Nootropic and Behavioural Actions of Saponins Isolated from Bark of Albizia lebbeck

Abstract

Objectives: In the previous study saponins isolated from leaves of Albizzia lebbeck exhibited nootropic activity in mice. The objectives of the present study were therefore to assess the nootropic activity of saponin containing fraction isolated from the bark of Albizzia lebbeck using different paradigms and to study its effect on the behaviour mediated by various neurotransmitters like acetylcholine, noradrenaline, serotonin, dopamine and gamma-aminobutyric acid. Materials and methods: The nootropic effect of saponin containing n-butanolic fraction (ALBF) obtained from dried bark of A. lebbeck was studied in male albino mice using passive shock avoidance, elevated plus maze, and object recognition. The effect of ALBF was studied on sodium nitrite-induced respiratory arrest (acetylcholine mediated behaviour), clonidine-induced hypothermia and passivity (noradrenaline mediated behaviour), baclofen-induced hypothermia and passivity (gamma-aminobutyric acid mediated behaviour), haloperidol-induced catalepsy (dopamine mediated behaviour), and lithium-induced head twitches (serotonin mediated behaviour). The effects were compared with those of piracetam. Results: ALBF reduced latency to reach shock free zone and number of mistakes in the passive shock avoidance paradigm. ALBF antagonized amnesic effect of scopolamine in this test. ALBF per se reduced transfer latency on the elevated plus maze. The inflexion ratio reduced by scopolamine was not increased significantly by ALBF. In the object recognition test, ALBF explored the familiar object significantly earlier compared to that by piracetam. Both piracetam and ALBF antagonized the amnesic effect of scopolamine in this experiment. ALBF potentiated hypothermic effect of clonidine but could not antagonize the baclofen-induced hypothermia significantly. ALBF increased clonidine-induced passivity and inhibited baclofen-induced passivity. ALBF was without any effect on sodium nitrite-induced respiratory arrest and haloperidol-induced catalepsy but reduced lithium-induced head twitches. Conclusion: The ALBF, saponins containing fraction of A. lebbeck per se exhibited nootropic activity and reversed amnesic effect of scopolamine. The ALBF exhibited decreased noradrenergic and serotonergic transmission and was without any effect on cholinergic and dopaminergic transmission. The study indicates that the saponins isolated from A. lebbeck possess potential nootropic activity. The absence of cholinergic and dopaminergic involvement in nootropic activity of ALBF may be utilized to study the involvement of other neurotransmitters in the cognitive function.