Step 1: Understanding the Question:
The question wants the antibiotic class whose main degradation pathway is oxidation triggered by light.
Step 2: Key Concept:
Light-catalysed autoxidation needs a chromophore, typically a run of conjugated double bonds, that can absorb light energy and pass it on to react with molecular oxygen.
Step 3: Detailed Explanation:
Polyene antibiotics, amphotericin B and nystatin, are named for exactly this feature, a stretch of conjugated double bonds within their macrolide ring. Light exposure excites this conjugated system, which then reacts with oxygen and breaks down, so these products are always stored protected from light. Beta-lactams degrade mainly by hydrolysis of the strained ring, sugar-based antibiotics degrade by glycosidic bond hydrolysis, and macrolides are mainly acid-labile, none of which is a light-driven oxidation mechanism.
Step 4: Final Answer:
Polyene antibiotics.