Which hypopigmenting agent used in melasma produces its effect primarily by chelating copper ions at the active site of tyrosinase?

• A Azelaic acid
• B Arbutin
• C Niacinamide
• D Kojic acid ✓

Explanation

Kojic acid, derived from Aspergillus and Penicillium species, binds copper at the tyrosinase active site and thereby inhibits the enzyme that catalyses melanin synthesis. Azelaic acid inhibits tyrosinase competitively and also affects proliferating melanocytes, arbutin releases hydroquinone slowly to inhibit melanogenesis, and niacinamide blocks melanosome transfer from melanocytes to keratinocytes. Recognising these distinct mechanisms separates agents commonly combined in melasma formulations.

Reference: Fitzpatrick's Dermatology, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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