ZEAXANTHIN (beta,beta-CAROTENE-3,3'-DIOL)

Carotenoids are plant pigments that involve in light harvesting to participate in energy transfer process in photosynthesis. They absorb light in the 400-500 nm region of the visible spectrum and impart coloration of yellow, orange, red, and purple. They are widely distributed in nature including vegetables, fruits, insects, fishes, and birds. Animals are incapable of synthesizing carotenoids, which should be obtained through diet. Chlorophyll is the generic name for green plant pigments which includes the open-chain bile pigments and the large ring compounds. The structure of chlorophyll molecule has four nitrogen-containing pyrrole rings bonded to a central magnesium atom, and the fifth ring containing only carbon atoms, and various long hydrocarbon tails attached to the pyrrole rings. Carotenoids contain sequences of conjugated isoprene units, alternating double and single carbon bonds. They are sometimes terminated by cyclic end-groups (rings) complemented with hydroxylated, oxidized and hydrogenated groups. The conjugated double bonds absorbs light and UV. The more number of double bonds result in the absorbance of red color wavelength. Changes in geometrical configuration about the double bonds result in the existence of many cis- and trans- isomers. Carotenoids are usually located in quantity in the grana of chloroplasts in the form of carotenoprotein complexes which give blue, green, purple, red, or other colors to the outer surfaces in plants, or eggs of crustaceans, such as the lobster and crab. Carotenoids are classified into carotenes (un-oxidized carotenoids, orange pigments) or xanthophylls (yellow pigments) which contains oxygen and are alcohol-soluble. It is known that more than 600 carotenoids are isolated from natural sources.