Appraising the Neurobehavioural Toxicity Potential of Aqueous Methanol Leaf Extract of Tapinanthus globiferus Growing on Azadirachta indica

The high prevalence and disease burden of anxiety disorders against the paucity and liabilities of existing anxiolytics indicates a need for the discovery of additional/new anti-anxiety agents. However, it is necessary to further screen these new/putative anxiolytic compounds/extracts to rule out the unwanted neurobehavioural toxicities inherent in the existing anti-anxiety drugs. Aqueous methanol leaf extract of Tapinanthus globiferus growing on Azadirachta indica host tree has previously demonstrated significant (p<0.05) anxiolytic effects in mice. This study, therefore, set out to counter-screen this extract for locomotion-suppressant, acute amnesic, sedative (myorelaxant) and hypnotic effects using standard mouse behavioural and biochemical paradigms. The leaf extract (150, 500 and 1500 mg/kg) did not cause significant (p>0.05) alterations in spontaneous locomotor activity, motor coordination/balance, sleep onset or duration, but dose-dependent and significant (p<0.05) increases (63.28±5.63, 65.63±4.12 and 69.18±3.69) in novel object recognition indices of extract-treated compared to 51.54±4.03 and 61.06±2.91 scores in diazepam- and aqua-treated mice, respectively. These findings indicate the aqueous methanol leaf extract is mostly devoid of the evaluated neurobehavioural toxicities and may possess short-term memory enhancement property in mice. These findings may justify the traditional use of Tapinanthus globiferus extracts for memory enhancement.