General Principle of Drug Action. Medicinal Chemistry Chapter-2


General Principle Of Drug Action 


Containts:- 






Introduction :-

Medicinal chemistry is a multidisciplinary subject involving Organic chemistry, Pharmacology and Biochemistry. It also involving Physiology, Microbiology, Texicology, along with Genetics and Computer modeling. 
It explains the design and production of compound that can be used for prevention, treatment or cure of human and animals diseases. More recently the IUPAC have recommended the following description for the meedicinal chemistry term. "Medicinal Chemistry is a chemistry based discipline, also involving aspects of Biological, Medical and Pharmaceutical sciences. It is concerned with the invention, discovery, design, identification and preparation of biologically active compounds, the study of their metabolism, the interpretation of their mode of action at the molecular level and construction of structure activity relationship (SAR)".


The earliest drug discoveries were made by random sampling of higher plants. 
The folklore medicines have found their root in the daily life of individuals. Beginning 
with AD 1800 there was a continuous activity in this area and many of the well known 
medicinal plants were analyzed and their active principle characterized. The Ephedrine 
was isolated from the Chinese drug Ma Huang used for the treatment of hay fever and 
respiratory ailments. Morphine was isolated fron1 opium poppy and Quinine was 
isolated from cinchona species.

Medicinal Chemistry CHAPTER-2,General Principles of Drug Action.pdf
By:- P. Valentina


The chemical knowledge of isolated compounds gave a way for many synthetic substances. Hundreds and thousands of new organic chemicals are prepared annually throughout the world and many of them are entered into pharmacological screens to determine whether they have useful biological activity or not. This process of random screening has been considered the identification of new inefficent, but it has resulted in the identification of new 'lead compound' whose structure has been optimized to produce clinical agents.

The modern drug research owes its rationality to the German Physician and 
imn1tmologist, Paul Ehlrich, who coined intellectual tools of Medicinal science, such as 
receptor for drugs. The antibacterial agent Prontosil laid the foundation of the concept 
of biochemical metabolites and stearic analogues. This enabled the Medicinal chemists 
to 'drug design'. 

The drug design was based on modification of the structure of a "lead" compound. The lead compound was suffering from some therapeutically undesirable side effect. The efficiency of it's increased recently by high-throughput screening (HTPS) system utilizing cell line culture systems with enzyme linked immune system assay (ELISA) and receptor molecules derived from gene cloning. 

The techniques of molecular graphics and computational chemistry have provided novel chemical structure that have led to new drugs with potent medicinal activates. 





Medicinal chemistry covers the following stages: 
  • In the first stage new active substance or drugs are identified and prepared from natural sources, organic chemical reactions or biotechnological processes. They are known as lead molecules. 
  • The second stage is optimization of lead molecule to improve potency, selectivity and to reduce toxicity. 
  • The next stage involves optimization of synthetic route for bulk production and modification of pharmacokinetic and pharmaceutical properties of active substance to render it clinically useful. 
It is hoped that new research program's will come to the rescuer and ailing humanity in this or 21st century to control dreaded diseases like AIDS Cancer,etc.



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