Lycopene

Lycopene is a bright red carotenoid hydrocarbon found in tomatoes and other red fruits and vegetables, such as red carrots, watermelons, gac, and papayas, but it is not in strawberries or cherries. Although lycopene is chemically a carotene, it has no vitamin A activity.

Structure and physical properties

Lycopene is a symmetrical tetraterpene assembled from eight isoprene units. It is a member of the carotenoid family of compounds, and because it consists entirely of carbon and hydrogen, is also a carotene. Isolation procedures for lycopene were first reported in 1910, and the structure of the molecule was determined by 1931. In its natural, all-trans form, the molecule is long and straight, constrained by its system of 11 conjugated double bonds. Each extension in this conjugated system reduces the energy required for electrons to transition to higher energy states, allowing the molecule to absorb visible light of progressively longer wavelengths. Lycopene absorbs all but the longest wavelengths of visible light, so it appears red.

Sources and intake

Fruits and vegetables that are high in lycopene include autumn olive, gac, tomatoes, watermelon, pink grapefruit, pink guava, papaya, seabuckthorn, wolfberry (goji, a berry relative), and rosehip. Ketchup is a common dietary source of lycopene. Although gac (Momordica cochinchinensis Spreng) has the highest content of lycopene of any known fruit or vegetable (multiple times more than tomatoes), tomatoes and tomato-based sauces, juices, and ketchup account for more than 85% of the dietary intake of lycopene for most people. The lycopene content of tomatoes depends on species and increases as the fruit ripens.

Health effects

Despite the association between intake of lycopene or tomato products and decreased risk of certain cancers, there is insufficient evidence to conclude that lycopene supplementation can prevent cancer or any other disease. Lycopene is not an essential nutrient for humans, but is commonly included in the diet, mainly from dishes prepared with tomato sauce. When absorbed from the stomach, lycopene is transported in the blood by various lipoproteins and accumulates in the liver, adrenal glands, and testes.

See also

• Carotenoid
• Tomato
• Vitamin A

References

Lycopene Resources
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