Evaluation of the antidepressant effect of Melilotus officinalis fruit ethanolic extract in murine models

Melilotus officinalis (Papilionaceae family) possess potent antioxidant, anxiolytic, anti-inflammatory, and anticonvulsant activities. According to the mentioned cases, the aim of the current study was to investigate the antidepressant effect of the M. officinalis ethanolic extract (MOEE) in the murine models.

In this study, the acute toxicity of the MOEE was evaluated by Lorek's method. Adult male NMRI mice were treated with normal saline, fluoxetine (20 mg/kg, i.p.), or MOEE (50, 100, and 200 mg/kg, i.p.), and then it was performed to forced swimming test(FST) and tail suspension test (TST).  The locomotion of the mice was also evaluated in the open-field test (OFT).

The results showed that the LD50 of the extract was found to be greater than 5000 mg/kg. Intraperitoneal administration of MOEE (except the dose of 25 mg/kg in FST)  reduces immobility time in all groups of the FST and TST. Also, this extract increased the duration of swimming time without significant change in the climbing time in the FST. The locomotion of mice was not affected by the MOEE in OFT.

The results of this study show that Melilotus officinalis is a non-toxic compound and has antidepresant activity similar to fluoxetine. Therefore, this plant has therapeutic potential for depression. However, more studies are necessary to determine the exact mechanism of the anti-depressant effect and the absence of adverse effects in chronic administration.
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