Carotenoids - Natural Products Chemistry: Sources, Separations, and Structures - page 124

Lycopene is an essential intermediate in the biosynthesis of many carotenoids
including β-carotene. Although not substantiated, it is considered as a potential
agent for prevention of some types of cancers (i.e., prostate cancer).
11.8 ISOLATION OF LYCOPENE
Typically, lycopene can be isolated from the juice of tomatoes. First, tomato pulp is
obtained by centrifugation and the resulting pulp is then dissolved in methanol, with
additions of calcium carbonate and celite as filtering agents. After centrifugation,
the colored supernatant is filtered. The colored filter papers are resuspended in the
acetone/hexane solvent to redissolve the lycopene. The lycopene is then partitioned
using an aqueous acetone/hexane mixture. The organic phase containing lycopene
can be dried with anhydrous Na 2 SO 4 to remove any residual water. For analysis, an
HPLC system consisting of a C 30 reverse phase column eluting with various ratios of
methanol in methyl tertiary butyl ether is used.
SUMMARY
Selected carotenoids are described including β-carotene, lutein, zeaxanthin, and
lycopene. Separation and isolation techniques for these molecules are also discussed.
QUESTIONS
1. Give examples of other carotenoids found in nature.
2. Describe some typical purification steps to isolate carotenoids.
3. Why is UV spectroscopy so important for studying carotenoids?
4. For carotenoids, why is UV much more useful than IR spectroscopy?
5. Can UV be helpful to differentiate between cis and trans isomers?
FURTHER READING
C arotenoidS
G. Britton, S. Liaaen-Jensen, and H. Pfander. 2009. Carotenoids. Vol. 5: Nutrition and Health .
Birkhauser Verlag GmbH.
N. I. Krinsky and E. J. Johnson. 2005. Carotenoid actions and their relation to health and dis-
ease. Mol Aspects Med 26(6):459-516.
J. T. Landrum, ed. 2009. Carotenoids: Physical, Chemical, and Biological Functions and
Properties . CRC Press.
Y. Li, A. S. Fabiano-Tixier, V. Tomao, G. Cravotto, and F. Chemat. 2013. Green ultrasound-
assisted extraction of carotenoids based on the bio-reinery concept using sunflower oil
as an alternative solvent. Ultrason Sonochem 20(1):12-18.
A. Z. Mercadante, A. Steck, and H. Pfander. 1999. Carotenoids from guava ( Psidium guajava l.):
Isolation and structure elucidation. J Agric Food Chem 47(1):145-151.
D. Ren and S. Zhang. 2008. Separation and identification of the yellow carotenoids in
Potamogeton crispus L. Food Chem 106(1):410-414.
T. L. Sourkes. 2009. The discovery and early history of carotene. Bull Hist Chem 34(1):32-38.