Which antibiotic is associated with the chemical structure Rifampicin?

• A. Ofloxacin
• B. Minocycline
• C. Rifampicin
• D. Amoxicillin

Answer: (C)

This item hinges on recognizing the distinctive scaffold of the rifamycin family. Rifampicin is the antibiotic tied to that structure because rifampicins possess a large macrocyclic core (the ansa-bridge linked to a naphthoquinone-containing ring) that sets them apart from other antibiotic classes. This rifamycin-style structure is unique among common antibiotics: Ofloxacin has a fluoroquinolone core, minocycline is built on a tetracycline four-ring system, and amoxicillin contains a beta-lactam ring fused to a thiazolidine moiety. The structure shown is the hallmark rifampicin, the representative member of that class.