Amelioration of Chronic Unpredictable Mild Stress-Induced Behavioural Perturbations by Noni Juice in Mice: Possible Involvement of Antioxidant System

Aims: Noni juice is a natural herbal formulation containing Morinda citrifolia widely acclaimed as an immune system stimulant and mood enhancer. The aim of the study was to explore the antidepressant- and anxiolytic-like behavioural effects of Noni ­­juice and to further evaluate the possible mechanisms of action in terms of biomarkers of oxidative stress on chronic unpredictable mild stress (CUMS) induced depressive model in mice.

Methods: CUMS was used to induce behavioural deficits (depressive- and anxiety-like behaviours) and oxidative imbalance in mice. Mice were pretreated with Noni juice (2.5, 5 and 10 mL/kg, p.o) and thereafter subjected to different stress paradigms daily for a period of 21 days. Thereafter, sucrose preference test, behavioural despair tests, open field exploratory behaviour, Y-maze test as well as elevated plus maze, and light and dark maze tests were used to assess antidepressant- and anxiolytic-like behaviours, while standard biochemical protocols were used to assay for the biochemical alterations [Glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA)].

Results: The results showed that Noni ­­juice demonstrated significant (P < 0.05) inhibition of CUMS induced depressive- and anxiety-like behaviours in mice; by increasing the preference for sucrose, locomotor activity in the open field exploratory test, memory performance, decrease immobility in the behavioural despair tests and anxiety-related depressive behaviours. Furthermore, Noni ­­juice decreased MDA concentration (33.2, 58.7 and 70.2%) in a dose-related manner. Moreover, Noni ­­juice significantly (P < 0.05) prevented the decrease in SOD and CAT activities, and increased GSH concentration in brain tissues.

Conclusion: These data provides a rationale for evaluating Noni juice as a novel psychotropic agent against depressive- and anxiety-related behaviours and suggest that its mechanisms of action may be related to the modulation of endogenous antioxidant defense system.