<prompt> Depigmenting agent of choice in in treatment of dermatological disorders is -HydroquinoneZincKojic acidAzelaic acid  <response>: DEPIGMENTING AGENTS:- Include agents like hydroquinone2-5,azelaic acid 10-20, glycolic acid 6-12 and monobenzene. They act by inhibiting tyrosinase enzyme. Hydroquinone is most commonly used.It can be combined with steroids and retinoids in the treatment of melasma. Kligmans regimen- 5 hydroquinone0.1 tretinoin 0.1 hydrophilic ointment. Newer agents-Arbutin and kojic acid.They lighten hyperpigmented patches. Used in melasma, freckles. Reference: IADVL textbook of dermatology, vishalakshi Vishwanath pg no.379 