Skin-depigmenting Agent Research Articles

519 Design of a new molecule proven to be safe and effective for topical depigmenting and antiaging method

Skin hyperpigmentation is a biological process that results in an excess production of melanin. Tyrosinase inhibition is an effective approach to this condition, although inhibitors reported in the literature lack clinical efficacy or show toxic effects. Chalcone derivatives are well known tyrosinase inhibitors but insoluble in aqueous phase limiting its use in final product formulations. The aim of this study is to develop a new chalcone-related molecule that is safe and effective as a skin depigmenting and antiaging agent.

Arbutin as a Skin Depigmenting Agent with Antimelanogenic and Antioxidant Properties.

Arbutin is a compound of hydroquinone and D-glucose, and it has been over 30 years since there have been serious studies on the skin lightening action of this substance. In the meantime, there have been debates and validation studies about the mechanism of action of this substance as well as its skin lightening efficacy and safety. Several analogs or derivatives of arbutin have been developed and studied for their melanin synthesis inhibitory action. Formulations have been developed to improve the stability, transdermal delivery, and release of arbutin, and device usage to promote skin absorption has been developed. Substances that inhibit melanin synthesis synergistically with arbutin have been explored. The skin lightening efficacy of arbutin alone or in combination with other active ingredients has been clinically evaluated. Combined therapy with arbutin and laser could give enhanced depigmenting efficacy. The use of arbutin causes dermatitis rarely, and caution is recommended for the use of arbutin-containing products, especially from the viewpoint that hydroquinone may be generated during product use. Studies on the antioxidant properties of arbutin are emerging, and these antioxidant properties are proposed to contribute to the skin depigmenting action of arbutin. It is hoped that this review will help to understand the pros and cons of arbutin as a cosmetic ingredient, and will lead to future research directions for developing advanced skin lightening and protecting cosmetic products.

A mouse model of vitiligo induced by monobenzone

The paucity of vitiligo animal models limits the understanding of vitiligo pathogenesis and the development of therapies for the skin disorder. In this study, we developed a new mouse model of vitiligo by topically applying the skin-depigmenting agent monobenzone on mice. We demonstrated that monobenzone-induced skin depigmentation on the non-exposed sites and that the severity of lesions depended on drug dosage. The result of the histological examination of the depigmented skin indicated loss of epidermal melanocytes and perilesional accumulation of CD8⁺ T cells. Furthermore, the monobenzone-induced depigmentation of the Rag1 gene knockout did not appear on the non-exposed sites, supporting the involvement of infiltrating CD8⁺ T cells in melanocyte destruction. Resemblance in histological characteristics and pathogenesis between monobenzone-induced depigmentation and active human vitiligo suggests good potential of our mouse model for use in vitiligo research.

Monobenzone‐induced depigmentation: from enzymatic blockade to autoimmunity

Autoimmune side-effects such as vitiligo regularly occur during melanoma immunotherapy. As vitiligo development is associated with a superior prognosis, the active induction of vitiligo in melanoma patients can be a useful tactic. The potent skin-depigmenting agent monobenzone can be used successfully for this purpose. However, until recently, the mechanism of action behind monobenzone-induced skin depigmentation was unclear. Lately, the mechanistic basis for the augmented immunogenicity of monobenzone-exposed pigmented cells has been unveiled, and their active role in the induction of autoimmune T-cell-mediated vitiligo has become apparent. Here, we provide an immunological framework in which we condense this knowledge to an integrated theory of the generation of monobenzone-induced vitiligo.

Effective Melanoma Immunotherapy in Mice by the Skin-Depigmenting Agent Monobenzone and the Adjuvants Imiquimod and CpG

BackgroundPresently melanoma still lacks adequate treatment options for metastatic disease. While melanoma is exceptionally challenging to standard regimens, it is suited for treatment with immunotherapy based on its immunogenicity. Since treatment-related skin depigmentation is considered a favourable prognostic sign during melanoma intervention, we here aimed at the reverse approach of directly inducing vitiligo as a shortcut to effective anti-melanoma immunity.Methodology and Principal FindingsWe developed an effective and simple to use form of immunotherapy by combining the topical skin-bleaching agent monobenzone with immune-stimulatory imiquimod cream and cytosine-guanine oligodeoxynucleotides (CpG) injections (MIC therapy). This powerful new approach promptly induced a melanoma antigen-specific immune response, which abolished subcutaneous B16.F10 melanoma growth in up to 85% of C57BL/6 mice. Importantly, this regimen induced over 100 days of tumor-free survival in up to 60% of the mice, and forcefully suppressed tumor growth upon re-challenge either 65- or 165 days after MIC treatment cessation.ConclusionsMIC therapy is effective in eradicating melanoma, by vigilantly incorporating NK-, B- and T cells in its therapeutic effect. Based on these results, the MIC regimen presents a high-yield, low-cost and simple therapy, readily applicable in the clinic.

Inhibitory effects of 1,3-thiazine derivatives on melanogenesis

Abstract Objectives The aim of this study was to identify a novel skin-depigmenting agent from synthetic 1,3-thiazine derivatives. Methods We investigated the inhibitory effects of six kinds of 1,3-thiazine derivative on melanogenesis by examining their effects on tyrosinase activity and melanin biosynthesis in melan-a cells and the zebrafish model. Key findings Of the six compounds, 4-hydroxy-2,6-dimethyl-5,6-dihydro-4H-1,3-thiazine (TZ-6) had the strongest anti-melanogenic effects in cultured melan-a cells (30.4% inhibition at 100 μM). In addition, TZ-6 exhibited an inhibitory effect on mushroom and cellular tyrosinase. Based on the results of Western blotting, TZ-6 reduced the expression of tyrosinase at 100 mM. Additionally, TZ-6 reduced body pigmentation and inhibited tyrosinase activity in the zebrafish model. Conclusions The results have provided useful information for the development of a skin whitening agent.

Inhibitory effects of 1,3-thiazine derivatives on melanogenesis

The aim of this study was to identify a novel skin-depigmenting agent from synthetic 1,3-thiazine derivatives. We investigated the inhibitory effects of six kinds of 1,3-thiazine derivative on melanogenesis by examining their effects on tyrosinase activity and melanin biosynthesis in melan-a cells and the zebrafish model. Of the six compounds, 4-hydroxy-2,6-dimethyl-5,6-dihydro-4H-1,3-thiazine (TZ-6) had the strongest anti-melanogenic effects in cultured melan-a cells (30.4% inhibition at 100 microm). In addition, TZ-6 exhibited an inhibitory effect on mushroom and cellular tyrosinase. Based on the results of Western blotting, TZ-6 reduced the expression of tyrosinase at 100 microm. Additionally, TZ-6 reduced body pigmentation and inhibited tyrosinase activity in the zebrafish model. The results have provided useful information for the development of a skin whitening agent.

A Reactiveortho-Quinone Generated by Tyrosinase-Catalyzed Oxidation of the Skin Depigmenting Agent Monobenzone: Self-Coupling and Thiol-Conjugation Reactions and Possible Implications for Melanocyte Toxicity

Monobenzone (hydroquinone monobenzylether, 1) is a potent skin depigmenting agent that causes irreversible loss of epidermal melanocytes by way of a tyrosinase-dependent mechanism so far little understood. Herein, we show that 1 can be oxidized by mushroom tyrosinase to an unstable o-quinone (1-quinone) that has been characterized by comparison of its properties with those of a synthetic sample obtained by o-iodoxybenzoic acid-mediated oxidation of 1. Preparative scale oxidation of 1 with tyrosinase and catalytic l-DOPA, followed by reductive workup and acetylation, led to the isolation of two main products that were identified as the acetylated catechol derivative 4 and an unusual biphenyl-type dimer of 4, acetylated 5, arising evidently by coupling of 4 with 1-quinone. In the presence of l-cysteine or N-acetyl-l-cysteine, formation of 4 and 5 was inhibited, and the reaction led instead to monoadducts (6 or 9) and diadducts (7 and 8). A similar behavior was observed when the tyrosinase-promoted oxidation of 1 was carried out in the presence of sulfhydryl-containing peptides, such as reduced glutathione, or proteins, such as bovine serum albumin (BSA), as inferred by detection of adduct 9 by high pressure liquid chromatography-electrochemical detection (HPLC-ED) after acid hydrolysis. The generation and reaction chemistry of 1-quinone described in this article may bear relevance to the etiopathogenetic mechanisms of monobenzone-induced leukoderma as well as to the recently proposed haptenation hypothesis of vitiligo, a disabling pigmentary disorder characterized by irreversible melanocyte loss.

Synthesis, discovery and mechanism of 2,6-dimethoxy- N-(4-methoxyphenyl)benzamide as potent depigmenting agent in the skin

In this study, a new skin-depigmenting agent, 2,6-dimethoxy- N-(4-methoxyphenyl)benzamide (DMPB), was synthesized using a combination of benzoic acid and aniline. DMPB exhibited significant depigmentation ability on the UV B-induced hyperpigmentation of the brown guinea pig skin. In addition, the 100 ppm treatment with this compound had a 30% inhibitory effect on melanin pigment generation in the melan-a cell line without significant cell toxicity. To search for relationship with the depigmentation, the effects of DMPB on the tyrosinase and dopachrome tautomerase were evaluated. DMPB had no effect on tyrosinase. However, it accelerated dopachrome transformation into 5,6-dihydroxyindole-2-carboxylic acid (DHICA) in the presence of dopachrome tautormerase. In addition, intracellular level of dopachrome tautomerase in melan-a cells was increased by treatment of DMPB. These results suggest that the pigment-lightening effects of DMPB might be due to biased production of DHICA-eumelanin induced by dopachrome tautormerase activation.

Prevention of the photodamage in the hairless mouse dorsal skin by kojic acid as an iron chelator

Kojic acid, a fungal metabolic product, has been used as a skin-depigmenting agent in skin care products marketed in Japan. Iron in the skin is known to be involved in wrinkling as a result of chronic photodamage. Kojic acid was expected to have anti-wrinkling activity, since it possesses iron-chelating activity. We now evaluated the anti-wrinkling activity of kojic acid by using hairless mice exposed to chronic solar-simulating ultraviolet (UV) irradiation as model animal. At the end of a 20-week irradiation period, topical application of kojic acid before UV irradiation was observed to dramatically prevent: (1) the wrinkling, (2) hyperplasia of the epidermis, (3) fibrosis of the lower dermis, and (4) the increase of extracellular matrix components in the upper dermis. These findings indicate that kojic acid is a typical agent preventing wrinkling of the skin due to chronic photodamage.

Contact allergy to kojic acid in skin care products

Kojic acid (5-hydroxy-2-(hydroxymethyl)-4-pyrone), a fungal metabolic product, has increasingly been used as a skin-depigmenting agent in skin care products marketed in Japan since 1988. In order to determine its frequency of sensitization, during 1 year from October 1992 to September 1993, we performed patch testing with it in 220 female patients with suspected cosmetic-related contact dermatitis. Of the 220 patients, 8 used at least 1 skin care product containing kojic acid, 5 of whom reacted to kojic acid as well as to 1 or more their own products containing 1% kojic acid, but not to their other products not containing it, and 3 of whom were negative to kojic acid and all their own products. Patch testing with kojic acid in the remaining group of 212 patients, who had not previously used skin care products containing it, was negative without exception. The 5 kojic-acid-sensitive patients, aged 34 to 58 years, developed facial dermatitis 1-12 months after starting application of kojic-acid-containing products. Kojic acid is considered to have high sensitizing potential, as a comparatively high frequency of contact sensitivity was observed in patients using products containing it (5 out of 8).

2 Final Report on the Safety Assessment of p-Hydroxyanisole

p-Hydroxyanisole is used as an antioxidant in cosmetic products at concentrations of up to 1.0 percent. The acute oral LD50 of p-Hydroxyanisole in rats was estimated as 1630 mg/kg. Undiluted p-Hydroxyanisole is a severe skin and ocular irritant in rabbits but produced minimal eye irritation at 0.1 percent and minimal rabbit skin irritation at 5 percent. Skin sensitization to p-Hydroxyanisole occurred when guinea pigs were treated at 0.5 M. p-Hydroxyanisole is a skin-depigmenting agent at concentrations approximating those used in cosmetic products. p-Hydroxyanisole was nonmutagenic in the Ames assay. No local toxic changes or tumors were observed following long-term application of 5 and 10 percent p-Hydroxyanisole. The antioxidant was inactive as a tumor promoter. Solutions of p-Hydroxyanisole produced embryotoxicity but not teratogenicity. The function of p-Hydroxyanisole in cosmetics is that of an antioxidant; it is not intended for use as a skin lightener or skin-depigmenting agent. Because of the depigmenting action of p-Hydroxyanisole in black guinea pigs at reported concentrations approaching those used in cosmetics, it is concluded that p-Hydroxyanisole is unsafe for use as a cosmetic ingredient.

Depigmenting Action of Hydroquinone Depends on Disruption of Fundamental Cell Processes

The effect of the skin-depigmenting agent hydroquinone (HQ) on 2 melanotic and 3 nonmelanotic cell lines was studied. Significant differences in its effect on DNA and RNA synthesis were observed between cell lines. HQ caused inhibition of cellular metabolism in all cells tested, but the dose that caused 50% inhibition of tritiated thymidine incorporation was approximately 30 times lower for melanotic cells. Tritiated uridine incorporation was found to be 85 times more sensitive to HQ in the melanotic cells. These results suggest that HQ exerts its depigmenting effect by selective action on melanocyte metabolism rather than a specific effect on melanin synthesis. Further, the effects of UV irradiation on this system were investigated and found to be negligible, in spite of the stimulation of in vivo melanin synthesis by UV radiation.