Which statement best describes why Best carmine is considered a carbohydrate staining technique?

• A. It stains carbohydrates
• B. It stains proteins
• C. It stains lipids
• D. It stains nucleic acids

Answer: (A)

Best carmine is a carbohydrate-staining technique because it relies on chemical changes in carbohydrate residues to create dye-binding sites. Carbohydrates in tissues are oxidized to form aldehyde groups, which then react with the carmine to produce a vivid red color. This makes carbohydrate-rich structures—like glycogen and mucopolysaccharides—stain strongly, while proteins, lipids, or nucleic acids don’t generate the same reactive aldehydes under these conditions and therefore are not stained in the same way. In short, the stain’s selectivity for carbohydrate-containing substances explains why it’s categorized as a carbohydrate stain.