Coffee Chemistry : Caffeine

Featured Photo: Crystalline caffeine. (Credit: Annie Cavanagh and David McCarthy, Wellcome Images.)

Coffee has all sorts of interesting organic compounds that have helped cement it as a longtime favorite for sleep-deprived people around the world. Arguably, the most famous and relevant of these compounds is 1,3,7-trimethylxanthine, better known as caffeine.

It’s pretty common knowledge that caffeine, at least in a very rough empirical sense, keeps you awake and/or gives you a boost in energy when you drink it. What this implies is that caffeine is doing something to your internal brain chemistry to make this happen – and where there’s neurochemistry, there’s a ton of crazy internal mechanisms that actually make that effect happen.

One can easily and efficiently extract large amounts of caffeine using simple methods.

Now, caffeine has fairly good solubility in a variety of environments thanks to all those myriad polar and non-polar functional groups hanging off of it, which results in a wide range of possibilities for means of extraction, collection, and storage. One can easily and efficiently extract large amounts of caffeine using simple methods like exposure to hot water, and like other organic compounds that you might want to wash away (like, say, a sauce stain) it follows a fairly intuitive relationship between temperature and/or duration of extraction versus the actual amount of it you get out once you’re done.

In case drinking your caffeine just wasn't enough, some stores like ThinkGeek will sell topically applied stuff online.
In case drinking your caffeine just wasn’t enough, some stores like ThinkGeek will sell topically applied stuff online.

The relatively easy mass transport of caffeine from one phase to another also plays a factor in its ability to be absorbed into the human bloodstream in just about any way you can think of, from drinking it to inhaling it to literally rubbing it on your face and letting it diffuse through your skin. (Though, in that last case, it bears mentioning that scientific articles discussing the exact mechanism of topical absorption of caffeine suggest that while caffeine does in fact diffuse through both the water-based and lipid-based compounds of your skin cells themselves, it’s actually mostly being transported through sweat pores and hair follicles. But that’s neither here nor there. And kind of gross.)

It should be noted that the high diffusivity of caffeine is hardly a unique property, however. There are plenty of other compounds that have similar chemical backbone structures and will behave very similarly in a variety of different conditions. One notable case of such similarity, adenosine (ADO), shares the purine skeleton and oxygenated pendant groups. Together, the two molecules look like this:

Caffeine (left) and adenosine (right). That pentagon with the nitrogen molecules (blue) next to the hexagon with the nitrogens, along with the floating oxygen molecules (red), lead to some commonalities in how your brain perceives them.

Adenosine is a neuromodulating compound, which means it has very tangible effects on the way the brain (and subsequently the whole body) functions. While it has many uses in the body, adenosine notably comprises a major part of adenosine triphosphate (ATP), which is what your entire body uses as a means of shuttling energy from one place to another on an intracellular level. Adenosine on its own (as seen above, bereft of any phosphate groups) will show up when you’ve been up and awake for a while, and the ATP molecules that should be producing energy start to break down where many molecules, adenosine included, are generated.

Your body has adapted to this phenomena by having some receptors in your neural cells to detect adenosine’s presence – if enough of them form, your brain registers that you’re starting to deplete your energy-bearing ATP molecules, and hey, maybe you should take a break so you can recover. The binding of adenosine to those receptors causes your neural activity to slow down and makes you want to go to sleep.

Caffeine throws a chemical wrench in those works.

When you drink enough caffeine, not only is your drowsiness decreasing, your fight-or-flight stimlation is increasing.

See, the similar structure of caffeine to adenosine allows it to act as an adenosine receptor antagonist – Basically, it’s able to park itself on the receptor the same way as adenosine does, but because it’s not adenosine none of the subsequent effects take place. If you’ve got caffeine floating around, your body doesn’t “notice” as much adenosine and the urge to sleep drops. Furthermore, some of the other pathways that caffeine undergoes in the bloodstream prompts the production of epinephrine, better known as adrenaline – so when you drink enough caffeine, not only is your drowsiness decreasing, your fight-or-flight stimlation is increasing. Quite the useful effect, early on a Monday morning!

Caffeine has some other effects on the human body, but that can be tackled and discussed further another time. But at least now we have a little more insight on why we get that delightful kick-start when we dive into the first coffee of the day.

Until next time, take care!