Caffeine
Caffeine, also known as trimethylxanthine, coffeine, theine,
mateine, guaranine, methyltheobromine and 1,3,7-trimethylxanthine,
is a xanthine alkaloid found naturally in such foods as coffee
beans, tea, kola nuts, Yerba mate, guarana berries, and (in small
amounts) cacao beans and Yaupon Holly. For the plant, caffeine acts
as a natural pesticide since it paralyzes and kills some of the
insects that attempt to feed on the plant.
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Caffeine-containing beverages, such as coffee, enjoy great
popularity. Additionally, it is occasionally used medically in the
formulation of some analgesics. Caffeine's main pharmacological
properties are: a stimulant action on the central nervous system
with psychotropic effects and stimulation of respiration, a
stimulation of the heart rate, and a mild diuretic effect.
It is very difficult to know the exact amount of caffeine in a
particular drink that is not automatically prepared. The amount of
caffeine in a single serving of coffee varies considerably due to
many variables. Concentration can vary from bean to bean within a
given bush; preparation of the raw bean will affect concentration,
as well as multiple variables involved in brewing.
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To extract caffeine takes some time (about two hours) and requires
chemicals unavailable for everyday use and a nice system of
distillation and sublimation. To extract caffeine, one must take the
beverage one wants to extract the caffeine from and mix it with a
solvent with a finer affiliation to the caffeine and a different
density. Chloroform is known to possess both these properties.
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Caffeine will go in the solvent it is the most soluble in, and it is
more soluble in chloroform than water. Using a separating funnel,
one should take about 30 ml of chloroform and 200 ml of the beverage
one wants to extract the caffeine from and agitate for about two
minutes. The bottom phase will be the chloroform and the caffeine,
so one will keep this phase. Repeating this step about five times
should ensure extraction of most of the caffeine.
The next step is a distillation using a standard distillation
column where one gets rid of most of the chloroform. Finally,
one has to sublimate the caffeine under vacuum. If the result is
a fine white powder, one's extraction has succeeded.
One common source of caffeine is the coffee plant, the beans of
which are used to make coffee. Caffeine content varies
substantially between Arabica and Robusta species and to a
lesser degree between varieties of each species.
One 'shot' of coffee contains about 40 mg of caffeine. Thus, a
"double shot" espresso contains about 80 mg. A single serving (6
fl oz / 150 ml) of strong drip coffee or one-half caffeine
tablet would deliver about 100 mg. However, there is a large
variation in the amount of caffeine per serve, ranging from
about 40 mg to 120 mg. Such variability was shown to be even
higher in a study conducted in 2005 by Ben Desbrow, a dietitian
of Griffith University. His survey of 99 short blacks found
caffeine content ranging from 25 mg to 214 mg. Generally, dark
roast coffee has less caffeine than lighter roasts since the
roasting process reduces caffeine content of the bean.
Tea is another common source of caffeine in many cultures.
Tea contains somewhat less caffeine per serving than coffee,
(usually about half as much, depending on the strength of the
brew), though certain types of tea, such as black and oolong,
contain more caffeine.
Caffeine is also common in soft drinks such as cola. Such drinks
typically contain about 15 mg to 40 mg of caffeine per serving.
Most energy drinks such as Red Bull contain 80 mg.
Mateine and guaranine are other names for caffeine. The names
come from yerba maté and guarana respectively,
caffeine-containing plants used for tea and other things. Many
yerba maté enthusiasts insist that mateine is a stereoisomer of
caffeine and thus a different substance altogether. However,
this is impossible; caffeine is an achiral molecule with no
stereogenic centers (also known as a chiral centers), and
therefore has no stereoisomers. Similar claims are sometimes
made of guaranine.
Caffeine is sometimes called theine when it is found in tea, as
the caffeine in tea was once thought to be a separate compound
to the caffeine found in coffee. But tea does contain another
xanthine, theophylline whose chemical formula is C7H8N4O2
compared to caffeine's C8H10N4O2.
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