etio·porphyrin noun orae·tio·porphyrin\|ē]d.ē(ˌ)ō also |e]+\ Etymology:etio-, aetio- + porphyrin : any of four isomeric porphyrins C20H6N4(CH3)4(C2H5)4; especially: a violet crystalline pigment occurring in nature (as in petroleum and coal) and formed by degradation of chlorophyll and of heme