Polyphenols: A Potential New Strategy for the Prevention and Treatment of Anxiety and Depression

Following recent evidence that disturbances in oxidative metabolism are involved in anxiety disorders, high anxiety levels and depression, the use of antioxidants has been proposed as a novel approach for the prevention or treatment of these conditions. Polyphenols are naturally-occurring antioxidant substances which can have pharmacological actions on the central nervous system. This mini-review aims to examine the current evidence for the potential use of dietary polyphenols as neuroprotective agents to reduce anxiety and to manage depression. I will outline recent findings which demonstrate that polyphenols have anti-anxiety effects at higher doses (300/60/30/20 mg/kg body weight) as well as at lower doses (2-4 mg/kg); this can be compared to conventional anxiolytics, which only have anxiolytic effects at lower doses (1-5 mg/kg). To circumvent problems associated with polyphenols (e.g., quercetin) having difficulty crossing the blood-brain barrier and to effectively reduce the active dose, intranasal administration in the form of liposomes could be an interesting approach. I also suggest that dietary polyphenols could be a new alternative approach to treat depression, because they exhibit antidepressant activity with relatively lower doses (0.3-2 mg/kg) than commonlyused antidepressants such as imipramine (10 mg/kg). The polyphenols discussed in this mini-review are found in vegetables and fruits such as apples, plums, cherries, onions and tea. Therefore, a varied diet that is rich in naturallyoccurring polyphenols could be an effective means to prevent (or delay) anxiety, depression and other diseases linked to oxidative stress.