medicinal chemistry

1. Gurunanak Institute of
Pharmaceutical Sc. & Technology
Topicon:
CLASSIFICATION OF ANTIBIOTICS
Presentedby;SumelAshique
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2. Antibiotics: An antibiotic is a naturally occurring
semisynthetic or synthetic type of agent that
destroy or inhibit the growth of pathogenic
microorganism & used in the treatment of
external & internal infections.
Ideal characteristics of antimicrobials:
Kill or inhibit the growth of pathogens
Cause no allergic reaction to host cell
Don’t cause damage to host cell
Should be stable when stored in liquid or
solid form.

3. According to chemical structure:
 Sulphonamides- Sulfone, PAS.
 Quinolones- Nalidixic acid, ciprofloxacin.
 Beta lactum- Penicillin, cephalosporin.
 Amino glycoside- Streptomycin,Gentamycin.
 Tetracyclin- Oxytetracyclin, doxytetracyclin.
 Nitrobengene derivatives-Chloramphenicol.
 Macrolids- Azithromycin, Erthromycin.
 Polypeptide-Polymyxin B.

4. Continue….
 Nitrofuran-Nitrofurantoin
 Nitroimidazole-Metronidazole
 Nicotinic acid-Isoniazid
 Polyene-Nystatin
 According to mechanism of action:
 Inhibition of cell wall synthesis
 Interference with cell membrane Integrity
 Nucleic acid synthesis inhibitors
 Inhibition of protein synthesis

5. Continue…..
 Inhibition of certain metabolic pathway.
Inhibition of cell wall synthesis:
Target- peptidoglycan.
Beta lactum antibiotics bind to the PBPs.
Activation of autiolytic enzyme in the cell wall
Degradation of peptidoglycan due to removal od
terminal D-alanine which is required for cross linking

6. Interference with cell membrane
Antibiotics have affinity for phospholipid of cell
membrane
Come close to the bilayer.
Orient itself within phospholipid according to their
hydrophilic –hydrophobic portion.
Formation of pseudopore from where ions, elec
trolytes leak out
Cell death
Example-Polymyxin B against Gm( -ve) bacteria only.

7. Nucleic acid synthesis Inhibitors:
Sulphonamides inhibit tetrahydrofolate &
Trimethoprim inhibit Di-hydrofolate reductase ( that
inhibit purine synthesis).
Trimethoprim & sulfa-methaxazole produce
sequential blocking.
Example-Novobiocin inhibit beta subunit of DNA
gyrase.
Rifampicin binds to DNA dependent RNA
polymerase that block the initiation of bacterial
RNA synthesis

8. Inhibition of protein synthesis
Aminoglycosides attached to specific receptor
Blockage of activity of m-RNA on recognition region
Wrong amino acid inserted thus activity slowly
stopped.
Example-chloramphenicol inhibit peptydyl
transferase which prevent synthesis new peptide
bonds.

9. Inhibition of certain metabolic pathway
Folate inhibitors
Inhibit folic acid synthesis that is required for DNA
synthesis.
When folic is inhibited then metabolic pathway is
disrupted.
Cell death occurs.
Example- Sulfadoxine, sulfasalazine.

10.  According to Spectrum of activity:
 Broad spectrum antibiotic: Acts against wide
range of disease.
Example-Tetracycline, Chloramphenicol.
 Short spectrum antibiotic: Acts against narrow
range of disease.
 Example- Penicillin G, vancomycin.
 According to mode of action:
 Bacteriostatic: Agents that stop reproducing the
bacteria but not necessarily killing them.
 Example-Tetracycline

11. Continue…
 Bactericidal: That kills the bacteria.
Example- Penicillin, Cephalosporin.
According to absorbability from site of
administration:
 Locally acting- Polymixin B .
 Systemic acting-Tetracycline HCL.

12. Conclusion:
Antibiotics are the agents that derived from
microorganism or produced synthetically that
destroy or limits the growth of a living
orgnism.They are classified according to their
spectrum of activity, mode of action, according to
their chemical structure and so on.

13. Reference.
FOYE’S Principles of Medicinal Chemistry
Edition-6th, Page no- (1036 to 1053)
Thank you..