ABSTRACT
The term ‘‘retinoids’’ includes both naturally occurring molecules and also synthetic compounds showing biological activities that are characteristic for vitamin A. The current definition of retinoids does not require a chemical analogy to vitamin A (i.e., the ‘‘four isoprenoid units joined in a head-to-tail manner’’ structure), as it was defined by the IUPAC-IUB Joint Commission on Biochemical Nomenclature in 1982. In general, retinoids bind and activate specific nuclear receptors, although this may not be a necessary precondition for their action.
