Study of Monoamine Oxidase Inhibitory Effects of Seven Iranian Medicinal Plant Extracts

Background: Monoamine oxidase (MAO) enzymes abundantly found in the central nervous system (CNS) play an essential role in CNS disorders, so monoamine oxidase inhibitors (MAOIs) have been used for the treatment of neurological ailments such as depression, Parkinson’s, and Alzheimer’s disease. Therefore, finding the new selective MAOIs is still on the focus of researchers’ attention. This study aimed to evaluate MAO-A and MAO-B inhibitory effects of seven methanolic extracts of Iranian medicinal plants including Sanguisorba minor, Cerasus microcarpa, Ferulago angulata, Stachys pilifera, Amygdalus scoparia, Rosa canina, and Alhagi pseudalhagi. 
Materials and Methods: The dried aerial parts of the plants were extracted with methanol by the maceration method. The inhibitory effects of extracts on MAO-A and MAO-B enzymes of rat brain mitochondria were measured by the fluorimetric method by using kynuramine as a substrate. 
Results: Among the extracts, S. minor (IC50 = 7.133 μg/mL) and C. microcarpa (IC50 = 49.53 μg/mL) were the most potent MAO-A and MAO-B inhibitors, respectively. A comparison of the IC50 value indicated that A. scoparia and S. pilifera had a higher affinity for MAO-A inhibition, whereas C. microcarpa and R. canina selectively inhibited the MAO-B enzyme. Moreover, F. angulata was recognized as a non-specific MAO inhibitor. The A. pseudalhagi and S. minor extracts did not show any MAO-B inhibitory effect. 
Conclusion: Our study showed that studied extracts have different MAO-A and MAO-B inhibitory effects. Therefore, they can be used for the treatment of various CNS disorders; also, these extracts are an excellent source for finding new compounds with MAO-A or MAO-B inhibitory effects.