Recent Updates on Pyrazoline Derivatives as Promising Candidates for Neuropsychiatric and Neurodegenerative Disorders

Pyrazolines are five-membered heterocyclic compounds containing two nitrogen atoms that represent a privileged scaffold for various bioactive compounds with diverse pharmacological activities. Chalcones and hydrazine derivatives are excellent precursors for pyrazolines, which provide easy access for fabricating the pyrazoline ring at N1, C3 and C5 positions that give rise to a wide range of pyrazoline designs. In addition, this method institutes a new asymmetric center at C5 position and extent of the conjugation between phenyl group at C3 position to N1 that could greatly enhance the physicochemical and pharmacological properties towards the target enzymes and hence they are reported to have a wide spectrum of biological activities such as anti-cancer, antiinflammatory, etc. Most importantly, they have remarkable effects on the central nervous system (CNS). Several reports show that the pyrazoline derivatives have a significant inhibitory effect towards the monoamine oxidase enzymes (MAOs), which are known to be responsible for neurodegenerative disorders. These enzymes have two isoforms, namely MAO-A and MAO-B which are, in particular, responsible for psychiatric and neurological disorders, respectively. Chalcones are generally potential and more selective inhibitors towards MAO-B isoform whereas pyrazolines derived from chalcones mostly turned into selective inhibitors of MAO-A isoform may be due to the presence of two nitrogen heteroatoms. Therefore, these two derivatives have received much attention from medicinal chemists as they could solve entire CNS-related issues; however pyrazolines have not been studied as much as chalcones. Our group already documented the importance of pyrazolines towards MAO-A inhibition in 2013. With their growing importance, several studies on pyrazolines have constantly been reported for their MAO inhibitions. Therefore, in this review, we report up-to-date developments (after 2014) on pyrazolines as potential MAO inhibitors.