4-tert-Butylphenol, also known as butylphen or PTBP, belongs to the class of organic compounds known as phenylpropanes. These are organic compounds containing a phenylpropane moiety. 4-tert-Butylphenol is a leather and oakmoss tasting compound. 4-tert-Butylphenol has been detected, but not quantified, in herbs and spices. 4-Tert-butylphenol is structurally similar to the melanin precursor tyrosine, and acts as a substrate for tyrosinase. 4-tert-Butylphenol is a potentially toxic compound. Tyrosinase oxidizes 4-tert-butylphenol to a quinone (4-tert-butylcyclohexa-3,5-diene-1,2-dione) which in turn rapidly reacts with glutathione (GSH). A depletion of the GSH defence system may allow the quinone to generate reactive oxygen species that damage melanocytes and induce apoptosis, leading to leukoderma/vitiligo.