Unit I MEDICINAL CHEMISTRY – III Typing Notes B.Pharmacy

 

BP601T. MEDICINAL CHEMISTRY – III

Unit I

 

 

β-Lactam antibiotics:-  Penicillin, Cepholosporins, β- Lactamase inhibitors,Monobactams

 

(i) Penicillin :-

 

1) Historical background:-

1)    Alexander  Fleming discovered the first antibiotic  penicillin .

2)    Penicillin is derived from the Penicillium mould .

3)      Penicillin is a group of antibiotics that used to treat different types of gram positive and gram negative bacterial infections.

2) Nomenclature :-

1)   Sulfur  atom at 1st position and nitrogen atom at 4th position then called 1-thia-4aza-bicyclo(3.2.0) -heptane's.     

2)    Sulfur  atom at 4st position and nitrogen atom at 1st position then called 1-aza-4-thia-bicyclo(3.2.0) -heptane's.

3) Steriochemistry:-

1)    The penicillin molecule contains three chiral carbon atoms at C-3, C-5 and C-6

2)    All natural and synthetic penicillins have the same absolute configuration

3)    The absolute stereochemistry of the penicillins is designated as 35: 5R: 6R.

 

  4) Mechanism of action:-

             It destroys bacteria by inhibiting the enzyme- transpeptidase responsible for the formation of the cell wall and cross-linking in the bacterial cells.

   5) Chemical Degradation:-

             The Penicillins gets degraded under the acidic and basic conditions as well as in the presence of β-lactamases.

   6) Uses :-

      respiratory tract infections, fever, ear, skin, gum, mouth, and throat infections.

 

(ii) Cephalosporins:-

1)    used to treat  wide range of infections from gram-positive and gram-negative bacteria.

2)    used to treat  Skin infection, resistant bacteria, meningitis, and other infections.

     Mechanism of Action:-

1)    It destroys bacteria by inhibiting the enzyme- transpeptidase responsible for the formation of the cell wall and cross-linking in the bacterial cells

2)    Activation of Autolytic enzymes: Autolysins or Murein Hydrolases

         Uses:-

1)     used as antibiotics.

2)    Alternative to Penicillins

3)     Gonorrhoea

4)     Typhoid fever

5)     Meningitis

(iii) Beta-lactamase inhibitors:-

1)    these are drugs that are used to prevent antimicrobial resistance

2)    inhibit serine beta-lactamases.

3)    It  breaks the beta-lactam ring and allows penicillin-like antibiotics to work.

(iv) Monobactams:-

1)    They are resistant to active against aerobic gram-negative rods.

2)    They have no activity against gram-positive bacteria or anaerobes.

3)    It is administered either IV or IM.

4)    nontoxic, but it may cause skin rash and, abnormal liver function tests.

5)    Penicillin-allergic patients tolerate can without reaction.

 

Aminoglycosides:- : Streptomycin, Neomycin, Kanamycin

 1. Streptomycin:-

1)    it is the first aminoglycoside antibiotic the used in treatment of tuberculosis.

2)    It inhibits bacterial growth by inhibiting protein synthesis.

3)    it binds to the 16S rRNA of the bacterial ribosome

4)    interfere  with the binding of formylmethionyl-tRNA .

5)    It is chemically stable and rapidly bactericidal and have broad spectrum.

 2. Neomycin:-

1)    Most potent aminoglycoside.

2)    is used to prevent or treat skin infections caused by bacteria. It is not effective against fungal or viral infections.

3)    Neomycin comes in cream and ointment that is applied to the skin.

 

  Side effect:-

1)    irritation

2)    burning

3)    redness

4)    rash

5)    itching

6)    hearing difficulty

7)    decreased urination

3. Kanamycin:-

1)    Kanamycin is made up of 3 rings.

2)    Ring II is sugar group and ring I and III are non-sugar group.

3)    Kanamycin B is a more potent antibiotic than kanamycin  A or C.

4)    is used to treat serious  bacterial infections in many different parts of the body.

Mechanism:-

1)    It  bind to 30S proteins and 16S rRNA.

2)    Specifically Kanamycin binds  to four nucleotides of 16S rRNA and a single amino acid of protein S12.

3)    So incorrect  amino acids are inserted into the polypeptide.

Clinical Uses:-

1)    gram-negative infection

2)    skin, bone or soft tissue infection

3)    urinary tract infection

4)    Sepsis

5)    severe intra-abdominal infections

6)    Severe pelvic inflammatory disease

7)    Endocarditis

8)    Mycobacterium infection

 (Write these uses for all above three Drugs)

Tetracyclines:- Tetracycline,Oxytetracycline, Chlortetracycline, Minocycline, Doxycycline.

Tetracycline:-

1)    Tetracycline is used to treat a wide variety of infections.

2)    It is an antibiotic that works by stopping the growth of bacteria.

3)    This antibiotic treats only bacterial infections.

    Mechanism of action:-

1)    These  are protein synthesis inhibitors.

2)    They inhibit the initiation of translation.

3)    They inhibit the binding of aminoacyl-tRNA to the mRNA translation complex.

    Uses:-

1)    Used to treat infections caused by pneumonia and other respiratory tract infections.

2)    sexually transmitted infections.

3)    certain infections of skin, eye, lymphatic, intestinal, genital and urinary systems; and certain other infections that are spread by ticks, lice, mites, and infected animals.

(Write Same for  Oxytetracycline, Chlortetracycline, Minocycline, Doxycycline.)

 

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