Synthesis and evaluation of 2-methylbenzothiazole derivatives as monoamine oxidase inhibitors

Neurodegenerative disorders are caused by the progressive death of neuronal cells in specific regions of the brain and spinal cord. The most common neurodegenerative disorders are Alzheimer’s disease and Parkinson’s disease. The inhibition of enzymes that metabolise neurotransmitter amines is an important approach in the treatment of these disorders and monoamine oxidase (MAO) B inhibitors have thus been used for the treatment of Parkinson’s disease. Inhibitors of the MAO-A isoform, in turn, are used clinically for the treatment of affective (e.g., major depression) and anxiety disorders. Recent studies have shown that benzothiazole derivatives act as potent MAO inhibitors. Based on these findings, the present study group synthesised thirteen 2-methylbenzo[d]thiazole derivatives and evaluated their in vitro MAO inhibition properties. The results showed that the benzothiazole derivatives were potent and selective inhibitors of human MAO-B, with all compounds exhibiting IC₅₀ values < 0.017 µM. The most potent MAO-B inhibitor (4d) had an IC₅₀ value of 0.0046 µM, while the most potent MAO-A inhibitor (5e) had an IC₅₀ value of 0.132 µM. It may be concluded that active benzothiazole derivatives may serve as potential leads for the development of MAO inhibitors for the treatment of neuropsychiatric and neurodegenerative disorders.