Occurrence and distribution
Fruit and vegetables:
Carrots (α-, β-carotenes)
Red peppers (capsanthin)
Sweet potatoes (β-carotene)
Occurrence and distribution
• All green vegetables contain carotenoids
but their color is masked by the green
• All carotenoids are lipophilic compounds
and thus are soluble in oils and organic
• they can be isomerized by heat, acid, light
• many carotenoids exhibit spectral shifts
with various reagents and these spectral
changes are used for identification
• Carotenoids are easily oxidized because of
large number of conjugated double bonds
• Such reactions cause color loss of
carotenoids in foods
• Destability of a particular pigment to
oxidation is highly dependent on its
• Carotenoids are familiar to all of us through the orangered colors of popular foods like oranges, tomatoes and
carrots, and the yellow colors of many flowers.
• They are also added as colorants to many manufactured
foods, drinks and animal feeds, either in the form of
natural extracts (e.g annatto) or as pure compounds
manufactured by chemical synthesis. The production of
carotenoids by biotechnology is of increasing interest.
Carotenoids are essential to plants for photosynthesis,
acting in light-harvesting and, especially, in protection
against destructive photooxidation. Without carotenoids
photosynthesis in an oxygenic atmosphere would be
• But carotenoids are not simply pigments of
terrestrial plants. They occur widely in bacteria,
fungi and algae, where they can be useful taxonomic
markers. The production of carotenoids in seaweed
runs to hundreds of million tons per year.
• Some animals use carotenoids for coloration,
especially birds (yellow and red feathers), fish (g.g.
goldfish and salmon) and a wide variety of
invertebrate animals, where complexion with
protein may modify their color to blue, green or
Carotenoids are important factors in human
health. The essential role of beta-carotene and
others as the main dietary source of vitamin A
has been known for many years. More recently,
protective effects of carotenoids against serious
disorders such as cancer, heart disease and
degenerative eye disease have been recognized,
and have stimulated intensive research into the
role of carotenoids as antioxidants and as
regulators of the immune response system.
• Currents carotenoid research encompasses a wide
veriety of fields and interests including plant
physiology, food science, environmental science,
taxonomy, industrial chemical synthesis,
biotechnology and medical research. All the work
must be based on a solid foundaation of carotenoid
chemistry and reliable methods for handling and
analysing these rather unsatble substances.
Of the various classes of pigments in Nature the carotenoids are
among the most widespread and important ones, especially due to
their most varied functions.
In 1831 Wackenroder isolated carotene from carrots and in 1837
Berzelius named the yellow pigments from autumn leaves
xanthophylls. This marks the beginning of
carotenoid research and since then continuous developments have
Because of their ubiquitous occurrence, different functions (see
below), and interesting properties carotenoids are the subject of
interdisciplinary research in chemistry, biochemistry, biology, medicine, physics, and many other branches
• As already mentioned, the carotenoids are a class of
natural pigments that is very widespread and it was
demonstrated that they occur in all the three
domains of life, i.e. in the eubacteria, the archea and
in the eucarya. A rich source for carotenoids are the
algae and more than 100 carotenoids have been
isolated and characterized from these organisms. For
humans the most important source for carotenoids
are plants, where often the brilliant colors of the
carotenoids are masked by chlorophyll, e.g. in green
The carotenoids are responsible for the beautiful
colors of many fruits (pine-apple, citrus fruits,
tomatoes, paprika, rose hips) and flowers
(Eschscholtzia, Narcissus), as well as the colors of
many birds (flamingo, cock of rock, ibis, canary),
insects (lady bird), and marine animals (crustaceans,
• Carotenoids found in yellow maize are
located in the corn predominantly. Main
carotenoids are Zeaxanthin and
• Zeaxanthin contains a hydroxy function at
each end group. Therefore, increased
polarity results. Zeaxanthin-glucosides and
Zeaxanthin-diglucosides have been found in
Archaea (e.g. Sulfolobus shibatae).
• Due to their amphiphilic properties, it was
postulated, that these carotenoids act as
reinforcers in membrane architecture.
Capsanthin is the main carotenoid in red pepper (Capsicum
Natural carotenoid extracts of pepper are available as food colours.
Oleoresin of paprika is the oil extract of paprika, Capsicum annuum.
The colour of a food product containing paprika may range from a
deep red to a pale pinkish-yellow, depending on the concentrations
used. The material can be used in salad dressings, sauces and
particularly in meat products, including sausages, where it is
allowed as an additive. It is often used in combination with annatto
to dye processed cheese.
• This oleoresin contains about 37 to 54 pigments
depending on the mode of preparation (extract of
unbleached or bleached paprika), of which only few
could be completely or even tentatively identified. The
main pigments are in general esters of capsanthin and
capsorubin. Most assay methods are therefore based on
the determination of these two carotenoids.
• According to a tradition, a lot of research is done in
Hungary, where pepper is cultivated extensively. The
picture below shows the separation of a natural paprika
extract by means of open-top column chromatography.
In natural products the most common carotenoid is the
yellow-orange pigment of the carrot (Daucus carota), the
ß,ß-carotene. It was isolated in crystalline form as early
as in 1831 by Wackenroder. Later, it gave the name to
the entire class of these compounds.
• Total synthesis of b,b-Carotene was developped in 1950
by Karrer, Eugster, Inhoffen and Milas. Just four years
later b,b-carotene was produced commercially and used
as pigment in food and feed. In 1995 capacity for the
synthesis of more than 500 tons of b,b-Carotene per year
• Because of its pro-vitamin A activity b,b-carotene is one
of the most important carotenoids. The first step in
biosynthesis is the cleavage of the central double bond of
b,b-carotene which results in two molecules of retinal.
This reaction is catalyzed by the enzyme b-carotene15,15'-deoxygenase. Afterwards, retinal is reduced to
vitamin A (retinol).
the b,b-carotene content can vary depending on the
variety, the season and the degree of ripening; • the
bioavailability of b,b-carotene from fruits and
vegetables depends on the method of preparation
b,b-Carotene is one of six individual carotenoids
produced industrially by Hoffmann-La Roche AG
and BASF AG companies. These are namely
canthaxanthin, astaxanthin and the apo-carotenoids
b-apo-8'-carotenal, b-apo-8'-carotenoic acid ethyl
ester and citranaxanthin.
The chart below shows the content of b,b-carotene in various
fresh fruits and vegetables. The values indicated can only
serve as an approximation since:
The main carotenoids in tomato fruit (Lycopersicon
Phytoene, phytofluene, z-carotene, neurosporene,
lycopene, b-zeacarotene, b,y-carotene and b,b
-carotene (The carotenoid content and composition
are highly dependent on the tomato variety and on
the ripeness of the fruit.)
• All carotenoids may be derived formally from
the acyclic C40H56 structure, having a long
central chain of conjugated double bonds, by
hydrogenation, dehydrogenation, cyclization, or
oxidation or any combination of these processes.
Tomato paste, tomato sauce, and tomato-based soups are
rich in carotenoid compounds and are frequently consumed.
Foods such as these, which are high in carotenoid content,
were individually identified and quantified by reversedphase HPLC . The carotenoids detected and quantified
included lycopene, lutein, alpha-, beta-, gamma-, and zetacarotenes, neurosporene, phytoene, and phytofluene. As
expected, lycopene was the most abundant carotenoid,
ranging in concentration from 0.3 mg/100 g in vegetable
beef soup to 55 mg/100 g in tomato paste. The
concentration of beta-carotene ranged from 0.23 mg/100 g
in tomato soup to 1.51 mg/100 g in vegetable beef soup.
SOFT DRINKS (e.g. FANTA)
A common composition (%w) of soft drinks is as
80 % Water
15 % Sugar
4 % Fruit Juice
Natural and Synthetical Flavours Stabilizer
NOMENCLATURE AND STRUCTURE
• Carotenoids are a class of hydrocarbons (carotenes)
and their oxygenated derivatives (xanthophylls).
They consist of eight isoprenoid units joined in such
a manner that the arrangement of isoprenoid units is
reversed at the center of the molecule so that the two
central methyl groups are in a 1,6-position
relationship and the remaining nonterminal methyl
groups are in a 1,5-position relationship.
All carotenoids may be formally derived from the
acyclic C40H56 structure (I) (Fig. 1), having a long
central chain of conjugated double bonds, by (I)
hydrogenation, (2) dehydrogenation, (3) cyclization,
or (4) oxidation, or any combination of these
processes. The class also includes compounds that
arise from certain rearrangements or degradations of
the carbon skeleton (I), provided that the two central
methyl groups are retained.
About 600 carotenoids have been isolated from natural
sources; they are listed with their trivial and
semisystematic names which also includes literature
references for their spectroscopic and other properties. It
must be pointed out, however, that for many of the
carotenoids listed the structure (this term includes the
stereochemistry) is still uncertain and in all these cases a
reisolation, followed by structural elucidation with all
the modern spectroscopic methods (especially high
resolution nuclear magnetic resonance (NMR)
spectroscopy) is absolutely necessary. About 370 of the
naturally occurring carotenoids are chiral, bearing from
one to five asymmetric carbon atoms, and in most cases
one carotenoid occurs only in one configuration in
Rules for the nomenclature of carotenoids (semisystematic
names) have been published by the International Union of
Pure and Applied Chemistry (IUPAC) and IUPACInternational Union of Biochemists (IUB) Commissions on
Nomenclature (1975). For the most common carotenoids
trivial names are normally used. If these trivial names are
used in a paper, the semisystematic name should always be
given, in parentheses or in a footnote, at the first mention.
All specific names are based on the stem name carotene,
which corresponds to the structure and numbering in II (Fig.
The name of a specific compound is constructed by adding two
Greek letters as prefixes (Figure 3) to the stem name carotene;
the Greek letter prefixes are cited in alphabetical order.
The oxygenated carotenoids (xanthophylls) are
named according to the usual rules of organic
chemical nomenclature. The functions most
frequently observed are hydroxy, methoxy, carboxy,
oxo, and epoxy.
• canthaxanthin (beta,beta-carotene-4,4'-dione) (XI),
• astaxanthin ((3S,3'S)-3,3'-dihydroxy-beta,beta-carotene4,4'-dione) (XII).
• Derivatives in which the carbon skeleton has been
shortened by the formal removal of fragments from one
or both ends of a carotenoid are named apo- and
diapocarotenoids, respectively, e.g. beta-apo-8'-carotenal
(8'-apo-beta-caroten-8'-al) (XIII). Other structural
variations are encountered in the norcarotenoids, in
which one or more carbon atoms have been eliminated
from within the typical C40-skeleton. A prominent
example is the C37-skeleton of peridinin
((3S,5R,6R,3’S,5’R,6’R)-epoxy-3,5,3’-trihydroxy-6,7didehydro-5,6,5’,6’-tetrahydro-10,11,20-trinorbeta,beta-caroten-19’,11’-olide 3-acetate) (XIV)
characteristic of diatoms.
• This cis-trans or (E/Z)-isomerism of the carboncarbon double bonds is another interesting feature of
the stereochemistry of the carotenoids, because it
was demonstrated that the (E/Z)-isomers may have
different biological properties. The literature in this
field is extensive: the first comprehensive review of
the cis-trans isomerism of carotenoids and vitamin
A was published in 1962 (Zechmeister, 1962).
According to the number of double bonds a great
number of (E/Z)-isomers exist for each carotenoid,
e.g. 1056 for lycopene (I) and 272 for b-carotene
• In view of the (E/Z)-isomerism the double bonds of
the polyene chain can be divided into two groups:
(I) double bonds with no steric hindrance of the (Z)isomer (central 15,15'-double bond and the double
bonds bearing a methyl group, such as the 9-, 9'-,
13-, and 13'-double bonds) and (2) double bonds
with steric hindrance (7-, 7'-, 11-, and 11’-double
bonds). Although isomers with sterically hindered
(Z)-double bonds are known ((11Z)-retinal) the
number of possible (Z)-isomers is in practice
reduced considerably, e.g., for lycopene (I) to 72.
• Normally carotenoids occur in Nature as the
(all-E)-isomer; however, exceptions are
known, such as the (15Z)-phytoene isolated
from carrots, tomatoes, and other
organisms. On the other hand, some
carotenoids undergo isomerization very
easily during workup; therefore many (Z)isomers that are described in the literature
as natural products are artifacts.
• For experimental work it must be kept in
mind that (E/Z)-isomerization may occur
when a carotenoid is kept in solution.
Normally the percentage of the (Z)-isomers
is rather low, but it is enhanced at higher
temperature. Furthermore, the formation of
(Z)-isomers is increased by exposure to
Carotenoids are synthesized in Nature by plants and
many microorganisms. Animals can metabolize
carotenoids in a characteristic manner, but they are
not able to synthesize carotenoids.
Carotenoids, being terpenoids, are synthesized from the basic C5terpenoid precursor, isopentenyl diphosphate (IPP) (XVII)
(Fig.1). This compound is converted to geranylgeranyl
diphosphate (C20) (XVIII). The dimerization of XVIII leads to
phytoene (7,8,11,12,7’,8’,11’,12’-octahydro-gamma,gammacarotene) (XIX) and the stepwise dehydrogenation via
phytofluene (15Z,7,8,11,12,7’,8’-hexahydro-gamma,gammacarotene (XX), zeta-carotene (7,8,7’,8’-tetrahydrogamma,gamma-carotene) (XXI), and neurosporene (7,8-dihydrogamma,gamma-carotene) (XXII) gives lycopene (I). Subsequent
cyclizations, dehydrogenations, oxidations, etc., lead to the
individual naturally occurring carotenoids, but little is known
about the biochemistry of the many interesting final structural
modifications that give rise to the hundreds of diverse natural
There are now exciting prospects for rapid progress
through the application of molecular genetics
techniques in combination with other biochemical
and chemical approaches. The benefits of this are
not purely academic. The industrial production of
natural carotenoids through microbial biotechnology
is already established and expanding, mainly
through the exploitation of some microalgae
(particularly Dunaliella) which can synthesize large
amount of carotenoid.
Carotenoids in Human Retina
Macula: retinal area of highest visual
High concentrations of xanthophyll
carotenoids lutein and zeaxanthin
Role of carotenoids: optical filtering;
antioxidants (protection of macula from
Individuals with high dietary intakes
and blood levels of lutein and
zeaxanthin have a lower rate of visual
loss from age-related macular
degeneration (AMD), the leading cause
of blindness in the elderly.