Question

Which ring of warfarin is essential for its therapeutic activity:

• A. Purine
• B. Pyrimidine
• C. Lactone
• D. Coumarin

Hint:

The coumarin ring is the active pharmacophore of warfarin, responsible for its anticoagulant activity by inhibiting vitamin K epoxide reductase.

Answer 1

The Correct Option is D

Step 1: Structure of warfarin. Warfarin is an anticoagulant that inhibits vitamin K-dependent clotting factors. Its structure contains a coumarin ring, which is crucial for its interaction with vitamin K epoxide reductase, the enzyme it inhibits. 

Step 2: Role of the coumarin ring. The coumarin ring in warfarin mimics the structure of vitamin K. This allows warfarin to competitively inhibit the enzyme, reducing the activation of clotting factors and exerting its anticoagulant effect. 

Step 3: Why other options are incorrect. 
- (A) Purine: Purine rings are found in nucleotides, not relevant for warfarin. 
- (B) Pyrimidine: Pyrimidine rings are also part of nucleotides, not essential for warfarin. 
- (C) Lactone: While lactone is a functional group, the coumarin ring is the active pharmacophore of warfarin.