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Green Tea
Camellia sinensis |
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A natural stimulant containing caffeine &
theophylline, also an anti-oxidant, preventing formation of free
radicals associated with aging |
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| Green tea consists of
the rapidly dried, freshly picked leaves and leaf buds of Camellia
sinensis, a plant of the Theaceae family which is indigenous to the
rainy Asian forests and is cultivated widely in China, Sri Lanka, India,
Japan, Indonesia, and the African continent. This shrub or small tree
grows wild and is greatly branched, with alternate, evergreen leaves
which are limp and downy when young, but become coriaceous and glabrous
once matured. The word tea comes from the Greek word, thea, which
means goddess, whereas sinensis refers to its Chinese origin.
Green tea is prepared by picking fresh leaves, drying them rapidly and
rolling them up as they dry. Black tea is prepared from fresh green tea
leaves which are initially dried slowly, rolled and heaped, which allows
them to begin to ferment. Once fermentation has occurred the leaves are
rapidly dried. Oolong tea is prepared from semifermented leaves. Tea
leaves appear to be crumpled, bright green or blackish green masses of
dried plant matter. Its odor is pleasantly aromatic and agreeable, with
an astringent and mildly bitter taste. Caffeine is the primary active
constituent in tea. Caffeine also occurs in coffee, cacao, kola, guarana,
and mate, as well as in tea. Because there are many different varieties
of the cultivated plant, as well as different methods of preparation,
the average caffeine content of tea ranges from about one to more than
four percent. Tea leaves also contain theophylline, xanthine, and
theobromine, which are purine alkaloids with similar chemical structures
to caffeine. They also consist of adenine, gallotannic acid, which is
responsible for tea’s astringency, and a yellow volatile oil that is
solid at room temperature. This volatile oil is strongly aromatic and
imparts much flavor to tea. The stimulant activity of tea is primarily
due to its content of caffeine and other purine alkaloids. Theophylline
and related compounds are utilized in their purified forms as smooth
muscle relaxants for the symptomatic relief and prevention of bronchial
asthma and for the treatment of reversible bronchospasm associated with
chronic bronchitis and emphysema. Theophylline also has bronchiodilating
properties. Theophylline and caffeine are both diuretic in action. These
purine alkaloids competitively inhibit phosphodiesterase, which results
in increased concentrations of adenosine monophosphate with a subsequent
release of endogenous epinephrine (adrenalin). This results in a direct
relaxation of the smooth muscles of the bronchi and pulmonary blood
vessels, a stimulation of the central nervous system, an increase in
gastric acid secretion, induction of diuresis, and inhibition of uterine
contractions. Green tea also contains phenolic acids, such as
chlorogenic and caffeic acids, flavonoids, (theaflavins) and several
proanthocyanidins. These compounds are thought to have angioprotective
and antioxidant properties, preventing lipid peroxidation and formation
of free radicals associated with aging, counteracting the mutagenicity
and carcinogenicity of various toxins. Intense tea consumption can lead
to digestive disorders. Adding milk will reduce the chlorogenic acid and
other tannins, preventing this problem. Excessive use can lead to
panicky states of anxiety, irritability, insomnia, vertigo, loss of
appetite, vomiting, diarrhea and headache. Do not use if pregnant. |
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