Drugs In The 19th Century

Drugs have played a most important role in increasing average life expectancy in the world in the previous century. In the 19Th and previous centuries, natural product extracts, mainly those derived from botanical species, provided the major source of folk medicines. In 19Th century, biologically-active organic molecules began to be isolated in pure form for medicinal use. For example, salicyclic acid, the precursor of aspirin, was isolated from willow bark in 1874. Painkillers, such as codeine and morphine, were isolated from the opium poppy. The quinine (anti-malarial agent) was separated from cinchona. [1].

Synthetic sulfa drugs, the natural antibiotic penicillin, from Penicillium notatum was discovered by Alexander Fleming, the semi-synthetic
But, the era of DNA and medicine was mainly stimulated by the elucidation of the double-helical structure of DNA by Watson and Crick in 1953. The ramifications of this discovery in DNA replication, transcription and translation led to a much better understanding of viral replication. This laid the foundation for antiviral drug discovery in subsequent decades as molecular targets in the viral replication cycle began to be identified. The 1950s also saw the discovery of vancomycin, a glycopeptide which was developed much later for use against methicillin-resistant staphylococci infections. The era of recombinant DNA technology and molecular cloning began around the mid-1970s. The PCR (polymerase chain reaction) of the 1980s resulted in major advances in biotechnology that have significant impact in drug discovery. In the 1990s, combinatorial chemistry, high-throughput screening, molecular modeling and bioinformatics contributed to the discovery of newer generation drugs based on genomics and proteomics
Such was the birth of QSARs (quantitative structure–activity relationships) followed in the 1980s and 1990s by computer graphics and molecular modeling. but, computer sciences rapidly ceased to be a simple tool in drug discovery and pharmacology [2].

Twenty one century will see further advances in drug discovery that will likely be based, among other areas, such as chemistry and chemical biology, enzyme-based molecular syntheses, advances in cellular biology and microbiology, cell signaling pathways and their consequences, advanced high-throughput screening (HTS), gene and cell therapy, Bioinformatics and Cheminformatics [1].

1.1.2 Drug Design
Drug designing is an intense, lengthy, an inter-disciplinary and time-consuming process [3]. Drug design, sometimes referred to as rational drug design, is the inventive process of finding new medications based on the knowledge of biological targets [4]. Rational drug design can be generally divided into two categories: development of small molecules with desired properties toward targets, biomolecules (proteins or nucleic acids), whose functional roles in cellular processes and 3D structural information are known. This approach in drug design is well established, being applied extensively by the pharmaceutical industries. Another approach is development of small