Quinoxaline: A Chemical Moiety with Spectrum of Interesting Biological Activities

Quinoxaline (C8H6N2), commonly called 1,4-diazanaphthalene, 1,4-benzodiazine, or benzopyrazine, is a very potent nitrogenous heterocyclic moiety consisting of a benzene ring fused with the pyrazine ring. A number of different methods for the synthesis of quinoxaline derivatives have been reported in the literature, but the most effective method, commonly used for the synthesis of quinoxaline analogues involves the condensation of substituted o-phenylenediamines with 1, 2- dicarbonyl compounds in the presence of different catalyst(s). The presence of different types of catalysts and their concentration affects the overall yield of the product. Quinoxaline not only plays an important role as an organic reaction intermediate but also has a wide spectrum of interesting biological activities viz. antibacterial, antifungal, anticancer, anti-inflammatory, antiviral, and antiprotozoal activity, etc. Some commercially available drug molecules containing quinoxaline moiety are echinomycin (as antibacterial, antineoplastic, and nucleic acid inhibitor), triostins (cyclic desipeptide as an antibacterial agent), dioxidine and mequindox (as antibacterial agents), carbadox (controlling swine dysentery), desoxycarbadox (as swine growth promoter) and panadipion (as hepatoprotective agent), etc. A large number of quinoxaline analogues possessing different biological activities and their synthetic procedures have been patented worldwide.