Novel Ocimumoside A and B as anti-stress agents: Modulation of brain monoamines and antioxidant systems in chronic unpredictable stress model in rats

Therapies targeting central stress mechanisms are fundamental for the development of successful treatment strategies. Ocimum sanctum (OS) is an Indian medicinal plant traditionally used for the treatment of various stress-related conditions. Previously, we have isolated and characterized three OS compounds; Ocimarin, Ocimumoside A and Ocimumoside B. However, their role in modulating chronic stress-induced central changes is unexplored. Thus, in the present study the efficacy of these OS compounds have been evaluated on the chronic unpredictable stress (CUS)-induced alterations in the monoaminergic and antioxidant systems in the frontal cortex, striatum and hippocampus, along with the changes in the plasma corticosterone levels. CUS (two different types of stressors daily for seven days) resulted in a significant elevation of plasma corticosterone level, which was reversed to control levels by pretreatment with Ocimumoside A and B (40 mg/kg p.o.), while Ocimarin showed no effect. The levels of NA, DA and 5-HT were significantly decreased in all the three brain regions by CUS, with a selective increase of DA metabolites. A significant decrease in the glutathione (GSH) content, the activities of superoxide dismutase and catalase with a significant increase in the glutathione peroxidase activity and lipid peroxidation was observed in all the three regions of the brain by CUS. The OS compounds alone did not cause any significant change in the baseline values of these parameters. However, Ocimumoside A and B (40 mg/kg body p.o.) attenuated these CUS-induced alterations with an efficacy similar to that of standard anti-stress (Panax quinquefolium; 100 mg/kg p.o.) and antioxidant (Melatonin; 20 mg/kg i.p.) drugs. While, Ocimarin failed to modulate these CUS-induced alterations. Therefore, this is the first report which identified the anti-stress activity of novel Ocimumoside A and B at the level of central monoamines and antioxidant properties, implicating their therapeutic importance in the prevention of stress-related disorders.