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Beverage
Cocoa dry leaves as potential source of
bioactive beverage
Epidemiological studies have
shown that consumption of food and
beverages rich in phenolic content can
reduce the risk of heart disease, slowing
the progression of atherosclerosis by
acting as antioxidants towards low-density
lipoprotein (LDL). The emergence of
natural extracts possessing antioxidant
properties will help in reducing the
current dependency on synthetic
antioxidants in food applications. Towards
the efforts to balance the conservation of
biodiversity and encouraging controlled
exploitation of plant resources for
economic gains, especially in
biopharming, wastage of valuable
resources should be minimized. With this
objective scientists at School of Chemical
Sciences and Food Technology, University
Kebangsaan Malaysia, Malaysia attempted
to assess the antioxidative potential of
phenolic extracts from cocoa,
Theobroma cacao Linn. leaves which
are normally wasted during frequent
pruning.
The cocoa leaves were given a
similar treatment to that in green tea
processing. To assess the antioxidation
potential of dried cocoa leaves, they were
compared to green tea and butylated
hydroxyanisole (BHA), a common
synthetic antioxidant widely used in edible
oil industries. Cocoa shoot (CS), young
leaves (CL) and tea leaves (GT) were
processed according to green tea
processing procedures. Polyphenol
components were extracted and analysed
using
high
pressure
liquid
chromatography.
The
total
polyphenol of
CS, CL and GT
were 19.0,
28.4 and 17.3
mg/100 mg,
respectively.
The
main
catechinpolyphenols in
extracts were
epicatechin (EC), epigallocatechin gallate
(EGCG), epigallocatechin (EGC), gallic
acid (GA) and epicatechin gallate (ECG).
The concentrations of caffeine for CS, CL
and GT were 2.24, 1.33 and 3.34 mg/100
mg, respectively. The concentrations of
EGCG, in both cocoa leaves, were lower
than commercial green tea. However, the
concentrations of EC in CS (5.93 mg/100
mg) and in CL (2.82 mg/100 mg) were
significantly higher than those found in
green tea (0.65 mg/100 mg). The
antioxidation properties of the polyphenol
extracts were tested, using ferric chloride
reduction, and compared
against a synthetic
antioxidant (BHA). The
polyphenol extracts (CS
and CL) showed similar
antioxidation powers to GT
and BHA throughout the
entire concentration range
(100–2000 ppm). In the
oil-based test medium; the
antioxidative performance
of polyphenol extracts
were better than BHA at 50 ppm. At 200
ppm, the performance is quite similar to
BHA. At higher concentration (400 ppm)
the antioxidant activities are much better
than BHA. In the presence of Cu 2+
prooxidant (20 ppm), BHA (200 ppm)
and all the extracts (200 ppm) showed
similar performances. Since the oxidation
test was conducted at 65°C, the 8 days of
stability provided by 200 ppm addition of
CL and CS extracts, can be equated to 8
months of room temperature (25°C)
stability. Hence, the cocoa leaves extracts
have the potential to complement or
replace synthetic antioxidants in aqueous
and oil-based food applications. The
cocoa leaves extracts, especially the cocoa
shoot, have similar antioxidant activities
to green tea. With proper pruning
management, the waste leaves from cocoa
plantations can be utilized as a new source
of natural bioactive extract. [Osman H,
Nasarudin R and Lee SL, Extracts of cocoa
(Theobroma cacao L.) leaves and their
antioxidation potential, Food Chem, 2004, 86
(1), 41-46].
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Vol 4(3) May-June 2005
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Beverage
Effects of black tea consumption in
patients with coronary heart disease
Numerous epidemiological
studies have reported inverse associations
between tea consumption and
cardiovascular events. Among the many
mono- and polymeric polyphenolic
compounds found in green and black tea,
investigators have recently focused on the
catechins, in part because they are more
readily measurable, but also because
catechin intake correlates inversely with
cardiovascular risk. Scientists working in
USA and Netherlands conducted studies to
investigate potential mechanisms of the
effect of black tea consumption in patients
with coronary artery disease. They recently
reported that chronic black tea
consumption improves endothelial function
and increases total plasma catechins in
patients with coronary artery disease. The
present study was conducted to investigate
the possible contribution of individual
catechins to the observed improvement in
endothelial function. In addition, they
measured systemic markers of oxidative
stress and inflammation to gain further
insight into the potential mechanisms of
benefit.
This relatively large and wellcontrolled study provides further evidence
that consumption of black tea does not have
a readily measurable systemic antioxidant
or anti-inflammatory effect that would
account for improved endothelial function
or reduced cardiovascular risk. In addition,
the study provides no evidence that
catechins specifically account for the
observed improvement in endothelial
function during tea consumption, a finding
that is consistent with their relatively low
concentration in black tea. In contrast, total
flavonoid intake correlates with endothelial
function after adjusting for potential
confounders. The plasma EC level also
correlated with endothelial function and
appears to relate to total flavonoid intake,
although further studies will be needed to
confirm and explain these observations.
These findings are consistent with the
possibility that complex polyphenols in tea,
rather than individual monomeric
components, may account for the benefit.
This possibility is consistent with the recent
recommendation by the American Heart
Association suggesting that antioxidants
should be consumed as whole foods rather
than as purified individual components
[Widlansky Michael E, Duffy Stephen J, Hamburg
Naomi M, Gokce Noyan, Warden Beverly A,
Wiseman Sheila, Keaney John F Jr, Frei Balz and
Vita Joseph A, Effects of black tea consumption on
plasma catechins and markers of oxidative stress
and inflammation in patients with coronary artery
disease, Free Radical Biol Med, 2005, 38 (4),
49s9-506].
Green tea antioxidant properties
Drinking tea, especially green
tea, is associated with a lower incidence
of human cancer. The desirable cancerprotective or putative therapeutic
properties of green tea polyphenols have
also been considered to depend on their
antioxidant properties. Polyphenolic
compounds extracted from green tea
leaves have been reported to be able to
scavenge free radicals, to protect DNA
from oxidative damage and to be good
antioxidants against lipid peroxidation in
phospholipid bilayers, in low-density
lipoproteins, in red blood cells, in
epidermal microsomes, in synaptosomes
and in animal model systems.
The synergistic antioxidant
mechanism of α-tocopherol (vitamin E)
with green tea polyphenols, i.e.,
(−)-epicatechin (EC), (−)-epigallocatechin
(EGC), (−)-epicatechin gallate (ECG),
(−)-epigallocatechin gallate (EGCG), and
gallic acid (GA), was studied at National
Laboratory of Applied Organic Chemistry,
Lanzhou University, Lanzhou, Peoples’
Republic of China by assaying the kinetics
of the reaction of α-tocopheroxyl radical
with green tea polyphenols by stoppedflow electron paramagnetic resonance, the
inhibition of linoleic acid peroxidation by
these antioxidants and the decay of αtocopherol during the peroxidation. It was
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found that the green tea polyphenols could
reduce α-tocopheroxyl radical to
regenerate α-tocopherol with rate
constants of 0.45, 1.11, 1.31, 1.91, and
0.43 × 102 M-1 s-1 for EC, EGC, ECG, EGCG,
and GA, respectively, in sodium dodecyl
sulfate micelles. In addition, these secondorder rate constants exhibited a good
linear correlation with their oxidation
potentials, suggesting that electron
transfer might play a role in the reaction.
[Zhou Bo, Wu Long-Min, Yang Li and Liu
Zhong-Li, Evidence for α-tocopherol
regeneration reaction of green tea
polyphenols in SDS micelles, Free Radical
Biol Med, 2005, 38(1), 78-84].
Natural Product Radiance
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