Organic Lab #5    Caffeine: Extraction From Tea           Return
Today, if your habits are similar to those of the average Canadian, you will ingest approximately 300 mg of the molecule caffeine. Each cup of coffee, tea, or bottle of cola contains about 100 mg of caffeine, a mild stimulant which occurs naturally in coffee and tea, and is added to cola beverages.
   North American schoolchildren learn that Christopher Columbus and countless others set sail across unknown seas in search of the treasures of the Indies - gold and spices. The school books often forget to mention drugs. The civilized residents of western Europe in Columbus's time were very poor in mind-affecting substances: no coffee, no tea, no tobacco, little opium, no LSD-like drugs, little intoxicants except alcohol. As a result, Europeans had to make use of alcohol in a variety of ways - as a social beverage, a before-meal aperitif, a thirst quenching beverage during meals, an after dinner drink, a evening drink, a nightcap, a tranquillizer, a sedative, a religious offering, an anesthetic, a deliriant, and a means of getting drunk. Alcohol thus permeated every aspect of European culture, and still does.

Whenever they went, however, the European explorers from Columbus onward found other mind-affecting drugs, and brought then home with them. Tobacco was discovered on Columbus's first voyage. Cocaine was found in large areas of South America. Caffeine and LSD-like drugs were found scattered all over the world. During the next two centuries, the Europeans not only adopted nicotine and caffeine but spread them everywhere. They also imported opium. In a remarkably short space of time, western Europe was converted from an alcohol-like culture to a multidrug culture.

The introduction of caffeine drinks into countries that had not previously known them - like the introduction of other exotic drugs such as nicotine and marijuana - aroused a sense of deep moral outrage and evoked efforts to repress the new drugs. The Mohammedans of Arabia, for example, first used the newly introduced coffee to help them stay awake during prolonged religious vigils. This "use as a devotional antisporific" stirred up fierce opposition on the part of the strictly orthodox and conservative section of the priests. Coffee to them was held to be an intoxicating beverage, and therefore prohibited by the Koran, and severe penalties were threatened to those addicted to its use. An early Arabian writer summed up: "The sale of coffee has been forbidden. The vessels used for this beverage... have been broken to pieces. The dealers in coffee have received the bastinado, and have undergone other ill-treatment without even a plausible excuse; they have been punished by loss of their money. The husks of the plant... have been more than once devoted to the flames, and in several instances persons making use of it... have been severely handled." "Notwithstanding threats of divine retribution and other devices", however, the coffee-drinking habit spread among the Arabian Mohammedans, and the growth of coffee and its use as a national beverage became as inseparably connected with Arabia as tea is with China.

Dr. Robert S. de Ropp notes that when coffee was introduced into Egypt in the sixteenth century, "the coffee bugaboo'... caused almost as much fuss as the 'marijuana bugaboo' in contemporary North America. Sale of coffee was prohibited; wherever stocks of coffee were found they were burned...All this fuss only had the result of interesting more people in the brew and its use spread rapidly."

In Europe, too, coffee became a popular drink despite (or perhaps because of) efforts at repressions and medical warnings. Yet, caffeine can be a dangerous drug. Contemporary scientists echo several of the early allegations made against caffeine. A reliable summary of current scientific opinion can be found in any modern pharmacological text. These texts should review both the desirable and hazardous effects of the caffeine found in coffee, tea, cocoa, cola drinks, and other popular drinks.

The desirable effects are remarkably similar to those of cocaine and the amphetamines. Caffeine stimulates all portions of the cerebral cortex. Its main action is to produce a more rapid and clearer flow of thought, and to allay drowsiness and fatigue. After taking caffeine one is capable of a greater sustained intellectual effort and a more perfect association of ideas. There is also a keener appreciation of sensory stimuli, and reaction time is diminished. This accounts for the hyperthesia, sometimes unpleasant, which some people experience after drinking too much coffee. In addition, motor activity is increased; typists, for example work faster and with fewer errors. However, recently acquired motor skill in a task involving delicate muscular coordination and accurate timing adversely affected. These effects may be brought on by the administration of 150 to 250 mg of caffeine, the amount contained in one or two cups of coffee or tea.

In addition to its effects on the cerebral cortex and other portions of the central nervous system, caffeine in modest doses (a few cupfuls of coffee or tea) affects the heart rate, heart rhythm, blood vessel diameter, coronary circulation, blood pressure, urination, and other physiological functions. The secretion of gastric acids is stimulated, a matter of concern in connection with peptic ulcers.

Is caffeine addicting? Opinions vary, depending on one's definition of addiction. One feature of heroin addiction is tolerance, the gradual fading of effects as the same dose is taken daily. An appreciable degree of tolerance may develop to certain effects of caffeine.

Another feature of heroin addiction is the withdrawal syndrome or physical tolerance. Caffeine unquestionably produces withdrawal symptoms at some dosage levels. There is no doubt that the excitation of the CNS (central nervous system) produced by large amounts of caffeine is followed by depression. There has been considerable controversy, however, as to whether this is also true after the mild physiological stimulation produced by the small amounts contained in the average cup of tea or coffee. Findings from 1969 demonstrate that physical dependence does occur with five or more cups of coffee a day.

When taken in very large doses, moreover, caffeine is a potent poison. A fatal dose of caffeine given to an animal produces convulsions because of the central stimulating effect. Early in the poisoning, these are epileptiform in nature; as the actio of the drug on the spinal cord becomes manifest, strychnine-like convulsions may appear. Death results from respiratory failure. The fatal caffeine dose in man is estimated at 10 g. (70 to 100) cups of coffee.

Even a single gram of caffeine (7 to 10 cups) produces acute toxic effects. Insomnia, restlessness, and exfeine given to an animal produces convulsions because of the central stimulating effect. Early in the poisoning, these are epileptiform in nature; as the actio of the drug on the spinal cord becomes manifest, strychnine-like convulsions may appear. Death results from respiratory failure. The fatal caffeine dose in man is estimated at 10 g. (70 to 100) cups of coffee.

Even a single gram of caffeine (7 to 10 cups) produces acute toxic effects. Insomnia, restlessness, and exe in tablet form is readily available without a prescription at drugstores and some supermarkets throughout this country. Sold under such trade names as NoDoz, it comes in 100 mg tablets priced at about 75 cents for fifteen tablets. Many North American's use caffeine in this concentrated form. How many, and how much of it they take at a time, is unknown - but ten tablets contain a gram of caffeine, enough to produce the symptoms of acute toxicity described above. Production of natural and synthetic caffeine in the United States in 1963 was 2.3 million pounds valued at $4,830,000. This amount is equivalent to over 10 billion, 100 mg does, or about 55 per capita.

Thus we come to the coffee paradox. The question of how a drug so fraught with potential hazard can be consumed in North America at the rate of more than a hundred billion doses a year without doing intolerable damage, and without arousing the kind of hostility, legal repression, and social condemnation aroused by the illicit drugs.

The answer is quite simple. Coffee, tea, cocoa, and the cola drinks have been domesticated. Caffeine has been incorporated into our way of life in a manner that minimizes (though it does not altogether eliminate) the hazards inherent in caffeine use. Instead of its being classified as an illicit drug, thereby grossly amplifying caffeine's potential for harm, ways to make caffeine safer have been searched for and found.

In the first place, people generally take caffeine in forms so diluted as to make it unlikely that excessive doses, more than 300 to 400 mg at a sitting, will be ingested. The contrast here with alcohol is noteworthy. Whisky, gin and other distilled spirits, in contrast to light wines and beer, increase the likelihood that excessive amounts of alcohol will be ingested.

Again, coffee is customary served with cream or milk, which may at least partially protect the lining of the stomach from the irritation that caffeine might otherwise produce.

People have also developed the custom of drinking coffee and tea after a meal, further protection for the stomach lining. Cocktails, in contrast, are usually drunk before a meal, increasing the inherent hazards.

By keeping coffee legal, society has avoided extortionate black market prices that might otherwise bankrupt coffee drinkers and lead them into lives of crime. And coffee drinkers are not stigmatized as criminals, driven into a deviant subculture with all that criminalization entails.

Caffeine is one of a large group of naturally occurring compounds known as alkaloids, other examples being nicotine, cocaine, and morphine. Most alkaloids show marked physiological activity, and crude extracts of various alkaloid-bearing plants have been used since antiquity because of their curative and poisonous effects. In fact it was the alkaloid oniine contained in the hemlock extract which killed Socrates. Many alkaloids, however, are of great value in medicine because of specific pharmacological actions. Thus, morphine and some of its related compounds are the best known agents for the relief of pain. The curare alkaloids produce paralysis of voluntary muscles and often are used as an adjunct to anaesthesia in surgery. The belladonna alkaloids prevent the normal response of smooth muscle to nervous impulses and when placed in the eye cause dilation of the pupil (resulting in a softening look of the eye, a cosmetic effect for which the belladonna alkaloids were named).

The first alkaloid, morphine, was discovered in 1804, and within a few years it was recognized as the first member if a new class of substances, originally called vegetable alkalies, and later alkaloids, meaning alkali-like, since most alkaloids are basic. Today over 2000 alkaloids are known, extracted from over 100 families of plants. Not all plants contain alkaloids - they are found most frequently in the higher seed-bearing plants, and only very rarely in the lower non-seed bearers. The function of the alkaloids in the plant are still a subject of speculation. The alkaloids are generally concentrated in the living tissue at points of intense cell activity, from which they are often cast aside and stored in such dead tissues as the seed hulls or outer bark. These facts have led to the view that the alkaloids are end products, or by-products, of amino acid metabolism in plants. Other theories regard the alkaloids as reserve materials stored for protein synthesis, protective substances which discourage animals or insect attack, plant stimulants or regulators similar to hormones, or detoxification products rendered harmless by the plant's defense mechanisms.

Caffeine was first unambiguously isolated from coffee and named by F.F. Runge in 1821. The same substance isolated from tea was known as theine until it was shown to be identical to caffeine in 1838. In 1861 Adolf Strecker correctly suggested that the molecular formula of caffeine was C8H10N4O2. In 1882 Emil Fisher, later to become famous for his brilliant determination of the structure of glucose, suggested a structure for caffeine which he revised 15 years later to the correct form.

You may notice the similarity between caffeine and uric acid.

caffeine                                        uric acid

Both contain the purine ring system, which also is found in the nucleic acid bases, adenine and guanine. Such substituted purines occur widely in nature, and play important roles in plant and animal metabolism.
Adenine                                      Guanine

In addition to extraction from natural sources, caffeine can be obtained by synthesis, and before the availability of caffeine from decaffeinated coffee, synthetic caffeine was used mainly in cola beverages.

The isolation of caffeine from dried tea leaves provides a particularly interesting and useful introduction to the principles and practise of extraction in that use is made of both of the two basic forms: Solid-Liquid and Liquid-Liquid extraction.

By treatment of the solid tea leaves with hot water, caffeine is extracted into the aqueous medium along with several other compounds including related alkaloids and coloured tannins (glucose esters of phenolic aromatic acids). Inclusion of calcium carbonate in the initial hot water treatment precipitates the tannins as insoluble calcium salts which are removed by filtration and discarded along with the residual tea leaves, thus simplifying the subsequent isolation of the caffeine from the aqueous solution by extraction with the solvent, chloroform. After the removal of the chloroform solvent, the solid residue of crude caffeine is subjected to a final purification by recrystallization.

Experimental Procedure
In a 600 mL beaker, place 30 g of dry tea leaves, 300 mL of distilled water and 15 g of powdered calcium carbonate. Add 2-3 boiling chips and boil the mixture gently, with occasional stirring for 20 minutes over a wire gauze and flame.

During the heating periods, the following preparations for filtration of the tea extract should be carried out. First, line the walls of a second 600 mL beaker with multilayered cheese cloth. This will be the primary filter. Next prepare 2 or 3 long-necked filter funnels with fluted filter paper. These will be the secondary filters.

When the heated solution is ready, let it cool until it is easily handled, then pour it all in one pour into the cheese-cloth filter. Grab the ends of the cheese cloth and squeeze the tea leaves to remove as much water as possible. Discard your tea leaves but keep the cheese cloth.

Take your filtrate and start filtering it through the secondary paper filters.

Transfer the cold filtrate to a 250 mL separatory funnel and extract with three successive 30 mL portions of chloroform. Each extraction must be done with care to avoid the formation of a tight emulsion. To minimize emulsion formation, DO NOT SHAKE the contents of the separatory funnel vigorously, but only GENTLY SWIRL the two immiscible layers together for a longer period of time (eg. 5 minutes).


Filter the chloroform extracts through a cotton wool plug in a short stem funnel. Take the filtrate and in a water bath under the fume hood evaporate the caffeine to dryness. (DO NOT BURN IT)


Dissolve the solid residue of crude caffeine (usually slightly greenish in colour) in a minimum amount of boiling methanol (approximately 4-8 mLs will be required). Transfer the resultant solution to a small 25 mL Erlenmeyer flask by means of a small pipette. Cork the flask and allow the solution to cool to room temperature. Complete the crystallization by chilling the flask in an ice-bath. Collect the crystals of pure caffeine by filtration and wash with one mL of ice cold methanol.

Weight the pure, recrystallized caffeine and calculate the percentage caffeine contained in tea. Submit your sample of caffeine in a labelled baggie for grading.