Medicinal chemistry as the name indicates, deals with chemistry of medicines.
It is an important branch of chemistry as it directly relates to health care.
Medicinal chemistry tries to interlinks health, disease and medicine in a scientific manner.
It purely emphasizes on the chemistry of medicine, mechanism of action, synthesis.
What is Medicinal chemistry
Medicinal chemistry is one which deals with chemistry of medicines in the following way.
1. It defines the chemical structure of any medicine in terms of type of compound, functional groups, bonds within etc.
2. It analyses the physical and chemical properties of medicines.
Physical properties like solubility, melting point, light sensitivity, crystalline or amorphous are studied. Solubility decides how the medicine is to be formulated. If it is water insoluble, it is converted to some salt form.
Crystalline or amorphous nature indicates the flow properties which are needs during making tablets, capsules etc.
Light sensitivity indicates how the medicine has to preserved. If light sensitive, it is packed in opaque packs.
Melting point indicates how far the compound is stable at room temperature and how it should be handled during medicine formulation. Also if the melting point is so low, it may need to be stored in cold temperatures.
Chemical properties like pH, internal bonds, saturation, help in different ways. If a compound is acidic, it means it is insoluble in acidic medium like stomach but soluble in basic medium like intestine. So the pH of the compound helps design simple tablet or sustained release one so as to release medicine in the intestine.
Chemical saturation indicates, its reactive tendencies with other molecules.
3. It also describes the functional groups present in the drug and their relation to the rest of the molecule. This helps us know which part of molecule contributes to the medicinal effects. And suitable alterations can be done for better effect.
4. It helps to differentiate which stereo-isomeric forms are effective for treatment. The organic compounds have isomer like dextro and levo rotatory forms. Among medicines one isomer is active than other. For example, (levo) DOPA is used in parkisons disease. While its (dextro) DOPA form is inactive.
Similarly Amphetamine is active in dextro form and less active in levo.
5. It explains the mechanism of action of drugs in a disease condition. A drugs acts to bring desired effect by suitable means. Medicinal chemistry tries to establish the mechanism of action of all drugs.
6. It also covers the synthesis procedure for established drugs. Every drug molecule is synthesized in a proper way. This taught in medicinal chemistry.
7. It can also predict the metabolites of a drug after metabolism.
Applications of medicinal chemistry:
It helps to develop even more effective medicines, minimize toxicity, produce medicine in an inexpensive manner.
1) Effective medicine: A medicine is effective when it is able to kill the parasite, or rectify a deficiency or alter a physiological state to the desired level of well being. The effectiveness of medicine depends on factor like
a) Reach the remote parts of disease by solubility in non-aqueous regions of the body.
b) kill the parasite or produce desired effect at low concentrations so as to minimize the bulk of medicine preparation.
c) Avoid development of resistance by the disease causing agent or system.
2) Minimal toxicity: Any medicine we take is a foreign substance to the body. So it is metabolized in liver and excreted by urine. So the medicine prepared should safe for the body and preferably less toxic. Medicinal chemistry strives to prepare water soluble drug molecules which will be easily metabolized. Or if lipid solubility is desired then the molecule which can easily be converted to water soluble forms are created. Thus the accumulation of drug toxins is controlled by medicinal chemistry.
3) Inexpensive drugs: Most drugs used in life threatening diseases are expensive. Medicinal chemistry can help find alternative drug molecules or manufacturing methods to minimize the cost of the drug. This helps the drug to reach people of all economic status.
4) Discover new drug molecules: This is done by a method of QSAR which is qualitative structure activity relationship. Since people develop insensitivity to drugs or there is resistance to drugs by microbes, medicinal chemistry helps to keep adding new molecules to treat diseases more effectively.
Alternatively when a substance is found to show some therapeutic effects, that substance is isolated and tested for its chemical characteristics. Then a similar molecule is made with all the desirable properties to make a better drug molecule.
It also minimizes the time required for drug discovery. In past all the molecules with expected therapeutic value were synthesized and then tested on animals. This is quite expensive and time taking procedure. Currently medicinal chemistry uses the technique of computer aided drug discovery (CAD) to minimize the time taken for drug discovery. It avoids the need to synthesize all the test molecules and also test them on many animals. By use of CAD, the drug molecule and its ability to work on a receptor is predicited.