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 (CH 3 ) 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
(CH 3 ) 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 (CH 3 ) 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!