Humankind has historically used advantageous compounds derived from plants and
animals. For instance, various extracts from plants have been used as teas, potions,
medicines and poisons. Though these extracts can contain a mixture of many different
chemicals, often only one or few are responsible for the activity of the extract. For
decades such extracts were used directly from their natural sources. This practice has
many disadvantages, as the composition of the extract can vary from time to time and it is
highly dependent on the availability of the natural source. At the beginning of the 19th
century chemists made the first attempts to isolate the active components within these
natural mixtures. The first compound to be isolated and purified was morphine from
opium. Sertürner accomplished this by extracting opium with hot water and precipitating
morphine with ammonia. He obtained colorless crystals that were poorly soluble in water
but soluble in acids and alcohol. To make sure that the effect of the compound was
identical to that of raw opium he tested the crystals on himself…
Following this initial experimentation, many natural products were isolated and their
structures were determined. Once a structure was elucidated, chemists were able to devise
synthetic methods to synthesize these compounds. This was the beginning of modern
pharmaceutical chemistry. Today, researches are still looking for new compounds from
natural sources. Potential drugs are often isolated from sea creatures, like sponges or
slugs, parts of plants that were used in traditional medicine, or new a species discovered
in the rain forest.
In this lab we will extract and purify caffeine from tea leaves. First water soluble
compounds will be extracted from dry tea leaves with boiling water. Then, caffeine will
be preferentially extracted from the water into organic solvent. The solvent will be
removed and the crude material will be purified by sublimation.