Abstract
Diets rich in fruits and vegetables are associated with better psychological wellbeing and cognitive functions, although it is unclear which molecules and mechanisms are involved. One potential explanation is the inhibition of monoamine oxidases (MAOs), which have been linked to several neurological disorders. The present study investigated the ability of kiwifruit to inhibit MAO-A and MAO-B, refining an in vitro assay to avoid confounding effects. Ultra-performance liquid chromatography/mass spectrometry (UPLC-QTOF) and nuclear magnetic resonance spectroscopy (NMR) were used to select individual kiwifruit metabolites for further analysis. Moreover, extracts of other common fruits and vegetables were screened to identify promising candidate inhibitors. Multiple extracts and compounds inhibited both enzymes, and the selective inhibition of MAO-B by the major kiwifruit specialized metabolite D-(−)-quinic acid was observed. These results suggest that fruits and vegetables contain metabolites that inhibit the activity of MAO-A and -B, offering a potential natural option for the treatment of neurological disorders, in which MAOs are involved.
Highlights
The beneficial effects of a diet rich in fruits, vegetables, nuts, and vegetable-based ingredients are widely recognized, in the context of cardiovascular disease [1].More recent studies have linked such diets to mental health, including observational and small intervention studies focusing on the benefits of a so-called Mediterranean diet.These reports revealed a positive impact on cognitive performance [2], depression [3], and psychological wellbeing [4,5]
Microplate assays to test the ability of compounds to inhibit monoamine oxidases (MAOs)-A and -B were optimized for use with fruit and vegetable extracts by testing freshly extracted kiwifruit juice
The inhibition of the MAOs through diet could contribute to the control of pathologies dependent on the activity of these enzymes
Summary
The beneficial effects of a diet rich in fruits, vegetables, nuts, and vegetable-based ingredients are widely recognized, in the context of cardiovascular disease [1].More recent studies have linked such diets to mental health, including observational and small intervention studies focusing on the benefits of a so-called Mediterranean diet.These reports revealed a positive impact on cognitive performance [2], depression [3], and psychological wellbeing [4,5]. More recent studies have linked such diets to mental health, including observational and small intervention studies focusing on the benefits of a so-called Mediterranean diet. Observational and interventional studies on the effect of whole dietetic patterns on brain health, while being powerful tools, cannot determine which fruits and vegetables (and which molecules) are responsible for the positive effects. This would require interventional studies with a single fruit or vegetable, which have been carried out, just to give some examples, with gold kiwifruit [7], orange juice [8], and sour cherry [9]
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