Cr(III) protoporphyrin IX is a protoporphyrin IX. Protoporphyrin IX is a heterocyclic organic compound, which consists of four pyrrole rings, and is the final intermediate in the heme biosynthetic pathway[1].
[1] Sachar M, et al. Protoporphyrin IX: the Good, the Bad, and the Ugly. J Pharmacol Exp Ther. 2016;356(2):267-275. doi:10.1124/jpet.115.228130
