The Collaborative International Dictionary of English v.0.48:

Quinoxaline \Quin*ox"a*line\, n. [Quinoline + glyoxal.] (Chem.)
   Any one of a series of complex nitrogenous bases obtained by
   the union of certain aniline derivatives with glyoxal or with
   certain ketones. [Written also chinoxaline.]
   [1913 Webster]