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.
Keywords: Polyphenols, antioxidants, oxidative stress, neuroprotective, anxiety and depression