1
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Sextius P, Warrick E, Prévot-Guéguiniat A, Lereaux G, Boirre F, Baux L, Hassine SB, Qiu J, Huang X, Xu J, Grégoire S, Ito S, Wakamatsu K, Marat X. 2-Mercaptonicotinoyl glycine, a new potent melanogenesis inhibitor, exhibits a unique mode of action while preserving melanocyte integrity. Pigment Cell Melanoma Res 2024; 37:462-479. [PMID: 38560773 DOI: 10.1111/pcmr.13168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 02/29/2024] [Accepted: 03/18/2024] [Indexed: 04/04/2024]
Abstract
Research on new ingredients that can prevent excessive melanin production in the skin while considering efficacy, safety but also environmental impact is of great importance to significantly improve the profile of existing actives on the market and avoid undesirable side effects. Here, the discovery of an innovative technology for the management of hyperpigmentation is described. High-throughput screening tests on a wide chemical diversity of molecules and in silico predictive methodologies were essential to design an original thiopyridinone backbone and select 2-mercaptonicotinoyl glycine (2-MNG) as exhibiting the most favorable balance between the impact on water footprint, skin penetration potential and performance. The effectiveness of 2-MNG was confirmed by topical application on pigmented reconstructed epidermis and human skin explants. In addition, experiments have shown that unlike most melanogenesis inhibitors on the market, this molecule is not a tyrosinase inhibitor. 2-MNG binds to certain melanin precursors, preventing their integration into growing melanin and leading to inhibition of eumelanin and pheomelanin synthesis, without compromising the integrity of melanocytes.
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Affiliation(s)
| | | | | | | | | | - Ludwig Baux
- L'Oréal Research and Innovation, Aulnay, France
| | | | - Jie Qiu
- L'Oréal Research and Innovation, Shanghai, China
| | | | - Jinzhu Xu
- L'Oréal Research and Innovation, Aulnay, France
| | | | - Shosuke Ito
- Institute for Melanin Chemistry, Fujita Health University, Toyoake, Aichi, Japan
| | - Kazumasa Wakamatsu
- Institute for Melanin Chemistry, Fujita Health University, Toyoake, Aichi, Japan
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2
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Geng Y, Liu X, Yu Y, Li W, Mou Y, Chen F, Hu X, Ji J, Ma L. From polyphenol to o-quinone: Occurrence, significance, and intervention strategies in foods and health implications. Compr Rev Food Sci Food Saf 2023; 22:3254-3291. [PMID: 37219415 DOI: 10.1111/1541-4337.13182] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2022] [Revised: 05/07/2023] [Accepted: 05/08/2023] [Indexed: 05/24/2023]
Abstract
Polyphenol oxidation is a chemical process impairing food freshness and other desirable qualities, which has become a serious problem in fruit and vegetable processing industry. It is crucial to understand the mechanisms involved in these detrimental alterations. o-Quinones are primarily generated by polyphenols with di/tri-phenolic groups through enzymatic oxidation and/or auto-oxidation. They are highly reactive species, which not only readily suffer the attack by nucleophiles but also powerfully oxidize other molecules presenting lower redox potentials via electron transfer reactions. These reactions and subsequent complicated reactions are capable of initiating quality losses in foods, such as browning, aroma loss, and nutritional decline. To attenuate these adverse influences, a variety of technologies have emerged to restrain polyphenol oxidation via governing different factors, especially polyphenol oxidases and oxygen. Despite tremendous efforts devoted, to date, the loss of food quality caused by quinones has remained a great challenge in the food processing industry. Furthermore, o-quinones are responsible for the chemopreventive effects and/or toxicity of the parent catechols on human health, the mechanisms by which are quite complex. Herein, this review focuses on the generation and reactivity of o-quinones, attempting to clarify mechanisms involved in the quality deterioration of foods and health implications for humans. Potential innovative inhibitors and technologies are also presented to intervene in o-quinone formation and subsequent reactions. In future, the feasibility of these inhibitory strategies should be evaluated, and further exploration on biological targets of o-quinones is of great necessity.
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Affiliation(s)
- Yaqian Geng
- College of Food Science and Nutritional Engineering, National Engineering Research Centre for Fruits and Vegetables Processing, Key Laboratory of Fruits and Vegetables Processing, Ministry of Agriculture, Engineering Research Centre for Fruits and Vegetables Processing, Ministry of Education, China Agricultural University, Beijing, China
| | - Xinyu Liu
- College of Food Science and Nutritional Engineering, National Engineering Research Centre for Fruits and Vegetables Processing, Key Laboratory of Fruits and Vegetables Processing, Ministry of Agriculture, Engineering Research Centre for Fruits and Vegetables Processing, Ministry of Education, China Agricultural University, Beijing, China
| | - Yiran Yu
- College of Food Science and Nutritional Engineering, National Engineering Research Centre for Fruits and Vegetables Processing, Key Laboratory of Fruits and Vegetables Processing, Ministry of Agriculture, Engineering Research Centre for Fruits and Vegetables Processing, Ministry of Education, China Agricultural University, Beijing, China
| | - Wei Li
- College of Food Science and Nutritional Engineering, National Engineering Research Centre for Fruits and Vegetables Processing, Key Laboratory of Fruits and Vegetables Processing, Ministry of Agriculture, Engineering Research Centre for Fruits and Vegetables Processing, Ministry of Education, China Agricultural University, Beijing, China
| | - Yao Mou
- College of Food Science and Nutritional Engineering, National Engineering Research Centre for Fruits and Vegetables Processing, Key Laboratory of Fruits and Vegetables Processing, Ministry of Agriculture, Engineering Research Centre for Fruits and Vegetables Processing, Ministry of Education, China Agricultural University, Beijing, China
| | - Fang Chen
- College of Food Science and Nutritional Engineering, National Engineering Research Centre for Fruits and Vegetables Processing, Key Laboratory of Fruits and Vegetables Processing, Ministry of Agriculture, Engineering Research Centre for Fruits and Vegetables Processing, Ministry of Education, China Agricultural University, Beijing, China
| | - Xiaosong Hu
- College of Food Science and Nutritional Engineering, National Engineering Research Centre for Fruits and Vegetables Processing, Key Laboratory of Fruits and Vegetables Processing, Ministry of Agriculture, Engineering Research Centre for Fruits and Vegetables Processing, Ministry of Education, China Agricultural University, Beijing, China
| | - Junfu Ji
- College of Food Science and Nutritional Engineering, National Engineering Research Centre for Fruits and Vegetables Processing, Key Laboratory of Fruits and Vegetables Processing, Ministry of Agriculture, Engineering Research Centre for Fruits and Vegetables Processing, Ministry of Education, China Agricultural University, Beijing, China
| | - Lingjun Ma
- College of Food Science and Nutritional Engineering, National Engineering Research Centre for Fruits and Vegetables Processing, Key Laboratory of Fruits and Vegetables Processing, Ministry of Agriculture, Engineering Research Centre for Fruits and Vegetables Processing, Ministry of Education, China Agricultural University, Beijing, China
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3
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Nishimaki-Mogami T, Ito S, Cui H, Akiyama T, Tamehiro N, Adachi R, Wakamatsu K, Ikarashi Y, Kondo K. A cell-based evaluation of human tyrosinase-mediated metabolic activation of leukoderma-inducing phenolic compounds. J Dermatol Sci 2022; 108:77-86. [PMID: 36567223 DOI: 10.1016/j.jdermsci.2022.12.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 09/04/2022] [Accepted: 12/08/2022] [Indexed: 12/15/2022]
Abstract
BACKGROUND Chemical leukoderma is a skin depigmentation disorder induced through contact with certain chemicals, most of which have a p-substituted phenol structure similar to the melanin precursor tyrosine. The tyrosinase-catalyzed oxidation of phenols to highly reactive o-quinone metabolites is a critical step in inducing leukoderma through the production of melanocyte-specific damage and immunological responses. OBJECTIVE Our aim was to find an effective method to evaluate the formation of o-quinone by human tyrosinase and subsequent cellular reactions. METHODS Human tyrosinase-expressing 293T cells were exposed to various phenolic compounds, after which the reactive o-quinones generated were identified as adducts of cellular thiols. We further examined whether the o-quinone formation induces reductions in cellular GSH or viability. RESULTS Among the chemicals tested, all 7 leukoderma-inducing phenols/catechol (rhododendrol, raspberry ketone, monobenzone, 4-tert-butylphenol, 4-tert-butylcatechol, 4-S-cysteaminylphenol and p-cresol) were oxidized to o-quinone metabolites and were detected as adducts of cellular glutathione and cysteine, leading to cellular glutathione reduction, whereas 2-S-cysteaminylphenol and 4-n-butylresorcinol were not. In vitro analysis using a soluble variant of human tyrosinase revealed a similar substrate-specificity. Some leukoderma-inducing phenols exhibited tyrosinase-dependent cytotoxicity in this cell model and in B16BL6 melanoma cells where tyrosinase expression was effectively modulated by siRNA knockdown. CONCLUSION We developed a cell-based metabolite analytical method to detect human tyrosinase-catalyzed formation of o-quinone from phenolic compounds by analyzing their thiol-adducts. The detailed analysis of each metabolite was superior in sensitivity and specificity compared to cytotoxicity assays for detecting known leukoderma-inducing phenols, providing an effective strategy for safety evaluation of chemicals.
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Affiliation(s)
| | - Shosuke Ito
- Institute for Melanin Chemistry, Fujita Health University, Aichi, Japan.
| | - Hongyan Cui
- National Institute of Health Sciences, Kanagawa, Japan
| | | | | | - Reiko Adachi
- National Institute of Health Sciences, Kanagawa, Japan
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The effect of a topical vitamin D3 analog on repigmentation in mice with rhododendrol-induced leukoderma. J Dermatol Sci 2022; 106:127-129. [DOI: 10.1016/j.jdermsci.2022.04.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Revised: 04/09/2022] [Accepted: 04/12/2022] [Indexed: 11/18/2022]
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5
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Alfieri ML, Cariola A, Panzella L, Napolitano A, d'Ischia M, Valgimigli L, Crescenzi O. Disentangling the Puzzling Regiochemistry of Thiol Addition to o-Quinones. J Org Chem 2022; 87:4580-4589. [PMID: 35266705 PMCID: PMC8981336 DOI: 10.1021/acs.joc.1c02911] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
![]()
The addition of thiol
compounds to o-quinones,
as exemplified by the biologically relevant conjugation of cysteine
to dopaquinone, displays an anomalous 1,6-type regiochemistry compared
to the usual 1,4-nucleophilic addition, for example, by amines, which
has so far eluded intensive investigations. By means of an integrated
experimental and computational approach, herein, we provide evidence
that the addition of glutathione, cysteine, or benzenethiol to 4-methyl-o-benzoquinone, modeling dopaquinone, proceeds by a free
radical chain mechanism triggered by the addition of thiyl radicals
to the o-quinone. In support of this conclusion,
DFT calculations consistently predicted the correct regiochemistry
only for the proposed thiyl radical-quinone addition pathway. These
results would prompt a revision of the commonly accepted mechanisms
for thiol-o-quinone conjugation and stimulate further
work aimed at assessing the impact of the free radical processes in
biologically relevant thiol–quinone interactions.
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Affiliation(s)
- Maria L Alfieri
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia 21, Naples I-80126, Italy
| | - Alice Cariola
- Department of Chemistry "Giacomo Ciamician", University of Bologna, Via S. Giacomo 11, Bologna I-40126, Italy
| | - Lucia Panzella
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia 21, Naples I-80126, Italy
| | - Alessandra Napolitano
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia 21, Naples I-80126, Italy
| | - Marco d'Ischia
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia 21, Naples I-80126, Italy
| | - Luca Valgimigli
- Department of Chemistry "Giacomo Ciamician", University of Bologna, Via S. Giacomo 11, Bologna I-40126, Italy
| | - Orlando Crescenzi
- Department of Chemical Sciences, University of Naples Federico II, Via Cintia 21, Naples I-80126, Italy
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Bjerke DL, Wu S, Wakamatsu K, Ito S, Wang J, Laughlin T, Hakozaki T. A framework to mitigate the risk of chemical leukoderma: Consumer products. Regul Toxicol Pharmacol 2022; 131:105157. [DOI: 10.1016/j.yrtph.2022.105157] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Accepted: 03/10/2022] [Indexed: 11/16/2022]
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7
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Oxidative Transformations of 3,4-Dihydroxyphenylacetaldehyde Generate Potential Reactive Intermediates as Causative Agents for Its Neurotoxicity. Int J Mol Sci 2021; 22:ijms222111751. [PMID: 34769179 PMCID: PMC8583873 DOI: 10.3390/ijms222111751] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 10/25/2021] [Accepted: 10/27/2021] [Indexed: 11/16/2022] Open
Abstract
Neurogenerative diseases, such as Parkinson’s disease, are associated, not only with the selective loss of dopamine (DA), but also with the accumulation of reactive catechol-aldehyde, 3,4-dihydroxyphenylacetaldehyde (DOPAL), which is formed as the immediate oxidation product of cytoplasmic DA by monoamine oxidase. DOPAL is well known to exhibit toxic effects on neuronal cells. Both catecholic and aldehyde groups seem to be associated with the neurotoxicity of DOPAL. However, the exact cause of toxicity caused by this compound remains unknown. Since the reactivity of DOPAL could be attributed to its immediate oxidation product, DOPAL-quinone, we examined the potential reactions of this toxic metabolite. The oxidation of DOPAL by mushroom tyrosinase at pH 5.3 produced conventional DOPAL-quinone, but oxidation at pH 7.4 produced the tautomeric quinone-methide, which gave rise to 3,4-dihydroxyphenylglycolaldehyde and 3,4-dihydroxybenzaldehyde as products through a series of reactions. When the oxidation reaction was performed in the presence of ascorbic acid, two additional products were detected, which were tentatively identified as the cyclized products, 5,6-dihydroxybenzofuran and 3,5,6-trihydroxybenzofuran. Physiological concentrations of Cu(II) ions could also cause the oxidation of DOPAL to DOPAL-quinone. DOPAL-quinone exhibited reactivity towards the cysteine residues of serum albumin. DOPAL-oligomer, the oxidation product of DOPAL, exhibited pro-oxidant activity oxidizing GSH to GSSG and producing hydrogen peroxide. These results indicate that DOPAL-quinone generates several toxic compounds that could augment the neurotoxicity of DOPAL.
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8
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Detection of Raspberry Ketone after Percutaneous Absorption of Rhododendrol-Containing Cosmetics and Its Mechanism of Formation. COSMETICS 2021. [DOI: 10.3390/cosmetics8040097] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Here, we aimed to elucidate the mechanism of rhododendrol (RD)-induced leukoderma. We investigated the skin permeability of RD in an aqueous solution and in different cosmetic formulations (lotion and emulsion) in an in vitro skin permeation study. The samples were analyzed using high-performance liquid chromatography (HPLC), and an unknown substance appeared on the spectrum. For identification, we analyzed various possible substances, such as raspberry ketone (RK) and rhododendrol quinone, using HPLC and then compared the detected absorption spectra and further verified the matched components using liquid chromatography–mass spectrometry. The unknown substance was found to be RK. To clarify the mechanism of formation of RK, we conducted a 24-h skin permeation test on heat-treated skin. By quantifying the RK in the samples using HPLC, we observed that an enzyme in the skin seemed to be the cause of RK generation and that the components of the emulsion formulation could also be a cause. To investigate the enzyme, we reacted alcohol dehydrogenase with RD and observed that it was one of the converting enzymes. As RK has been reported to be a substance that causes leukoderma, the intraepidermal metabolism of RD to RK may be one of the mechanisms of susceptibility to leukoderma.
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9
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The Oxidation of Equol by Tyrosinase Produces a Unique Di- ortho-Quinone: Possible Implications for Melanocyte Toxicity. Int J Mol Sci 2021; 22:ijms22179145. [PMID: 34502054 PMCID: PMC8431114 DOI: 10.3390/ijms22179145] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Revised: 08/19/2021] [Accepted: 08/23/2021] [Indexed: 12/30/2022] Open
Abstract
Equol (7-hydroxy-3-(4′-hydroxyphenyl)-chroman, EQ), one of the major intestinally derived metabolites of daidzein, the principal isoflavane found in soybeans and most soy foods, has recently attracted increased interest as a health-beneficial compound for estrogen-dependent diseases. However, based on its structure with two p-substituted phenols, this study aimed to examine whether EQ is a substrate for tyrosinase and whether it produces o-quinone metabolites that are highly cytotoxic to melanocyte. First, the tyrosinase-catalyzed oxidation of EQ was performed, which yielded three EQ-quinones. They were identified after being reduced to their corresponding catechols with NaBH4 or L-ascorbic acid. The binding of the EQ-quinones to N-acetyl-L-cysteine (NAC), glutathione (GSH), and bovine serum albumin via their cysteine residues was then examined. NAC and GSH afforded two mono-adducts and one di-adduct, which were identified by NMR and MS analysis. It was also found that EQ was oxidized to EQ-di-quinone in cells expressing human tyrosinase. Finally, it was confirmed that the EQ-oligomer, the EQ oxidation product, exerted potent pro-oxidant activity by oxidizing GSH to the oxidized GSSG and concomitantly producing H2O2. These results suggest that EQ-quinones could be cytotoxic to melanocytes due to their binding to cellular proteins.
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Inoue S, Katayama I, Suzuki T, Tanemura A, Ito S, Abe Y, Sumikawa Y, Yoshikawa M, Suzuki K, Yagami A, Masui Y, Ito A, Matsunaga K. Rhododendrol-induced leukoderma update II: Pathophysiology, mechanisms, risk evaluation, and possible mechanism-based treatments in comparison with vitiligo. J Dermatol 2021; 48:969-978. [PMID: 33951216 PMCID: PMC8360127 DOI: 10.1111/1346-8138.15878] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2020] [Revised: 01/29/2021] [Accepted: 03/18/2021] [Indexed: 12/14/2022]
Abstract
A small proportion of individuals utilizing cosmetics containing rhododendrol developed leukoderma with various pathological conditions, in some cases indistinguishable from vitiligo. In this review, we investigate and evaluate the major considerations for developing rhododendrol‐induced leukoderma based on data from original or review articles published in the literature to provide a wide range of information regarding the pathophysiology, mechanisms, risk evaluation, and possible mechanism‐based treatments. We compile and discuss the latest information, including data related to the cytotoxicity of rhododendrol, cytoprotective functions, and involvement of the immune system, and consider the possibility of novel treatments based on the differences between individual patients and on the mechanism underlying the onset of the condition. Understanding the pathophysiology of rhododendrol‐induced leukoderma helps not only elucidate the mechanisms of non‐segmental vitiligo onset and progression, but also suggests prevention and treatment.
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Affiliation(s)
- Shintaro Inoue
- Department of Cosmetic Health Science, Gifu Pharmaceutical University, Gifu, Japan
| | - Ichiro Katayama
- Department of Pigmentation Research and Therapeutics, Osaka City University, Osaka, Japan
| | - Tamio Suzuki
- Department of Dermatology, Faculty of Medicine, Yamagata University, Yamagata, Japan
| | - Atsushi Tanemura
- Department of Dermatology Course of Integrated Medicine, Osaka University Graduate School of Medicine, Suita, Japan
| | - Shosuke Ito
- Department of Chemistry, Fujita Health University School of Medical Sciences, Toyoake, Japan
| | - Yuko Abe
- Department of Dermatology, Faculty of Medicine, Yamagata University, Yamagata, Japan
| | - Yasuyuki Sumikawa
- Department of Dermatology, Sapporo Medical University School of Medicine, Sapporo, Japan.,Sumikawa Dermatology and Allergy Clinic, Sapporo, Japan
| | - Momoko Yoshikawa
- Department of Dermatology, Sapporo Medical University School of Medicine, Sapporo, Japan
| | - Kayoko Suzuki
- Department of Allergology, Fujita Health University School of Medicine, Nagoya, Japan
| | - Akiko Yagami
- Department of Allergology, Fujita Health University School of Medicine, Nagoya, Japan
| | - Yukiko Masui
- Departent of Dermatology, Nagata Clinic, Niigata, Japan
| | - Akiko Ito
- Departent of Dermatology, Nagata Clinic, Niigata, Japan.,Department of Integrative Medical Science for Allergic Disease, Fujita Health University School of Medicine, Nagoya, Japan
| | - Kayoko Matsunaga
- Department of Integrative Medical Science for Allergic Disease, Fujita Health University School of Medicine, Nagoya, Japan
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Sugumaran M, Umit K, Evans J, Muriph R, Ito S, Wakamatsu K. Oxidative Oligomerization of DBL Catechol, a potential Cytotoxic Compound for Melanocytes, Reveals the Occurrence of Novel Ionic Diels-Alder Type Additions. Int J Mol Sci 2020; 21:ijms21186774. [PMID: 32942764 PMCID: PMC7555913 DOI: 10.3390/ijms21186774] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 09/12/2020] [Accepted: 09/14/2020] [Indexed: 12/16/2022] Open
Abstract
The exposure of human skin to 4-(4-hydroxyphenyl)-2-butanone (raspberry ketone, RK) is known to cause chemical/occupational leukoderma. RK is a carbonyl derivative of 4-(4-hydroxyphenyl)-2-butanol (rhododendrol), a skin whitening agent that was found to cause leukoderma in skin of many consumers. These two phenolic compounds are oxidized by tyrosinase and the resultant products seem to cause cytotoxicity to melanocytes by producing reactive oxygen species and depleting cellular thiols through o-quinone oxidation products. Therefore, it is important to understand the biochemical mechanism of the oxidative transformation of these compounds. Earlier studies indicate that RK is initially oxidized to RK quinone by tyrosinase and subsequently converted to a side chain desaturated catechol called 3,4-dihydroxybenzalacetone (DBL catechol). In the present study, we report the oxidation chemistry of DBL catechol. Using UV–visible spectroscopic studies and liquid chromatography mass spectrometry, we have examined the reaction of DBL catechol with tyrosinase and sodium periodate. Our results indicate that DBL quinone formed in the reaction is extremely reactive and undergoes facile dimerization and trimerization reactions to produce multiple isomeric products by novel ionic Diels-Alder type condensation reactions. The production of a wide variety of complex quinonoid products from such reactions would be potentially more toxic to cells by causing not only oxidative stress, but also melanotoxicity through exhibiting reactions with cellular macromolecules and thiols.
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Affiliation(s)
- Manickam Sugumaran
- Department of Biology, University of Massachusetts, Boston, MA 02125, USA;
- Correspondence: ; Tel.: +1-617-287-6598
| | - Kubra Umit
- Department of Biology, University of Massachusetts, Boston, MA 02125, USA;
| | - Jason Evans
- Department of Chemistry, University of Massachusetts, Boston, MA 02125, USA; (J.E.); (R.M.)
| | - Rachel Muriph
- Department of Chemistry, University of Massachusetts, Boston, MA 02125, USA; (J.E.); (R.M.)
| | - Shosuke Ito
- Department of Chemistry, Fujita Health University School of Medical Sciences, Toyoake, Aichi 451-0052, Japan; (S.I.); (K.W.)
| | - Kazumasa Wakamatsu
- Department of Chemistry, Fujita Health University School of Medical Sciences, Toyoake, Aichi 451-0052, Japan; (S.I.); (K.W.)
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12
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Ito S, Sugumaran M, Wakamatsu K. Chemical Reactivities of ortho-Quinones Produced in Living Organisms: Fate of Quinonoid Products Formed by Tyrosinase and Phenoloxidase Action on Phenols and Catechols. Int J Mol Sci 2020; 21:ijms21176080. [PMID: 32846902 PMCID: PMC7504153 DOI: 10.3390/ijms21176080] [Citation(s) in RCA: 52] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 08/19/2020] [Accepted: 08/20/2020] [Indexed: 12/27/2022] Open
Abstract
Tyrosinase catalyzes the oxidation of phenols and catechols (o-diphenols) to o-quinones. The reactivities of o-quinones thus generated are responsible for oxidative browning of plant products, sclerotization of insect cuticle, defense reaction in arthropods, tunichrome biochemistry in tunicates, production of mussel glue, and most importantly melanin biosynthesis in all organisms. These reactions also form a set of major reactions that are of nonenzymatic origin in nature. In this review, we summarized the chemical fates of o-quinones. Many of the reactions of o-quinones proceed extremely fast with a half-life of less than a second. As a result, the corresponding quinone production can only be detected through rapid scanning spectrophotometry. Michael-1,6-addition with thiols, intramolecular cyclization reaction with side chain amino groups, and the redox regeneration to original catechol represent some of the fast reactions exhibited by o-quinones, while, nucleophilic addition of carboxyl group, alcoholic group, and water are mostly slow reactions. A variety of catecholamines also exhibit side chain desaturation through tautomeric quinone methide formation. Therefore, quinone methide tautomers also play a pivotal role in the fate of numerous o-quinones. Armed with such wide and dangerous reactivity, o-quinones are capable of modifying the structure of important cellular components especially proteins and DNA and causing severe cytotoxicity and carcinogenic effects. The reactivities of different o-quinones involved in these processes along with special emphasis on mechanism of melanogenesis are discussed.
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Affiliation(s)
- Shosuke Ito
- Department of Chemistry, Fujita Health University School of Medical Sciences, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan
- Correspondence: (S.I.); (K.W.); Tel.: +81-562-93-9849 (S.I. & K.W.); Fax: +81-562-93-4595 (S.I. & K.W.)
| | - Manickam Sugumaran
- Department of Biology, University of Massachusetts, Boston, MA 02125, USA;
| | - Kazumasa Wakamatsu
- Department of Chemistry, Fujita Health University School of Medical Sciences, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan
- Correspondence: (S.I.); (K.W.); Tel.: +81-562-93-9849 (S.I. & K.W.); Fax: +81-562-93-4595 (S.I. & K.W.)
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13
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Kim M, Lee CS, Lim KM. Rhododenol Activates Melanocytes and Induces Morphological Alteration at Sub-Cytotoxic Levels. Int J Mol Sci 2019; 20:ijms20225665. [PMID: 31726751 PMCID: PMC6888388 DOI: 10.3390/ijms20225665] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Revised: 11/06/2019] [Accepted: 11/07/2019] [Indexed: 12/11/2022] Open
Abstract
Rhododenol (RD), a whitening cosmetic ingredient, was withdrawn from the market due to RD-induced leukoderma (RIL). While many attempts have been made to clarify the mechanism underlying RIL, RIL has not been fully understood yet. Indeed, affected subjects showed uneven skin pigmentation, but the features are different from vitiligo, a skin hypopigmentary disorder, alluding to events more complex than simple melanocyte cytotoxicity. Here, we discovered that rhododenol treatment reduced the number of melanocytes in a pigmented 3D human skin model, Melanoderm™, confirming the melanocyte toxicity of RD. Of note, melanocytes that survived in the RD treated tissues exhibited altered morphology, such as extended dendrites and increased cell sizes. Consistently with this, sub-cytotoxic level of RD increased cell size and elongated dendrites in B16 melanoma cells. Morphological changes of B16 cells were further confirmed in the immunocytochemistry of treated cells for actin and tubulin. Even more provoking, RD up-regulated the expression of tyrosinase and TRP1 in the survived B16 cells. Evaluation of mRNA expression of cytoskeletal proteins suggests that RD altered the cytoskeletal dynamic favoring cell size expansion and melanosome maturation. Collectively, these results suggest that RD not only induces cytotoxicity in melanocytes but also can lead to a profound perturbation of melanocyte integrity even at sub-cytotoxic levels.
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Affiliation(s)
- Minjeong Kim
- College of Pharmacy, Ewha Womans University, Seoul 03760, Korea;
| | - Chang-Seok Lee
- Department of Beauty and Cosmetic Science, College of Health Science, Eulji University, Seongnam-si 13135, Korea
- Correspondence: (C.-S.L.); (K.-M.L.)
| | - Kyung-Min Lim
- College of Pharmacy, Ewha Womans University, Seoul 03760, Korea;
- Correspondence: (C.-S.L.); (K.-M.L.)
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14
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Darvishi S, Pick H, Lin TE, Zhu Y, Li X, Ho PC, Girault HH, Lesch A. Tape-Stripping Electrochemical Detection of Melanoma. Anal Chem 2019; 91:12900-12908. [DOI: 10.1021/acs.analchem.9b02819] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Affiliation(s)
- Sorour Darvishi
- Laboratory of Physical and Analytical Electrochemistry, École Polytechnique Fédérale de Lausanne (EPFL), Valais Wallis, Rue de l’Industrie 17, CH-1950 Sion, Switzerland
| | - Horst Pick
- Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne, EPFL, CH-1015 Lausanne, Switzerland
| | - Tzu-En Lin
- Institute of Biomedical Engineering, College of Electrical and Computer Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan
| | - Yingdi Zhu
- Laboratory of Physical and Analytical Electrochemistry, École Polytechnique Fédérale de Lausanne (EPFL), Valais Wallis, Rue de l’Industrie 17, CH-1950 Sion, Switzerland
| | - Xiaoyun Li
- Department of Oncology, University of Lausanne, Ch. des Boveresses 155, CH-1015 Epalinges, Switzerland
- Ludwig Institute for Cancer Research, University of Lausanne, Ch. des Boveresses 155, CH-1015 Epalinges, Switzerland
| | - Ping-Chih Ho
- Department of Oncology, University of Lausanne, Ch. des Boveresses 155, CH-1015 Epalinges, Switzerland
- Ludwig Institute for Cancer Research, University of Lausanne, Ch. des Boveresses 155, CH-1015 Epalinges, Switzerland
| | - Hubert H. Girault
- Laboratory of Physical and Analytical Electrochemistry, École Polytechnique Fédérale de Lausanne (EPFL), Valais Wallis, Rue de l’Industrie 17, CH-1950 Sion, Switzerland
| | - Andreas Lesch
- Department of Industrial Chemistry “Toso Montanari”, University of Bologna, Viale del Risorgimento 4, IT-40136 Bologna, Italy
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15
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Goto N, Tsujimoto M, Nagai H, Masaki T, Ito S, Wakamatsu K, Nishigori C. 4-(4-Hydroxyphenyl)-2-butanol (rhododendrol)-induced melanocyte cytotoxicity is enhanced by UVB exposure through generation of oxidative stress. Exp Dermatol 2019; 27:754-762. [PMID: 29630780 DOI: 10.1111/exd.13555] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/18/2018] [Indexed: 02/06/2023]
Abstract
4-(4-Hydroxyphenyl)-2-butanol (rhododendrol, RD), a skin-whitening agent, was reported to cause skin depigmentation in some users, which is attributed to its cytotoxicity to melanocyte. It was reported that cytotoxicity to melanocyte is possibly mediated by oxidative stress in a tyrosinase activity-dependent manner. We examined the effect of UV radiation (UVR) on RD-induced melanocyte cytotoxicity as an additional aggravating factor. UVR enhanced RD-induced cytotoxicity in normal human epidermal melanocytes (NHEMs) via the induction of endoplasmic reticulum (ER) stress. Increased generation of intracellular reactive oxygen species (ROS) was detected. Pretreatment with N-acetyl cysteine (NAC), antioxidant and precursor of glutathione significantly attenuated ER stress-induced cytotoxicity in NHEMs treated with RD and UVR. Increase in cysteinyl-RD-catechol and RD-pheomelanin in NHEMs treated with RD and UVR suggested that, after UVR excitation, RD or RD metabolites are potent ROS-generating substances and that the tendency to produce RD-pheomelanin during melanogenesis amplifies ROS generation in melanocytes. Our results help to elucidate the development mechanisms of RD-induced leukoderma and provide information for innovation of safe skin-whitening compounds.
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Affiliation(s)
- Noriko Goto
- Department of Dermatology, Graduate School of Medicine, Kobe University, Kobe, Japan
| | - Mariko Tsujimoto
- Department of Dermatology, Graduate School of Medicine, Kobe University, Kobe, Japan
| | - Hiroshi Nagai
- Department of Dermatology, Graduate School of Medicine, Kobe University, Kobe, Japan
| | - Taro Masaki
- Department of Dermatology, Graduate School of Medicine, Kobe University, Kobe, Japan
| | - Shosuke Ito
- Department of Chemistry, Fujita Health University School of Health Sciences, Toyake, Aichi, Japan
| | - Kazumasa Wakamatsu
- Department of Chemistry, Fujita Health University School of Health Sciences, Toyake, Aichi, Japan
| | - Chikako Nishigori
- Department of Dermatology, Graduate School of Medicine, Kobe University, Kobe, Japan
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16
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Wakamatsu K, Nakao K, Tanaka H, Kitahori Y, Tanaka Y, Ojika M, Ito S. The Oxidative Pathway to Dopamine-Protein Conjugates and Their Pro-Oxidant Activities: Implications for the Neurodegeneration of Parkinson's Disease. Int J Mol Sci 2019; 20:ijms20102575. [PMID: 31130632 PMCID: PMC6567298 DOI: 10.3390/ijms20102575] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 05/22/2019] [Accepted: 05/23/2019] [Indexed: 12/23/2022] Open
Abstract
Neuromelanin (NM) is a dark brown pigment found in dopaminergic neurons of the substantia nigra (SN) and in norepinephrinergic neurons of the locus coeruleus (LC). Although NM is thought to be involved in the etiology of Parkinson's disease (PD) because its content decreases in neurodegenerative diseases such as PD, details are still unknown. In this study, we characterized the biosynthetic pathway of the oxidation of dopamine (DA) by tyrosinase in the presence of thiol peptides and proteins using spectroscopic and high-performance liquid chromatography (HPLC) methods and we assessed the binding of DA via cysteine residues in proteins by oxidation catalyzed by redox-active metal ions. To examine whether the protein-bound DA conjugates exhibit pro-oxidant activities, we measured the depletion of glutathione (GSH) with the concomitant production of hydrogen peroxide. The results suggest that the fate of protein-bound DA conjugates depends on the structural features of the proteins and that DA-protein conjugates produced in the brain possess pro-oxidant activities, which may cause neurodegeneration due to the generation of reactive oxygen species (ROS) and the depletion of antioxidants.
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Affiliation(s)
- Kazumasa Wakamatsu
- Department of Chemistry, Fujita Health University School of Medical Sciences, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan.
| | - Kenta Nakao
- Department of Chemistry, Fujita Health University School of Medical Sciences, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan.
| | - Hitomi Tanaka
- Department of Chemistry, Fujita Health University School of Medical Sciences, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan.
| | - Yuki Kitahori
- Department of Chemistry, Fujita Health University School of Medical Sciences, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan.
| | - Yui Tanaka
- Department of Chemistry, Fujita Health University School of Medical Sciences, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan.
| | - Makoto Ojika
- Department of Applied Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University, Chikusa-ku, Nagoya 464-8601, Japan.
| | - Shosuke Ito
- Department of Chemistry, Fujita Health University School of Medical Sciences, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan.
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17
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Tsutsumi R, Sugita K, Abe Y, Hozumi Y, Suzuki T, Yamada N, Yoshida Y, Yamamoto O. Leukoderma induced by rhododendrol is different from leukoderma of vitiligo in pathogenesis: A novel comparative morphological study. J Cutan Pathol 2018; 46:123-129. [PMID: 30456919 DOI: 10.1111/cup.13396] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2018] [Revised: 10/29/2018] [Accepted: 11/15/2018] [Indexed: 11/28/2022]
Abstract
BACKGROUND Rhododendrol (rhododenol), an inhibitor of tyrosinase activity, is used as a skin-whitening component. Many cases of leukoderma after the application have been reported, termed rhododenol-induced leukoderma (RIL). The aim of this study was to clarify the pathogenesis of RIL morphologically through comparison with vitiligo. METHODS We examined 14 cases of RIL and 15 cases of vitiligo using routine histopathology and immunohistochemistry. Thirteen cases of RIL, six cases of vitiligo and specimens of the RIL mouse model were evaluated by electron microscopy. RESULTS There were common findings in RIL and vitiligo at the light-microscopic level: (a) vacuolar changes in the dermo-epidermal junction, (b) melanophages in the papillary dermis, (c) perifollicular lymphocyte infiltration, (d) loss or decrease of basal melanin pigment and (e) decrease of melanocytes in the lesions. The ultrastructural observations showed specific findings of RIL: (a) remaining melanocytes in depigmented lesions, (b) inhomogeneous melanization in melanocytes and (c) degenerated melanosomes in melanocytes. Some of the findings were observed in a RIL mouse model. Furthermore, it is notable that cell organelles of melanocytes were intact in our RIL cases. CONCLUSION Morphological changes of RIL targeting melanosomes in melanocytes without degeneration of organelles reflect the reversible clinical course of most cases.
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Affiliation(s)
- Reiko Tsutsumi
- Division of Dermatology, Department of Medicine of Sensory and Motor Organs, Faculty of Medicine, Tottori University, Yonago, Japan
| | - Kazunari Sugita
- Division of Dermatology, Department of Medicine of Sensory and Motor Organs, Faculty of Medicine, Tottori University, Yonago, Japan
| | - Yuko Abe
- Department of Dermatology, Yamagata University Faculty of Medicine, Yamagata, Japan
| | - Yutaka Hozumi
- Department of Dermatology, Yamagata University Faculty of Medicine, Yamagata, Japan
| | - Tamio Suzuki
- Department of Dermatology, Yamagata University Faculty of Medicine, Yamagata, Japan
| | - Nanako Yamada
- Division of Dermatology, Department of Medicine of Sensory and Motor Organs, Faculty of Medicine, Tottori University, Yonago, Japan
| | - Yuichi Yoshida
- Division of Dermatology, Department of Medicine of Sensory and Motor Organs, Faculty of Medicine, Tottori University, Yonago, Japan
| | - Osamu Yamamoto
- Division of Dermatology, Department of Medicine of Sensory and Motor Organs, Faculty of Medicine, Tottori University, Yonago, Japan
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18
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Kim DJ, Choi K, Rho HS. Synthesis and Biological Evaluation of Amide-Type Phytoalexins as Depigmenting Agents. B KOREAN CHEM SOC 2018. [DOI: 10.1002/bkcs.11589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Dong Jae Kim
- Department of Chemical and Material Engineering, Beauty Science Research Center; The University of Suwon; Hwaseong 18323 Republic of Korea
| | - Kyungoh Choi
- Department of Chemical and Material Engineering, Beauty Science Research Center; The University of Suwon; Hwaseong 18323 Republic of Korea
| | - Ho Sik Rho
- Department of Chemical and Material Engineering, Beauty Science Research Center; The University of Suwon; Hwaseong 18323 Republic of Korea
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19
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Ito S, Agata M, Okochi K, Wakamatsu K. The potent pro-oxidant activity of rhododendrol-eumelanin is enhanced by ultraviolet A radiation. Pigment Cell Melanoma Res 2018; 31:523-528. [PMID: 29474003 DOI: 10.1111/pcmr.12696] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 02/09/2018] [Indexed: 12/19/2022]
Abstract
RS-4-(4-hydroxyphenyl)-2-butanol (rhododendrol, RD), a skin-whitening agent, is known to induce leukoderma in some consumers. To explore the mechanism underlying this effect, we previously showed that the oxidation of RD with mushroom or human tyrosinase produces cytotoxic quinone oxidation products and RD-eumelanin exerts a potent pro-oxidant activity. Cellular antioxidants were oxidized by RD-eumelanin with a concomitant production of H2 O2 . In this study, we examined whether this pro-oxidant activity of RD-eumelanin is enhanced by ultraviolet A (UVA) radiation because most RD-induced leukoderma lesions are found in sun-exposed areas. Exposure to a physiological level of UVA (3.5 mW/cm2 ) induced a two to fourfold increase in the rates of oxidation of GSH, cysteine, ascorbic acid, and NADH. This oxidation was oxygen-dependent and was accompanied by the production of H2 O2 . These results suggest that RD-eumelanin is cytotoxic to melanocytes through its potent pro-oxidant activity that is enhanced by UVA radiation.
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Affiliation(s)
- Shosuke Ito
- Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Japan
| | - Misa Agata
- Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Japan
| | - Kotono Okochi
- Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Japan
| | - Kazumasa Wakamatsu
- Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Japan
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20
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Ito S, Wakamatsu K. Biochemical Mechanism of Rhododendrol-Induced Leukoderma. Int J Mol Sci 2018; 19:E552. [PMID: 29439519 PMCID: PMC5855774 DOI: 10.3390/ijms19020552] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Revised: 02/09/2018] [Accepted: 02/10/2018] [Indexed: 01/12/2023] Open
Abstract
RS-4-(4-hydroxyphenyl)-2-butanol (rhododendrol (RD))-a skin-whitening ingredient-was reported to induce leukoderma in some consumers. We have examined the biochemical basis of the RD-induced leukoderma by elucidating the metabolic fate of RD in the course of tyrosinase-catalyzed oxidation. We found that the oxidation of racemic RD by mushroom tyrosinase rapidly produces RD-quinone, which gives rise to secondary quinone products. Subsequently, we confirmed that human tyrosinase is able to oxidize both enantiomers of RD. We then showed that B16 cells exposed to RD produce high levels of RD-pheomelanin and protein-SH adducts of RD-quinone. Our recent studies showed that RD-eumelanin-an oxidation product of RD-exhibits a potent pro-oxidant activity that is enhanced by ultraviolet-A radiation. In this review, we summarize our biochemical findings on the tyrosinase-dependent metabolism of RD and related studies by other research groups. The results suggest two major mechanisms of cytotoxicity to melanocytes. One is the cytotoxicity of RD-quinone through binding with sulfhydryl proteins that leads to the inactivation of sulfhydryl enzymes and protein denaturation that leads to endoplasmic reticulum stress. The other mechanism is the pro-oxidant activity of RD-derived melanins that leads to oxidative stress resulting from the depletion of antioxidants and the generation of reactive oxygen radicals.
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Affiliation(s)
- Shosuke Ito
- Department of Chemistry, Fujita Health University School of Health Sciences, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan.
| | - Kazumasa Wakamatsu
- Department of Chemistry, Fujita Health University School of Health Sciences, 1-98 Dengakugakubo, Kutsukake-cho, Toyoake, Aichi 470-1192, Japan.
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21
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Ito S, Okura M, Wakamatsu K, Yamashita T. The potent pro-oxidant activity of rhododendrol-eumelanin induces cysteine depletion in B16 melanoma cells. Pigment Cell Melanoma Res 2017; 30:63-67. [PMID: 28132436 DOI: 10.1111/pcmr.12556] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 10/17/2016] [Accepted: 10/26/2016] [Indexed: 11/27/2022]
Abstract
RS-4-(4-Hydroxyphenyl)-2-butanol (rhododendrol, RD), a skin-whitening agent, is known to induce leukoderma in some people. To explore the mechanism underlying this effect, we previously showed that the oxidation of RD with mushroom or human tyrosinase produces cytotoxic quinone oxidation products. We then examined the metabolism of RD in B16F1 melanoma cells in vitro and detected RD-pheomelanin and RD-quinone bound to non-protein and protein thiols. In this study, we examined the changes in glutathione (GSH) and cysteine in B16 cells exposed to RD for up to 24 h. We find that the levels of cysteine, but not those of GSH, decrease during 0.5- to 3-h exposure, due to oxidation to cystine. This pro-oxidant activity was then examined using synthetic melanins. Indeed, we find that RD-eumelanin exerts a pro-oxidant activity as potent as Dopa-pheomelanin. GSH, cysteine, ascorbic acid, and NADH were oxidized by RD-eumelanin with a concomitant production of H2 O2 . We propose that RD-eumelanin induces cytotoxicity through its potent pro-oxidant activity.
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Affiliation(s)
- Shosuke Ito
- Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Japan
| | - Masae Okura
- Department of Dermatology, Sapporo Medical University School of Medicine, Sapporo, Japan
| | - Kazumasa Wakamatsu
- Department of Chemistry, Fujita Health University School of Health Sciences, Toyoake, Japan
| | - Toshiharu Yamashita
- Department of Dermatology, Sapporo Medical University School of Medicine, Sapporo, Japan
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22
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Hagiwara K, Okura M, Sumikawa Y, Hida T, Kuno A, Horio Y, Yamashita T. Biochemical effects of the flavanol-rich lychee fruit extract on the melanin biosynthesis and reactive oxygen species. J Dermatol 2017; 43:1174-1183. [PMID: 26970333 DOI: 10.1111/1346-8138.13326] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 01/11/2016] [Indexed: 12/11/2022]
Abstract
An ingredient of fruit polyphenol, resveratrol, is known to have an inhibitory effect on melanogenesis. In order to examine the functional differences between resveratrol and other fruit polyphenols, we compared biochemical effects of a resveratrol-free polyphenol, flavanol-rich lychee fruit extract (FRLFE), with other phenolic compounds including resveratrol. FRLFE as well as hydroquinone and resveratrol suppressed growth of B16F1 melanoma cells more significantly than rhododendrol or arbutin. Resveratrol suppressed mushroom tyrosinase at the lowest concentration (23.0 μmol/L) among the compounds tested. FRLFE and hydroquinone suppressed tyrosinase at almost the same concentration (half maximal inhibitory concentration [IC50 ], 83.5 and 94.6 μmol/L, respectively), which was higher than rhododendrol, ascorbic acid and arbutin (IC50 , 245, 345 and 421 μmol/L, respectively). Western blot analysis revealed that although resveratrol decreased expressions of tyrosinase and tyrosinase-related protein 1, FRLFE did not affect their expressions. Both FRLFE and resveratrol suppressed antimycin A-mediated reactive oxygen species (ROS) production in melanocytic cells. Resveratrol-mediated ROS suppression was inhibited by nicotinamide, a SIRT1 inhibitor. However, FRLFE-mediated suppression was not affected by nicotinamide. Moreover, FRLFE directly decreased superoxide in vitro, as detected by superoxide dismutase-like scavenging activity assay. These results suggest that FRLFE can protect melanocytes from cytotoxicity caused by an excess amount of melanin and ROS in a different manner from resveratrol.
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Affiliation(s)
- Kazuya Hagiwara
- Department of Dermatology, and Pharmacology, Sapporo Medical University School of Medicine, Sapporo, Japan
| | - Masae Okura
- Department of Dermatology, and Pharmacology, Sapporo Medical University School of Medicine, Sapporo, Japan
| | - Yasuyuki Sumikawa
- Department of Dermatology, and Pharmacology, Sapporo Medical University School of Medicine, Sapporo, Japan
| | - Tokimasa Hida
- Department of Dermatology, and Pharmacology, Sapporo Medical University School of Medicine, Sapporo, Japan
| | - Atsushi Kuno
- Department of Pharmacology, Sapporo Medical University School of Medicine, Sapporo, Japan
| | - Yoshiyuki Horio
- Department of Pharmacology, Sapporo Medical University School of Medicine, Sapporo, Japan
| | - Toshiharu Yamashita
- Department of Dermatology, and Pharmacology, Sapporo Medical University School of Medicine, Sapporo, Japan.
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23
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Ito S, Hinoshita M, Suzuki E, Ojika M, Wakamatsu K. Tyrosinase-Catalyzed Oxidation of the Leukoderma-Inducing Agent Raspberry Ketone Produces (E)-4-(3-Oxo-1-butenyl)-1,2-benzoquinone: Implications for Melanocyte Toxicity. Chem Res Toxicol 2017; 30:859-868. [PMID: 28219012 DOI: 10.1021/acs.chemrestox.7b00006] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The exposure of human skin to 4-(4-hydroxyphenyl)-2-butanone (raspberry ketone, RK) is known to cause chemical/occupational leukoderma. RK has a structure closely related to 4-(4-hydroxyphenyl)-2-butanol (rhododendrol), a skin whitening agent that was found to cause leukoderma in the skin of consumers in 2013. Rhododendrol is a good substrate for tyrosinase and causes a tyrosinase-dependent cytotoxicity to melanocytes, cells that are responsible for skin pigmentation. Therefore, it is expected that RK exerts its cytotoxicity to melanocytes through the tyrosinase-catalyzed oxidation to cytotoxic o-quinones. The results of this study demonstrate that the oxidation of RK by mushroom tyrosinase rapidly produces 4-(3-oxobutyl)-1,2-benzoquinone (RK-quinone), which is converted within 10-20 min to (E)-4-(3-oxo-1-butenyl)-1,2-benzoquinone (DBL-quinone). These quinones were identified as their corresponding catechols after reduction by ascorbic acid. RK-quinone and DBL-quinone quantitatively bind to the small thiol N-acetyl-l-cysteine to form thiol adducts and can also bind to the thiol protein bovine serum albumin through its cysteinyl residue. DBL-quinone is more reactive than RK-quinone, as judged by their half-lives (6.2 min vs 10.5 min, respectively), and decays rapidly to form an oligomeric pigment (RK-oligomer). The RK-oligomer can oxidize GSH to GSSG with a concomitant production of hydrogen peroxide, indicating its pro-oxidant activity, similar to that of the RD-oligomer. These results suggest that RK is cytotoxic to melanocytes through the binding of RK-derived quinones to thiol proteins and the pro-oxidant activity of the RK-oligomer.
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Affiliation(s)
- Shosuke Ito
- Department of Chemistry, Fujita Health University School of Health Sciences , Toyoake, Aichi 470-1192, Japan
| | - Maki Hinoshita
- Department of Chemistry, Fujita Health University School of Health Sciences , Toyoake, Aichi 470-1192, Japan
| | - Erina Suzuki
- Department of Chemistry, Fujita Health University School of Health Sciences , Toyoake, Aichi 470-1192, Japan
| | - Makoto Ojika
- Department of Applied Molecular Biosciences, Graduate School of Bioagricultural Sciences, Nagoya University , Nagoya 464-8601, Japan
| | - Kazumasa Wakamatsu
- Department of Chemistry, Fujita Health University School of Health Sciences , Toyoake, Aichi 470-1192, Japan
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24
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Ito S, Kolbe L. Tyrosine peptides provide a color palette upon tyrosinase oxidation: nanosize does matter. Pigment Cell Melanoma Res 2016; 30:4-5. [PMID: 27704681 DOI: 10.1111/pcmr.12540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2016] [Accepted: 09/22/2016] [Indexed: 11/29/2022]
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25
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Kondo M, Kawabata K, Sato K, Yamaguchi S, Hachiya A, Takahashi Y, Inoue S. Glutathione maintenance is crucial for survival of melanocytes after exposure to rhododendrol. Pigment Cell Melanoma Res 2016; 29:541-9. [DOI: 10.1111/pcmr.12494] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Accepted: 04/21/2016] [Indexed: 11/30/2022]
Affiliation(s)
- Masatoshi Kondo
- Biological Science Research Kao Corporation Odawara Kanagawa Japan
| | - Keigo Kawabata
- Biological Science Research Kao Corporation Odawara Kanagawa Japan
| | - Kohji Sato
- Analytical Science Research Kao Corporation Odawara Kanagawa Japan
| | - Sayuri Yamaguchi
- Biological Science Research Kao Corporation Odawara Kanagawa Japan
| | - Akira Hachiya
- Biological Science Research Kao Corporation Odawara Kanagawa Japan
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26
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Choi YJ, Kwon SS, Rho HS, Kim YJ, Lee JH, Oh SG, Kim JM. Evaluation of Kojyl Benzoate Derivatives as Potential Depigmenting Agents in Mouse B16/F1 Melanoma Cells. B KOREAN CHEM SOC 2016. [DOI: 10.1002/bkcs.10772] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Yeong Jin Choi
- Functional Material Laboratory, Department of Chemistry; Sungkyunkwan University; Suwon 16414 Republic of Korea
| | - Sun Sang Kwon
- Functional Material Laboratory, Department of Chemistry; Sungkyunkwan University; Suwon 16414 Republic of Korea
| | - Ho Sik Rho
- R & D Center; AmorePacific Corporation; Yongin 17074 Republic of Korea
| | - Yong-Jin Kim
- R & D Center; AmorePacific Corporation; Yongin 17074 Republic of Korea
| | - John Hwan Lee
- Department of Chemical Engineering; Hanyang University; Seoul 04763 Republic of Korea
| | - Seong-Geun Oh
- Department of Chemical Engineering; Hanyang University; Seoul 04763 Republic of Korea
| | - Ji Man Kim
- Functional Material Laboratory, Department of Chemistry; Sungkyunkwan University; Suwon 16414 Republic of Korea
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Arase N, Yang L, Tanemura A, Yang F, Suenaga T, Arase H, Katayama I. The effect of rhododendrol inhibition of NF-κB on melanocytes in the presence of tyrosinase. J Dermatol Sci 2016; 83:157-9. [PMID: 27174091 DOI: 10.1016/j.jdermsci.2016.05.002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Revised: 04/03/2016] [Accepted: 05/02/2016] [Indexed: 11/25/2022]
Affiliation(s)
- Noriko Arase
- Department of Dermatology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan; Department of Immunochemistry, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan.
| | - Lingli Yang
- Department of Dermatology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Atsushi Tanemura
- Department of Dermatology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Fei Yang
- Department of Dermatology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Tadahiro Suenaga
- Department of Immunochemistry, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan; Laboratory of Immunochemistry, WPI Immunology Frontier Research Center, Osaka University, Suita, Osaka, Japan
| | - Hisashi Arase
- Department of Immunochemistry, Research Institute for Microbial Diseases, Osaka University, Suita, Osaka, Japan; Laboratory of Immunochemistry, WPI Immunology Frontier Research Center, Osaka University, Suita, Osaka, Japan
| | - Ichiro Katayama
- Department of Dermatology, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
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Kim M, Baek HS, Lee M, Park H, Shin SS, Choi DW, Lim KM. Rhododenol and raspberry ketone impair the normal proliferation of melanocytes through reactive oxygen species-dependent activation of GADD45. Toxicol In Vitro 2016; 32:339-46. [PMID: 26867644 DOI: 10.1016/j.tiv.2016.02.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2015] [Revised: 12/11/2015] [Accepted: 02/06/2016] [Indexed: 11/28/2022]
Abstract
Rhododenol or rhododendrol (RD, 4-(4-hydroxyphenyl)-2-butanol) occurs naturally in many plants along with raspberry ketone (RK, 4-(4-hydroxyphenyl)-2-butanone), a ketone derivative, which include Nikko maple tree (Acer nikoense) and white birch (Betula platyphylla). De-pigmenting activity of RD was discovered and it was used as a brightening ingredient for the skin whitening cosmetics. Recently, cosmetics containing RD were withdrawn from the market because a number of consumers developed leukoderma, inflammation and erythema on their face, neck and hands. Here, we explored the mechanism underlying the toxicity of RD and RK against melanocytes using B16F10 murine melanoma cells and human primary epidermal melanocytes. Treatment with RD or RK resulted in the decreased cell viability in a dose-dependent manner which appeared from cell growth arrest. Consistently, ROS generation was significantly increased by RD or RK as determined by DCF-enhanced fluorescence. An antioxidant enzyme, glutathione peroxidase was depleted as well. In line with ROS generation, oxidative damages and the arrest of normal cell proliferation, GADD genes (Growth Arrest and DNA Damage) that include GADD45 and GADD153, were significantly up-regulated. Prevention of ROS generation with an anti-oxidant, N-acetylcysteine (NAC) significantly rescued RD and RK-suppressed melanocyte proliferation. Consistently, up-regulation of GADD45 and GADD153 was significantly attenuated by NAC, suggesting that increased ROS and the resultant growth arrest of melanocytes may contribute to RD and RK-induced leukoderma.
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Affiliation(s)
- Minjeong Kim
- College of Pharmacy, Ewha Womans University, Seoul, Republic of Korea
| | - Heung Soo Baek
- AmorePacific Corporation R&D Center, Yongin, Gyeonggi-do 446-729, Republic of Korea
| | - Miri Lee
- College of Pharmacy, Ewha Womans University, Seoul, Republic of Korea
| | - Hyeonji Park
- College of Pharmacy, Ewha Womans University, Seoul, Republic of Korea
| | - Song Seok Shin
- AmorePacific Corporation R&D Center, Yongin, Gyeonggi-do 446-729, Republic of Korea
| | - Dal Woong Choi
- Department of Public Health Science, Graduate School, Korea University, Seoul, Republic of Korea.
| | - Kyung-Min Lim
- College of Pharmacy, Ewha Womans University, Seoul, Republic of Korea.
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29
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Okubo A, Yasuhira S, Shibazaki M, Takahashi K, Akasaka T, Masuda T, Maesawa C. NAD(P)H dehydrogenase, quinone 1 (NQO1), protects melanin-producing cells from cytotoxicity of rhododendrol. Pigment Cell Melanoma Res 2016; 29:309-16. [PMID: 26847926 DOI: 10.1111/pcmr.12461] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Accepted: 01/26/2016] [Indexed: 11/30/2022]
Abstract
Rhododendrol (RD) is a potent tyrosinase inhibitor that is metabolized to RD-quinone by tyrosinase, which may underlie the cytotoxicity of RD and leukoderma of the skin that may result. We have examined how forced expression of the NAD(P)H quinone dehydrogenase, quinone 1 (NQO1), a major quinone-reducing enzyme in cytosol, affects the survival of RD-treated cells. We found that treatment of the mouse melanoma cell line B16BL6 or normal human melanocytes with carnosic acid, a transcriptional inducer of the NQO1 gene, notably suppressed the cell killing effect of RD. This effect was mostly abolished by ES936, a highly specific NQO1 inhibitor. Moreover, conditional overexpression of the human NQO1 transgene in B16BL6 led to an expression-dependent increase of cell survival after RD treatment. Our results suggest that NQO1 attenuates the cytotoxicity of RD and/or its metabolites.
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Affiliation(s)
- Ayaka Okubo
- Department of Tumor Biology, Institute of Biomedical Sciences, Iwate Medical University, Shiwa-gun, Japan
| | - Shinji Yasuhira
- Department of Tumor Biology, Institute of Biomedical Sciences, Iwate Medical University, Shiwa-gun, Japan
| | - Masahiko Shibazaki
- Department of Tumor Biology, Institute of Biomedical Sciences, Iwate Medical University, Shiwa-gun, Japan
| | - Kazuhiro Takahashi
- Department of Dermatology, School of Medicine, Iwate Medical University, Morioka, Japan
| | - Toshihide Akasaka
- Department of Dermatology, School of Medicine, Iwate Medical University, Morioka, Japan
| | - Tomoyuki Masuda
- Department of Pathology, School of Medicine, Iwate Medical University, Shiwa-gun, Japan
| | - Chihaya Maesawa
- Department of Tumor Biology, Institute of Biomedical Sciences, Iwate Medical University, Shiwa-gun, Japan
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30
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Action of ellagic acid on the melanin biosynthesis pathway. J Dermatol Sci 2016; 82:115-22. [PMID: 26899308 DOI: 10.1016/j.jdermsci.2016.02.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Revised: 01/07/2016] [Accepted: 02/10/2016] [Indexed: 11/23/2022]
Abstract
BACKGROUND Tyrosinase is an enzyme involved in the first steps of the melanogenesis process. It catalyzes the hydroxylation of monophenols to o-diphenols and the oxidation of the latter to o-quinones. Ellagic acid (EA) is a phenolic compound which has been described as a tyrosinase inhibitor and is used in the cosmetic industry as a whitening agent. However, it has hydroxyl groups in ortho position and could act as a substrate rather than inhibitor. This aspect should be taken into consideration when using this compound as a cosmetic ingredient due to the reactive character of o-quinones. OBJECTIVE To determine whether ellagic acid is a substrate or an inhibitor of tyrosinase, to characterize it kinetically and interpret its role in the melanogenesis process. METHODS UV-vis spectrophotometry was used to follow the action of tyrosinase on typical substrates and ellagic acid. A chronometric method was chosen for the kinetic characterization of ellagic acid. RESULTS Ellagic acid is not an inhibitor per se but an alternative substrate of tyrosinase. It is oxidized by the enzyme to an unstable o-quinone. Its kinetic characterization provided low Michaelis and catalytic constants (KM(EA)=138±13μM and kcat(EA)=0.47±0.02s(-1)). Furthermore, ellagic acid, which is a powerful antioxidant, may chemically reduce the o-quinones (o-dopaquinone) and semiquinones, in this way inhibiting the melanogenesis. CONCLUSION Ellagic acid is oxidized by tyrosinase, producing reactive o-quinones. As an antioxidant it can inhibit the melanogenesis process. This first aspect should be taken into consideration in its application as a cosmetic ingredient due to the toxicity of o-quinones and its ability to modify the redox status of the cell.
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The Metabolic Fate of ortho-Quinones Derived from Catecholamine Metabolites. Int J Mol Sci 2016; 17:ijms17020164. [PMID: 26828480 PMCID: PMC4783898 DOI: 10.3390/ijms17020164] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 01/16/2016] [Accepted: 01/22/2016] [Indexed: 01/18/2023] Open
Abstract
ortho-Quinones are produced in vivo through the oxidation of catecholic substrates by enzymes such as tyrosinase or by transition metal ions. Neuromelanin, a dark pigment present in the substantia nigra and locus coeruleus of the brain, is produced from dopamine (DA) and norepinephrine (NE) via an interaction with cysteine, but it also incorporates their alcoholic and acidic metabolites. In this study we examined the metabolic fate of ortho-quinones derived from the catecholamine metabolites, 3,4-dihydroxyphenylethanol (DOPE), 3,4-dihydroxyphenylethylene glycol (DOPEG), 3,4-dihydroxyphenylacetic acid (DOPAC) and 3,4-dihydroxyphenylmandelic acid (DOMA). The oxidation of catecholic substrates by mushroom tyrosinase was followed by UV-visible spectrophotometry. HPLC analysis after reduction with NaBH4 or ascorbic acid enabled measurement of the half-lives of ortho-quinones and the identification of their reaction products. Spectrophotometric examination showed that the ortho-quinones initially formed underwent extensive degradation at pH 6.8. HPLC analysis showed that DOPE-quinone and DOPEG-quinone degraded with half-lives of 15 and 30 min at pH 6.8, respectively, and >100 min at pH 5.3. The major product from DOPE-quinone was DOPEG which was produced through the addition of a water molecule to the quinone methide intermediate. DOPEG-quinone yielded a ketone, 2-oxo-DOPE, through the quinone methide intermediate. DOPAC-quinone and DOMA-quinone degraded immediately with decarboxylation of the ortho-quinone intermediates to form 3,4-dihydroxybenzylalcohol (DHBAlc) and 3,4-dihydroxybenzaldehyde (DHBAld), respectively. DHBAlc-quinone was converted to DHBAld with a half-life of 9 min, while DHBAld-quinone degraded rapidly with a half-life of 3 min. This study confirmed the fact that ortho-quinones from DOPE, DOPEG, DOPAC and DOMA are converted to quinone methide tautomers as common intermediates, through proton rearrangement or decarboxylation. The unstable quinone methides afford stable alcoholic or carbonyl products.
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Rhododenol-induced leukoderma in a mouse model mimicking Japanese skin. J Dermatol Sci 2016; 81:35-43. [DOI: 10.1016/j.jdermsci.2015.10.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Revised: 09/29/2015] [Accepted: 10/20/2015] [Indexed: 11/20/2022]
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Okura M, Yamashita T, Ishii-Osai Y, Yoshikawa M, Sumikawa Y, Wakamatsu K, Ito S. Effects of rhododendrol and its metabolic products on melanocytic cell growth. J Dermatol Sci 2015; 80:142-9. [DOI: 10.1016/j.jdermsci.2015.07.010] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Revised: 06/10/2015] [Accepted: 07/21/2015] [Indexed: 11/26/2022]
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A convenient screening method to differentiate phenolic skin whitening tyrosinase inhibitors from leukoderma-inducing phenols. J Dermatol Sci 2015; 80:18-24. [PMID: 26228294 DOI: 10.1016/j.jdermsci.2015.07.007] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Revised: 07/01/2015] [Accepted: 07/16/2015] [Indexed: 10/23/2022]
Abstract
BACKGROUND Tyrosinase is able to oxidize a great number of phenols and catechols to form ortho-quinones. Ortho-quinones are highly reactive compounds that exert cytotoxicity through binding with thiol enzymes and the production of reactive oxygen species. Certain phenolic (and catecholic) compounds are known to induce contact/occupational leukoderma through activation to ortho-quinones. OBJECTIVE We report a convenient screening method to follow the oxidation of those leukoderma-inducing phenols by mushroom tyrosinase. METHODS Oxidation of phenolic compounds by mushroom tyrosinase was followed periodically by UV-vis spectrophotometry. The production of ortho-quinones were confirmed by their absorptions around 400-420 nm. HPLC analysis after reduction with NaBH4 detected the corresponding catechols. RESULTS Leukoderma-inducing phenols, rhododendrol, raspberry ketone, 4-methoxyphenol, 4-benzyloxyphenol, 4-tert-butylphenol, and 4-tert-butylcatechol, were readily oxidized by mushroom tyrosinase to form ortho-quinones. On the other hand, phenolic skin whitening tyrosinase inhibitors, ellagic acid, 4-n-butylresorcinol, potassium 4-methoxysalicylate, and 2,2'-dihydroxy-5,5'-di-n-propylbiphenyl, were not oxidized by mushroom tyrosinase, while arbutin was only slowly oxidized. CONCLUSION This study has provided a convenient screening method to differentiate phenolic skin whitening tyrosinase inhibitors from leukoderma-inducing phenols. A common chemical feature of the latter group of compounds is that they are readily oxidized by tyrosinase to form reactive ortho-quinone species. The present results point out the necessity that tyrosinase inhibitors should also be examined as substrates if they are phenolic compounds.
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