The Functions of Tomato Lycopene and Its Role in Human Health

Carotenoids, compounds found in fruits and vegetables, benefit human health by playing an important role in cell function. The dietary necessity of the carotenoid beta-carotene, the precursor of vitamin A, has been recognized for many decades. More recently, lycopene has attracted substantial interest among carotenoid and medical researchers. Lycopene is the red carotenoid found predominantly in tomatoes and in a few other fruits and vegetables. Claims have been made that lycopene may be beneficial in diseases such as cancer and coronary heart disease as well as other chronic conditions. These claims have been studied extensively, through epidemiological studies, biochemical investigations of lycopene’s properties, and thorough examination of lycopene’s bioavailability from tomato-based diets. This article summarizes the current state of knowledge of the properties of lycopene, its possible role in human health, and areas for future lycopene research.Lycopene powder

Lycopene’s function in the human body

Although not considered an essential nutrient, research has shown that lycopene may have various benefits for human health. As a major carotenoid in human blood, lycopene protects against oxidative damage to lipids, proteins, and DNA. Lycopene is a potent quencher of singlet oxygen (a reactive form of oxygen), which suggests that it may have comparatively stronger antioxidant properties than other major plasma carotenoids.1 Lycopene has been found to be a potent and specific inhibitor of cancer cell proliferation,2, 3 which is regulated by an elaborated cellular process called “cell cycle.” Rapid and uncontrolled cell division is a hallmark of cancer cell metabolism; lycopene’s activity in retarding cell cycle progression may explain its demonstrated activity in retarding the spread of certain types of cancer. Lycopene may prevent malignant transformation (the cellular process which describes the transformation of a normal cell into a cancer cell). Contact inhibition is one of the mechanisms that controls excessive cell division. By this mechanism, a cell, in crowded surroundings, will stop multiplying. Special structures in the cell membrane, termed a “gap-junction,” function as communication channels between cells. Normal cells are both contact-inhibited and have a functional gap-junction whereas most tumor cells exhibit fewer of these structures. Lycopene was found to induce the formation of the protein connexin 43, one of the major building blocks of these channels, and thereby to restore gap junctions.4 Lycopene induces Phase II enzymes which help to eliminate carcinogens and toxins from the body. The change of the levels of so many regulatory proteins is related to lycopene’s ability to modulate various transcription factors which are key players in the process of new cellular protein synthesis.5, 6

Structure, intake absorption, and transport

Lycopene is defined chemically as an acyclic carotene with 11 conjugated double bonds, normally in the all-trans configuration (Fig. 1). The double bonds are subject to isomerization, and various cis isomers (mainly 5, 9, 13, or 15) are found in plants and also in blood plasma. Since the human body is unable to synthesize carotenoids from endogenously produced biochemicals, the body is totally dependent on dietary sourced (exogenous) carotenoids. In general, tomato fruit and tomato-based food products provide at least 85% of dietary lycopene in humans. The remaining 15% are usually obtained from watermelon, pink grapefruit, guava, and papaya—all fruits that are dietary sources of lycopene, although at much lower levels than tomatoes (Table 1).