6H-Indolo[2,3-b]quinoxaline, a planar fused heterocyclic compound exhibits a wide variety of pharmacological
activities. The mechanism of pharmacological action exerted by these compounds is predominantly DNA intercalation.
The thermal stability of the intercalated complex (DNA and 6H-indolo[2,3-b]quinoxaline derivatives) is an important
parameter for the elucidation of anticancer, antiviral and other activities. This thermal stability of the 6H-indolo[2,3-
b]quinoxaline–DNA complex depends on the type of substituents and side chains attached to the 6H-indolo[2,3-
b]quinoxaline nucleus and also the orientation of the side chain towards the GC rich minor groove of the DNA. Highly
active 6H-indolo[2,3-b]quinoxaline derivatives such as NCA0424, B-220 and 9-OH-B-220 have shown good binding
affinity to DNA as evident from high thermal stability of compound-DNA complex. Interestingly, these compounds
possessed poor inhibitory activity on topoisomerase II enzyme but have significant MDR modulating activity. This review
establishes ‘6H-indolo[2,3-b]quinoxaline’ as a valuable template for design and development of novel molecules with
different biological activities.