Semi-synthetic Chemical Medicines

In principle, the chemical production of semi-synthetic medicines is identical to that of fully synthetic medicines (see section on chemical medicines), although the starting point is different. Unlike fully synthetic medicines, which are created entirely in the laboratory using a stepwise combination of small chemical building blocks, semi-synthetic medicines are derived from naturally occurring substances extracted from sources such as plants, bacteria or animal cells.

The first step in isolating natural molecules from living tissue is a process called extraction; for example, to extract biomolecules from plants, leaf or root tissue may need to be washed, freeze-dried and ground to produce a clean and uniform sample. Also, the biomolecule may be isolated from a fermentation broth from, for example, genetically modified microorganisms. The sample is then purified to isolate the active ingredient by further steps, which may include filtration or the use of solvents such as ethanol (alcohol).

After extraction and purification, the isolated molecule can then be modified using standard laboratory techniques, for example by incorporating additional molecules such as phosphate or alcohol. This modification takes place in specialised factories under quality-controlled conditions.