Download Flavonoids are most commonly known for their antioxidant activity

INTRODUCTION
Flavonoids are "the most common group of polyphenolic compounds in
the human diet and are found ubiquitously in plants". Flavonoids are most
commonly known for their antioxidant activity. Flavonoids are also commonly
referred to as bioflavonoids– the terms are largely equivalent and
interchangeable, for most flavonoids are biological in origin. Flavonoids are
widely distributed in plants fulfilling many functions including producing yellow
or red/blue pigmentation in flowers and protection from attack by microbes
and insects. The widespread distribution of flavonoids, their variety and their
relatively low toxicity compared to other active plant compounds (for instance
alkaloids) mean that many animals, including humans, ingest significant
quantities in their diet.
Flavonoids have been referred to as "nature's biological response
modifiers" because of strong experimental evidence of their inherent ability to
modify the body's reaction to allergens, viruses, and carcinogens. They show
anti-allergic, anti-inflammatory, anti-microbial and anti-cancer activity.
The
beneficial effects of fruit, vegetables, and tea or even red wine have been
attributed to flavonoid compounds rather than to known nutrients and
vitamins. Flavonoids exist naturally in cocoa, but because they can be bitter,
they are often removed from chocolate, even the dark variety (Spencer,
2008).
Flavonoids are water soluble polyphenolic molecules containing
15 carbon atoms. Flavonoids belong to the polyphenol family. Flavanoids can
be visualized as two benzene rings which are joined together with a short
three carbon chain. One of the carbons of the short chain is always connected
to a carbon of one of the benzene rings, either directly or through an oxygen
bridge, thereby forming a third middle ring, which can be five or
six-membered. Flavonoids are further divided into five groups: flavonols,
flavones, flavanones, flavan-3-ols and anthocyanins.
Flavonols can be found in many common foods such as onions, leeks,
broccoli, red grapes, apples and blue berries. Flavones, such as luteolin and
apigenin, are less common and can be found in green vegetables such as
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celery and parsley. Flavanones are mainly found in citrus fruits, in the juice
but also the albedo. Isoflavones are also called plant estrogens because of
their structural similarity to human estrogen. They are mainly found in
soybeans.
Flavan-3-ols,
such
as
epicatechin,
epicatechin
gallate,
gallocatechin and catechin, are present in a variety of foods such as tea,
cocoa and fruits. Anthocyanins are the water-soluble pigments which give the
typical colour to fruits and vegetables such as blue berry, strawberry, red wine
and cabbage (Erdman et al., 2007).
Many of the health benefits associated with flavonoids appear to be
linked to their activity as antioxidants. Antioxidants are one of the body’s
defences against free radicals’, which are small molecules generated during
normal metabolic processes. Excessive free radical production causes
damage to cells and their components, including cell DNA (genetic material),
and is thought to have a key role in the ageing process and in many
degenerative and age-related diseases. Flavonoids act as antioxidants by
‘mopping up’ free radicals in cells, thereby limiting the damage they can
cause.
Cocoa flavonoids are thought to have a protective effect on
cardiovascular health through their ability to alter a number of pathological
processes involved in the development of Cardio Vascular Disease. These
include:
• Inhibiting the oxidation of LDL-cholesterol (‘bad’ cholesterol) by free
radicals, an important initial step in the formation of atherosclerotic
plaque.
• Suppressing the tendency for small blood cells, called platelets, to clump
together and form blood clots. This is often described as an ‘aspirin-like’
effect.
• Regulating inflammatory and immune responses in blood vessel walls,
which may be abnormal in CVD.
• Regulating vascular tone, or degree of constriction of small blood vessels,
which contributes to high blood pressure.
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In producing these beneficial effects, cocoa flavonoids appear to act
through a range of mechanisms, some of which are not thought to be linked to
antioxidant activity.
Cocoa is an important source of polyphenols, which comprise of
12 to 18 percent of its total weight on dry basis. The major phenolic
compounds are epicatechin, proanthocyanidins and catechin. The levels of
flavonoids contained are higher than the ones founds in apples, onions or
wine, foods known for their high amount of phenolic compounds. Cocoa and
cocoa products are important sources of flavonoids in our diet. The
bioavailability of these compounds depends on other food constituents, and
their interaction with the food matrix (Lamuela-Ravent, 2005).
The high antioxidant capacity of cocoa and chocolate are attributed to
their significant amount of procyanidins, the oligomeric form of the flavanol
monomeric units, (-) - epicatechin and (+)-catechin. These monomers, mainly
(-)-epicatechin, provide most of the total procyanidins content in chocolate,
however dimers (two monomer units) and up to 10 monomer units are also
present. Cocoa and chocolate, especially dark, have only recently been
identified as rich sources of flavonoids due to advances in technology and
analytical methods used in the detection of flavanoids (Engler, 2004).
Chocolate is made from different recipes and contains other
ingredients in addition to cocoa butter and powder (Bywaters et al., 1930).
The basic ingredients required for the manufacturing of chocolate are cocoa
liquor, sugar, other sweeteners, cocoa butter, oil, milk powder, milk crumb and
emulsifiers. Chocolates may have different percentages of non-fat cocoa
solids.
There are different percentages of cocoa butter, sugar, and milk
powder which are used in preparing different types of chocolates, namely dark
chocolate, milk chocolate, and white chocolate. The content of polyphenols
can vary tremendously depending on the source of beans, primary and
secondary processing conditions and the process employed in the
manufacturing of chocolates. Due to these factors, the ratio and types of
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polyphenols found in cocoa beans are unlikely to be the same as those found
in the finished products (Cooper et al., 2007).
Consumption of sweets like chocolates having high amount of
saturated fatty acids and has been known as an important factor in the
development of coronary heart disease and increasing cholesterol content of
blood. But, it is thought that some saturated fatty acids may not deserve this
reputation. The saturated fatty acids like lauric (12:0), myristic (14:0), and
palmitic (16:0) acids definitely raise blood cholesterol content. On the other
hand, stearic acid (18:0) has been considered as neutral effect on blood
cholesterol (Cardwell, 2004 and Connor, 1999).
The cocoa bean contain 31 percent fat of which 60 percent is saturated
fat. Two-thirds of the fat is in the form of stearic acid, a saturated fat and the
remainder in the form of oleic acid, a monounsaturated fat. Cocoa butter
(derived from the cocoa seed) has more stearate than any other common
edible fat or oil. Since cocoa butter is a vegetable fat, it does not contain any
cholesterol (Baba et al., 2000)
Because of its high saturated fat content, chocolate is often postulated
to have a hypercholesterolemic effect. However, clinical trials have shown that
chocolate consumption has neutral effects on serum total and Low density
lipoprotein (LDL) cholesterol (Etherton et al., 1994). This is probably due to
the high content of stearic acid (30 per cent of fatty acids), which is
considered to be neutral with respect to total and LDL cholesterol.
Consumption of cocoa or dark chocolate may actually have a beneficial effect
on serum lipids. Wan et al., (2001) in their study have shown that, the
consumption of cocoa with dark chocolate increased the serum concentration
of HDL cholesterol by four percent.
The flavonoids present in cocoa are mainly flavan-3-ols, either
monomeric (cathechin and epicatechin) or oligomeric procyanidins. Cocoa
polyphenols have been shown to have antioxidant and antimutagenic
activities invivo and invitro, increasing the total antioxidant capacity of serum,
which implies the bioavailability of cocoa polyphenols (Zhu et al., 2002).
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Over the past decade, at least 28 studies have been reported on the
health benefits of cocoa flavonoids. Most studies showed positive
relationships between cocoa and chocolate flavonoids on cardio-protective
effects. Most of the outcomes were based on the short-term effects of the
supplements between four days to six weeks (Cooper et al., 2008).
Bioavailability of ingested flavonoids present in cocoa or cocoa-based
products is of great importance as it may in turn reflect antioxidant status of
the subjects. Thus, it is important to consider both bioavailability and
antioxidant status while determining the relationship between cocoa
flavonoids and its health benefits. The measurement of plasma antioxidant
concentration and oxidative stress levels are examples of determining
antioxidant status. Effects of monomers up to decamers derived from cocoa
was dose dependent and prevented erytrocyte hemolysis in vitro and
enhanced plasma antioxidant capacity (Zhu et al., 2002). In addition,
methylxanthines, namely caffeine, theobromine and theophylline, have also
been identified in cocoa (Kelm, 2006).
The health-promoting properties of cocoa polyphenols have been
reported both in vitro and in vivo (Greer, 2001). In recent years, cocoa and
cocoa products have been shown to suppress the development of
atherosclerosis and hepato-carcinogenesis, increase dermal blood flow,
reverse endothelial dysfunction and inhibit the proliferation of human breast
cancer cells (Vinson, 2001). To a greater extent, cocoa-based products might
possess hypercholesterolemic and insulinaemic properties in normal,
hypercholesterolemic and hypertensive human subjects (Baba, 2007).
Dark chocolate supplementation for three weeks in healthy subjects
significantly
increased
High-Density
Lipoprotein
cholesterol
(HDL-c)
compared to their unsupplemented counterparts (Mursu et al., 2004). Milk
chocolate consumption increased HDL levels compared to high carbohydrate
snacks among young men (Etherton et al., 1994). Cocoa administration did
not exert their antioxidative properties in plasma of healthy subjects, although
there were significant health outcomes. This could be due to the status of
subjects recruited in the study.
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Low doses of dark chocolate (containing 30 mg polyphenols)
supplementation to pre-hypertension subjects for 18 weeks significantly
reduced systolic and diastolic blood pressure compared to polyphenols-free
white chocolate (Taubert 2007). Dark chocolate consumption (containing
180mg polyphenols) resulted in reduction of total and LDL cholesterol among
elevated serum cholesterol subjects (Allen 2008).
Atherosclerotic cardiovascular disease is the number one public health
problem in the United States, and by the year 2020 it is predicted this will be
true worldwide. Epidemiological, clinical, and animal studies have clearly
established an important role for dietary cholesterol and saturated fat in
atherosclerosis susceptibility. Numerous studies have shown that increased
consumption of cholesterol and saturated fat are associated with increased
plasma levels of LDL cholesterol and increased risk of cardiovascular
diseases, whereas low dietary cholesterol and low saturated fat have the
opposite effect (Steinberg et al., 2003). In human studies, increasing
saturated fat intake also increases cholesterol levels with similar inter
individual variability (Mathur et al., 2002). However, it has been repeatedly
observed that there is great inter-individual variation in plasma lipoprotein
responsiveness to dietary cholesterol and saturated fat. This variation is
presumably genetic but the specific genes involved are largely unknown.
It has been previously shown in humans that for each 100mg/day
increase in dietary cholesterol the mean plasma cholesterol level rises 7mg/dl,
but some individuals are unresponsive and have even decreasing cholesterol
levels, while others show an exaggerated response, with increases of more
than 2-fold the mean (Etherton et al., 2002). In human studies, it has been
suggested that the ability to down-regulate endogenous cholesterol synthesis
in response to a dietary challenge limits an individual’s plasma lipoprotein
responsiveness (Lotito et al., 2000).
Many reports support the possibility that procyanidins in cocoa can
prevent cardiovascular diseases by improving blood flow rate, improving
platelet function, changing inflammatory responses in endothelial cells of
blood vessels. Also reports have indicated that the susceptibility of lowdensity lipoprotein (LDL) to oxidation was significantly decreased in humans
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(Wang et al., 2000 and wan et al., 2001) and high cholesterolemic rabbits
(Oskabe et al., 2000) by dietary supplementation with cocoa or its
procyanidins fraction.
In the past 10 years, there has been increased interest in the potential
health related benefits of antioxidant- and phyto-chemical-rich dark chocolate
and cocoa (Adamson et al., 1999 and Steinberg et al., 1989). Research has
identified an array of potential mechanisms through which chocolate and
cocoa products may promote cardiovascular health and provide cardioprotective effects (Kondo et al., 2000). Specifically, chocolate and cocoarelated products have been shown to decrease or inhibit both LDL oxidation
(Waterhouse et al., 1996 and Osakabe et al., 2002) and platelet activation or
function, to enhance serum lipid profiles (Grassi et al., 2005), to favorably
modify eicosanoid synthesis (Taubert et al., 2003), to lower blood pressure, to
promote endothelium-dependent relaxation or dilation, and to inhibit free
radical– induced erythrocyte hemolysis. Furthermore, preliminary in vitro
investigations have suggested that cocoa flavanols or procyanidins may
possess immuno-regulatory effects and may help to modulate immune
responses (Mao et al., 2000).
The recent discovery of biologically active phenolic compounds in
cocoa has changed this perception and stimulated research on its effects
in ageing, blood pressure regulation, and atherosclerosis. Interestingly there
is also epidemiological evidence to support that the regular consumption
of cocoa containing foods may confer cardio-protective benefits. Intake of
flavonoid rich food, including chocolate, wine and tea is associated with better
performance across several cognitive abilities and that the associations are
dose dependent. Further studies should directly examine the flavonoid status
and take into account other bioactive dietary substances in these foods. The
present study focuses on cardiovascular effects of cocoa, and on the potential
mechanisms involved in the response to cocoa and the potential clinical
implications associated with its consumption. Considering these aspects the
present study was undertaken with the following objectives:
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•
To formulate and develop cocoa based home made chocolate
samples.
•
To analyze the physicochemical properties, composition, organoleptic
property, glycemic index, phytochemical content and antioxidant
properties of the standardized product.
•
To study the effect of supplementation of developed cocoa based
homemade chocolates on animal models.
•
To study the efficacy of the cocoa based homemade chocolates on the
lipid profile of the selected hyperlipidemics.
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