Neuropharmacological effects of standardized aqueous stem bark extract of Parkia biglobossa in Wistar rats

Objective: Parkia biglobossa stem bark decoction is a popular medicinal plant preparation used as calming agent for tensed patients in traditional medicine. The aim of this study was to evaluate the effects of aqueous stem bark extract of Parkia biglobossa (AEPB) and its active fraction AEPBF3 on anxiety, spontaneous alternation behavior, and locomotor activity. The open field apparatus was used to evaluate effects of AEPB and AEPBF3 on locomotion. The APBE and the active fraction AEPBF3 were standardized using reverse phase high performance liquid chromatography to establish finger print to ascertain identity and stability of the extracts over time. Materials and Methods: The oral median lethal doses (LD(50)) of AEPB and AEPBF3 were evaluated using modified Lorke’s method in rats. The effect of APBE (50-200 mg/kg p.o.), APBEF3 (25 and 50 mg/kg p.o.), diazepam (2.5 mg/kg, i.p.), and 10 ml normal saline/kg on anxiety-like behavior, spontaneous alternation behavior, and locomotion activity were evaluated in rats on elevated plus maze (EPM), Zero-maze, Y-maze, and open field apparatus, respectively. The oral LD(50) values of AEPB and AEPBF3 were estimated to be 5000 mg/kg and 3800 mg/kg body weight in rats, respectively. Results: AEPB and AEPBF3 significantly (F6, 41=2342, p<0.0001) increased time spent in the open arm of EPM and significantly (F6, 41=2323, p<0.0001) increased time spent in open arms of the Zero maze. The AEPB and AEPBF3 administration produced significant increase (F5, 35=154, p<0.0001) in spontaneous alternation behavior in rats. The AEPB extract and its fraction AEPBF3 significantly increased total locomotor activity (F6, 41=413, p<0.0001) and rearing (F6, 41=150, p<0.0001) in the open field apparatus. Conclusion: The results of the present study provided evidence for anxiolytic and nootropic effects of the AEPB and AEPBF3, thus providing scientific basis for its continuous use in the management of neuropsychiatric disorders characterized by apprehension and amnesia.