Antidepressant-like effect of 4-hydroxyisoleucine from Trigonella foenum graecum L. seeds in mice

Trigonella foenum graecum L. (Fabaceae), also known as fenugreek, is one of the oldest medicinal plants, and has a long history of medical use in traditional and modern literature. 4-hydroxyisoleucine (4-HI) constitutes about is 80% of the total content of free amino acids in Trigonella foenum graecum seeds. In present study, we report antidepressant-like effects of 4-HI in animal models of depression. The effects of 4-HI (10, 30 or 100 mg/kg) in Forced swim test, 5-hydroxytryptophan (5-HTP)-induced head twitches, and spontaneous motor activity (SMA) scores were assessed in mice. Oral acute administration of 4-HI showed the dose-dependent reversal in forced swim induced increased immobility behavior in normal and reserpinized mice in dose range of 3 to 30 mg/kg. The SMA scores were not affected by 4-HI in normal or reserpinized mice except for dose of 30 mg/kg, showing central rather than peripheral mechanism of 4-HI. Further, significant increase in number of 5-HTP (precursor of serotonin) induced head twitches was shown by 4-HI. In conclusion, 4-HI showed antidepressant-like effects in animal models of depression by brain serotonin turnover enhancement.