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Medicinal Chemistry

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Title: Medicinal Chemistry


1
Medicinal Chemistry
  • Chapter 1 Introduction
  • College of Pharmacy, SDU

2
Definition
  • Medicinal chemistry is a chemistry-based
    discipline, 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 the construction of
    structure-activity relationships (SARs).

3
  • In particular, Medicinal chemistry also involves
    the discovery of new chemical entities for the
    treatment of diseases and the systematic study of
    the structure-activity relationships of the
    active compounds. Such studies provide the basis
    for development of better medicinal agents from
    lead compounds found via random screening,
    systematic screening and rational design.

4
  • Drug is any substance presented for treating,
    curing or preventing disease in human beings or
    in animals. It may also be used for making a
    medical diagnosis or for restoring, correcting,
    or modifying physiological functions.

5
  • Structure-activity relationship (SAR) is the
    relationship between chemical structure and
    pharmacological activity for a series of
    compounds.
  • Lead compound is a compound that has a desirable
    biological activity with therapeutic relevance,
    but typically has some shortcoming that is likely
    to be overcome through the development of analogs.

6
Emphasis
  • 1. Chemcially structural feature,
    physico-chemical property, stability.
  • 2.Biological effect, adverse effects,
    biotransformation etc.
  • 3. Structure-activity relationship, drug targets
    in living bodies as well as mode of action.

7
The important role of drugs in human society
  • Drugs have irrevocably changed the fabric of
    society by improving both the individual quality
    of life and life expectancy.
  • Some examples are shown as follows

8
  • 1. Bacterial and virus infections polio,
    smallpox, tuberculosis and related diseases have,
    to a very major extent, become minor public
    health concerns.
  • 2. An increase in life expectancy resulting from
    drug therapy has also led to a shift in
    population demographics toward a more healthy,
    elderly population.
  • 3. Drug regimens for birth control have improved
    individual life choices and the quality of life.

9
  • 4. HIV protease and reverse transcriptase
    inhibitors for the treatment of HIV infections
    have changed a disease with a fatal prognosis to
    a potentially chronic one.
  • 5. Cancer is also being viewed as a potentially
    chronic, rather than fatal disease with newer,
    non-cytotoxic approaches.
  • Notes HIV, Human immunodeficiency virus

10
Section 1 Origins of Medicinal Chemistry
  • 1. Early investigations of natural products
  • 1.1.In the so-called pre-scientific era
  • Natural products having a history as folk
    remedies were in use. Fore examples, opium,
    belladonna, cinchona bark, etc. Many drugs
    originally used as folk remedies, nowadays, have
    been abandoned.

11
  • 1.2. In the late eighteenth and early nineteenth
    centuries, chemical experimentation led
    ultimately to its use in the discovery of new
    drugs.
  • In 1853, Henry How conceived the idea that
    functional groups in natural products might be
    modified by chemical reagents.
  • He heated morphine with methyl iodide, hoping
    to convert the alkaloid to codeine. He obtained,
    however, a new substance of the quaternary salt
    of morphine.

12
  • In 1898, the first commercially available
    semisynthetic morphine derivative (ethyl ether)
    was introduced as a cough sedative in preference
    to codeine or other opiates.
  • Meanwhile, diacetylmorphine was introduced as a
    safer pain reliever than morphine. It quickly
    became popular throughout the world.
  • Four years passed before its addictive properties
    of heroin were recognized. Laws were later passed
    by governments to restrict its use.

13
  • 1.3. Developments of MC Leading to Various
    Medicinal Classes of Drugs
  • During the 1840s, the first use of synthetic
    organic chemicals were introduced for anesthesia
    during a tooth removal, such as nitrous oxide,
    ether, and chloroform.
  • In 1864, barbituric acid had been synthesized as
    a useful hypnotic.

14
  • In 1875, salicylic acid was introduced as a
    possible cure for typhoid fever. It was found to
    be an effective antipyretic.
  • In 1899, Aspirin was marketed as an antipyretic
    without the unpleasant side effects. This
    indicated that the chemical structures from
    natural products were changed into better drugs.
  • Medicinal Chemistry began.

15
2. Fast Development from 1900s to 1960s
  • 1920s1930s Anesthetics, Hypnotics, Analgesics
    were used extensively. In research for functional
    pharmacophore, structure-function relationship
    was investigated gradually.

16
  • After 1930s The development of new drugs was
    speeded greatly by the close combination of
    Medicinal Chemistry and Experimental
    Pharmacology.
  • Theory of antimetabolite was formed by using
    metabolic products as lead compounds.
  • Discovery of penicillin which is the first
    antibiotics is an epoch-making achievement.
  • Afterward, tetracycline, streptomycin,
    chloramphenicol, erythromycin were introduced one
    after another.

17
  • In 1940s, the first drug used for treating
    cancer as a biological alkylating agent was
    nitrogen mustard, which began tumor chemical
    therapy.
  • In 1960s, oral steroidal contraceptive agents
    were discovered. Corticosteroids have become an
    important drugs.

18
  • After 1950s, aging disease, cerebrovascular and
    cardiovascular diseases became first reason for
    human death. New drugs design based on enzymes or
    receptors as drug targets.
  • In 1964, first ß-Adrenergic blocking agent,
    Propranolol, was marketed.
  • In 1979, Nifedipine, Calcium Channel Blocker was
    marketed.
  • In 1981, Captopril, Angiotensin Converting Enzyme
    (ACE) Inhibitor was launched.

19
Future of Medicinal Chemistry
  • New drugs will be discovered or invented by
    investigating human genomics and human disease
    genomics.

20
3. Drug Target and Drug Design
  • Mechanism based drug design
  • Structure based drug design
  • Known targets 480,receptors 45 enzymes 28
    (See p56)

21
3.1. Receptor Used as Drug Target
  • Receptors M acetylcholine receptor adrenergic
    receptor angiotensin receptor dopamine
    receptor serotonin receptor opioid receptor
    etc.
  • Drugs effecting on receptors
  • AgonistAntagonist

22
  • Agonist is an endogenous substance or a drug that
    can interact with a receptor and initiate a
    physiological or a pharmacological response
    (contraction, relaxation, secretion, enzyme
    activation, etc.).
  • Antagonist is a drug or a compound that opposes
    the receptor-associated responses normally
    induced by another bioactive agent.
  • Partial agonist is an agonist which is unable to
    induce maximal activation of a receptor
    population, regardless of the amount of drug
    applied.

23
3.2. Enzyme Used as Drug Target
  • Enzyme Angiotensin Converting Enzyme (ACE),
    Cycloxygenase(COX2),ß-Lactamase, Acetylcholine
    Esterase etc.
  • Drugs effecting on enzyme Enzyme Inhibitor

24
3.3. Ion Channal Used as Drug Target
  • Ion Channal Calcium Ion Channal, Potassium Ion
    Channal, Sodium Ion Channal, Chloride Ion
    Channal, etc.
  • Drugs effecting on Ion Channal Calcium Channal
    Blocker, Potassium Channal Blocker, Sodium
    Channal Blocker, etc.

25
3.4. Nucleic Acid Used as Drug Target
  • Nucleic Acid RNA, DNA
  • Drugs antiviral agent, quinolone agent, etc.

26
  • Antisense technology
  • Antisense drugs are short stretches of DAN
    analogs which bind to specific complementary
    areas of the mRNA. In doing so, they can induce a
    nuclease which cleaves the mRNA at the site of
    the binding or can physically block translation
    or other steps in mRNA processing and transport,
    thus stopping protein synthesis.

27
Flowchart for evaluation of new chemical entities
28
R D Model of Modern Drugs
29
Section 2 Nomenclature of Drug Substances
  • INN International Non-proprietary Names for
    Pharmaceutical Substance, that is, common names
    by national or international nomenclature
    commissions
  • Chemical Name by international union for pure
    and applied chemistry (IUPAC) and international
    union of biochemistry (IUB)

30
  • CADN Chinese Approved Drug Names
  • English Chemical Name based on nomenclature of
    chemical abstracts (CA)
  • Trade Name

31
Questions
  • 1. To master the following definitions medicinal
    chemistry, drug, structure-activity relationship,
    lead compound, Antisense drugs.
  • 2. to be familiar with main research contents of
    medicinal chemistry.
  • 3. To understand orgins of medicinal chemistry.
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