a1 DSM Nutritional Products Limited, Research and Development Human Nutrition and Health, PO Box 2676, CH-4002 Basel, Switzerland
a2 Leicester School of Pharmacy, De Montfort University, The Gateway, Leicester LE1 9BH, UK
A healthy, balanced diet is essential for both physical and mental well-being. Such a diet must include an adequate intake of micronutrients, essential fatty acids, amino acids and antioxidants. The monoamine neurotransmitters, serotonin, dopamine and noradrenaline, are derived from dietary amino acids and are involved in the modulation of mood, anxiety, cognition, sleep regulation and appetite. The capacity of nutritional interventions to elevate brain monoamine concentrations and, as a consequence, with the potential for mood enhancement, has not been extensively evaluated. The present study investigated an extract from oregano leaves, with a specified range of active constituents, identified via an unbiased, high-throughput screening programme. The oregano extract was demonstrated to inhibit the reuptake and degradation of the monoamine neurotransmitters in a dose-dependent manner, and microdialysis experiments in rats revealed an elevation of extracellular serotonin levels in the brain. Furthermore, following administration of oregano extract, behavioural responses were observed in mice that parallel the beneficial effects exhibited by monoamine-enhancing compounds when used in human subjects. In conclusion, these data show that an extract prepared from leaves of oregano, a major constituent of the Mediterranean diet, is brain-active, with moderate triple reuptake inhibitory activity, and exhibits positive behavioural effects in animal models. We postulate that such an extract may be effective in enhancing mental well-being in humans.
(Received April 12 2010)
(Revised October 09 2010)
(Accepted November 01 2010)
(Online publication December 21 2010)
Abbreviations: 5-HIAA, 5-hydroxyindoleacetic acid; 5-HT, 5-hydroxytryptamine; ASP, 4-(4-(dimethylamino)-styryl)-N-methylpyridinium; CAR, carvacrol; CLO, clobazam; DMSO, dimethylsulphoxide; FLU, fluoxetine; hDAT, human dopamine transporter; hNAT, human noradrenaline transporter; hSERT, human serotonin transporter; IC50, half maximal inhibitory concentration; IMI, imipramine; i.p., intraperitoneal; MAO, monoamine oxidase; NA, noradrenaline; p.o., per os; TQ, thymoquinone; VEH, vehicle; VEN, venlafaxine