UPLC-ESI-QToF-MS/MS profiling and anxiolytic-like effects of Simira paraensis (Baill.) Steyerm bark

Simira paraensis (Baill.) Steyerm (Rubiaceae), popularly known as araribá-rosa, is a small tree found mainly in the Amazon. Studies on the genus Simira report a chemical composition rich in indole alkaloids of the β-carboline class, which are associated with effects on the central nervous system. The present study aimed to characterize the chemical profile and evaluate the anxiolytic activity of S. paraensis bark through in vivo and in silico assays. The powdered bark was extracted with a hydromethanolic solution, yielding a red-colored extract (SP-EMB), which was analyzed by Ultra High Performance Liquid Chromatography coupled to Electrospray Ionization Mass Spectrometry and Quadrupole-Time-of-Flight Analyzer (UPLC-ESI-QToF-MS/MS). The neuropharmacological activity was evaluated in zebrafish (Danio rerio) using locomotor activity, light/dark, novel tank, GABAergic neuromodulation, and PTZ-induced seizure assays. UPLC-ESI-QToF-MS/MS analysis revealed 15 β-carboline alkaloids, 4 phenolic acid derivatives, and 1 phenolic glycoside. Harmane, the major constituent, was isolated by preparative HPLC and identified by UPLC-ESI-QToF-MS/MS and NMR analyses. SP-EMB exhibited anxiolytic-like effects in both light/dark and novel tank tests, with low acute toxicity (LD₅₀ > 400 mg·kg⁻¹) and reduced sedative effects compared to diazepam (DZP, 4 mg·kg⁻¹). Molecular docking showed that harmane and chlorogenic acid have high affinity for the GABA_A receptor, indicating their influence on the anxiolytic effect. Both compounds showed low toxicity (LD₅₀ > 40 mg·kg⁻¹) and dose-dependent anxiolytic-like activity without locomotor impairment. Furthermore, chlorogenic acid exhibited anxiolytic effects mediated by GABA_A receptors. These findings may suggest that S. paraensis is a promising alternative source of anxiolytic agents with lower sedative effects.