Monoamine Oxidase-B (MAO-B) Inhibitors in the Treatment of Alzheimer’s and Parkinson’s Disease

Background: The MAO enzyme is presented in the brain and peripheral tissues and is a significant enzyme that is responsible for the deamination of biogenic amines and thus the regulation of neurotransmitter levels. The reaction of these neurotransmitters with the MAO enzyme produces aldehyde and free amine. MAO enzyme consists of two isoforms, MAO-A and MAO-B, which are characterized by amino acid sequence, three-dimensional structure, substrate preference, and inhibitor selectivity. Dopamine, tyramine, and tryptamine are substrates of both MAO isoforms and MAO inhibitors such as clorgiline and selegiline, which are used as medications in neurodegenerative and neurological diseases. In particular, MAO-A inhibitors are used in the treatment of depression, while MAO-B inhibitors are used in the treatment of Parkinson's disease. It is also investigated whether MAO-B inhibitors are effective in the treatment of Alzheimer's disease. Nowadays, life expectancy has increased, as a result, neurodegenerative diseases such as Parkinson's and Alzheimer's disease have started to occur more frequently. The elderly population is increasing day by day. As a result of these common diseases in elderly people, these people are unable to do their jobs and need care. Therefore, these diseases have become a significant health problem in society. Methods: In this study, review, inclusion, and exclusion criteria were used. Peer-reviewed research articles were searched. The quality of the examined articles was evaluated with standard tools. The information obtained was analyzed conceptually by using qualitative content analysis methodology. Results: One hundred and five papers were included in the review. The current MAO-B inhibitors and their usage areas are discussed together with the structures of the drugs; also, their possible effects in Alzheimer’s and Parkinson’s treatment are evaluated. In addition, different articles have been compiled in which structures such as arylalkylamines, chalcones, benzoquinone, benzoxazinone, and chromen are substituted with various functional groups and aromatic rings, along with thestructures of 44 different compounds that have recently been developed and their inhibitory effects on MAO-B enzyme. As a result, the structure required for MAO-B inhibition and SAR studies is discussed. Conclusion: Many studies demonstrate that MAO-B activity increases with age in brain tissue, cerebrospinal fluid (CSF), and platelets in Alzheimer's patients. This suggests that MAO-B inhibitor drugs, which may be effective in the treatment of Parkinson's disease, may also be effective in the treatment of Alzheimer's disease. This article was written to explain the multifaceted MAO-B inhibitor molecules.