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Hydroquinone is used to reduce the activated silver ions to metallic silver. During this process, hydroquinone is oxidized to quinone. All silver halide not activated by light or reduced by hydroquinone is removed, leaving a negative by deposited silver where the film had been struck by light. [18]
Hydroquinone, also known as benzene-1,4-diol or quinol, is an aromatic organic compound that is a type of phenol, a derivative of benzene, having the chemical formula C 6 H 4 (OH) 2. It has two hydroxyl groups bonded to a benzene ring in a para position.
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The European Food Safety Authority (EFSA) and the United States Food and Drug Administration (FDA) [3] have evaluated TBHQ and determined that it is safe to consume at the concentration allowed in foods. [4]
The beetles' glands store enough hydroquinone and hydrogen peroxide to allow the beetle to release its chemical spray roughly 20 times. In some cases this is enough to kill a predator. [ 6 ] The main component of the beetle spray is 1,4-benzoquinone, an irritant to the eyes and the respiratory system of vertebrates.
Hydroquinone is the compound most frequently used in skin-whitening products. Due to concerns about its side effects, it was almost banned by the FDA in 2006, as medical issues of carcinogenicity and reports of disfiguring ochronosis existed. [10] In the European Union hydroquinone has been banned in cosmetic creams since 2000. [11]
Thus, the two substrates of this enzyme are UDP-glucose and hydroquinone, whereas its two products are UDP and hydroquinone-O-beta-D-glucopyranoside. This enzyme belongs to the family of glycosyltransferases, specifically the hexosyltransferases. The systematic name of this enzyme class is UDP-glucose:hydroquinone-O-beta-D-glucosyltransferase.