a complex tetracyclic compound, C20H28O6, based on a cyclopropabenzazulene skeleton. Various phorbol esters occur in croton oil (from Croton tiglium, of the family Euphorbiaceae, hence the name) and act as potent cocarcinogens.

| phoA, phloroglucinol, phlorizin | |
| phorbol ester, phosducin, phosphacan |




