Which urinary metabolite is measured by the Zimmerman Method using dinitrobenzene and yields a purple color?

• A. 17-ketosteroids
• B. 17-hydroxycorticosteroids
• C. Cortisol
• D. DHEA

Answer: (A)

The main idea here is that the Zimmermann reaction is used to detect 17-ketosteroids in urine. In this method, urine is treated with dinitrobenzene under alkaline conditions, and steroids that have a ketone at the C17 position react to form a colored complex that appears purple. The intensity of the purple color correlates with how much 17-ketosteroid is present, so this test is used to estimate the total excretion of 17-ketosteroids, i.e., androgen-derived metabolites.

That’s why the best answer is the class of 17-ketosteroids. Cortisol and 17-hydroxycorticosteroids do not have the necessary 17-keto group (they contain a 17-hydroxyl instead), so they do not produce the same purple color in this reaction. DHEA is indeed a 17-ketosteroid, but the Zimmermann method measures the total amount of 17-ketosteroids in urine rather than a single compound, so the correct framing is the set of 17-ketosteroids rather than one metabolite.