Synthetic and Natural Monoamine Oxidase Inhibitors as Potential Lead Compounds for Effective Therapeutics.

Monoamine oxidases A and B (MAO-A and B) play a critical role in the metabolism of intracellular neurotransmitters of the central nervous system. For decades, MAO inhibitors have proven their clinical efficacy as potential drug targets for several neurological and neurodegenerative diseases. Use of first generation non selective MAO inhibitors as neuropsychiatric drugs elicited several side effects like hypertensive crisis and cheese reaction. Therefore their use is now limited due to non-selectivity towards MAO isoforms and inhibition of metabolizing enzymes like cytochrome P450. Development of selective and specific MAO inhibitors like moclobemide, toloxatone improves their efficacy as disease-modifying effects in monotherapy as well as adjunctive therapy. Recently a lot of research has been done to elucidate the pharmacological potential of medicinal plants and their isolated bioactive constituents having MAO inhibitory activity. Herbs containing MAO inhibitors are extensively used for the development of potent synthetic drugs and as safe and effective alternatives to the available synthetic drugs in the treatment of neurodegenerative diseases such as depression, Parkinson and Alzheimer's. In several diseases like Parkinson natural MAO inhibitors prevented the neuron denaturalization by their dual action via enhancing neurotransmission of dopamine as well as lowering the generation of free radicals and toxins. Currently development of selective MAO inhibitors is still under study to achieve more effective therapies by using Computer Aided Drug Designing, Ligand-based models and structure-activity hypothesis. These approaches also facilitate understanding the interaction of newly designed molecule with MAO enzymes and the rationalization of probable mechanisms of action.