Effect of Citrus grandis [L.] Osbeck on monoamine oxidase inhibitory activities and depressive behavioral assessment in mice

Introduction: Monoamine oxidase (MAO) is an enzyme that located in brain, liver at the outer membranes and oxidized monoamine neurotransmitters. MAO has two isoenzymes, MAO-A and MAO-B. MAO-A plays an important role in psychiatric disorder such as depression and MAO-B involved in neuronal diseases such as Parkinson’s disease (PD) and Alzheimer’s diseases (AD). Monoamine hypothesis, one of the most important causes in depressive disorder and MAO inhibitor is an antidepressant, which have many side effects. Nowadays we look for antidepressant from natural product in order to reducing the unwanted side effects and safety for long term treatment. Objective: This study aimed to investigate antidepressant-like effect of the native economic fruit in Thailand, pomelo (Citrus grandis (L.) Osbeck), on monoamine oxidase (MAO) inhibitory effect and using two acute animal models of depression, forced swimming test (FST) and tail suspension test (TST). Materials and Methods: Three cultivars of pomelo, Tubtim Siam (TS), Thong-dee (TD) and Kao-Nampueng (KN) were used in this study as monoamine oxidase (MAO) inhibitors. Mice were administered the pomelo extract (250, 500 mg/kg, p.o.) and a reference antidepressant, imipramine (IMP, 20 mg/kg, i.p.) 1 hour before starting FST and TST to analyze depression-like behavior in ICR mice (Statistic: One-Way ANOVA followed by the Student-Newman-Keulstest). Results: The results showed that 3 cultivars of pomelo including TS, TD and KN inhibited the MAO-A activity with the IC50 values of 721.20±0.26, 426.68±0.33 and 1080±1.01 μg/ml and MAO-B activity with the IC50 values of 68.31±0.97, 144.51±0.31 and 749.31±1.12 μg/ml, respectively. In addition, only TS significantly decreased the immobility time in mice when compare with control group in both TST and FST. Conclusion: The results of this study suggest that TS ameliorated depressive-like symptom and the possible mechanism may be involve in its inhibitory effect on monoamine oxidase enzymes.