14
caffeine and the plant kingdom
“My Vegetable Love…”
It is probably significant that the most widespread words in the world—borrowed into virtually every language— are the names of the four great caffeine plants: coffee, cacao, cola, and tea.
—E.N.Anderson, The Food of China, 1988
Caffeine, a chemical sometimes called “theine,” “guaranine,” or “matein,” according to whether tea, guarana, or maté, rather than coffee, is regarded as its eponymous natural source, occurs in the nuts, berries, beans, seeds, pods, hulls, leaves, and barks of several dozen varieties of plants. Every year, more than 120,000 tons of caffeine are consumed worldwide, enough to spike 260 cups of coffee or tea per person per year, or about five cups a week for every man, woman, and child on earth. A little over half of this tonnage comes from coffee beans and a little less than half of it comes from tea leaves. The remaining tiny fraction comes mostly from cacao pods, and also from maté leaves, cola nuts, and a small residue from all other sources.1 (Because very little caffeine is synthesized in laboratories, we examine the provenance of caffeine exclusively in terms of its vegetable sources.)
Why Plants Contain Caffeine
Caffeine supplies people with a physical and mental boost. But why did plants evolve the ability to produce it? The answer is that caffeine provides plants with protection by killing harmful bacteria and fungi and causing sterility in certain destruc tive insects. Because, over the passage of years, caffeine permeates the surrounding soil, it may also inhibit the growth of weeds that might otherwise have choked the plants. Caffeine’s potent antibiotic, antifungal, pest-killing powers may explain why Coffea robusta, which produces a larger amount of the drug, is much hardier than its more delicate cousin, Coffea arabica.
Source Plant Part Approx. caffeine by percentage of weight Major sites of cultivation today Popular mode of consumption
Coffee bean
(Coffea arabica and Coffea robusta) Seed 1.1 (arabica)-
2.2 (robusta) Brazil, Colombia Coffee
Tea
(Camellia sinensis) Leaf, bud 3.5 India, China Tea
Cacao
(Theobroma cacao) Seed .03 West Africa, Brazil Cocoa and chocolate products
Cola nut
(Cola acuminata, Cola nitida) Seed 1.5 West Africa Chewing cola nuts and cola tree
Maté
(Ilex paraguariensis) Leaf <.7 South America Yerba maté
Yaupon
(Ilex cassine, Ilex vomitoria) Leaf, berry (unknown) (not cultivated) Cassina
Guarana
(Paulinia capana) Seed >4 Brazil Soft drinks and guarana bars
Yoco
(Paulliniayoco) Bark 2.7 South America Yoco tea
Adapted from Spiller, p. 187.
Caffeine Vincit Omnia
Worldwide, 120,000 tons of caffeine are consumed annually:
Coffee is the source of 54%
Tea is the source of 43%
Cocoa pods, cola nuts, maté leaves, guarana, are the source of 3%
1 ton=910,000 grams=9.1 million cups of coffee at 100 mg/cup 13.65 million cups of tea at 66 mg/cup
54% of 120,000=64,800 tons of caffeine from coffee per year
43% of 120,000=51,600 tons of caffeine from tea per year
58,968,000,000 grams »600 billion cups of coffee a year @ 100 mg per cup
70,434,000,000»700 billion cups of tea a year @ 65 mg per cup
This adds up to 1,300 billion or 1.3 trillion cups of coffee and tea per year.
Some of these data are adapted from Gilbert.
However, in using caffeine as a biochemical weapon, plants are indeed “hoisted by their own petard,” because the very drug that helps them destroy their enemies ultimately kills them as well. Nature’s intricacy is again instanced in the mechanisms that caffeine-containing plants use in a doomed attempt to limit damage to themselves from caffeine’s poisonous effects. For example, coffee seedlings produce and store caffeine away from the site of cell division, which are very sensitive to toxins. Nevertheless, caffeine eventually devastates the plants that produced it, for as caffeine-bearing bushes or trees age and the soil around them becomes increasingly rich in caffeine absorbed from the accumulation of fallen leaves and berries, it eventually attains a level toxic not only to microbial enemies but to the plant itself as well. It is partially because of this toxicity that coffee plantations tend to degenerate after ten to twenty-five years. In a sense, these plants lose their lives as a result of steadily producing the drug that humanity loves best.
One of the first scientists to explore the theory that caffeine production evolved to protect plants from insects was Dr. James Nathanson, a neurologist at Harvard Medical School. In an article published in 1984 in Science magazine, Nathanson proposed that caffeine and related compounds could be used as the basis for a new class of insecticides.2 His tests with powdered tea and coffee, as well as with chemically pure caffeine and other methylxanthines, found that these compounds interfered with the behavior and growth of many insects and insect larvae. Mosquito larvae drowned when they became so confused that they could not swim to the surface to breathe. Concentrated caffeine killed adult insects in hours or days after exposure. Caffeine also demonstrated a considerable synergistic killing power when combined with other natural insecticides, sometimes increasing the effectiveness of known agents by a factor of ten.
The neurotoxicity of caffeine as a natural chemical defense mechanism for plants against insects explains the discombobulation of the spiders enlisted for a recent NASA study of the ways exposure to various chemicals alters the ways they spin their webs.3 Some scientists think that spider web testing can replace some much more expensive toxicity testing in humans or higher animals. The theory is that the changes in the spider webs are a function of the degree of toxicity of the chemical administered prior to spinning. The more deformed a web becomes, the more toxic the chemical is supposed to have been. Because of the web’s structural similarities to crystal lattices, the degree of web deformation can be quantified with statistical crystallography techniques. Using an image data-analysis program, the NASA scientists analyzed the images of webs spun by spiders who were sober and intoxicated on various substances in terms of “numbers of cells and average areas, perimeters, and radii of cells.”4
The results are fairly clear and, if they can be generalized in any way to human beings, are not very encouraging for caffeine aficionados. In a “Talk of the Town” feature, a New Yorker columnist says that although they may not realize it, “scientists at NASA labs…have identified the chemical agent responsible for human error,” by which he means caffeine:
The structure of the web spun by the spider under the influence of marijuana is pretty close to the conventional one, but is unfinished. The benzedrine web is meticulous in places but has huge gaps. The chloral hydrate web is a stray collection of strands. The illuminating example is caffeine. Anyone who has ever had a tip from an excitable stockbroker go south, or had the rearview fall off his brand new car when he slammed the door and discovered it was made on the night shift, or examined the film of his baby’s christening and found streaks of light in place of his child’s beaming face will be struck by the slipshod, disorderly, ill-planned, chaotic, and slaphappy structure laid down by the spider intoxicated by caffeine.5
It should be remembered that if a range of doses has not been studied, comparisons as between different drugs are virtually meaningless. And, of course, in comparing the effects of caffeine with those of other chemicals, both the New Yorker and NASA seem to be forgetting that caffeine acts as a natural chemical defense mechanism for plants against insects, a fact that may go a long way in explaining the perplexity of the poor spider.6
Drawing of spider webs spun under the influence of various psychoactive drugs. The web spun by Araneus diadematus, the common house spider, is altered when the spider is exposed to chemicals. When juxtaposed with the drawing of a normal web, four drawings
of spider webs spun by spiders exposed to marijuana, benzedrine, chloral hydrate, and caffeine demonstrate varying degrees of malformation. The results are obvious, even without the use of a sophisticated graphic analyzer. Compared with the webs spun normally or under the influence of marijuana, benzedrine, or chloral hydrate, the one spun after the administration of caffeine is clearly the most deformed. Each of the other webs exhibits an evident “hub and spokes” pattern, presumably the most fundamental aspect of the web paradigm. The caffeine web has lost any trace of this design and is almost completely disrupted.
Despite caffeine’s neurotoxic effects on some harmful insects, one species of beneficial bugs seem to enjoy the caffeine rush, at least if we are to believe the account of John Klapac, an East Coast beekeeper who feeds his little buzzers with the dregs from 55-gallon commercial containers of soft drink syrup. Klapac explains, “The bees love it—they get hyper from all the caffeine.” Evidently his bees don’t have access to enough nectar to last through the winter, and the sugary syrup, which they transform into a honeylike substance, is a perfect nutritional supplement. “Strawberry syrup makes a red product with strawberry flavor,” he adds, “and cola syrup produces an almost black substance with a cola-like taste.”
The Coffee Shrub (genus Coffea)
Coffee is a tropical glossy-leafed evergreen shrub or bush belonging to the genus Coffea of the Rubiacæe, or madder, family that is the source of several powerful pharmaceutical agents in addition to caffeine, including ipecac and quinine. Most of the twenty-five-odd species of the coffee plant grow wild in the tropics of the eastern hemisphere. The branches of every species bear small, creamy white flowers with a sweet fragrance like jasmine blossoms. Although Coffea is divided botanically into four groups, the coffee we drink comes from plants that all belong to one of these groups, Eucoffea. Some wild members of the other three groups are used by African natives as decorative vegetation and others as stimulants, but their fruit is generally inedible, and they have no currency in commerce.
Engraving from Dufour, Traitez Nouveaux. This engraving shows a branch from the coffee tree, a cylindrical instrument for roasting coffee, and a few roasted coffee beans themselves. (The Library Company of Philadelphia)
The earliest known and cultivated species is Coffea arabica, “the coffee shrub of Arabia,” indigenous to the Ethiopian massif. Now grown mostly in Latin America, it accounts for 75 percent of all coffee consumption worldwide. The other commercially important species, Coffea canephora, the main variety of which is robusta, supposed to have originated in Uganda and the Congo, is widely cultivated in Africa and Madagascar. Both species are also cultivated in Asia.
Comparison of the Methylxanthine Content of Arabica and Robusta Coffee Beans
Component Arabica (mg/kg) Robusta (mg/kg)
Caffeine 9,000–14,000 15,000–26,000
Theobromine 35–40 25–80
Theophylline 7–23 86–344
Paraxanthine 3–4 8–9
Theacrine 0 11
Liberine 5 7–11
Methylliberine 0 3
Adapted from Garattini, “Composition of Coffee.”
In addition to Coffea arabica and Coffea robusta, the species Coffea liberica, native to Liberia, is much larger and sturdier than either and is under commercial cultivation in Africa. It is reported to produce an inferior-tasting brew that is high in caffeine. An allied Liberian species, Coffea excelsa, a vigorous plant discovered in 1905, yields beans that are small, bright yellow, and, like liberica, high in caffeine.
By the beginning of the eighteenth century, the Dutch, French, Spanish, Portuguese, and English began introducing Coffea arabica into tropical colonies from Java to Jamaica. After obtaining the plant in 1725, Brazil quickly became and still remains the world’s largest supplier of coffee.
The Tale of Gabriel d’Erchigny de Clieu and the Purloined Plant
One of the great romances in the history of caffeine is the saga of how, in 1723, the prolific progenitor of what was to become the great Latin American plantations made the journey to the New World in the exigent care of a young aristocratic French military officer. The story is rooted over a century earlier, at a time when the Dutch, foremost in international trade, became the first to cultivate the exotic coffee tree in Europe after successfully transporting a specimen from Mocha in 1616. Efforts to cultivate seedlings in France failed until 1714, when the French government negotiated the delivery of a healthy five-foot tree from the Amsterdam botanical gardens established by Willem Wissen, which was presented by the burgomaster to Louis XIV and ceremoniously planted by the famous botanist de Jussieu in the Jardin des Plantes in Paris. In a seminal historical position similar to that of three “Oriental” stallions, Darley Arabian, Godolphan Barb, and Byerly Turk, the acknowledged ancestors of all thoroughbred horses, this anonymous Arabian plant is known to have been the progenitor of most of the coffee trees of South America, Central America, and Mexico.
Gabriel d’Erchigny de Clieu, an enterprising naval officer, harbored a clandestine ambition when he temporarily returned to France from his post in colonial Martinique: He planned to secret a coffee plant from the royal gardens and introduce its cultivation to the West Indies. Getting his hands on one of the few rare bushes then under cultivation in Europe posed a daunting challenge. De Jussieu, conservator of the royal botanical gardens, guarded his precious charges with the jealousy of the dragon around the tree of golden apples. But, like Jason, de Clieu cannily circumvented the dreadful monitor that stood between him and the completion of his quest. We learn from his correspondence that, plunging into the intrigue of the court of Louis XIV, he employed the services of an aristocratic young lady to prevail on M. de Chirac, the royal physician, to purloin one of the exotic plants from the royal conservatory.
Embarking at Nantes in 1723, de Clieu, according to his published accounts, brought with him a single plant, which he installed in a glass-framed box intended to serve as a portable greenhouse. The crossing was a difficult one, and de Clieu heroically surmounted both human and natural adversities in order to triumphantly bring his charge to port in Martinique.
A fellow passenger, a young man who spoke French with a Dutch accent and was, perhaps, a Dutch espionage agent acting to protect his country’s trade interests, played the villain of the story by trying, unsuccessfully, to spoil de Clieu’s project. On one occasion de Clieu surprised the mysterious stranger when, after opening the framed glass enclosure, the interloper had reached in to snap off a twig. De Clieu writes:
It is useless to recount in detail the infinite care that I was obliged to bestow upon this delicate plant during a long voyage, and the difficulties I had in saving it from the hand of a man who, basely jealous of the joy I was about to taste, through being of service to my country, and being unable to get this coffee-plant away from me, tore off a branch.7
In addition to being menaced by this spiteful nemesis, de Clieu shared with his fellow passengers a narrow escape from capture by Tunisian pirates and another from destruction in a heavy storm, which smashed the greenhouse but left the slip unscathed. However, the greatest threat to survival, both of the people and the plant, was a long calm that sustained itself until the supply of drinking water was nearly exhausted and what was left had to be rationed for the remaining weeks of the trip. De Clieu writes:
Water was lacking to such an extent that for more than a month I was obliged to share the scanty ration of it assigned to me with my coffee plant, upon which my happiest hopes were founded and which was the source of my delight. It needed much succor, the more in that it was extremely backward, being no larger than the slip of a pink.8
De Clieu by no means relaxed his vigilant care when at last disembarking in Martinique, where he planted the precious slip on his estate at Precheur. He writes:
Arriving at home my first care was to set out my plant with great attention in the part of my garden most favorable to its growth. Although keeping it in view, I feared many times that it would
be taken from me; and I was at last obliged to surround it with thorn bushes and to establish a guard about it until it arrived at maturity.... This precious plant which had become still more dear to me for the dangers it had run and the cares it had cost me.
As a result of his ministrations, the tree “multiplied with extraordinary rapidity and success,” and the first harvest was gathered in 1726. De Clieu describes the ensuing tropical storms, in the course of which Martinique’s cacao plantations were apocalyptically destroyed, clearing the way for the progeny of his charge. He was so successful that he was “enabled to send plants to Santo Domingo, Guadeloupe and other adjacent islands,” where they also flourished.
Even without the advantage of a flood to clear the ground, coffee plantations sprang up in other French colonies in the New World and, in fact, the first coffee bush planted in Brazil, destined to become the world’s biggest coffee supplier, was a descendant of this French planting as well. By the end of the eighteenth century, coffee was under cultivation throughout the West Indies and in Mexico, Costa Rica, Venezuela, Guatemala, and Puerto Rico. In 1746, de Clieu, by then a ship’s captain and honorary commander of the Royal and Military Order of Saint Louis, was presented by the secretary of the navy at the court of Louis XV. The king, who, unlike his father Louis XIV, had learned to appreciate the beverage, honored de Clieu for his cultivation of coffee by returning him to Martinique as governor of the island.
The World of Caffeine Page 35