Caffeine Biosynthesis
  1. How does a coffee plant synthesize caffeine?
  2. How does the coffee plant make caffeine?
  3. Where does the caffeine in coffee come from?

Every morning, millions worldwide wake up and reach out for their cup of coffee (or tea) to get their caffeine fix. Approximately 90% of all adults consume caffeine daily in some form or other, and most of us can’t imagine getting through our day without that caffeine. Over 2 billion cups of coffee are consumed globally every single day, making coffee, caffeine by extension, the most widely consumed central nervous system stimulant and psychoactive compound. And yet, no Heisenberg or Walter White can be credited with producing this drug! Caffeine is, simply put, the result of millions of years of plant evolution and the struggle for existence at play.

What is Caffeine?

1, 3, 7 trimethylxanthine

In its pure form, caffeine is a bitter, white powder. The chemical name for caffeine is 1, 3, 7 trimethylxanthine. That sounds a lot scary, doesn’t it? Let’s stick to calling it Caffeine.

Caffeine is present not just in coffee, but also in tea, cacao, kola, yerba mate, guarana, guayuse, and the yaupon holly. To be precise, caffeine is present naturally in about 100 plant species.

A coffee plant makes caffeine work as a natural pesticide. It also gives caffeine give itself an edge against competing plants. While the caffeine present in coffee cherries deters animals and pests, the caffeine present in coffee blossoms attracts insects who would unwittingly help pollinate the blossoms, while also creating an unforgettable olfactory memory that would make the insects keep coming back to the plant. While coffee blossoms are very low on caffeine, coffee beans contain the highest caffeine in the plant.

How does a coffee plant make caffeine?

In coffee plants, the process of caffeine production begins with a precursor compound called Xanthosine. Xanthosine is naturally available in many plant species, however, not all plants can convert it to caffeine. The conversion of Xanthosine to Caffeine requires a special enzyme called Caffeine Synthase. This enzyme is naturally present in the leaves, stems, and fruits of the coffee plant, and it is present in very large volumes in the beans. Now you know why coffee beans have the highest caffeine content among all the different parts of the coffee plant.

Step # 1: Xanthosine to 7-Methylxanthosine

The first step in the caffeine biosynthesis process is the conversion of Xanthosine to 7-methylxanthosine. Here, a methyl group (CH3) gets added to the xanthosine molecule, converting it to a methylxanthosine.

Caffeine Biosynthesis Step 1: Xanthosine to 7-methylxanthosine

Step # 2: 7-Methylxanthosine to 7-Methylxanthine

The second step in the caffeine biosynthesis process is the conversion of 7-methylxanthosine to 7-methylxanthine. The methylxanthosine molecule is hydrolyzed to form methylxanthine. Simply put, the hydroxyl group (OH) is removed from the methylxanthosine molecule to form methylxanthine.

Caffeine Biosynthesis Step 2: 7-methylxanthosine to 7-methylxanthine


Step # 3: 7-Methylxanthine to Theobromine

The third step in the caffeine biosynthesis process is the conversion of 7-methylxanthine to theobromine. Here, the methylxanthine molecule is methylated (i.e. a methyl group is added once more) to form theobromine, catalyzed by 7-methylxanthine transferase aka theobromine transferase. Simply put, a methyl group (CH3) is added to the molecule.

Caffeine Biosynthesis Step 3: 7-methylxanthine to theobromine

Step # 4: Theobromine to Caffeine

This is the final step in the caffeine biosynthesis process in the plant. Here, one more methyl group (CH3) gets added to the molecule, converting theobromine to caffeine.

Caffeine Biosynthesis Step 4: Theobromine to Caffeine

The process of making caffeine is very similar in both tea and coffee plants, though the amounts of caffeine produced vary significantly in both.

If all this sounds very complex, let us give it to you in one easy sentence, the coffee plant (and the tea plant among others) have certain enzymes that remove some molecules and add some molecules to a xanthosine molecule naturally made in the plant to make caffeine.

For this, a hydroxyl group is removed and three methyl groups are added, and voila, you have caffeine.

Why do coffee plants make caffeine?

There are many reasons why a coffee plant makes caffeine.

One, when the coffee leaves mature and eventually fall to the ground, the caffeine in them makes its way into the soil, which deters other plants, especially weeds, from germinating in the vicinity of the coffee plant.

Two, the caffeine in the coffee blossoms attracts insects, birds, and even animals that would help pollinate the coffee blossoms by getting them addicted to the caffeinated nectar.

Three, in high doses, caffeine is quite toxic for insects and animals. This is a coffee plant’s built-in mechanism to protect its leaves and fruits from animals and pests, safeguarding its existence. Animals have evolved taste receptors to detect and in turn, avoid caffeine in what they eat.

Interestingly, the coffee plant attracts insects, birds, and animals by luring them with a sweet fragrance and then getting them hooked to the flower nectar laced with tiny amounts of caffeine, later once the pollination is complete and the fruits develop, the high dose of caffeine present in the berries and beans is meant to deter the insects, animals, and birds from consuming the fruits they were integral in the formation of! All this effort, so the coffee plant can survive and continue its existence!

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