Chapter 3 : Synthetic Dyes to Drugs: Atabrine and Chloroquine

Abstract:

This chapter presents the story of how synthetic dyes gave rise to antimalaria drugs. The benzene theory had a profound effect on the development of organic chemistry and in time gave rise to research on coal tar derivatives, particularly dyes. In turn, the dye industry influenced the development of medicines that did not require extraction from plants (i.e., natural products). Dyes were injected and allowed to diffuse into the tissues through a planned chemical synthesis called chemotherapy, which had a strong destructive effect upon the malaria parasites. Pamaquine analogs were synthesized with an extra benzene ring added to the quinoline ring to produce acridine dyes. Nitro group in the acridine compounds were replaced by a chlorine atom as a replacement for Entozon. There was clear evidence of antimalarial activity by this chloroacridine and it was named Atabrine. Atabrine was marketed throughout the world as a substitute for quinine; however, it was found to cause mental disturbances. A cooperative effort between universities and pharmaceutical industries enabled discovery of synthetic compounds better than Atabrine. The most important of these new compounds was SN-7618, which was renamed later as chloroquine. The story of the discovery of chloroquine makes clear that the reliance on the Roehl test and the convenience and ease of using bird malarias can be misleading unless the proper host-parasite combination is used.