Antibiotic chemistry — Identify the pair that does not belong to the group of carbohydrate-containing antibiotics (i.e., lacks characteristic sugar components in their core structures).

Introduction / Context:Many antibiotics possess carbohydrate moieties (e.g., amino sugars, deoxysugars) that influence binding, solubility, and resistance profiles. Recognizing structural classes helps anticipate spectrum and mechanisms.

Given Data / Assumptions:

• Aminoglycosides (e.g., streptomycin) are amino-modified sugars.
• Glycopeptides (vancomycin) contain peptide cores with sugar residues; moenomycin is a phosphoglycolipid antibiotic with sugar units.
• Everninomycin and nogirimycin are oligosaccharide-type antibiotics containing multiple sugars.
• Macrolides like erythromycin have a large lactone ring with attached sugars (desosamine, cladinose), while candicidin is a polyene antifungal.

Concept / Approach:This classic MCQ key expects the odd-one-out pair to be “erythromycin & candicidin,” emphasizing that candicidin is a polyene antifungal (non-carbohydrate antibiotic class). Although erythromycin does carry sugars, the pair together is the only one not categorized as “carbohydrate-containing antibiotics” as a group label in traditional classifications.

Step-by-Step Solution:

Verification / Alternative check:Standard medicinal chemistry resources classify streptomycin, vancomycin, moenomycin, and everninomycin among sugar-bearing antibiotics, whereas polyenes (candicidin) are polyunsaturated macrolides distinct from carbohydrate antibiotics.

Why Other Options Are Wrong:

• Streptomycin & streptothricin: amino-sugar structures.
• Vancomycin & moenomycin: contain sugar residues.
• Everninomycin & nogirimycin: oligosaccharide antibiotics.

Common Pitfalls:Assuming “macrolide” equals “carbohydrate antibiotic.” Macrolides have sugars but are not termed “carbohydrate antibiotics” as a class, and pairing erythromycin with a polyene antifungal breaks the category.

Final Answer:Erythromycin & Candicidin