Lycopene chemical properties

Nguyen, M. and Schwartz, S. 1999. Lycopene chemical and biological properties. Food Technol. 53(2) 38 45. 

Carotenoids are a class of lipophilic compounds with a polyisoprenoid structure. Most carotenoids contain a series of conjugated double bonds, which are sensitive to oxidative modification and cis-trans isomerization. There are six major carotenoids (ji-carotenc, a-carotene, lycopene, P-cryptoxanthin, lutein, and zeaxanthin) that can be routinely found in human plasma and tissues. Among them, p-carotene has been the most extensively studied. More recently, lycopene has attracted considerable attention due to its association with a decreased risk of certain chronic diseases, including cancers. Considerable efforts have been expended in order to identify its biological and physiochemical properties. Relative to P-carotene, lycopene has the same molecular mass and chemical formula, yet lycopene is an open-polyene chain lacking the P-ionone ring structure. While the metabolism of P-carotene has been extensively studied, the metabolism of lycopene remains poorly understood. 

Shi J and Le Maguer M. 2000. Lycopene in tomatoes chemical and physical properties affected by food processing. Crit Rev Food Sci Nutr 40(1) 1—42. 

Carotenoids are sensitive to heat, light, acid, oxygen and chemicals. They may react in various ways during the process of isolation. The most important change is the formation of cis-isomers. Lycopene is said to form 1056 isomers (36), each with different properties. In some cases, cis-isomers separate more easily than carotenoids that differ by rearrangement of a double bond, i.e., zeaxanthin and lutein. However, a mixture of isomers can often be identified by their failure to crystallize and to give sharp separations on chromatographic columns. 

Fig. I. Chemical structures of carotenoids, the dependence ofthe ground-state properties on their m-tra/ij configurations being described in Sec. II, (a) p-Carotene, (b) canthaxanthin, (c) zeaxanthin, (d) lutein, (e) /3-apo-8 -carotenal, (f) lycopene, (g) neurosporene, (h) spheroidene, (i) spirilloxanthin and (j) okenone. For each carotenoid, the number of conjugated C=C plus C=0 bonds is shown.

There are hundreds, possibly thousands, of chemical constituents in plants that may have health-promoting properties. Increasingly, food and drinks companies are looking to exploit the association between phytochemicals and reduced risks of developing cancer or cardiovascular disease. Phytochemicals that are currently attracting the most attention include the antioxidant vitamins C, E and P-carotene polyphenols sterols carotenoids (particularly lycopene and lutein) and the flavonoids (particularly phytoestrogens) [see Chapters 2, 3 and 4]. 

In this article, some key aspects of the chemical and physical properties, the dietary sources, biochemical status indices, and biological significance of lycopene will be described. 

Chemical and Physical Properties of Lycopene its Food Sources and Enterai Absorption... 

---