Compounds based on acridone, which have three linear rings, with the center ring containing a ring nitrogen and a keto oxygen opposite to each other. Many of them are naturally occurring alkaloids.
Compounds with three aromatic rings in linear arrangement with a SULFUR in the center ring.
Acridines are heterocyclic aromatic organic compounds containing two nitrogen atoms at positions 1 and 3 of a planar, unsaturated ring system, which have been widely used in chemotherapy and have also found applications in dye industries and fluorescence microscopy.