Caffeine

Caffeine molecular structure 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. Contents 1 Chemical properties 2 Physical properties 3 Caffeine extraction 4 Sources 4.1 Coffee 4.2 Teas and other infusions 4.3 Chocolate 4.4 Other sources 4.5 Equivalents to 200 mg of caffeine 5 History 6 Mechanism of Action 7 Metabolism and toxicology 8 Toxicity 9 Withdrawal 10 Abuse 11 References 12 External links 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 °C Boiling point: 178 °C (sublimes) Density: 1.2 g/cm³ Volatility: 0.5% Vapor pressure: 101 kPa @ 178 °C pH: 6.9 (1% solution) Solubility in water: 2.17% Vapor density: 6.7 g/m³ Molecular weight: 194.19 g/mol Caffeine extraction 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. 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. 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. 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 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. 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.[1] However, chocolate contains too little of these compounds for a reasonable serving to create effects in humans that are on par with coffee. 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 Caffeine is thought to act by blocking adenosine receptors on the surface of cells. This thereby blocks a pathway leading to breakdown of cyclic adenosine monophosphate (cAMP). The usual effect of adenosine in nerve cells is to inhibit nerve conduction by inhibiting post-synaptic potentials. The caffeine molecule, being structurally similar to adenosine, binds to the same receptors but does not stimulate them, thereby decreasing the adenosine action. The resulting increased nerve activity causes the release of the hormone epinephrine (adrenaline), 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. It also increases the levels of the neurotransmitter dopamine in the brain, similar to amphetamines. Other purported mechanisms of action of caffeine include mobilisation of intracellular calcium and inhibition of specific phosphodiesterases, however these only occur at high non-physiological concentrations. 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") headache[2]. 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. (1) 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. They can occur in some people after as little as 250 mg per day. More than 1,000 mg per day may result in muscle twitching, rambling flow of thought and speech, cardiac arrhythmia or tachycardia, and psychomotor agitation. Caffeine intoxication can lead to symptoms similar to those of panic disorder and generalized anxiety disorder. The minimum lethal dose ever reported is 3,200 mg, intravenously. The LD50 of caffeine is estimated between 13 and 19 grams for oral administration for an average adult. The LD50 of caffeine is dependent on weight and estimated to be about 150 to 200 mg per kg of body mass, roughly 140 to 180 cups of coffee for an average adult taken within a limited timeframe that is dependent on half-life. The half-life, or time it takes for the amount of caffeine in the blood to decrease by 50%, ranges from 3.5 to 10 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. In infants and young children, the half-life may be longer than in adults. With common coffee and a very rare half-life of 100 hours, it would require 3 cups of coffee every hour for 100 hours just to reach LD50. Though achieving lethal dose with coffee would be exceptionally difficult, there have been many reported deaths from intentional overdosing on caffeine pills. Studies in humans have shown that caffeine may cause miscarriage or may slow the growth of a developing fetus when given in doses greater than 300 mg (an amount equal to three cups of coffee) a day. In addition, use of large amounts of caffeine by the mother during pregnancy may cause problems with the heart rhythm of the fetus. Excessive ingestion of caffeine can result in increased blood pressure and pulse, increased urine production, vasoconstriction (tightening or constricting of superficial blood vessels) sometimes resulting in cold hands or fingers, increased amounts of fatty acids in the blood, and increased production of gastric acid. Those suffering from overdose should seek medical attention. If medical care is not possible, they should find a quiet place to rest. Within an hour after the effects first arise, peak influence on the body should occur, with a 15-30 minute plateau, after which the effects should abate and the sufferer can return to normal activity. Withdrawal Caffeine withdrawal usually manifests itself in long drawn-out headaches. A feeling of "pressure" is created and the sufferer has difficulty concentrating and maintaining a train of thought. Unless the user can identify the fact that they are going into caffeine withdrawal, usually they regard it as a common or garden headache. The feeling is sometimes described as similar to dehydration, but can be recognized by the fact that from soon after they get up (assuming morning usage) the feeling slowly comes on then stays steady. Although painkillers such as asprin can relieve symptoms, often a small dose of caffeine does the best job. A cup of white or black tea relieves the symptoms quite well and almost instantly. Abuse 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 easily available. These pills are sometimes used by college students and shift workers to last an entire night without 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 a North Carolina student, Jason Allen. He swallowed most of a bottle of 90 such pills [3]. This was the equivalent of about 250 cups of coffee (or, alternatively, a gallon and a half (5 liters) of espresso, or 22 gallons (~85 liters) of caffeinated Mountain Dew (this soft drink is not available in caffeinated form in all areas). Allen probably ingested about 18 grams of caffeine, since caffeine pills are restricted to 200 milligrams or less in the U.S., and most 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. Long periods of abuse can lead to detrimental effects on the esophagus; persons who consume high amounts of caffeine may have a risk for higher incidents of peptic ulcers, erosive esophagitis, and gastroesophageal reflux disease. They may also have heart problems, insomnia, chronic muscle tension, and nervousness. The term caffeinism has been coined to mean addiction to (or debilitating dependence on) caffeine. References Weinberg BA, Bealer BK. The world of caffeine. New York & London: Routledge, 2001. ISBN 0-415-92722-6. Note (1): Noever, R., J. Cronise, and R. A. Relwani. 1995. Using spider-web patterns to determine toxicity. NASA Tech Briefs 19(4):82. Published in New Scientist magazine, 27 April 1995. External links US National Library of Medicine: MedlinePlus® Drug Information: Caffeine Erowid Caffeine Vault Caffeine in chocolate? Caffeine Chemistry Site dedicated to "Caffeinism's Mimicry of Mental Illness" Why do plants make caffeine? Caffeine Content of Foods Is Caffeine a Health Hazard? The Caffeine FAQ Computational Chemistry Wiki Death by Caffeine Calculator (humor) Caffeine content of drinks, mints, chocolates, and pills Nescafe - Coffee company Stimulants edit Caffeine Nicotine Modafinil Adrafinil Synephrine Sympathomimetic amines edit Benzylpiperazine Cathinone Chlorphentermine Cocaine Diethylpropion Ephedrine Fenfluramine Mazindol Methcathinone Methylone Methylphenidate Pemoline Phendimetrazine Phenmetrazine Phentermine Phenylephrine Propylhexedrine Pseudoephedrine Sibutramine Synephrine Amphetamines edit 4-FMP Amphetamine Benzphetamine Dextroamphetamine dl-Amphetamine MDMA Methamphetamine Paramethoxyamphetamine ca:Cafeïna cs:Kofein da:Koffein de:Koffein es:Cafeína eo:Kafeino fr:Caféine ga:Caiféin io:Kafeino is:Kaffín it:Caffeina he:קפאין lt:Kofeinas hu:Koffein ms:Kafeina nl:Cafeïne ja:カフェイン no:Koffein nn:Koffein pl:Kofeina pt:Cafeína ru:Кофеин simple:Caffeine sk:Kofeín sl:Kofein fi:Kofeiini sv:Koffein th:คาเฟอีน vi:Caffein tr:Kafein uk:Кофеїн zh:咖啡因 Search Term: "Caffeine" Categories: Xanthines | Coffee | Caffeine

Caffeine: How much is too much?