Lycopene 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 (formerly Lycopersicon esculentum).
Structure and chemistry
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.
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. This is because lycopene is so insoluble in water and is so tightly bound to vegetable fiber. Thus processed tomato products such as pasteurized tomato juice, soup, sauce, and ketchup contain the highest concentrations of bioavailable lycopene. 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. Lycopene is fat-soluble, so the oil is said to help absorption.
Lycopene may be obtained from vegetables and fruits such as the tomato, but another source of lycopene is the fungus Blakeslea trispora.
Lycopene is the most powerful carotenoid quencher of singlet oxygen, being 100 times more efficient in the singlet-oxygen quenching action than Vitamin E, which in turn has 125 times the quenching action of glutathione (water soluble). Singlet oxygen produced during exposure to ultraviolet light is a primary cause of skin aging.
Given its antioxidant properties, some scientific research has investigated the correlation between lycopene consumption and general health. Early research suggested some amelioration of cardiovascular disease, cancer, diabetes, osteoporosis, and even male infertility. . The most recent study, however, has cast significant doubt on these benefits, showing no link between lycopene and cancer prevention. In fact, a related antioxidant, beta-carotene, was shown to increase the number of prostate cancer cases.
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), lycopene diffuses into plastic, making it impossible to remove with hot water, soap, or detergent. (Bleach will destroy lycopene, however.) Plastics are especially susceptible to staining if heated, scratched, oiled, or pitted, for example by acids.
Lycopene is available in the market as mix formulation with some other carotinoids and antioxidants. It is marketed by a number of pharmaceutical companies under different brand names. Some commonly available formulations are LYCORED, LYNET, LYCORICH etc.
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