Murexan \Mu*rex"an\, n. [From {Murexide}.] (Chem.)
A complex nitrogenous substance obtained from murexide,
alloxantin, and other ureids, as a white, or yellowish,
crystalline which turns red on exposure to the air; -- called
also {uramil}, {dialuramide}, and formerly {purpuric acid}.
[1913 Webster]