 19% and 11%, respectively. It also demonstrated potent enzyme inhibitory activity, with IC50 values of 5.76 ± 0.21 µg/mL for AChE, 3.82 ± 0.17 µg/mL for BChE, and 6.24 ± 0.50 µg/mL for AG. Molecular docking analysis revealed that myricetin and quercetin exhibited the most favorable binding affinities toward AChE, BChE, and AG. Myricetin showed docking scores of −11.188, −9.642, and −7.899 kcal/mol against AChE, BChE, and AG, respectively, supported by hydrogen-bonding, π–π stacking, and hydrophobic interactions within the enzyme active sites. Re-docking validation yielded RMSD values below 2.0 Å for all targets, confirming the reliability of the docking protocol. These findings demonstrate that H. sabdariffa leaf extract is a rich source of bioactive phenolics with promising antioxidant and enzyme inhibitory properties, while molecular docking provides structural evidence supporting the observed biological activities.