Sources of drugs and lead compounds

The discovery of a new drug is part luck and part structured investigation (see section 3.1). It originally started with drugs and lead compounds derived from natural sources, such as animals, plants, trees and microorganisms. Marine sources were not utilized to any extent until the mid-20th century. Today, natural sources are still important, but the majority of lead compounds are synthesized in the laboratory. The nature of these synthetic compounds is initially decided from a consideration of the biochemistry of the pathogenic condition. 

Natural sources are still important sources of lead compounds and new drugs. However, the large diversity of potential natural sources in the world makes the technique of random screening a rather hit or miss process. The screening of local folk remedies (ethnopharmacology) offers the basis of a more systematic approach. In the past this has led to the discovery of many important therapeutic agents, for example, the antimalarial quinine from cinchona bark, the 

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As noted in the Introduction, natural products have served historically as the major source of drugs and lead compounds for the treatment of cancer, and the examples provided in this short review indicate that important discoveries in this area are still being made. Despite this impressive track record,... 

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