Introduction: The structural diversity and biological importance of nitrogen containing heterocycles made them striking targets for synthesis and maintained the interest of researchers through many years of historical development of classical organic synthesis (Valverde and Torroba, 2005). Almost all synthetic drugs such as diazepam, benzodiazepines, barbiturates, methotrexate, pesticides, herbicides and some dyes are nitrogen heterocycles. These compounds are of great significance to life because their structural subunits exist in many natural drugs such as papaverine, theobromine, quinine, emetine, etc. (Chin et al., 2006, Koehn and Carter, 2005, Cordell and Farnsworth, 2001 and Hughes and Shanks, 2002. The classical period of the MAO inhibitors started with hydrazine derivatives. They were originally introduced as tuberculostatic agents, their prototype, iproniazid, was the first modern antidepressant and was introduced into the market under the trade name Marsilid (Cesura and Pletscher, 1992). Subsequently, research has been directed towards the preparation of heterocyclic hydrazines and hydrazides and their potential use as therapeutic agents for the treatment of CNS depression (Tipton, 1972, Mc Kenna et al., 1991 and Yamada et al., 1993). Literature survey revealed diversified nitrogen heterocycles, synthesized since decades and tested for their MAO inhibitory potentials. Therefore, the present review emphasizes synthetic aspects of nitrogen heterocycles as MAO inhibitors. The present book highlights synthetic methods of monoamine oxidase inhibitors (MAO) belonging to some of nitrogen heterocycles such as pyrazoline, indole, xanthine, oxadiazole, benzimidazole, pyrrole, quinoxaline, thiazole and other related compounds (1990-2012). Moreover, it emphasizes salient findings related to chemical structures and the bioactivities of these heterocycles as MAO inhibitors. The aim of this book is to find out different methods for the synthesis of nitrogen containing heterocycles and their bioactivity-related aspects as MAO inhibitors. The nonselective monoamine oxidase inhibitors (MAOls) currently available in the United States include phenelzine (Nardil), isocarboxazid (Marplan), and tranylcypromine (Parnate). These medications are irreversible inhibitors of the enzyme monoamine oxidase (MAO). Selegiline is a selective inhibitor of type B MAO (MAOs) and is currently approved by the United States Food and Drug Administration for parkinsonism. Moclobemide is a reversible inhibitor of type A MAO (MAOA) and is consequently believed to require fewer dietary restrictions. Reversible inhibitors of MAO have been well studied in the treatment of depression. Therefore, recent studies are going to find the new drugs with the less side effects, wider therapeutic scope, enhanced selectivity and fewer restrictions compared to the current medications.

Keyword: Pyrazolines as MAO inhibitor, lndole as MAO inhibitor, Xanthines as MAO inhibitor, Oxadiazoles as MAO inhibitor, Quinoxalines as MAO inhibitor, Pyrroles as MAO inhibitor, Benzimidazoles as MAO inhibitor, Thiazoles as MAO inhibitor, Other nitrogen heterocycles as MAO inhibitor, Piperines, Morpholines, lmidazolines, Heterocyclic substituted propargylamines, lndeno pyridazines, Quinolines, Pteridines, Most selective MAO inhibitors, Frequent side effects and problems of selective compounds