Both forms exist in nature and exhibit different biological properties. An interesting feature of carotenoid stereochemistry is that carotenes exist in two isomeric forms, cis and trans.

The Health Benefits of Lycopene and Its Use in Skincare and Protection Lycopene is the pigment responsible for the characteristic red color of ripe tomatoes, pink grapefruit, guava, and watermelon. Carotenoids are a class of hydrocarbons (carotenes) and their oxygenated derivatives (xanthophylls). There is increasing clinical evidence supporting the role of lycopene - an important carotenoid - as an antioxidant. In most cases, each carotenoid occurs solely in one configuration in Nature. The most notable of the carotenoids are lycopene and beta-carotene.

Based on the number of double bonds in the molecule, a great number of cis/trans isomers exist. Approximately 600 carotenoids have been isolated from natural sources and are all derived from the acyclic C40H56 structure.

They are composed of eight isoprenoid units arranged in such a manner that these units reverse at the center of the molecule with the two central methyl groups being in the 1,6-position relationship and the remaining non-terminal methyl groups in the 1,5-position.