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Why is caffeine found where it is?

Did you ever wonder why a fairly simple chemical like caffeine should be found in coffee, tea and a few other naturally growing vegetable products, and nowhere else?

Caffeine is not one of the more complicated organic compounds that a plant can synthesize. With only four elements in its molecule: oxygen, hydrogen, carbon and nitrogen-there can never be a shortage of its raw materials; and these building blocks are brought together in the form of the most simple components: oxygen and hydrogen in the form of water; carbon as carbon dioxide; and nitrogen from waste products in soil or ammonia in fertilizer. These elements are available to all vegetation, yet, with the exception of half a dozen wellknown products, no other plant can produce caffeine spontaneously the way these have.

Caffeine production in these plants is a modification of photosynthesis. Production occurs exclusively in the leaves. The modification is that, instead of producing sugar, nitrogen is inserted into the molecule to create the alkaloid, caffeine. Hundreds of other alkaloids are known to be created in other plants by insertion of nitrogen and/or other elements in other geometric configurations, but none are identical to caffeine. We should be eternally grateful to tea and coffee for introducing us to caffeine, else we might never have discovered its medicinal and soothing properties. Each species of plant seems to have developed its own characteristic agent through centuries of evolution.

The plants synthesize their caffeine exclusively in the leaves where sunlight provides the energy for the reaction. Most of the synthesis produces sugars which are converted to starch for energy storage, and subsequently to cellulose for structure and growth. Less than 1% results in caffeine.

Storage of the caffeine by the member of this group provides a point of departure for differentiation. Tea retains it in the leaves. Coffee, through its circulatory system, transports it to the seed within the cherry, where it may possibly serve as a stimulant for its germination at an appropriate moment. Somehow, the coffee plant has taught the seed in the fruit to concentrate caffeine in the heart of the cherry, so that for millenia no one suspected that it existed there. The tea bush, on the other hand, flaunted it in all of its leaves readily exposed, to be almost instantly extracted when contacted with boiling or even cold water. The cacao plant accumulated its caffeine and caffeine-like alkaloids in its rubs, to be immediately available for beverage or solid repast.

We have no idea as to when caffeine first began to appear in coffee or why, but can speculate from what we know of its physical properties and physiological action. We know that it has a bitter taste which is disliked by most of its predators. Accordingly, these avoided the plants that learned to synthesize caffeine in favor of the caffeine-free leaves, which rapidly disappeared. Protection from rapacious insects and grazing animals may well have been the primary purpose for plants' synthesis of caffeine.

Caffeine may also have growthstimulating properties for the host. Those synthesizing this agent may have found it produced hardier, healthier offsprings, with faster maturation from its invigoration. It also may serve as a tonic to its development. In any event, caffeinefree plants largely vanished, and caffeine plants prevailed.

The major function of caffeine in tea growth may be parallel to the preservation of the species. Its bitter taste is unappetizing to most ruminants. Animals early learn that most bitter foods contain substances that are toxic, or create gastric distress and, accordingly, avoid vegetation that has a bitter or unpleasant taste.

Long before man settled down to an agricultural existence, barely 1015,000 years ago, all plants grew wild and a jungle prevailed between plants, animals and insects, and it became a question of the survival of the fittest. Animals and insects had mobility and could travel for new sources of substinence as they depleted whole areas. Plants lacking this ability to move or hide from their predators had to develop new methods of defense. Most who survived developed a chemical defense, which they still utilize. A few were so successful that these predatots became an endangered species, or even disappeared.

Plants that survived learned to produce a chemical distasteful to its chief predator. The tobacco family learned to generate nicotine which is a powerful insect and animal poison. The coca plant is protected by the cocaine it synthesizes, while coffee, tea, and mate get longevity from caffeine.

How these plants learn to become chemical laboratories and build these protective chemicals is lost in the millions of years they grew wild. It may have been a sudden frost at a critical point in their photosynthesis, or a bolt of lightning, a prolonged drought, some accidental climactic condition, a contamination by a novel catalyst. We probably will never know. But it happened, and we should be happy it happened.

So we do not know exactly why caffeine is synthesized by tea, coffee, chocolate, mate and guarana plants and no others. Additional studies of photosynthesis may soon disclose the bio-technology of how plants accomplish it. We may learn in time to transfer the genes that control it to other plants. But for the botanical accident that initiated the growth of caffeine in tea and coffee, we probably never would have discovered the merits of caffeine in beverages. Nor would the F.D.A. have approved!
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Copyright 1992 Gale, Cengage Learning. All rights reserved.

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Title Annotation:possible explanations offered for presence of the agent in common plant sources like coffee and tea
Author:Lee, Samuel
Publication:Tea & Coffee Trade Journal
Article Type:Column
Date:Sep 1, 1992
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