Autoöxidation of L-Ascorbic Acid and Imidazole Nucleus

Imanaga, Yujiro

doi:10.1093/oxfordjournals.jbchem.a126573

Cited by 16 publications

(6 citation statements)

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“…There is also an increase in urea content (similar to the increase in aspartic acid; determined by urease (16). Similar products are given by ascorbate or photooxidation of histidine derivatives (17).…”

Section: (A)mentioning

confidence: 83%

Mechanisms of Some Reducing Compounds That Inactivate Polyphenol Oxidases

Osuga

Whitaker

1995

ACS Symposium Series

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Action of polyphenol oxidase (PPO) on substrates results in decrease of activity, some substrate reaction inactivation, some loss of copper from the active site of PPO, and modification of one or more of the histidine residues that ligand the copper. Incubation of PPO with ascorbate, especially in presence of added copper, results in decrease in activity and release of copper from the enzyme with some loss of histidine and methionine residues and increase in aspartic acid, glutamic acid, alanine and glycine residues. Incubation of PPO with sodium bisulfite or thiol compounds results in decrease of enzyme activity, with release of copper. Polyphenol oxidases catalyze the ο-hydroxylation of monophenols to odihydroxyphenols (Equation 1) and the oxidation of 0-dihydroxyphenols to obenzoquinones (Equation 2). The reactions in Equations 1 and 2 are often OH OH (1) CH3 p-Cresol CH3 4-Methylcatechol OH ΟCatechol 0-Benzoquinone

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Section: (A)mentioning

confidence: 83%

Mechanisms of Some Reducing Compounds That Inactivate Polyphenol Oxidases

Osuga

Whitaker

1995

ACS Symposium Series

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“…In addition to light absorption, the generation of reactive species from chemicals following the absorption of UV-visible light is seen as a key determinant for causing direct phototoxic reactions [ 31 ]. The ROS assay can be used as an in chemico screening tool for evaluating the photoreactivity of chemicals.…”

Section: Resultsmentioning

confidence: 99%

Comparative Studies on the Photoreactivity, Efficacy, and Safety of Depigmenting Agents

Mota,

Rosa,

Barreto

et al. 2023

Pharmaceuticals

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Depigmenting products are increasingly used to counteract skin hyperpigmentation and related psychosocial issues. This study aimed to compare different depigmenting agents—4-butylresorcinol; bakuchiol; tranexamic acid; ascorbyl glucoside; α-arbutin; and ascorbic acid—for photoreactivity; tyrosinase inhibition; and safety. Photoreactivity was assessed using the Reactive Oxygen Species assay. In vitro tyrosinase inhibition was compared, and cell viability was assessed in B-16V melanocytes to evaluate safety. Results showed 4-butylresorcinol, ascorbyl glucoside, and α-arbutin are non-photoreactive, while for ascorbic acid and bakuchiol it was not possible to reach conclusive results due to the lack of specificity of the ROS assay. 4-Butylresorcinol, acting as a competitive inhibitor, displayed potent tyrosinase inhibition, followed by ascorbic acid and bakuchiol. Both 4-butylresorcinol and bakuchiol reduced cell viability in a concentration-dependent manner. The insights obtained in this work support the development of depigmenting products by providing useful scientific guidance on the photostability, tyrosinase inhibitory efficacy, and skin safety of depigmenting agents.

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“…Some skin-lightening cosmetics may also have potent reducing properties that interfere with ROS determinations. Ascorbic acid also accelerates the oxidation of imidazole derivatives (26), providing false positive prediction in the ROS assay.…”

mentioning

confidence: 99%

“…Data from three wells for each chemical concentration is used to calculate mean and standard deviation. Criteria for data acceptance 26.…”

mentioning

confidence: 99%

TG 495: Ros (Reactive Oxygen Species) Assay for Photoreactivity

2019

OECD Guidelines for the Testing of Chemicals, Section 4

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Autoöxidation of L-Ascorbic Acid and Imidazole Nucleus

Cited by 16 publications

References 0 publications

Mechanisms of Some Reducing Compounds That Inactivate Polyphenol Oxidases

Mechanisms of Some Reducing Compounds That Inactivate Polyphenol Oxidases

Comparative Studies on the Photoreactivity, Efficacy, and Safety of Depigmenting Agents

TG 495: Ros (Reactive Oxygen Species) Assay for Photoreactivity

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