Biological activity oF lycopene - Śląski Uniwersytet Medyczny w

Biological activity oF lycopene - Śląski Uniwersytet Medyczny w

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Abstract:
Not only are fruit and vegetables a source of nutrients, but
they also contain substances which have preventive properties in forestalling many diseases of civilization, such
as tumors or cardiovascular diseases. Among compounds
of natural provenience which have beneficial effects on
human body, antioxidants, such as vitamin C and E, carotenoids, flavonoids and selenium are the most important.
Among these, carotenoids deserve special attention due to
their omnidirectional effects, which are widely researched,
particularly the antioxidative properties. Lycopene has
the most powerful antioxidative properties among carotenoids – it is a red colorant contained in tomatoes and
processed products based on them, as well as water melons, red grapefruit, and papaya. As a result of research it
has been established that frequent eating of food rich in
lycopene, both natural and processed, effectively protects
against - among others - prostate and liver cancer. It also
reduces the risk of getting arteriosclerosis and forestalls
its further development.
Streszczenie
Warzywa i owoce są źródłem nie tyko składników odżywczych, ale zawierają również substancje mające profilaktyczne działanie w zapobieganiu wielu chorób cywilizacyjnych, takich jak choroby nowotworowe czy choroby
układu sercowo naczyniowego. Wśród związków pochodzenia naturalnego wpływających korzystnie na organizm
człowieka największe znaczenie mają antyoksydanty takie
jak witamina C i E, karotenoidy, flawonoidy oraz selen.
Wśród nich na szczególną uwagę zasługuje bardzo liczna
grupa karotenoidów, których wielokierunkowe działanie,
szczególnie przeciwutleniające, jest obecnie szeroko badane. Najsilniejsze właściwości antyoksydacyjne w grupie karotenoidów posiada likopen – czerwony barwnik,
którego głównym źródłem są pomidory i ich przetwory,
a także arbuzy, czerwone grejfruty, papaja. W wyniku
przeprowadzonych badań stwierdzono, że częste spożywanie zarówno produktów naturalnych jak i przetworzonych bogatych w likopen skutecznie chroni przed zachorowalnością, m.in. na raka prostaty czy wątroby oraz
zmniejsza ryzyko powstawania i rozwoju miażdżycy.
Key words: lycopene, carotenoids, antioxidants
Słowa kluczowe: likopen, karotenoidy, antyoksydanty
Progressing chemisation of food – i.e. adding large
amounts of non-nutritional ingredients to food, such as preservatives, colourants, artificial flavours, antioxidants and
synergents, stabilizers and emulsifiers causes consumer
anxiety about the health aspect of food they consume. Consequently, natural substances displaying the aforementioned
characteristics are more and more intensely sought in order
to add them to food products. It has to be stressed that the
fact that a given substance is to be found in nature does not
guarantee its safety for health. Only after a number of tests
can it be qualified as a food additive – or not.
Lycopene – a natural colourant belonging to the group of
carotenoids, designated as E160d, has been recognized as an
absolutely safe ingredient in foodstuffs. It can be added to:
drinks based on fruit and vegetable juices, drinks based on
milk, cereals, fats, sauces, soups, bakery products, confectionery products, drinks such as wine and spirits, ice-cream,
edible rinds on maturing cheeses and edible coating.
Lycopene (Fig.1) is an acyclic isomer of β−carotene with
the same empirical formula C40H56. Contrary to β−carotene,
which is an aliphatic - alicyclic polyene, lycopene does not
have closed chains of β−ionone. It belongs to chain polyunsaturated aliphatic hydrocarbons and does not display
features characterizing vitamin A, such as β−carotene In its
molecules it contains eleven conjugated double bindings,
which, playing the role of a chromophore, determine its ruby
red hue [1].
Lycopene is usually found in the most thermodynamically stable trans configuration. Exposed to light and temperature it undergoes partial isomerization, from trans form
to cis form [2]. It is most abundantly present in tomato skin,
but it can also be found in some fruit (Table 1). Processing fresh tomatoes causes change in the amount of active
substances they contain and influences their bioavailability.
Apart from lycopene, in processed tomato products the following are to be found: 5,6–epoxylycopene, 5,6-dihydroxy5,6-dihydrolycopene, β−carotene, γ- carotene [3]. Lycopene
is a relatively stable compound and while tomatoes are
being processed its amount does not change significantly,
while its bioavailability grows. This is due to the fact that
in high temperature cell walls rupture and lycopene is freed
from tomato tissues. Furthermore, a beneficial change takes
place in the configuration of some lycopene molecules from
trans to cis form. Lycopene cis isomers crystallize and aggregate to a lesser extent, they can be more effectively dissolved in lipophilic solvents and are more easily transported
by biofilms [4].
While lycopene trans form dominates in tomatoes ingested, in blood serum lycopene is to be found mainly in cis
configuration. It is not entirely clear whether this is due to
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Table I. Lycopene content in tomatoes, tomato products and in fruit [3, 6].
Product
fresh tomato
cooked tomato
yellow tomato
tomato sauce
tomato puree
tomato soup
tomato juice
ketchup
watermelon
pink guava
pink grapefruit
papaya
apricot
the fact that cis form is more easily absorbed, or whether
after absorption trans form lycopene is isomerized into cis
form and then absorbed by tissues [5].
Absorption of lycopene from food increases when fats
are present, especially those containing unsaturated fatty
acids. Research shows that a single dose of unprocessed
tomato juice does not change the saturation of lycopene in
blood serum, contrary to juice cooked for one hour in the
presence of 1% maize oil, which does change the saturation
significantly [6]. It has also been observed that absorption of
lycopene is greater if it is ingested with other carotenoids
than if it is consumed separately [7].
In human body lycopene is amassed in greatest amounts
in adrenal glands, testicles, liver and prostate gland. To some
extent it is also accumulated in breast, pancreas, lungs, kidneys, ovaries and fat tissue, as well as in the stomach, which
suggests, that in these organs the compound plays a natural
biological role and influences the course of disease process.
Lycopene is also present in body fluids such as blood serum,
mother’s milk and semen [6].
Among carotenoids lycopene is characterized by the
strongest antioxidative properties. It plays an important role
in prevention and therapy of tumours and cardiovascular
diseases [8 – 10]. Determined by its polyene structure and
compliance with addition reactions, antioxidative properties
of polyene result from its direct reactions with hydrogen superoxide, organic radicals generated in the process of lipid
peroxidation, nitrogen dioxide and sulfhydryl radicals [11].
It can also quench singlet oxygen. Lycopene (LK) reaction
with superoxide radical (LOO•) takes place in a few stages:
LOO• + L → LOO-LK•
LOO-LK• + LOO• → LOO-LK•-OOL
•
LOO-LK -OOL + LOO-LK•-OOL → (LOO)2-LK-(OOL)2
Numerous tests confirm protective effects of lycopene
on development of tumours, especially of those organs in
which it accumulates in the greatest amounts i.e. prostate and
liver. There have been many publications indicating the relationship between consuming lycopene and decreasing the
risk of developing prostate cancer [12]. It has been proved
that a tenfold increase in weekly consumption of lycopene
decreases the risk of cancer disease by almost 35%. Protective effects of lycopene bring results also in the cases of
advanced prostate tumour [13]. It has also been shown that
Lycopene content (mg/100g of the product)
0,88-4,20
3,70
0,50
6,20-14,10
20,94-49,33
7,99
5,0-11,60
9,90-13,44
2,30-7,20
5,40
3,36
2,0-5,30
0,86
Figure 1. Structure of lycopene
daily consumption of tomato paste by men with hyperplasia
of prostate cells lowers the saturation of prostate gland antigen (PSA) in blood [14].
As a result of tests carried out on young healthy rats
which have been administered lycopene it has been established that the greatest amount of lycopene is accumulated
in the left prostate lobe, in which local expression of IGF-I is
decreased, as well as the level of transcription of pro-inflammatory cytokines, immunoglobulines and immunoglobuline
receptors.
It has been also shown that consumption of lycopene
gently, but significantly, reduces the expression of genes of
enzymes metabolizing androgens and androgen receptors
[15].
The mechanism of anticarcinogenous influence of lycopene is probably connected with the improvement of intercellular connectivity by inducing gap junctions as a result of
stimulating the body to biosynthesize connexin B, the protein responsible for correct intercellular communication [1].
Lycopene can probably also impede the carcinogenic process by deactivation of insulin growth agent I (IGF I) [16].
In tests carried out on liver cancer cells of SK-Hep 1 line
it has been established that lycopene inhibits their growth,
limits their number and impedes their adhesion to the base
and decreases the activity of metaloproteinases MMP-2 and
MMP-9, which they secrete. Furthermore, liver cancer cells
subjected to the activity of lycopene exhibited reduced ability to invade and migrate, in comparison with other SK-Hep1
cells [17].
Consumption of products containing lycopene decreases
the risk of developing cancer of oral cavity, pharynx and
trachea [18], gastro-intestinal tract [16], large bowel [19],
bladder [20] and breast [21].
The role of lycopene in prevention of cardiovascular
diseases consists mainly in the protection of lipoproteins of
LDL fraction from oxidation, happening as a result of antioxidative properties of lycopene. If oxidation of LDL lipo-
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proteins takes place, they stimulate the walls of a vessel to
produce adhesive particles MCP-1, ICAM-1 and VCAM-1,
which attracts monocytes to it. It has been shown that lycopene limits the expression of adhesive particles and the adhesion of monocytes to the walls of a vessel. Apart from its
antioxidative activity, lycopene decreases the synthesis of
cholesterol by blocking 3 –hydroxy -3 methyloglutaric-CoA
reductase (an enzyme necessary for its synthesis) and it increases the degradation of LDL lipoprotein [6].
Much attention is given to the protective properties of
lycopene against harmful effects of UV radiation on skin.
It has been shown that exposition of skin to UV radiation
causes lowering in the level of lycopene saturation in skin
of about 31-46% in comparison with unexposed skin. Protective effect of lycopene on skin consists in decreasing the
thickness of epidermis, stimulating proliferation and differentiation of keranocytes, inhibiting the intercellular activity
of type I colagenaze and on maintaining the right density of
skin [22].
Due to the proven healthiness of lycopene, it is available
in the form of many pharmaceutical preparations, used as
diet supplements. However, processed tomatoes are thought
to be the best source of lycopene.
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Address for correspondence:
dr n. med. Ewa Kurzeja
Katedra i Zakład Żywności i Żywienia
Wydział Farmaceutyczny z Oddziałem Medycyny Laboratoryjnej
Śląskiego Uniwersytetu Medycznego w Katowicach
41-200 Sosnowiec, ul. Jedności 8;
tel. 032/3641172
e-mail: [email protected]