hydroquinone 1,4-Benzenediol benzene-1,4-diol Benzene-1,4-diol Hydroquinone Eldoquin p-Benzenediol Quinol hydroquinone Benzene-1,4-diol benzene-1,4-diol p-hydroxyphenol 4-Hydroxyphenol A benzenediol comprising benzene core carrying two hydroxy substituents <em>para</em> to each other. p-Hydroquinone 1,4-Dihydroxybenzene benzenediol antioxidant cofactor hydroquinones carcinogenic agent mouse metabolite human xenobiotic metabolite Escherichia coli metabolite skin lightening agent