Caffeine Molecular Structure - Metabolism and Toxicology

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Caffeine Molecular Structure - Metabolism and Toxicology JoAnn Guest May 31,

2005 17:27 PDT

 

 

Caffeine Molecular Structure -Metabolism and Toxicology

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Caffeine is thought to act on the brain by *blocking* adenosine

receptors.

Adenosine, when bound to receptors of nerve cells,

" slows down " nerve cell activity;

this happens,

among other times, during sleep.

 

The caffeine molecule, being similar to adenosine,

" binds " to the same " receptors "

but doesn't cause the cells to slow down;

instead, the caffeine " blocks " the " receptors "

and thereby the " adenosine action " .

 

The resulting increased nerve activity causes the release of the hormone

epinephrine, which in turn leads to several effects such as higher

" heart rate " , " increased " blood pressure,

increased blood flow to muscles,

" decreased " blood flow to the skin and inner organs, and " release " of

" glucose " by the liver.

 

In addition, caffeine, similar to " amphetamines " , " increases " the levels

of the " neurotransmitter dopamine " in the brain.

 

Continued consumption of caffeine can lead to tolerance.

 

Upon withdrawal, the body becomes " oversensitive " to " adenosine " ,

causing the blood pressure to drop dramatically, leading to headache and

other symptoms.

 

Too much caffeine can lead to caffeine " intoxication " .

 

The symptoms of this disorder are restlessness, nervousness, excitement,

insomnia, flushed face, diuresis, and gastrointestinal complaints.

 

They can occur in some people after as little as 250 mg per day.

 

More than 1 g per day may result in " muscle twitching " , rambling flow of

" thought " and s " peech " ,

" cardiac arrhythmia " or tachycardia, and " psychomotor agitation " .

 

Caffeine intoxication can lead to symptoms similar to " panic disorder "

and " generalized anxiety " disorder.

 

The LD50 is estimated to be about 192 mg/kg of body mass, or about 72

cups of coffee for an average adult, while the half life ranges from 3.5

to 100 hours.

 

In adults the half life is generally around 5 hours.

 

However contraceptive pills increase this to around 12 hours and for

women over 3 months pregnant it varies from 10 to 18 hours.

 

While safe for humans, caffeine and its related compounds theobromine

and theophylline are considerably more " toxic " to some other animals

such as dogs and horses, due to differences in " liver metabolism " .

 

 

Abuse and addiction

Caffeine, in its many forms, has been used for its stimulating effects.

In modern times, though, the substance can be produced in much higher

quantities, and has found its way into many products.

 

Purer forms, such as those in caffeine pills, are available easily.

These pills are often used by college students and graveyard shift

workers to last an entire night with no sleep.

 

Caffeine pills have been under media fire for recent and past deaths of

students, usually take on the form of a " caffeine overdose " .

 

One such example of this was the death of North Carolina student, Jason

Allen. He swallowed most of a bottle of 90 such pills, which is the

equivalent of 250 cups of coffee

(or, alternatively, a gallon and a half (5L) of espresso,

or 22 gallons (~150 L) of Mountain Dew,

which is not caffeinated in Canada for legal reasons).

 

This was probably 18 grams (not milligrams) of caffeine, since caffeine

pills are restricted to 200 milligrams or less in the U.S., and most pep

pill manufacturers make them in that size.

 

A few other deaths by caffeine overdose have been known, almost always

in the case of massive " pill consumption " on dares.

 

One dangerous form of caffeine use is to stay alert when one is under

the influence of alcohol or in severe sleep debt.

This " tricks " users into thinking they are more alert than they really

are. Taking part in certain activities, such as driving may be dangerous

in such cases.

 

 

History

Caffeine was " isolated " by the German chemist Friedrich Ferdinand Runge

in 1819.

According to the legend, he did this at the instigation of Johann

Wolfgang von Goethe (Weinberg & Bealer 2001).

 

 

References

Salazar-Martinez E, Willet WC, Ascherio A, Manson JE, Leitzmann MF,

Stampfer MJ, Hu FB. Coffee consumption and risk for type 2 diabetes

mellitus. Ann Intern Med 2004;140:1-8.

 

Weinberg BA, Bealer BK. The world of caffeine. New York & London:

Routledge, 2001. ISBN 0-415-92722-6.

 

Kruszelnicki. Munching Maggots, Noah's Ark and TV Heart Attacks.

HarperCollinsPublishers, 1998. ISBN 0-7322-5858-8.

 

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External links

 

Caffeine Content in Beverages

(http://www.erowid.org/chemicals/caffeine/caffeine_info1.shtml)

 

Caffeine Content of Foods (http://www.cspinet.org/new/cafchart.htm)

 

Caffeine Intoxication

(http://www.digitalnaturopath.com/cond/C569985.html)

 

Caffeine Intoxication (http://www.drowning.com/caffeine.html)

 

Caffeine Health (http://www.coffeeforums.com/viewforum.php?f=4)

 

Description of the Yerba Mate

(http://platense.dyn.dhs.org/personal/argentina/mate_desc.htm)

 

Is Caffeine a Health Hazard?

(http://www.benbest.com/health/caffeine.html)

 

Why do plants make caffeine ?

(http://www.thenakedscientists.com/html/columnists/dalyacolumn2.htm)

 

The Caffeine Faq (http://www.coffeefaq.com/caffaq.html)

http://www.answers.com/main/ntquery?method=4 & dsid=2222 & dekey=Caffeine & gwp=8 & curt\

ab=2222_1

 

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caffeine (k#259;f#275;n') , odorless, slightly bitter alkaloid found

in coffee, tea, kola nuts (see cola), ilex plants (the source of the

Latin American drink maté) and in cocoa (see cacao).

 

It can also be prepared " synthetically " from *uric acid*.

 

It is the most commonly used " mind-altering " *drug* in the world.

 

When used in moderation, caffeine acts as a " mild stimulant " to the

" nervous system " ,

*blocking* the neurotransmitter " adenosine "

and resulting in a " feeling " of well-being and alertness.

 

It " increases " the heart rate, blood pressure, and urination and

stimulates secretion of stomach acids; excessive intake can result in

restlessness, insomnia, and " heart irregularities " .

 

The effects of caffeine vary from person to person, as people " excrete "

it at different rates.

 

Physical dependence and unpleasant symptoms upon withdrawal (headache,

fatigue, depression) are common in regular caffeine users.

 

---

The Columbia Electronic Encyclopedia, Sixth Edition 2003,

Columbia University Press. Licensed from Columbia University Press. All

rights reserved. www.cc.columbia.edu/cu/cup/

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Caffeine molecular structure

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Caffeine is an alkaloid found naturally in such foods as coffee beans,

tea, kola nuts, Yerba maté, guarana, and cacao beans.

It is added to some soft drinks such as colas,

Irn-Bru and Mountain Dew.

 

Caffeine has a characteristic intensely bitter taste.

 

Its 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

diuretic effect.

 

Caffeine consumption leads to " pharmacologic tolerance " with defined

withdrawal symptoms.

 

--

 

Chemical properties

 

Caffeine is an alkaloid of the methylxanthine family, which also

includes the similar compounds " theophylline " and " theobromine " . In its

pure state it is an intensely bitter white powder.

 

Its chemical formula is C8H10N4O2, its systematic name is

1,3,7-trimethylxanthine or

3,7-dihydro-1,3,7-trimethyl-1H-purine-2,6-dione, and its structure is

shown above.

 

 

One dose of caffeine is generally considered to be 100 mg, delivered by

one 5 fl oz / 150 ml cup of drip coffee or one (or one-half) caffeine

tablet.

 

Real-world coffee varies considerably in caffeine content per cup, from

about 75 to 250 mg. Black tea contains somewhat less caffeine per

serving than coffee, depending on the strength of the brew, and green

tea contains significantly less.

 

Colas also typically contain less than coffee, but some " energy " colas

and similar drinks can have considerably more (the caffeine strength of

soft drinks being controlled entirely by the manufacturer, with " high

caffeine " content a popular marketing feature).

 

The amount of caffeine in some common consumables is approximately as

follows:

 

Chocolate, bittersweet - 25 mg/oz (875 mg/kg)

Chocolate, milk - 3 to 6 mg/oz (100 to 210 mg/kg)

Cocoa - 0.5 mg/floz (17 mg/litre)

 

 

Coffee, brewed (drip) - 4 to 20 mg/floz (130 to 680 mg/litre) (40 to 170

mg per 5 fl oz cup)

Coffee, decaffeinated - 0.4 to 0.6 mg/floz (13 to 20 mg/litre)

Coffee, instant - 4 to 12 mg/floz (130 to 400 mg/litre)

Espresso - 100 mg/floz (3400 mg/litre)

 

Teas and other infusions

Black tea, brewed (USA) - 2.5 to 11 mg/floz (85 to 370 mg per litre)

Black tea, brewed (other) - 3 to 14 mg/floz (100 to 470 mg/litre)

Black tea, canned iced - 2 to 3 mg/floz (70 to 100 mg/litre)

Black tea, instant - 3.5 mg/floz (120 mg/litre)

 

Oolong, 3.75 mg/floz (120 mg per litre) (12 to 55 mg per tea bag, i.e.

one serving)

Green tea, 2.5 mg/floz (85 mg/litre) (8 to 30 mg per tea bag, i.e. one

serving)

White tea, 2.0 mg/floz (68 mg/litre) (6 to 25 mg per tea bag, i.e. one

serving)

Decaf, 0.5 mg/oz (17 mg/litre) (1 to 4 mg per tea bag, i.e. one serving)

 

 

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 structure " is C7H8N4O2 compared to

caffeine's C8H10N4O2.

 

The mateine described in some literature as the primary " psychoactive

constituent " of yerba mate is also generally considered to be identical

to caffeine.

 

Tisanes (i.e. Herbal teas) - caffeine content depends on the herb, e.g.

Chamomile and Rooibos " teas " have no caffeine

while Yerba maté and Guarana do contain varying quantities.

 

Many tea drinkers characterise herbal tea simply as that which, unlike

black or green tea, contains no caffeine.

 

Energy drink - 10 mg/floz (340 mg/litre).

Some countries limit the caffeine content at 135 mg/litre.

 

Soft drink (caffeinated) -

3 to 8 mg/floz (100 to 270 mg/litre)

Pill (caffeine) - 200 mg (100 mg in many countries within EU)

 

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Equivalents 200 mg of Caffeine

 

One caffeine pill (Two in some countries where these are 100 mg)

 

One shot of espresso (2 oz)

 

~2 cups (5 floz) of regular coffee

 

~1.3 L soft drink (these can vary widely in content)

 

~1 kg (~2 lb) of milk chocolate or ~0.25 kg of bittersweet chocolate

(~0.5 lb)

 

~5 cups (8 floz) of black tea or ~10 cups (8 oz) of green tea

 

In the European Union, a warning must be placed on packaging if the

caffeine content of any beverage exceeds 150 mg per litre.

 

This includes caffeine from any source

(including guarana, which is often found in energy drinks).

 

In many countries, caffeine is classified as a flavouring.

 

=====================================================================

Posted: Thu Mar 10, 2005 5:37 pm

Post subject: Caffeine, even in small doses, may hurt arteries

 

www.alternative-medicine-message-boards.info

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By Alison McCook

(Reuters Health)

 

NEW YORK (Reuters Health) - Small doses of caffeine--even as little as

that in one cup of coffee--can cause temporary " stiffening " of the blood

vessel walls, according to two small studies released here this week at

the American Society of Hypertension's annual meeting.

 

Researchers led by Dr. Charalambos Vlachopoulos of Athens Medical School

in Greece looked at the effect of caffeine in people with mild

hypertension, or high blood pressure, and in individuals with normal

blood pressure.

 

The researchers found that people with mild hypertension who took a pill

that contained 250 milligrams (mg) of caffeine, equivalent to the amount

contained in 2 to 3 cups of coffee, experienced a " temporary increase "

in blood pressure and in the stiffness of the " aorta " ,

the main artery leaving the heart.

 

In the other study, a small group of people with normal blood pressure

who were given a pill containing as much caffeine as one cup of coffee

also experienced a temporary increase in the stiffening of arterial

walls.

 

Vlachopoulos and his team measured arterial stiffness by looking at

pulse velocity in the aorta.

 

Arteries need to be supple enough to expand when muscles--including the

heart--demand more oxygen,

and a " loss of elasticity " spells trouble for the body.

 

Arterial stiffening places an extra load on the heart, and is a primary

" cause " of hypertension.

 

In the general population, hypertension is a major risk factor for

serious conditions such as heart disease, stroke and kidney disease.

 

Blood pressure is considered high when systolic pressure--the first

number in a blood pressure reading--is above 140 mm Hg, and diastolic

pressure--the second number in the reading--goes over 90 mm Hg.

 

In the first study, Vlachopoulos and his team gave 10 mildly

hypertensive people a high-dose caffeine pill and placebo.

 

Caffeine increased systolic pressure by 11.4 mm Hg relative to placebo.

 

In the other study, the caffeine equivalent of one cup of coffee also

increased arterial stiffness in 10 non-hypertensive patients, and raised

their systolic blood pressure by 3 mm Hg and their diastolic reading by

6.5 mm Hg.

 

Pulse velocity eventually returned to its normal levels, Vlachopoulos

noted, but remained higher than average even three hours after patients

took the caffeine pills.

 

Vlachopoulos explained that the increased arterial stiffness that comes

with caffeine might worsen hypertension in people who already have high

blood pressure, and may also increase the risk that these individuals

have of suffering a serious cardiovascular event such as heart attack or

stroke.

 

The increased stiffness also reduces the " amount " of oxygen that is

" supplied " to the heart, he noted.

 

Both studies used only a small number of patients, the Greek researcher

noted, and further research is needed before doctors can make specific

recommendations about who should avoid caffeine and who should simply

reduce the amount they consume.

 

In the meantime, however, Vlachopoulos said that certain patients, such

as those whose arteries are already stiff, may wish to start reducing

caffeine consumption now.

 

2002 Reuters Limited. All rights reserved.

 

Reprinted from:

reutershealth.com/archive/2002/05/17/eline/links/20020517elin006.html

_________________

 

JoAnn Guest

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