Beneficial effects of carotenoid-rich fruits and vegetables on cancer risk have been found in many epidemiological studies; however, the metabolism and molecular biological properties of carotenoids remain to be determined through further research.Carotenoids are lipophilic plant pigments with polyisoprenoid structures, typically containing a series of conjugated double bonds in the central chain of the molecule, which makes them susceptible to oxidative cleavage and isomerization from trans to cis forms.This cleavage can result in the formation of potentially bioactive metabolites, such as retinoids (vitamin A and its derivatives) and other biological compounds.For provitamin A carotenoids, such as-carotene,-carotene, and-cryptoxanthin, central cleavage is a major pathway leading to vitamin A formation.