Dyes and Pharmacy

The process of dyeing fabric using plants, berries and crustaceans has been around for centuries. Celtic tribes in Europe used lichen to produce various purplish-red and blue colours. The Romans used Murex brandaris or Murex trunculus molluscs to dye cloth Royal or "Tyrian" purple. Thousands of them had to be used to dye just one robe making it incredibly expensive. According to myth the dye was discovered by a sheep dog belonging to Hercules when he was walking along a beach in Tyre. The dog bit into a mollusc and his mouth turned deep purple!

Plants were used by apothecaries and pharmacists to produce medicines and also to produce dyes. Saffron was used to colour manuscripts and food in the middle ages. Saffron is the dried stigmas of the saffron crocus plant, as shown here. In the 1600s and 1700s it was used to colour prints and maps. It was during this period that it became known as an antidepressant.

Madder was used to produce red, purple, orange and yellow dyes. It has been used medicinally for burns and skin rashes, since Roman times. Later pharmacies were used by artists purchasing pigments. This tradition has continued with pharmacies selling numerous dye products for colouring hair, clothes and even straw hats!

Discovery of synthetic dyes

It was only in the late 1800s that the synthetic dyes that we use now and are sold in pharmacies were invented. In 1855 William Henry Perkin, who was a research chemist, discovered the dye aniline mauve, also called mauveine when he was only 17 years old. He was trying to synthesise quinine, which was used to treat malaria. In one experiment he ended up with a black substance. Once dried he added spirits of wine and found he had produced a purple dye. He tried it on silk cloth and found that it was a strong, deep colour that did not fade. These discoveries brought in the taste for bright colours and the dyeing industry increased rapidly.

The chemistry behind his discovery subsequently led to developments in the following fields:

• Other fabric dyes
• Artificial musk
• Hair dyes
• Plastics
• Explosives
• Food colouring
• Photography
• Saccharin (artificial sweeteners)
• Medical advances

Medical advances using dyes

Paul Ehrlich (1854-1915), a German medical scientist, carried out pioneering work into haematology, immunology and chemotherapy. He also developed the first effective treatment of syphilis, Salvarsan. He made some of his early medical advances through his research into dyes. Inspired by the aniline dyes discovered by William Perkin, Ehrlich’s doctoral dissertation was on the theory and practice of staining animal tissues.

One of his fundamental discoveries was that chemical dyes derived from coal tar did not simply colour cells or tissues, but often combined with them to form a chemical reaction. For example, dyes reacted with various components of blood cells, an important discovery for future work in haematology.

In 1882, he published his method of staining the tubercule bacillus, which enabled its diagnosis using a microscope. He also began to test methylene blue and found that it could act as a diagnostic in bacteriological work, and was also a mild antiseptic.

His work on dyes established the search for a "magic bullet" in medicine - a drug that could highlight and then target specific disease-causing micro-organisms by altering the chemical structure of these targeted molecules. This idea formed the basis of chemotherapy.

He was awarded the Nobel Prize for Medicine in 1908 for his later work on immunology.

Other medical dyes:

• Prontosil red (an orange-red dye) was found by a German biochemist, Gerhard Domagt, to be antibacterial. It combated streptococcal infections. This discovery led to the development of a large number of pioneering sulfa/sulphonamide drugs
• Scarlet red stimulates the growth of particular cells and has been used to treat chronic ulcers and burns