Behavioural and biochemical indications of the antidepressant activities of essential oils from Monodora myristica (Gaertn) seed and Xylopia aethiopica (Dunal) fruit in rats

Monodora myristica and Xylopia aethiopica are two underutilised spices that are hypothesized to be important in the management and treatment of certain stress-induced diseases such as depression. The present study was designed to test the anti-depressant effects of the essential oils of Monodora myristica (EOMM) and Xylopia aethiopica (EOXA) and the possible underlying mechanisms in a chronic unpredictable mild stress (CUMS) - induced depression in the rat. Forty-two male Wistar rats were assigned to seven groups (n = 6); group I received corn oil (p.o, unstressed control), group II (stressed control) administered corn oil, groups III-IV received EOMM (150 & 300 mg/kg, p.o), groups V – VI received EOXA (150 & 300 mg/kg, p.o) whereas group VII had fluoxetine (10 mg/kg, p.o in d/w). Corn oil served as the vehicle for the delivery of the essential oils and the doses were administered via gastric intubation to rat once daily for six consecutive weeks from the 2nd week. Open-field, tail suspension (TST), and forced swimming (FST) tests were used to evaluate the behavioural activity in addition to the biochemical parameters (catalase, superoxide dismutase, reduced glutathione, monoamine oxidase, corticosterone, protein carbonyl compound, malondialdehyde and nitric oxide). The result showed that the administration of EOMM (150 and 300 mg/kg b.wt.) and EOXA (150 and 300 mg/kg b.wt.) during CUMS significantly ameliorated these behavioural activities and some biochemical parameters in rats. EOMM and EOXA exhibited significant antidepressant-like effects in a rat model of CUMS. At treatment doses of especially 300 mg/kg b.wt, the antidepressant effects of EOMM and EOXA are comparable to a standard antidepressant drug, fluoxetine (Prozac ™). The EOXA especially at a dose of 300 mg/kg b.wt is more effective than EOMM even at 300 mg/kg dose level in ameliorating depression in stressed rats. In conclusion, the study revealed that both the EOXA and EOMM relieved depression-like states through the mitigation of oxidative stress with a reduction in serum Corticosterone (CORT) and brain Monoamine Oxidase-A (MAO-A) levels.