Definition of porphyrins

Natural pigments containing a fundamental skeleton of four pyrrole nuclei united through the -positions by four methine groups to form a macrocyclic structure (porphyrin is designated porphine in Chemical Abstracts indexes). See also corrinoids. BNRD, The Nomenclature of Tetrapyrroles, Rule TP-1.1 (p. 281).

porphyrin