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Lycopene (molecular formula: C40H56) is a bright red carotenoid pigment, a phytochemical found in tomatoes and other red fruits. Lycopene is the most common carotenoid in the human body and is one of the most potent carotenoid antioxidants. Its name is derived from the tomato's species classification, Solanum lycopersicum.
Structure and Chemistry Lycopene is a terpene assembled from 8 isoprene units. The color of lycopene 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 light of progressively longer wavelengths. Lycopene absorbs most of the visible spectrum, so it appears red. If lycopene is oxidized (for example, by reacting with bleaches or acids), the double bonds between carbon atoms will be broken, cleaving the molecule into smaller molecules each double-bonded to an oxygen atom. Although C=O bonds are also chromophoric, the much shorter molecules are unable to absorb enough light to appear colorful. A similar effect occurs if lycopene is reduced; reduction may saturate (convert the double bonds to single bonds) the lycopene molecule, diminishing its ability to absorb light. Dietary Sources Fruits and vegetables that are high in lycopene include tomatoes, watermelon, pink grapefruit, papaya, and rosehip. Unlike other fruits and vegetables, where nutritional content such as vitamin C is diminished upon cooking, processing of tomatoes increases the concentration of bioavailable lycopene. Lycopene in tomato paste is four times more bioavailable than in fresh tomatoes. Thus processed tomato products such as pasteurized tomato juice, soup, sauce, and ketchup contain the highest concentrations of bioavailable lycopene. Because lycopene is so insoluble in water and is so tightly bound to vegetable fiber, the bioavailablity of lycopene is increased by food processing. Cooking and crushing tomatoes (as in the canning process) and serving in oil-rich dishes (such as spaghetti sauce or pizza) greatly increases assimilation from the digestive tract into the bloodstream. Nutritional Benefits Lycopene is the most powerful carotenoid quencher of singlet oxygen•. Singlet oxygen from ultraviolet light is a primary cause of skin aging•. There is evidence that frequent intake of such products is associated with reduced risk of cardiovascular disease, cancer (especially prostate cancer), diabetes, osteoporosis, and even male infertility. • Lycopene may also be related to a reduced risk of oesophageal, colon, and mouth cancer. Food Coloring Due to its ubiquity, lycopene has been licensed for use as a food coloring. Lycopene is not water-soluble and instantly stains any sufficiently porous material, including most plastics. While a tomato stain can be fairly easily removed from fabric (provided the stain is fresh), discolored plastic defies all efforts to drive out the lycopene with hot water, soap, or detergent. (Bleach will destroy lycopene, however.) Plastics are especially susceptible to staining if heated, scratched, oiled, or pitted by acids (such as those found in tomatoes). | ||||||||
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