Molecule of the Day: Caffeine
Caffeine (C8H10N4O2) is a white solid that is sparingly soluble in water. It is a naturally occurring alkaloid and is the most commonly consumed drug worldwide. It is consumed for its ability to promote wakefulness and reduce lethargy.
It does so by acting as an antagonist to adenosine receptors in the central nervous system. Since the binding of adenosine to the receptors leads to drowsiness, this inhibition temporarily promotes alertness. Furthermore, it promotes the release of neurotransmitters such as acetylcholine, resulting in its stimulant effects.
Caffeine can be found in many different beverages:
Caffeine is usually extracted from coffee beans using supercritical carbon dioxide. While carbon dioxide normally sublimes and deposits under normal pressures, bypassing the liquid phase, under high pressures, it can exist as a supercritical liquid. Liquid carbon dioxide is a good solvent for caffeine extraction, as it is non-polar and leaves the aroma chemicals intact.
While caffeine is readily available from decaffeination processes, it can still be synthesised from dimethylurea and malonic acid:
In nature, it is biosynthesised from xanthosine instead:
Caffeine consumption results in a mild form of drug dependence; furthermore, upon regular consumption, tolerance can be built up, resulting in the need for an increasing amount of caffeine to produce the same effects. In small doses, caffeine reduces cardiovascular problems, but it increases its probability in larger doses (over 5 cups of coffee).