Transcript Carotenoids as Antioxidants

Samar Almohaimeed
What is Carotenoids?
Carotenoids are a class of
more than 600 naturally
occurring pigments
synthesized by plants, algae,
and photosynthetic bacteria.
These richly colored
molecules are the sources of
the yellow, orange, and red
colors of many plants.
International Agency for Research on Cancer. IARC Handbooks of Cancer Prevention:
Carotenoids. Lyon: International Agency for Research on Cancer; 1998.
Carotenoids family
The most common dietary
carotenoids are:
Alpha-carotene
beta-carotene
beta-cryptoxanthin
Lutein
Lycopene
zeaxanthin
the most prominent member of this group is b-carotene.
Fruits and vegetables provide most of the
carotenoids in the human diet.
Jane Higdon. 2009.Carotenoids Alpha-Carotene, Beta-Carotene, Beta
Cryptoxanthin, Lycopene, Lutein, and Zeaxanthin. Linus Pauling Institute
Carotenoids classes
Carotenoids classified into two classes:
Carotenes:
alpha-carotene
beta-carotene
lycopene
Xanthophylls:
beta-cryptoxanthin
Lutein
zeaxanthin
Carotenoids Functions
Berg_et_al-2000. Journal_of_the_Science_of_Food_and_Agriculture
Why we do need Carotenoid?
Diets high in carotenoid-rich
fruits and vegetables are
associated with reduced risk of:
cardiovascular disease
some cancers
many other chronic diseases
http://www.everydayhealth.com/breast-cancer/1210/eat-orange-red-or-yellow-food-to-prevent-breast-cancer-3394.aspx
Eat Orange, Red, or Yellow Food
CHEMICAL PROPERTIES
With their extended system of conjugated double bonds
the carotenoids contain a reactive electronic system which
is susceptible to reactions with electrophilic compounds.
Such reactions are responsible for the instability of
carotenoids towards oxidation.
In the presence of oxygen, carotenoids tend to autoxidise.
The reaction of carotenoids with oxidising agents or free
radicals depends on the length of the polyene chain and
the nature of the end groups.
Carotenoid Bioavailability
Absorption of carotenoids are influenced by many factors:
dietary lipid
fiber
presence of vitamins
minerals
Carotenoids are highly hydrophobic  it are easily
dissolved in oil.
Fat in the diet has the potential to improve the absorption of
carotenoids.
What is Antioxidants ?
Antioxidants protect cells against the effects of free
radicals,
which are potentially damaging compounds produced as
by-products of metabolism, as well as through exposure
to toxins and pollutants
Free radicals can cause cell damage that may contribute
to the development of cardiovascular disease and
cancers.
Carotenoids as Antioxidants
Carotenoids are one of the major
groups of antioxidants found in
fruits and vegetables.
The polyene chain is the structural
feature that determines the
chemical reactivity of carotenoids
toward free radicals, then its
antioxidant properties.
Ehab A. Abourashed. 2013. Bioavailability of Plant-Derived
Antioxidants. Antioxidants 2013, 2(4), 309-325;
ANTIOXIDANT PROPERTIES
Carotenoids are highly lipophilic
incorporated within cell membrane or associated with
lipoproteins. Therefore, interaction of carotenoids
with free radicals is greater.
Therefore, antioxidant activity of carotenoids to
scavenge free radicals is higher in a hydrophobic
environment
localization of carotenoids in the
lipophilic component of the cell
provides a greater resistance of
lipid and lipoproteins to oxidative
damage
(Tsuchihashi et al., 1995)
(Clevidence and Bieri, 1993; Ribaya-Mercado et al., 1995a)
Antioxidant Stability
Post-harvest changes in carotenoid levels depend on:
the item
the length of time of storage
the conditions (light, temperature, relative humidity)
During storage, spoilage occurs owing to a high relative
humidity, which ultimately results in enzymatic
degradation of the structure, allowing carotenoids to
oxidise.
To extend carotene shelf-life:
reducing the water content/activity
or removing oxygen
Lycopene is a member of the
carotenoid family, and it is the
naturally occurring compound
that gives the characteristic
red color to the tomato,
watermelon, pink grapefruit,
and orange.
Biological Function of lycopene
The biological function of lycopene is
determined by its structure.
Lycopene is a lineal acyclic isomer of
β-carotene. It contains 11 conjugated double
bonds in the center part of the molecule and 2
unconjugated double bonds at each end
Since lycopene doesn’t contain β-ionone
ring structure at the end of the molecule,
it cannot be converted to vitamin A.
Lycopene Antioxidant
Lycopene, α-carotene, and β-carotene were
studied for their inhibitory effects on
hydroperoxide formation during oxidation of
methyl linoleate.
Lycopene displayed a higher antioxidant effect
compared to α-carotene and β-carotene,
which is in accordance with the results of
increased reactivity of lycopene with singlet
oxygen and free radicals.
lycopene oxidative degradation
Lycopene can be converted into peroxyl radicals
capable of acting as pro-oxidants and of
undergoing autoxidation themselves.
Oxygen is introduced into lycopene in two ways:
(a) oxidation of a methyl or methylene group
(b) addition to a carbon-carbon double bond.
Oxidative degradation can occur at either end of
the C40-carbon skeleton.
References
Jane Higdon. 2009. Carotenoids Alpha-Carotene, Beta-Carotene, Beta Cryptoxanthin, Lycopene, Lutein, and
Zeaxanthin. Linus Pauling Institute
Ehab A. Abourashed. 2013. Bioavailability of Plant-Derived Antioxidants. Antioxidants, 2(4), 309-325
Berg et al.2000. The potential for the improvement of carotenoid levels in foods and the likely systemic effects.
Journal of the Science of Food and Agriculture. 80:880±912
Karrer, P. and Jucker, E. 1950. Carotenoids. Elsevier, New York. Kawaguchi, A., Yutani, C., and Yamamoto, A. 2003.
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Tsuchihashi, H., Kigoshi, M., Iwatsuki, M., and Niki, E. 1995. Action of beta- carotene as an antioxidant against lipid
peroxidation. Arch. Biochem. Biophys., 323:137–147.
Clevidence, B.A. and Bieri, J.G. 1993. Association of carotenoids with human plasma lipoproteins. Methods
Enzymol., 214:33–46.
Ribaya-Mercado, I.D., Ordovas, I.M., and Russell, R.M. l995a. Effect of β-carotene supplementation on the
concentrations and distributions of carotenoids, vitamin E, vitamin A, and cholesterol in plasma lipoprotein and
nonlipoprotein fractions in healthy older women. J. Am. Coll. Nutr., 14:614– 620.
Anguelovea, T. and Warthesen, J. 2000. Degradation of lycopene, α-carotene, and β-carotene during lipid
peroxidation. J. Food Sci., 65:71– 75.
Erdman, J.W., Poor, C.L., and Dietz, J.M. 1988. Factors affecting the bioavail- ability of vitamin A, carotenoids, and
vitamin E. Food Technol., 10:214– 221.
Agarwal, S. and Rao, A.V. 2000b. Role of antioxidant lycopene in cancer and heart disease. J. Am. Coll. Nutr.,
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