Anhydrous (dry) USP grade 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.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.
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. Its International Chemical Identifier is InChI=1/C8H10N4O2/c1-10-4-9-6-5(10)7(13)12(3)8(14)11(6)2/h4H,1-3H3.
Physical properties
Pure caffeine occurs as odorless, white, fleecy masses, glistening needles or powder. *''Melting point'': 238 AC- ''Boiling point'': 178 AC (sublimes)
- ''Density'': 1.2 g/cm
- ''Volatility'': 0.5%
- ''Vapor pressure'': 101 kPa @ 178 AC
- ''pH'': 6.9 (1% solution)
- ''Solubility in water'': 2.17%
- ''Vapor density'': 6.7 g/m
- ''Molecular weight'': 194.19 g/mol
Caffeine extraction
Sources
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 matAc and guarana respectively, caffeine-containing plants used for tea and other things. Many yerba matAc 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.Coffee
''All fluid ounces are U.S. fluid ounces.''- Coffee, brewed (drip) - 4 to 20 mg/floz (130 to 680 mg/litre) (20 to 100 mg/5 floz)
- 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 Arabica - ~40 mg/floz (1.36 g/litre)
- Espresso Robusta - ~100 mg/floz (3.4 g/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)
- Tisanes (i.e. Herbal teas) - caffeine content depends on the herb, e.g. Chamomile and Rooibos "teas" have no caffeine while Yerba mate and Guarana do contain varying quantities. Many tea drinkers characterise herbal tea simply as that which, unlike black or green tea, contains no caffeine.
Chocolate
Chocolate is a weak stimulant due to content of theobromine, theophylline, and caffeine.http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15549276
Other sources
- 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, some countries limit the caffeine content in cola drinks to 200 mg/l)
- Pill (caffeine) - 200 mg (100 mg in Canada and many countries within EU)
- Buckfast Tonic Wine - 375 mg/litre (0.05% of caffeine by weight)
- Jolt Gum - 45 mg/piece
- Bawls - 67mg per 10oz, 80 per 12oz
Equivalents to 200 mg of caffeine
- One caffeine pill (Two in some countries where these are 100 mg)
- ~2 shots of espresso from robusta beans (2 floz)
- ~2 "5 floz containers" of regular coffee (10 floz)
- ~1.3 L soft drink (these can vary widely in content)
- ~5 cups (8 floz) of black tea or ~10 cups (8 floz) of green tea
- ~5 cans of soda (these can vary widely in content)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.
History
Although tea consumption in China began thousands of years ago, the first documented use of caffeine in a beverage for its pharmacological effect was by the sufis of Yemen, who used coffee to stay awake during prayers in the 15th century. In the 16th century there were coffeehouses in Cairo and Mecca. Coffeehouses opened in Europe in the 17th century. 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).Mechanism of Action
Metabolism and toxicology
Caffeine is completely absorbed from the stomach and small intestine, within 45 minutes of ingestion. It is widely distributed in total body water and is eliminated by apparent first-order kinetics that can be described by a one-compartment open-model system. Caffeine is metabolized in the liver by the cytochrome P-450 enzyme system. The first metabolic products of caffeine are three dimethylxanthines: paraxanthine (84%), theobromine (12%) and theophylline (4%). Paraxanthine increases lipolysis, leading to elevated glycerol and free fatty acid levels in the blood plasma. Theobromine, the principal alkaloid in cocoa (chocolate), can dilate blood vessels and increase urine volume. Theophylline relaxes smooth muscles of the bronchi and is used to treat asthma. However, the therapeutic dose is many time greater than the levels achieved from caffeine metabolism.Each of these metabolites is further metabolised and then excreted in the urine.Caffeine is quickly and completely removed from the brain, and, unlike other CNS stimulants or alcohol, its effects are short-lived. In many people, caffeine does not negatively affect concentration or higher mental functions, and hence caffeinated drinks are often consumed in the course of work.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. Any accumulated sleep debt will be fully felt on withdrawal as well. Intravenous caffeine (in the form of caffeine benzoate 500 mg over 1 hour) is occasionally used medically to treat post-lumbar puncture ("spinal tap") headachehttp://www.emedicine.com/neuro/topic557.htm.Although caffeine solutions are often used as a chemical standard for bitterness, caffeine is added to some soft drinks such as colas, Irn-Bru and Mountain Dew ostensibly for its taste.The effect of caffeine on spider web construction.]]While safe for humans, caffeine and its related compounds theobromine and theophylline are considerably more toxic to some other animals such as dogs, horses and parrots due to a much poorer ability to metabolize these compounds. Caffeine does more damage to spiders than most drugs.Toxicity
Too much caffeine can lead to caffeine intoxication. The symptoms of this disorder are restlessness, nervousness, excitement, insomnia, flushed face, diuresis, gastrointestinal complaints, even hallucinations.
