One of a class of tetraterpenoids (C40), formally derived from the acyclic parent, psi,psi-carotene by hydrogenation, dehydrogenation, cyclization, oxidation, or combination of these processes. This class includes carotenes, xanthophylls and certain compounds that arise from rearrangement of the skeleton of psi,psi-carotene or by loss of part of this structure. Retinoids are excluded.

Synonyms: carotenoid