Lycopene is a carotenoid pigment, found in tomatoes and other red fruits, like watermelon, papaya, pink grapefruit and pink guava. Its name is derived from the tomato’s species classification, Solanum lycopersicum.
Lycopene, similar to other carotenoids, is a natural fat-soluble pigment (red, in the case of lycopene) which is synthesized by some plants and micro-organisms but not by animals, where it serves as an accessory light-gathering pigment and to protect these organisms against the toxic effects of oxygen and light.
Carotenoids are the principal pigments responsible for the colors of vegetables and fruits: these include ß-carotene, lutein, zeaxanthin and lycopene which is responsible for the red color of red tomatoes and other fruits it is found in. Its colour is due to its many conjugated carbon double bonds: each double bond reduces the energy required for electrons to transition to higher energy states, allowing the molecule to absorb visible lengths of progressively longer wavelengths. Lycopene absorbs most of the visible spectrum, so it appears red.
Lycopene is an acyclic isomer of ß -carotene. It is a 40 carbon atom, open chain polyisoprenoid with 11 conjugated double bonds. Its molecular formula is C40H56. The structural formula of lycopene is represented in the diagram above.
(All-E)-lycopene is the predominant geometric isomer found in plants. (Z)-isomers of lycopene are also found in nature, including (5Z)-, (9Z)-, (13Z)- and (15Z)- isomers. Lycopene found in human plasma is a mixture of approximately 50% (Z)-lycopene and 50% (all-E)-lycopene. Lycopene in processed foods, is mainly in the form of (all-E)-lycopene.
Lycopene is the most common carotenoid in the human body and is one of the most potent carotenoid antioxidants. Lycopene is easily absorbed by the organism and is naturally present in human plasma and tissues in higher concentrations than the other carotenoids. Its level is affected by several biological and lifestyle factors. Because of its lipophilic nature, lycopene concentrates in low-density and very-low-density lipoprotein fractions of the serum. Lycopene is also found to concentrate in the adrenal, liver, testes, and prostate. However, unlike other carotenoids, lycopene levels in serum or tissues do not correlate well with overall intake of fruits and vegetables.