1,2-dehydro-N-acetyldopamine precursor N-acetyldopamine (NADA) is synthesized in the cytosol of epidermal cells from dopamine. During pre- or post-ecdysis, NADA is transported into the cuticular matrix and converted sequentially to the corresponding ortho-quinone, para-quinone methide, and hydro-NADA. These various reactive products react with cuticular proteins and chitin, forming adducts and crosslinks that result in the hardening of the cuticle, a process known as sclerotization. NADA derivatives are colorless. (Adapted from PMID:19932179 and FBrf0246618.)