https://doi.org/10.1351/goldbook.T06291
Natural pigments containing four pyrrole rings joined by one-carbon units linking position 2 of one pyrrole ring to position 5 of the next. ![Not defined](/img/inline/T06291.png)
Porphyrins
are macrocyclic tetrapyrroles. E.g. bilin (a linear tetrapyrrole). ![Not defined](/img/inline/T06291.png)