Acute toxicity (LD50 values) and neuropharmacological profile of n-hexane fraction of Petiveria alliacea L. (Phytolaccaceae) in mice

Background: Petiveria alliacea L. (Phytolaccaceae) ethnomedically is known for its sedative property and beneficial treatment of other central nervous system (CNS) disorders. However, the neuropharmacological properties of the n-hexane extract of this aromatic plant leaf have not been reported, hence this study. Objective: To determine the acute toxicity profile (LD50) and some CNS activities of the n-hexane extract of fresh leaf of P. alliacea (NHEPA) in mice. Method: The fresh leaf of Petiveria alliacea was collected and the n-hexane extract obtained using appropriate technique. The LD50 was determined for both the oral and intraperitoneal (i.p.) route. All treatments were administered via i.p. route. Behavioural activity was evaluated using the novelty-induced behaviour (NIB) to assess rearing, grooming and locomotion; sedative activity was tested on ketamine-induced hypnosis while the anticonvulsant potential was assessed using chemo-convulsants. The mechanism of action was determined using amphetamine as agonist and flumazenil as an antagonist. Results: The LD50 values obtained for the extract was 2450 and 346 mg/kg for oral and intraperitoneal routes respectively. The extract displayed significant CNS depressant activity on all NIB parameters. NHEPA significantly prolonged sleep latency and total sleeping time at 100 and 150 mg/kg. i.p. The extract also offered some mild protection against convulsion across the model used. The probable mechanism of action may include inhibition of monoamine pathways and augmentation of the GABAA- benzodiazepine complex pathway. Conclusion: NHEPA showed CNS depressant activity, exhibited significant sedative activity and mild anticonvulsant activity.