The melanogenesis and mechanisms of skin-lightening agents--existing and new approaches

Integrating Skincare into Medical Practice

The integration of skincare into medical practice can enhance patient care. Understanding the anatomy and physiology of the skin is the foundation for effective skincare interventions. Genetic and inflammatory conditions play a significant role in aesthetic skin physiology. There are key active ingredients that are pivotal in addressing various skin concerns. Sunscreens provide crucial protection against UV radiation, while pigment control agents such as hydroquinone, kojic acid, and arbutin target the melanin pathway. Exfoliating agents and skin turnover enhancers such as retinoids and hydroxy acids promote skin renewal and rejuvenation. In addition, ingredients such as hyaluronic acid, ceramides, niacinamide, antioxidants, peptides, and botanicals contribute to improving skin quality. Adding skincare to medical practice requires careful product selection, patient education, and marketing strategies.

Precision Drug Repurposing: A Deep Learning Toolkit for Identifying 34 Hyperpigmentation-Associated Genes and Optimizing Treatment Selection

BACKGROUND

Hyperpigmentation is a skin disorder characterized by a localized darkening of the skin due to increased melanin production. When patients fail first line topical treatments, secondary treatments such as chemical peels and lasers are offered. However, these interventions are not devoid of risks and are associated with postinflammatory hyperpigmentation. In the quest for novel therapeutic potentials, this study aims to investigate computational methods in the identification of new targeted therapies in the treatment of hyperpigmentation.

METHODS

We used a comprehensive approach, which integrated text mining, interpreting gene lists through enrichment analysis and integration of diverse biological information (GeneCodis), protein-protein association networks and functional enrichment analyses (STRING), and plug-in network centrality parameters (Cytoscape) to pinpoint genes closely associated with hyperpigmentation. Subsequently, analysis of drug-gene interactions to identify potential drugs (Cortellis) was utilized to select drugs targeting these identified genes. Lastly, we used Deep Learning Based Drug Repurposing Toolkit (DeepPurpose) to conduct drug-target interaction predictions to ultimately identify candidate drugs with the most promising binding affinities.

RESULTS

Thirty-four hyperpigmentation-related genes were identified by text mining. Eight key genes were highlighted by utilizing GeneCodis, STRING, Cytoscape, gene enrichment, and protein-protein interaction analysis. Thirty-five drugs targeting hyperpigmentation-associated genes were identified by Cortellis, and 29 drugs, including 16 M2PK1 inhibitors, 11 KRAS inhibitors, and 2 BRAF inhibitors were recommended by DeepPurpose.

CONCLUSIONS

The study highlights the promise of advanced computational methodology for identifying potential treatments for hyperpigmentation.

Anti-Melanogenic Activity of Ethanolic Extract from Garcinia atroviridis Fruits Using In Vitro Experiments, Network Pharmacology, Molecular Docking, and Molecular Dynamics Simulation

Melanin, the pigment responsible for human skin color, increases susceptibility to UV radiation, leading to excessive melanin production and hyperpigmentation disorders. This study investigated the ethanolic extract of Garcinia atroviridis fruits for its phenolic and flavonoid contents, antioxidant activity, and impact on melanogenesis pathways using qRT-PCR and Western blot analysis. Utilizing network pharmacology, molecular docking, and dynamics simulations, researchers explored G. atroviridis fruit extract's active compounds, targets, and pharmacological effects on hyperpigmentation. G. atroviridis fruit extract exhibited antioxidant properties, scavenging DPPH• and ABTS•+ radicals radicals and chelating copper. It inhibited cellular tyrosinase activity and melanin content in stimulated B16F10 cells, downregulating TYR, TRP-1, phosphorylated CREB, CREB, and MITF proteins along with transcription levels of MITF, TYR, and TRP-2. LC-MS analysis identified thirty-three metabolites, with seventeen compounds selected for further investigation. Network pharmacology revealed 41 hyperpigmentation-associated genes and identified significant GO terms and KEGG pathways, including cancer-related pathways. Kaempferol-3-O-α-L-rhamnoside exhibited high binding affinity against MAPK3/ERK1, potentially regulating melanogenesis by inhibiting tyrosinase activity. Stable ligand-protein interactions in molecular dynamics simulations supported these findings. Overall, this study suggests that the ethanolic extract of G. atroviridis fruits possesses significant antioxidant, tyrosinase inhibitory, and anti-melanogenic properties mediated through key molecular targets and pathways.

Synthesis and evaluation of coumarin derivatives on antioxidative, tyrosinase inhibitory activities, melanogenesis, and in silico investigations

New coumarin derivatives were designed using a 2-(2-oxo-2H-chromen-4-yl)acetic acid scaffold conjugated with amino acid esters or tyramine. The anti-tyrosinase and anti-lipid peroxidation activities of the synthesized compounds were investigated. Coumarin derivatives 7,9, 11-13, 15-18 showed strong anti-lipid peroxidation activity. Compound 13 exhibited uncompetitive tyrosinase inhibitory activity with an IC50 value of 68.86 µM. Compound 14 (% activity = 123.41) showed stronger tyrosinase activating activity than 8-methoxypsolaren (8-MOP, % activity = 109.46). In silico studies revealed different poses between the inhibitors and activators near the tyrosinase catalytic site. Compounds 13 (25-50 μM) and 14 (25-100 μM) did not show cytotoxicity against B16F10 cells. In contrast to the tyrosinase inhibition assay, compound 13 (50 μM) suppressed melanogenesis in B16F10 cells with two times higher potency than KA (100 μM). Compound 14 at 100 μM showed melanogenesis enhancement in B16F10 cells in a dose-dependent manner, however, inferior to the 8-MOP. Based on the findings, compound 13 and 14 offer potential for development as skin-lightening agents and vitiligo therapy agents, respectively.

A Bayesian network meta-analysis of 14 molecules inhibiting UV daylight-induced pigmentation

INTRODUCTION

Hyperpigmentation disorders are very frequent, affect the quality of life and may become a psychological burden for afflicted patients. Many anti-pigmenting or depigmenting agents are available with various efficacy and almost no comparative data. 2-mercaptonicotinoyl glycine (2-MNG) was recently proposed as a viable candidate showing safe and effective results on hyperpigmentation control in vitro and in vivo.

OBJECTIVES

A Bayesian network meta-analysis (BNMA) was conducted to map and rank the anti-pigmenting and depigmenting efficacy of 2-MNG 0.5% on UV daylight (UVDL)-induced pigmentation together with 13 other reference molecules. A comparison in the kinetics of 2-MNG 0.5% was also performed.

METHODOLOGY

Fourteen studies were conducted, for each, on 15-30 women of skin phototype III in Shanghai, China and Paris, France. The products were applied on mini zone, in randomized and blinded protocol, on the back, 5 days a week during 6 weeks, at a dose of 4 mg/cm2 . During the second week, volunteers were exposed under to varying minimum erythemal dose of UVDL during 4 consecutive days-adapted to obtain a similar induction of skin pigmentation regardless of the population. Assessments were performed instrumentally using Chromameter®. Ascorbic acid 7% was used as a positive control for all experiments. A Bayesian network meta-analysis was then established to map and follow the kinetics of 2-MNG 0.5% performance with 13 reference molecules (glutathione 2%, kojic acid 1%, hydroquinone 4%, ascorbyl glucoside 2%, niacinamide 4%, etc.).

RESULTS

2-MNG 0.5% dominated the ranking at all time points with a significant high probability of strong efficacy against UVDL-induced pigmentation. Ascorbic acid 7% ranks second after 4 days of irradiations (D12 ) whereas hydroquinone 4% ranks second 1 month after irradiations (D40 ). In the kinetics, 2-MNG at 0.5% was effective as from the end of irradiations (D12 ) to the study endpoint (D40 ). This suggested an immediate and persistent efficacy across all timepoints evaluated.

CONCLUSION

The BNMA revealed a rapid and lasting efficacy of 2-MNG 0.5% on the anti-pigmenting and depigmenting phases of the clinical protocol. 2-MNG 0.5% ranked first, with immediate and lasting effect compared to 13 other references. This study is the first allowing comparison between reference anti-pigmenting and depigmenting agents and will help clinicians for proposing the most effective approach for their patients.

Phytochemical Profiles and Biological Activities of Frankenia Species: A Review

The relatively small Frankeniaceae family is represented by halophyte plants, growing in arid and semi-arid climates in saline, alkaline or calcareous soils. Due to their living conditions, they usually produce a large diversity of compounds, which often exhibit bioactivities. Some species of this genus have long been used as traditional herbal medicines to treat dysentery, diarrhea, gonorrhea, vaginal leucorrhea, respiratory diseases and wounds. To date, several studies on either phytochemical or pharmacological aspects, or both, have revealed that this genus is a rich source of diverse and novel bioactive chemicals, including phenolics, flavonoids, alkaloids and fatty acids. This review describes all the reported chemical profiles of Frankenia species, as well as the corresponding biological properties, when available. The aim of this review is to show the potential of these plants for various applications, especially therapeutic ones.

In vitro and in vivo anti-pigmentation effects of 2-mercaptobenzimidazoles as nanomolar tyrosinase inhibitors on mammalian cells and zebrafish embryos: Preparation of pigment-free zebrafish embryos

Recently, 10 2-mercaptobenzo[d]imidazole (2-MBI) compounds (1-10) were synthesized. Although all 2-MBI compounds are tyrosinase inhibitors that inhibit mushroom tyrosinase at extremely low concentrations (IC50 values: 20-740 nM) and effectively inhibit the browning of apples, to our knowledge, no studies have determined whether 2-MBI compounds inhibit mammalian tyrosinase. Mammalian tyrosinase is different from mushroom tyrosinase in its distribution within the cell and has structural characteristics that are different from mushroom tyrosinase in amino acid sequence and in the presence of a quaternary structure. Thus, the effect of the 10 2-MBI compounds on mammalian tyrosinase activity was investigated in B16F10 cells. Six compounds (1-6) exhibited stronger intracellular tyrosinase inhibition than that of kojic acid and phenylthiourea (PTU), which are known to be the most potent tyrosinase inhibitors; their strong tyrosinase inhibitory activity robustly inhibited intracellular melanin production in B16F10 cells. None of the tested 2-MBI compounds exhibited appreciable cytotoxicity in HaCaT and B16F10 cells. To confirm the anti-melanogenic efficacy of the 2-MBI compounds in vivo, a zebrafish embryo model was used. At concentrations 100 times lower than kojic acid, most 2-MBI compounds demonstrated much stronger depigmentation efficacy than that of kojic acid, and three 2-MBI compounds (2-4) showed depigmentation activity similar to or more potent than that of PTU, resulting in nearly pigment-free zebrafish embryos. These results suggest that 2-MBI compounds may be potential therapeutic agents for hyperpigmentation-related disorders.

Anti-Photoaging Effects of Upcycled Citrus junos Seed Anionic Peptides on Ultraviolet-Radiation-Induced Skin Aging in a Reconstructed Skin Model

Side streams and byproducts of food are established sources of natural ingredients in cosmetics. In the present study, we obtained upcycled low-molecular-weight anionic peptides (LMAPs) using byproducts of the post-yuzu-juicing process by employing an enzyme derived from Bacillus sp. For the first time, we isolated anionic peptides less than 500 Da in molecular weight from Citrus junos TANAKA seeds via hydrolysis using this enzyme. The protective effect of LMAPs against UVR-induced photoaging was evaluated using a reconstructed skin tissue (RST) model and keratinocytes. The LMAPs protected the keratinocytes by scavenging intracellular reactive oxygen species and by reducing the levels of paracrine cytokines (IL-6 and TNF-α) in UVR (UVA 2 J/cm2 and UVB 15 mJ/cm2)-irradiated keratinocytes. Additionally, the increase in melanin synthesis and TRP-2 expression in RST caused by UVR was significantly inhibited by LMAP treatment. This treatment strongly induced the expression of filaggrin and laminin-5 in UVR-irradiated RST. It also increased type I collagen expression in the dermal region and in fibroblasts in vitro. These results suggest that a hydrolytic system using the enzyme derived from Bacillus sp. can be used for the commercial production of LMAPs from food byproducts and that these LMAPs can be effective ingredients for improving photoaging-induced skin diseases.

Clinical Assessment, Diagnosis, and Management of Infraorbital Wrinkles and Pigmentation

Lower eyelid skin is unique and different from that of other areas. In addition to being an area of high exposure to the sun and elements, there are anatomic considerations and specific histologic characteristics that can cause the skin in this area to be more sensitive. These attributes can readily cause under-eye wrinkling and pigmentation. This review aims to present an updated overview of the current knowledge regarding the clinical characteristics, diagnosis, and management of wrinkles and pigmentation in this area. These disorders are usually caused by different factors, such as genetics, aging, sun exposure, lack of sleep, and stress.

A mechanism of melanogenesis mediated by E-cadherin downregulation and its involvement in solar lentigines

OBJECTIVE

Intensive studies have revealed that pleiotropic melanocytic factors are associated with age-spot formation. Dysfunctional keratinocyte differentiation is thought to be an upstream cause of age-spot formation. Although it has been shown that keratinocyte differentiation is mediated by the cell-cell contact factor E-cadherin, its involvement in age-spot formation remains unknown. Thus, to determine the origin of age-spots and an integrated solution for the same, we focused on E-cadherin expression in the present study.

METHODS

First, we assessed the solar lentigines in cutaneous and cultured cells by means of immunofluorescence staining. Following that, keratinocytes treated with siRNAs against E-cadherin were co-cultured with melanocytes, and the secreted factors were identified by means of proteomic analysis of the culture supernatants. We also performed quantitative PCR to assess melanogenesis activity and screen ingredients. For behavioural analysis of melanocytes, we performed time-lapse imaging using confocal laser scanning microscopy.

RESULTS

E-cadherin expression was downregulated in the epidermis of the solar lentigines, suggesting its involvement in age-spot formation. E-cadherin knocked down keratinocytes not only promoted the secretion of melanocytic/inflammatory factors but also increased melanogenesis by upregulating the expression of melanogenesis factors. Furthermore, live-imaging showed that the downregulation of E-cadherin inhibited melanocyte dynamics and accelerated melanin uptake. Finally, we identified Rosa multiflora fruit extract as a solution that can upregulate E-cadherin expression in keratinocytes.

CONCLUSION

Our findings showed that E-cadherin downregulation triggers various downstream melanocytic processes, such as the secretion of melanocytic factors and melanogenesis. Additionally, we showed that the Rosa multiflora fruit extract upregulated E-cadherin expression in keratinocytes.

Antioxidant activity, anti-tyrosinase activity, molecular docking studies, and molecular dynamic simulation of active compounds found in nipa palm vinegar

Tyrosinase is a key enzyme in melanogenesis and its inhibitors have become increasingly because of their potential activity as hypopigmenting agents which have less side effects. Nipa palm vinegar is an aqueous product that is normally used as a food supplement. The aim of this study was to study the determination of antioxidant activity and tyrosinase inhibitory activities of aqueous extract of original nipa palm vinegar (AE O-NPV), nipa palm vinegar powder (NPV-P) and aqueous extract of nipa palm vinegar powder (AE NPV-P) were examined. Nipa palm vinegars were evaluated the phenolic and flavonoid content, and the active compounds which were submitted to molecular docking and molecular dynamic simulation, chemoinformatics, rule of five, skin absorption and toxicity. The highest phenolic and flavonoid contents in the AE O-NPV were 2.36 ± 0.23 mg gallic acid equivalents/g extract and 5.11 ± 0.59 mg quercetin equivalents/g, and the highest ABTS radical cation scavenging activity was also found. The AE O-NPV, NPV-P and AE NPV-P showed anti-mushroom tyrosinase activity. The HPLC analysis showed that there were vanillic acid and three flavonoids (catechin, rutin and quercetin). The molecular docking study revealed that the binding of the vanillic acid and three flavonoids occurred in the active site residues (histidine and other amino acids). Moreover, the number of hydrogen bond acceptors/donors, solubility, polar surface area and bioavailability score of the vanillic acid and three flavonoids were acceptable compared to Lipinski's Rule of Five. The molecular dynamic simulation showed that vanillic acid interacts with HIS284 through π-π stacking hydrophobic interactions and forms a metal-acceptor interaction with the copper molecule at the tyrosinase active site. All compounds revealed good skin permeability and nontoxicity. Nipa palm vinegar could be a promising source of a new ingredient for tyrosinase inhibition for cosmetics or pharmaceutical products.

Melanin: a unifying theory of disease as exemplified by Parkinson's, Alzheimer's, and Lewy body dementia

Melanin, a ubiquitous dark pigment, plays important roles in the immune system, including scavenging reactive oxygen species formed in response to ultraviolet radiation absorption, absorbing metals, thermal regulation, drug uptake, innate immune system functions, redox, and energy transduction. Many tissue types, including brain, heart, arteries, ovaries, and others, contain melanin. Almost all cells contain precursors to melanin. A growing number of diseases in which there is a loss of melanin and/or neuromelanin are increasingly thought to have infectious etiologies, for example, Alzheimer's disease (AD), Parkinson's disease (PD), Lewy Body Dementia (LBD), and vitiligo. AD, PD, LBD, and vitiligo have been linked with herpesvirus, which enters melanosomes and causes apoptosis, and with gut dysbiosis and inflammation. Herpesvirus is also linked with gut dysbiosis and inflammation. We theorize that under normal healthy states, melanin retains some of the energy it absorbs from electromagnetic radiation, which is then used to fuel cells, and energy from ATP is used to compliment that energy supply. We further theorize that loss of melanin reduces the energy supply of cells, which in the case of AD, PD, and LBD results in an inability to sustain immune system defenses and remove the plaques associated with the disease, which appear to be part of the immune system's attempt to eradicate the pathogens seen in these neurodegenerative diseases. In addition, in an attempt to explain why removing these plaques does not result in improvements in cognition and mood and why cognitions and moods in these individuals have ebbs and flows, we postulate that it is not the plaques that cause the cognitive symptoms but, rather, inflammation in the brain resulting from the immune system's response to pathogens. Our theory that energy retained in melanin fuels cells in an inverse relationship with ATP is supported by studies showing alterations in ATP production in relationship to melanin levels in melanomas, vitiligo, and healthy cells. Therefore, alteration of melanin levels may be at the core of many diseases. We propose regulating melanin levels may offer new avenues for treatment development.

Aspacochioside C from Asparagus cochinchinensis attenuates eumelanin synthesis via inhibition of TRP2 expression

Aspacochioside C (ACC) is a steroidal saponin isolated from Asparagus cochinchinensis. Steroidal saponins, such as pseudoprotodioscin and dioscin, are known to inhibit melanogenesis, but the role of ACC in melanogenesis remains unknown. Due to the toxic effect of the commonly used skin whitening agents like arbutin, kojic acid and α-lipoic acid alternative plant products are recentlybeen studied for their anti-hypergmentation effect. This study explores the role of ACC in melanogenesis in both in vivo and in vitro models. Here, we for the first time demonstrate that ACC attenuated α-MSH- and UVB-induced eumelanin production by inhibiting tyrosinase-related protein (TRP)-2 protein expression in both murine B16F10 and human melanoma MNT1 cells. However, ACC had no significant effect on pheomelanin concentration. ACC also decreased the pigmentation density in zebrafish embryos, which indicates that ACC targets TRP2 and inhibits eumelanin synthesis. Our results demonstrate that ACC inhibits TRP2, thereby attenuating eumelanin synthesis both in in vitro and in vivo zebrafish model. Therefore, ACC can potentially be used as an anti-melanogenic agent for both aesthetic and pharmaceutical purposes.

Photoaging and Topical Rejuvenation

Photoaging is a complex process of skin changes associated with chronic ultraviolet exposure. Prevention with photoprotection and treatment with topical retinoids are the core components of a topical antiaging regimen. Other topicals such as hydroquinone, vitamin C, niacinamide, and alpha hydroxyl acid can be added based on specific concerns. However, caution must be used with some of these products as the stability and absorption are major considerations. A simple topical regimen will reduce irritability and enhance compliance.

The Mixture of Natural Products SH003 Exerts Anti-Melanoma Effects through the Modulation of PD-L1 in B16F10 Cells

Melanoma is the most invasive and lethal skin cancer. Recently, PD-1/PD-L1 pathway modulation has been applied to cancer therapy due to its remarkable clinical efficacy. SH003, a mixture of natural products derived from Astragalus membranaceus, Angelica gigas, and Trichosanthes kirilowii, and formononetin (FMN), an active constituent of SH003, exhibit anti-cancer and anti-oxidant properties. However, few studies have reported on the anti-melanoma activities of SH003 and FMN. This work aimed to elucidate the anti-melanoma effects of SH003 and FMN through the PD-1/PD-L1 pathway, using B16F10 cells and CTLL-2 cells. Results showed that SH003 and FMN reduced melanin content and tyrosinase activity induced by α-MSH. Moreover, SH003 and FMN suppressed B16F10 growth and arrested cells at the G2/M phase. SH003 and FMN also led to cell apoptosis with increases in PARP and caspase-3 activation. The pro-apoptotic effects were further enhanced when combined with cisplatin. In addition, SH003 and FMN reversed the increased PD-L1 and STAT1 phosphorylation levels induced by cisplatin in the presence of IFN-γ. SH003 and FMN also enhanced the cytotoxicity of CTLL-2 cells against B16F10 cells. Therefore, the mixture of natural products SH003 demonstrates therapeutic potential in cancer treatment by exerting anti-melanoma effects through the PD-1/PD-L1 pathway.

Extraction Optimization, Characterization and Biological Activities of Polysaccharide Extracts from Nymphaea hybrid

In this study, polysaccharide-rich Nymphaea hybrid extracts (NHE) were obtained using the ultrasound-assisted cellulase extraction (UCE) method optimized by response surface methodology (RSM). The structural properties and thermal stability of NHE were characterized by Fourier-transform infrared (FT-IR), high-performance liquid chromatography (HPLC) and thermogravimetry-derivative thermogravimetry (TG-DTG) analysis, respectively. Moreover, the bioactivities of NHE, including the antioxidant, anti-inflammatory, whitening and scratch healing activities were evaluated by different in vitro assays. NHE conveyed a good ability to scavenge against the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radicals and inhibit the hyaluronidase activity. NHE can effectively protect the HaCaT cells against oxidative damage by inhibiting the intracellular reactive oxygen species (ROS) production in the H₂O₂ stimulation assays and promoting the proliferation and migration in the scratch assays. In addition, NHE was proven to inhibit melanin production in B16 cells. Collectively, the above results seem to be the evidence needed to promote the potential of NHE to be regarded as a new functional raw material in the cosmetics or food industries.

Characterization and screening of anti-melanogenesis and anti-photoaging activity of different enzyme-assisted polysaccharide extracts from Portulaca oleracea L

BACKGROUND

The flavonoids and polysaccharides in Portulaca oleracea L. (PO) have significant antibacterial and antioxidant effects, which can inhibit common bacteria and remove free radicals in the body. However, there was little research on the use of PO to alleviate hyperpigmentation and photoaging damage.

PURPOSE

This study was to investigate the anti-photoaging and whitening activity mechanism of polysaccharide of PO (POP) in vitro and in vivo.

METHOD

In this study, 16 fractions obtained by four enzyme-assisted extraction from PO and their scavenging capabilities against 2,2-diphenyl-1-picrylhydrazyl and hydroxyl radicals were evaluated. Among these fractions, a polysaccharide fraction (VPOP3) showed the strongest biological activity. VPOP3 was characterized by Fourier-transform infrared spectroscopy, molecular weight (MW), and monosaccharide composition analysis, and the protective effect of VPOP3 on photoaging and hyperpigmentation was researched.

RESULTS

VPOP3 is a low-MW acidic heteropolysaccharide with MW mainly distributed around 0.71KDa, arabinose as its main monosaccharide component. VPOP3 reliably reduced the reactive oxygen species levels in cells and zebrafish and the level of lipid peroxidation in zebrafish. In addition, VPOP3 inhibited UVB-induced apoptotic body formation and apoptosis by downregulating caspase-3 and Bax and upregulating Bcl-2 in mitochondrion-mediated signaling pathways. On the other hand, VPOP3 at high concentrations significantly downregulated the expression of microphthalmia-associated transcription factor, tyrosinase (TYR), and TYR-related protein-1 and TYR-related protein-2 in the melanogenic signaling pathway to achieve a whitening effect.

CONCLUSION

The above results showed that VPOP3 has superior activities of anti-photoaging and anti-melanogenesis and can be utilized as a safe resource in the manufacture of cosmetics.

Our evolved understanding of the human health risks of mercury

Mercury (Hg) is a chemical of health concern worldwide that is now being acted upon through the Minamata Convention. Operationalizing the Convention and tracking its effectiveness requires empathy of the diversity and variation of mercury exposure and risk in populations worldwide. As part of the health plenary for the 15th International Conference on Mercury as a Global Pollutant (ICMGP), this review paper details how scientific understandings have evolved over time, from tragic poisoning events in the mid-twentieth century to important epidemiological studies in the late-twentieth century in the Seychelles and Faroe Islands, the Arctic and Amazon. Entering the twenty-first century, studies on diverse source-exposure scenarios (e.g., ASGM, amalgams, contaminated sites, cosmetics, electronic waste) from across global regions have expanded understandings and exemplified the need to consider socio-environmental variables and local contexts when conducting health studies. We conclude with perspectives on next steps for mercury health research in the post-Minamata Convention era.

Neurog1-Derived Peptides RMNE1 and DualPep-Shine Penetrate the Skin and Inhibit Melanin Synthesis by Regulating MITF Transcription

Anti-pigmentation peptides have been developed as alternative skin-lightening agents to replace conventional chemicals that have adverse effects on the skin. However, the maximum size of these peptides is often limited by their low skin and cell penetration. To address this issue, we used our intra-dermal delivery technology (IDDT) platform to identify peptides with hypo-pigmenting and high cell-penetrating activity. Using our cell-penetrating peptides (CPPs) from the IDDT platform, we identified RMNE1 and its derivative RMNE3, "DualPep-Shine", which showed levels of α-Melanocyte stimulating hormone (α-MSH)-induced melanin inhibition comparable to the conventional tyrosinase inhibitor, Kojic acid. In addition, DualPep-Shine was delivered into the nucleus and regulated the gene expression levels of melanogenic enzymes by inhibiting the promoter activity of microphthalmia-associated transcription factor-M (MITF-M). Using a 3D human skin model, we found that DualPep-Shine penetrated the lower region of the epidermis and reduced the melanin content in a dose-dependent manner. Furthermore, DualPep-Shine showed high safety with little immunogenicity, indicating its potential as a novel cosmeceutical ingredient and anti-pigmentation therapeutic agent.

Dimethyl Itaconate Inhibits Melanogenesis in B16F10 Cells

Itaconate is a metabolite produced to counteract and resolve pro-inflammatory responses when macrophages are challenged with intracellular or extracellular stimuli. In the present study, we have observed that dimethyl itaconate (DMI) inhibits melanogenesis in B16F10 cells. DMI inhibits microphthalmia-associated transcription factor (MITF) and downregulates the expression of MITF target genes, such as tyrosinase (TYR), tyrosinase-related protein 1 (TRP-1), and tyrosinase-related protein 2 (TRP-2). DMI also decreases the level of melanocortin 1 receptor (MC1R) and the production of α-melanocyte stimulating hormone (α-MSH), resulting in the inhibition of extracellular signal-regulated kinase 1/2 (ERK1/2) and MITF activities. The structure–activity relationship (SAR) study illustrates that the α,β-unsaturated carbonyl moiety in DMI, a moiety required to target KELCH-like ECH-associated protein 1 (KEAP1) to activate NF-E2-related factor 2 (NRF2), is necessary to inhibit melanogenesis and knocking down Nrf2 attenuates the inhibition of melanogenesis by DMI. Together, our study reveals that the MC1R-ERK1/2-MITF axis regulated by the KEAP1-NRF2 pathway is the molecular target responsible for the inhibition of melanogenesis by DMI.

The Skin-Whitening and Antioxidant Effects of Protocatechuic Acid (PCA) Derivatives in Melanoma and Fibroblast Cell Lines

The skin is the most voluminous organ of the human body and is exposed to the outer environment. Such exposed skin suffers from the effects of various intrinsic and extrinsic aging factors. Skin aging is characterized by features such as wrinkling, loss of elasticity, and skin pigmentation. Skin pigmentation occurs in skin aging and is caused by hyper-melanogenesis and oxidative stress. Protocatechuic acid (PCA) is a natural secondary metabolite from a plant-based source widely used as a cosmetic ingredient. We chemically designed and synthesized PCA derivatives conjugated with alkyl esters to develop effective chemicals that have skin-whitening and antioxidant effects and enhance the pharmacological activities of PCA. We identified that melanin biosynthesis in B16 melanoma cells treated with alpha-melanocyte-stimulating hormone (α-MSH) is decreased by PCA derivatives. We also found that PCA derivatives effectively have antioxidant effects in HS68 fibroblast cells. In this study, we suggest that our PCA derivatives are potent ingredients for developing cosmetics with skin-whitening and antioxidant effects.

The CNC-family transcription factor Nrf3 coordinates the melanogenesis cascade through macropinocytosis and autophagy regulation

Melanin is a pigment produced from the amino acid L-tyrosine in melanosomes. The CNC-family transcription factor Nrf3 is expressed in the basal layer of the epidermis, where melanocytes reside, but its melanogenic function is unclear. Here, we show that Nrf3 regulates macropinocytosis and autophagy to coordinate melanogenesis cascade. In response to an exogenous inducer of melanin production, forskolin, Nrf3 upregulates the core melanogenic gene circuit, which includes Mitf, Tyr, Tyrp1, Pmel, and Oca2. Furthermore, Nrf3 induces the gene expression of Cln3, an autophagosome-related factor, for melanin precursor uptake by macropinocytosis. Ulk2 and Gabarapl2 are also identified as Nrf3-target autophagosome-related genes for melanosome formation. In parallel, Nrf3 prompts autolysosomal melanosome degradation for melanocyte survival. An endogenous melanogenic inducer αMSH also activates Nrf3-mediated melanin production, whereas it is suppressed by an HIV-1 protease inhibitor, nelfinavir. These findings indicate the significant role of Nrf3 in the melanogenesis and the anti-melanogenic potential of nelfinavir.

Protopanaxadiol-Enriched Rice Extracts Suppressed Oxidative and Melanogenic Activities in Melan-a Cells

Concerns about hyperpigmentation and skin appearance have led to increasing research into the prevention and altering of skin pigmentation. Natural compounds may be of interest in the search for skin-lightening actives. Protopanaxadiol (PPD), a gut microbiome-induced ginseng metabolite, has been reported to have anti-melanogenic effects. This study aimed to evaluate the antioxidative and anti-melanogenic effects of PPD-enriched rice seed extracts on melan-a cells. The antioxidant and cytotoxicity activities of the extracts were investigated in melan-a cells before measuring their responses to melanogenic activities. The extracts significantly enhanced the antioxidant potency compared with normal rice seed extract. PPD-enriched rice seed extracts (i) significantly downregulated microphthalmia-associated transcription factor, which led to a reduction in tyrosinase and tyrosinase-related protein-1 and -2, (ii) decrease in the cellular tyrosinase activity and melanin content, (iii) reduction in the number of melanin-containing cells, (iv) promotion of melanogenesis downregulators, phosphorylation of extracellular signal-regulated kinase 1/2 and protein kinase B, and (v) downregulation of the phosphorylated p38 mitogen-activated protein kinase and melanin synthesis. These results indicate the feasibility of PPD-enriched rice seed extracts as a novel agent for suppressing melanogenesis and controlling hyperpigmentation.

Arctigenin-Enriched Burdock Seed Oil (ABSO): A New Skin Brightening Botanical Extract

The Arctium lappa L. plant, commonly known as burdock, has been used therapeutically for hundreds of years. Arctigenin (ATG) is an active ingredient in burdock, albeit at low quantities or mostly in the form of acrtiin (arctigenin-4-glucoside). ATG has been touted for its anti-inflammatory properties in many cell types and disease states; however, its role in skin and melanin production has not been extensively studied. Our aims for this study were to develop a burdock seed extract enriched for ATG that is amenable to quasi-drug development, determine in vitro brightening activity, and evaluate safety and skin brightening efficacy clinically in human subjects. Arctiin and ATG content were measured by high-performance liquid chromatography (HPLC). In vitro studies utilized EpiDermTM tissues for skin irritation test, and MelanoDermTM tissues for melanin reduction capacity. A 45 subject clinical study was performed in adult subjects ranging in age from 30 to 60 years old (mean = 41.9 ± 6.7) to test the safety and skin brightening potential of 1% ABSO lotion. We demonstrate by HPLC that ABSO is a natural extract that contains ~5-times more arctigenin than BSO. Furthermore, ABSO inhibits melanin production better than BSO and retains the same melanin-reducing capacity as synthetic ATG in vitro in MelanoDerm™ 3D skin cultures. ABSO also adheres to quasi-drug criteria according to the Japanese Standards of Quasi-Drug Ingredients as determined by infrared absorption spectrum method, unsaponifiable matter, heavy metal and arsenic content, and acid, saponification, and iodine value methods. Clinical assessment of 1% ABSO lotion shows it is well-tolerated in human skin and demonstrates improved brightness and skin tone evenness. ABSO is a natural arctigenin-enriched burdock seed extract that reduces melanin content in vitro and clinically improves skin brightness.

Anti-Melanogenesis Effects of a Cyclic Peptide Derived from Flaxseed via Inhibition of CREB Pathway

Linosorbs (Los) are cyclic peptides from flaxseed oil composed of the LO mixture (LOMIX). The activity of LO has been reported as being anti-cancer and anti-inflammatory. However, the study of skin protection has still not proceeded. In particular, there are poorly understood mechanisms of melanogenesis to LO. Therefore, we investigated the anti-melanogenesis effects of LOMIX and LO, and its activity was examined in mouse melanoma cell lines. The treatment of LOMIX (50 and 100 μg/mL) and LO (6.25-50 μM) suppressed melanin secretion and synthesis, which were 3-fold increased, in a dose-dependent manner, up to 95%. In particular, [1-9-NαC]-linusorb B3 (LO1) and [1-9-NαC]-linusorb B2 (LO2) treatment (12.5 and 25 μM) highly suppressed the synthesis of melanin in B16F10 cell lines up to 90%, without toxicity. LOMIX and LOs decreased the 2- or 3-fold increased mRNA levels, including the microphthalmia-associated transcription factor (MITF), Tyrosinase, tyrosinase-related protein 1 (TYRP1), and tyrosinase-related protein 2 (TYRP2) at the highest concentration (25 μM). Moreover, the treatment of 25 μM LO1 and LO2 inhibited the expression of MITF and phosphorylation of upper regulatory proteins such as CREB and PKA. Taken together, these results suggested that LOMIX and its individual LO could inhibit melanin synthesis via downregulating the CREB-dependent signaling pathways, and it could be used for novel therapeutic materials in hyperpigmentation.

Potential application of natural bioactive compounds as skin-whitening agents: A review

BACKGROUND

Melanin is a skin pigment that gives color to the skin, hair, and eyes. The accumulation or over production of melanin can lead to aesthetic problems as well as serious diseases associated with hyperpigmentation. Skin lightening is described as the procedure of using natural or synthetic products to lighten the skin tone or provide an even skin complexion by reducing the amount of melanin in the skin; therefore, skin lightening products help people to treat their skin problems. Ingredients such as hydroquinone, ascorbic acid, and retinoic acid were used as whitening agents to lighten the skin. However, they have many adverse effects on the skin and body health, such as skin irritation.

AIM

In this review, firstly, discuss on the directly/indirectly target melanogenesis-related signal pathways. Secondly, summarize potential natural bioactive ingredients with skin lightening properties from plants, marine organisms, microorganisms. Finally, the remaining problems and future challenges are also discussed.

METHODS

For relevant literature, a literature search was conducted using Google Scholar and Web of Science. Natural bioactive compounds, tyrosinase inhibitors, and other related topics were researched and evaluated.

RESULTS

Natural products isolated from plant and animal resources are potential active cosmetic candidates for lightening the skin tone and skin whitening and protection against UV irradiation. Natural bioactive ingredients as cosmetic whitening additives have attracted increasingly attention due to their safety and cost effectiveness, with few side effects.

CONCLUSION

Although natural active substances have been advocated for use in whitening cosmetics in recent years, there are still many challenges due to the fact that traditional inhibitors are used perennial in cosmetics which cannot be easily changed and the research on natural active substances is still in its infancy. In the future, by improving the extraction technique of natural extracts, it is achieved to give a qualitative and quantitative analysis of the active ingredients of the extracts, to determine the effect of the active components of action, and to find the substances that have the best possible whitening effect in natural organisms.

Inhibitory Effect of Curcumin-Inspired Derivatives on Tyrosinase Activity and Melanogenesis

Tyrosinase is a well-known copper-containing metalloenzyme typically involved in the synthesis of melanin. Recently, curcumin and several synthetic derivatives have been recognized as tyrosinase inhibitors with interesting anti-melanogenic therapeutic activity. In this study, three curcumin-inspired compounds 1, 6 and 7 were prepared in yields ranging from 60 to 88 % and spectrophotometric, electrochemical, in vitro and in silico analyses were carried out. The viability of PC12 cells, a rat pheochromocytoma derived-cell line, with compounds 1, 6 and 7, showed values around 80% at 5 µM concentration. In cell proliferation assays, compounds 1, 6 and 7 did not show significant toxicity on fibroblasts nor melanoma cells up to 10 µM with viability values over 90%. The inhibition of tyrosinase activity was evaluated both by a UV-Vis spectroscopic method at two different concentrations, 0.2 and 2.0 µM, and by amperometric assay with IC₅₀ for compounds 1, 6 and 7 ranging from 11 to 24 nM. Melanin content assays on human melanoma cells were performed to test the capability of compounds to inhibit melanin biosynthesis. All compounds exerted a decrease in melanin content, with compound 7 being the most effective by showing a melanogenesis inhibition up to four times greater than arbutin at 100 µM. Moreover, the antioxidant activity of the selected inhibitors was evaluated against H₂O₂ in amperometric experiments, whereby compound 7 was about three times more effective compared to compounds 1 and 6. The tyrosinase X-ray structure of Bacterium megaterium crystal was used to carry out molecular docking studies in the presence of compounds 1, 6 and 7 in comparison with that of kojic acid and arbutin, two conventional tyrosinase inhibitors. Molecular docking of compounds 6 and 7 confirmed the high affinity of these compounds to tyrosinase protein.

Extraction and Concentration of Waste Pueraria lobata Stems with Antioxidants and Anti-Melanogenesis Activity as a Novel Skin Whitening Agent for Natural Cosmetic Prototypes

The root of Pueraria lobata (Willd.) is used commercially in different products, including dietary supplements, cosmetics, and teas, but its stem part is rarely used and studied. Therefore, this study evaluated the antioxidant and anti-melanogenesis activities of the bioactive fraction of P. lobata stem and investigated whether the activated carbon decolorization technique would have an impact on its activity and chemical composition. We observed that the dichloromethane fraction of P. lobata stem (DCM-PLS) has excellent antioxidant and anti-melanin synthesis activity at a concentration of 50 μg/mL. For the investigation of the anti-melanogenesis mechanism, we evaluated the mRNA expression of tyrosinase, which was depressed by the DCM-PLS. Daidzin was identified as the main active ingredient in DCM-PLS by using a high-performance liquid chromatography-diode array detector-hyphenated with tandem mass spectrometry. In addition, the activated carbon decolorization technology has no negative impact on the main components and bioactivity of DCM-PLS. DCM-PLS also did not induce any skin response in the human skin safety test. Collectively, DCM-PLS could be used as a natural type of skin-whitening agent in skin care products.

Biological activities and safety data of kojic acid and its derivatives - a review

Kojic acid presents a variety of applications for human use, especially as a depigmenting agent. Its derivatives are also proposed in order to prevent chemical degradation, prevent adverse effects and improve efficacy. The aim of this study was to peer review the current scientific literature concerning the biological activities and safety data of kojic acid or its derivatives, aiming at human use, and trying to elucidate the action mechanisms. Three different databases were assessed and the word "kojic" was crossed with "toxicity", "adverse effect", "efficacy", "effect", "activity" and "safety". Articles were selected according to pre-defined criteria. Besides the depigmenting activity, kojic acid and derivatives can act as antioxidant, antimicrobial, anti-inflammatory, radioprotector, anticonvulsant and obesity management agents, and present potential as antitumor substances. Depigmenting activity is due to the molecules, after penetrating the cell, binding to tyrosinase active site, regulating melanogenesis factors, leucocytes modulation and free radical scavenging activity. Hence, polarity, size and ligands are also important factors for activity. Kojic acid and derivatives present cytotoxicity to some cancerous cell lines, including melanoma, hepatocellular carcinoma, ovarian cancer, breast cancer and colon cancer. Regarding safety, kojic acid or its derivatives are safe molecules for human use in the concentrations tested. Kojic acid and its derivatives have great potential for cosmetic, pharmaceutical and medical applications.

Self-Assembled pH-Responsive Metal-Organic Frameworks for Enhancing the Encapsulation and Anti-Oxidation and Melanogenesis Inhibition Activities of Glabridin

Metal organic frameworks (MOFs) are formed by self-assembly of metal ions and organic ligands. A special type of MOF called ZIF-8, which is formed by self-assembly of zinc ions and 2-methylimidazole, shows excellent stability in aqueous solutions and disintegrates under acidic conditions. These properties make ZIF-8 a suitable carrier material for pH-stimulated drug delivery systems. Glabridin is an isoflavane compound that is widely present in the roots of licorice. Because of its outstanding skin whitening properties, glabridin is widely used as a whitener in the cosmetics industry. In this study, ZIF-8 was employed to encapsulate glabridin. Glabridin-loaded ZIF-8 was successfully prepared with a drug encapsulation efficiency of 98.67%. The prepared sample showed a fusiform or cruciate flower-like structure, and its size was about 3 μm. ZIF-8 enabled pH-controlled release of glabridin. Moreover, ZIF-8 encapsulation significantly enhanced the intracellular anti-oxidant activity and melanogenesis inhibitory activity of glabridin. This study provides a new approach that shows great potential to improve the biological application of glabridin.

Incobotulinum Toxin Type A for Treatment of Ultraviolet-B-Induced Hyperpigmentation: A Prospective, Randomized, Controlled Trial

Incobotulinum toxin A (IncoBoNT-A) is effective in preventing ultraviolet B (UVB)-induced hyperpigmentation. This prospective, randomized, controlled study aimed to evaluate the effect of IncoBoNT-A on the treatment of UVB-induced hyperpigmentation in 15 volunteers. Five hyperpigmentation squares (2 × 2 cm) were induced by local UVB on the abdomen at baseline. At Day 7, each site was randomized to receive no treatment (control), normal saline, or intradermal IncoBoNT-A injection with 1:2.5, 1:5, and 1:7.5 dilutions (12, 6, and 4 units, respectively). The mean lightness index (L*), hyperpigmentation improvement score evaluated by blinded dermatologists, and participant satisfaction scores were obtained at Days 21, 28, and 35. At Day 21, improvements in mean L* of 1:2.5, 1:5, and 1:7.5 IncoBoNT-A-treated, saline-treated, and control sites were 14.30%, 12.28%, 6.62%, 0.32%, and 4.98%, respectively (p = 0.86). At Day 28, the improvement in mean L* in IncoBoNT-A-treated groups was superior to that in the other groups. In terms of the hyperpigmentation improvement score, 12 participants (80%) experienced better outcomes with the IncoBoNT-A-injected site compared with the other sites. IncoBoNT-A, especially at higher concentrations, showed some positive effects on the treatment of UVB-induced hyperpigmentation. This may serve as an adjuvant treatment for hyperpigmentary conditions that are aggravated by UVB.

Synthesis and Tyrosinase Inhibitory Activity of (E)-5-Benzyl-7- (3-Bromobenzylidene)-3-(3-Bromophenyl)-2-Phenyl-3,3a, 4,5,6,7-Hexahydro-2H-Pyrazolo[4,3-c]Pyridine

The tyrosinase enzyme plays an essential role in the pigmentation of human skin, fruits, and vegetables. It has been tied with several human skin diseases and post-harvest problems. Hence, the tyrosinase enzyme becomes an excellent therapeutic target to overcome these issues. This study aimed to screen tyrosinase inhibitors by synthesizing halogen-substituted pyrazolopyridine derivatives. The pyrazolopyridine compound was obtained through two stages of synthesis. First, the intermediate compound, a derivative of 3,5-bis(arylidene)-4-piperidone, was synthesized through the Cleisen-Schmidt condensation reaction of 4-piperidone and benzaldehyde derivatives. Furthermore, the intermediate compound was reacted with phenylhydrazine through a cyclocondensation reaction to produce the titled compound with an 11% yield. The chemical structure of the target compound was identified through the interpretation of UV, FTIR, NMR, and HRMS spectra. Then an in vitro assay was conducted on the tyrosinase enzyme of the fungus Agaricus bisporus by detecting the presence of dopachrome at a wavelength of 492 nm. As a result, the in vitro assay showed that the titled compound had a weak inhibitory activity, and the IC50 value was > 500 µM. Thus, the synthesized compound is considered inactive.

Exploration of Osmanthus fragrans Lour.'s composition, nutraceutical functions and applications

Osmanthus fragrans (Thunb.) Lour. has been cultivated in China for over 2500 years. Due to the unique and strong fragrance, O. fragrans flowers have long been added into food, tea, and beverages. Not only the O. fragrans flowers, but also leaves, barks, roots, and fruits possess some beneficial effects such as relieving pain and alleviating cough in Traditional Chinese Medicine. Modern pharmacological researches demonstrated that O. fragrans possesses a broad spectrum of biological activities including antioxidant, neuroprotective, antidiabetic and anticancer activities etc. A large number of phytochemicals identified in O. fragrans are responsible for its health promoting and disease preventing effects. The components of volatile compounds in O. fragrans are complex but the content is less abundant. The present review mainly focuses on the bioactive ingredients identified from O. fragrans, the therapeutic effects of O. fragrans and its applications in food, cosmetics and medicines.

Molecular Docking, Tyrosinase, Collagenase, and Elastase Inhibition Activities of Argan By-Products

The argan tree (Argania spinosa (L.) Skeels) is one of the most important floristic resources in Morocco. This Moroccan endemic tree is known for its numerous therapeutic and medicinal uses. In addition to some medicinal and cosmetic uses, argan fruit pulp and press cake are traditionally used by the Berber population for heating and feeding livestock. Molecular docking is an in silico approach that predicts the interaction between a ligand and a protein. This approach is mainly used in chemistry and pharmacology of natural products as a prediction tool with the purpose of selecting plant extracts or fractions for in vitro tests. The aim of this research is to study the evaluation of potential tyrosinase, collagenase, and elastase inhibitory activities of argan fruit press-cake and pulp extracts. Extracts were evaluated for their total phenolic content (TPC), and the major polyphenols of both press-cake and pulp extracts were submitted to molecular docking in order to determine the mechanisms of action of these compounds. Obtained results revealed that fruit pulp had the strongest dermocosmetic activities, as well as the highest TPC, with values above 55 mg gallic-acid equivalent per gram of dry matter (mgeq AG/gDM). Moreover, those results were positively correlated with the docking findings, suggesting that the pulp lead compounds have higher affinity with tyrosinase, collagenase, and elastase action sites. The results here presented are very promising and open new perspectives for the exploitation of argan-tree by-products as cosmetic agents towards the development of new anti-aging products.

Efficacy and Safety of Topical Therapy With Botanical Products for Melasma: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Botanical products have been increasingly popular in topical therapies for melasma, as presumed safer and milder than fully synthetic products. Although the efficacy of different topical botanicals has recently been substantiated through randomized controlled trials (RCTs), there is a lack of sufficiently pooled evidence on their efficacy and safety for the treatment of melasma. Herein, a systematic review and meta-analysis was conducted on the efficacy and safety of topical botanical products for the treatment of melasma, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). All RCTs on the use of topical botanical products for the treatment of melasma in humans were included, except for trials enrolling pregnant patients. The primary outcome was Melasma Area and Severity Index (MASI) or its variation. The secondary outcomes included Mexameter^® reading, melasma improvement evaluated by participants, and any reported adverse events (AEs). As a result, twelve eligible trials comprising 695 patients with melasma from 6 different countries were included. The topical botanical products contained active ingredients which varied among trials as follows: herb-derived molecule, extracts of a single herb, and extracts of compound herbs. Topical therapy with botanical products significantly improved melasma with a large effect on MASI reduction (SMD −0.79, 95% CI −1.14 to −0.44, p < 0.00001), and a moderate effect on Mexameter^® reading reduction (SMD −0.52, 95% CI −0.81 to 0.23, p = 0.0005), when compared with placebo. It also showed a similar improvement of melasma with a better safety profile (RR 0.37, 95% CI 0.15–0.88, p = 0.02), when compared with active-comparators. Botanical products were well-tolerated across studies, with no serious AEs reported. Despite the limitations such as small sample size, short duration of follow up and varied botanical products, this work still represents the best level of evidence currently available on topical use of botanical products on melasma. Moreover, it should be noted that more well-designed studies are needed before recommending topical botanical products as a viable treatment option for melasma.

Ethnobotanical Survey on Skin Whitening Prescriptions of Traditional Chinese Medicine in Taiwan

The increasing interest and demand for skin whitening products globally, particularly in Asia, have necessitated rapid advances in research on skin whitening products used in traditional Chinese medicine (TCM). Herein, we investigated 74 skin whitening prescriptions sold in TCM pharmacies in Taiwan. Commonly used medicinal materials were defined as those with a relative frequency of citation (RFC) > 0.2 and their characteristics were evaluated. Correlation analysis of commonly used medicinal materials was carried out to identify the core component of the medicinal materials. Of the purchased 74 skin whitening prescriptions, 36 were oral prescriptions, 37 were external prescriptions, and one prescription could be used as an oral or external prescription. After analysis, 90 traditional Chinese medicinal materials were obtained. The Apiaceae (10%; 13%) and Leguminosae (9%; 11%) were the main sources of oral and external medicinal materials, respectively. Oral skin whitening prescriptions were found to be mostly warm (46%) and sweet (53%), while external skin whitening prescriptions included cold (43%) and bitter (29%) medicinal materials. Additionally, mainly tonifying and replenishing effects of the materials were noted. Pharmacological analysis indicated that these medicinal materials may promote wound healing, treat inflammatory skin diseases, or anti-hyperpigmentation. According to the Spearman correlation analysis on interactions among medicinal materials with an RFC > 0.2 in the oral skin whitening prescriptions, Paeonia lactiflora Pall. (white) and Atractylodes macrocephala Koidz. showed the highest correlation (confidence score = 0.93), followed by Ziziphus jujuba Mill. (red) and Astragalus propinquus Schischkin (confidence score = 0.91). Seven medicinal materials in external skin whitening prescriptions with an RFC > 0.2, were classified as Taiwan qī bái sàn (an herbal preparation), including Angelica dahurica (Hoffm.) Benth. & Hook. f. ex Franch. & Sav., Wolfiporia extensa (Peck) Ginns, Bletilla striata (Thunb.) Rchb. f., Atractylodes macrocephala Koidz., Ampelopsis japonica (Thunb.) Makino, Paeonia lactiflora Pall. (white), and Bombyx mori Linnaeus. Skin whitening prescriptions included multiple traditional Chinese medicinal materials. Despite the long history of use, there is a lack of studies concerning skin whitening products, possibly due to the complex composition of traditional Chinese medicine. Further studies are required to assess the efficacy and safety of these traditional Chinese medicinal materials for inclusion in effective, safe, and functional pharmacological products.

Rhamnazin suppresses melanosome transport by promoting the ubiquitin-mediated proteasomal degradation of melanophilin

BACKGROUND

Melanosomes are intracellularly transported from the perinuclear region to the cell periphery and then to neighboring keratinocytes. We recently reported that the flavonoid rhamnazin suppresses melanosomal transport within pigment cells, yet the action mechanism remained unclear.

OBJECTIVE

Our aim was to elucidate how rhamnazin influences the intracellular transport of melanosomes.

METHODS

A melanosome distribution assay and immunostaining were performed using B16F10 mouse melanoma cells and normal human epidermal melanocytes, respectively. Expression levels of melanosome transport-related proteins, including melanophilin (MLPH), RAB27A, and myosin VA (MYO5A), were analyzed by immunoblotting. Ubiquitinated MLPH was detected using a commercial ubiquitin detection kit. To investigate the interaction between rhamnazin and MLPH, we prepared rhamnazin conjugated with magnetic FG beads.

RESULTS

Immunoblotting analysis revealed that rhamnazin specifically reduces the expression of MLPH but not RAB27A or MYO5A proteins. The ubiquitin detection assay, which made use of a proteasome inhibitor, showed that MLPH accumulated as a polyubiquitinated protein after treatment with rhamnazin. We speculated that the affinity of rhamnazin for the components of the melanosome transport-related tripartite complex may alter the stability of the formation of the tripartite assembly. By using affinity-based techniques with B16F10 whole cell lysates or recombinant MLPH and RAB27A proteins, we revealed the interaction of rhamnazin with the components of the tripartite complex.

CONCLUSION

We found that rhamnazin inhibits intracellular transport of melanosomes through proteasomal degradation of MLPH. Our results suggest that topical application of rhamnazin may provide a new approach for treating skin pigmentation disorders.

Inhibitory Effect of Chlorogenic Acid Analogues Comprising Pyridine and Pyrimidine on α-MSH-Stimulated Melanogenesis and Stability of Acyl Analogues in Methanol

In continuation of studies for α-MSH stimulated melanogenesis inhibitors, we have evaluated the design, synthesis, and activity of a new series of chlorogenic acid (CGA) analogues comprising pyridine, pyrimidine, and diacyl derivatives. Among nineteen synthesized compounds, most of them (fifteen) exhibited better inhibitions of melanin formation in B16 melanoma cells. The results illustrated that a pyridine analogue 6f and a diacyl derivative 13a of CGA showed superior inhibition profiles (IC50: 2.5 ± 0.7 μM and 1.1 ± 0.1 μM, respectively) of α-MSH activities than positive controls, kojic acid and arbutin (IC50: 54 ± 1.5 μM and 380 ± 9.5 μM, respectively). The SAR studies showed that both -CF3 and -Cl groups exhibited better inhibition at the meta position on benzylamine than their ortho and para positions. In addition, the stability of diacyl analogues of CGA in methanol monitored by HPLC for 28 days indicated the steric bulkiness of acyl substituents as a key factor in their stability.

Highly Potent Inhibition of Tyrosinase by Mulberrosides and the Inhibitory Mechanism in Vitro

Many stilbene glycosides can alleviate skin hyperpigmentation due to their inhibitory effect on tyrosinase. Mulberrosides in Morus alba L. are stilbene glycosides. In the present study, the inhibition of tyrosinase by five mulberrosides (S1-5), isolated from Morus alba L. was investigated and compared, and the inhibitory mechanism was explored. These five mulberrosides exhibited obvious inhibitory effects on tyrosinase only in a concentration-dependent manner, without time-dependence, indicating that they are reversible inhibitors of tyrosinase. S2, S1 and S5 inhibited tyrosinase activity with IC₅₀ values of 28.93, 75.94 and 151.72 μM, respectively, and were more active than kojic acid (IC₅₀ =169.13 μM). Kinetic studies revealed that S1, S2 and S4 were competitive inhibitors, while S3 and S5 were mixed inhibitors. Analysis of the fluorescent spectra showed that mulberrosides S1, S2 and S4 quenched the intrinsic fluorescence intensity of tyrosinase. A molecular docking study indicated that the interaction of tyrosinase with mulberrosides was reflected by compound scores as follows: S2>S5>S1>S3/S4>kojic acid, and hydroxy groups in the side chain of mulberrosides may play a crucial role in the binding of the enzyme. Our results suggest that mulberrosides in Morus alba L. could be further developed as whitening agents for enhanced performance against hyperpigmentation.

Thiamidol® in moderate-to-severe melasma: 24-week, randomized, double-blind, vehicle-controlled clinical study with subsequent regression phase

Thiamidol^® was the most potent inhibitor of human tyrosinase out of 50 000 screened substances. In vivo, it was well tolerated and improved melasma significantly. This was the first 24-week, randomized, double-blind, vehicle-controlled, cosmetic clinical study to assess the efficacy and tolerability of thiamidol in moderate-to-severe melasma of phototype III-V subjects with subsequent regression phase. Females allocated to verum (n = 23), applied daily Dual Serum followed either by Day Care SPF30 in the morning or by Night Care in the evening, all containing Thiamidol. The vehicle group (25 females) followed the same skin care routine using the corresponding vehicle formulations. Subjects came back for a follow-up visit 13-20 weeks after treatment (regression phase). Assessments included clinical photography, Melasma Area and Severity Index (MASI), skin lightness, quality of life, and tolerability. Baseline demographics and hyperpigmentation were well balanced across the treatment groups. Clinical photography and MASI improved with Thiamidol significantly versus baseline (p < 0.001) and vehicle (p < 0.001-0.043) at all time points up to treatment end. At follow-up, the MASI was still significantly lower than at baseline but similar for verum and vehicle. Skin lightness and quality of life improved significantly versus baseline without significant differences between verum and vehicle. This study demonstrated that Thiamidol is well tolerated and superior in improving melasma compared to baseline and vehicle over a treatment period of 24 weeks.

Evaluation of Anti-Melanogenesis Activity of Enriched Pueraria lobata Stem Extracts and Characterization of Its Phytochemical Components Using HPLC-PDA-ESI-MS/MS

The root of Pueraria lobata (Willd.) is a widely used herbal medicine worldwide, whereas the stem of the plant is discarded or used as feed for livestock. To reuse and exploit the stem of P. lobata as a resource, we investigated its potential as a skin-whitening agent. We found that the developed, enriched P. lobata stem (PLS) extract significantly inhibited melanin production in the 3-isobutyl-1-methylxanthine-induced B16/F10 cells at a concentration of 50 μg/mL. To further confirm the mechanism of the antimelanogenic effect of the enriched PLS extracts, we examined the mRNA expression of tyrosinase, which was suppressed by the extracts. To standardize and implement effective quality control of the enriched PLS extracts, its major chemical constituents were identified by high-performance liquid chromatography-photodiode array-electrospray ionization-mass spectrometry. In total, 12 constituents were identified. In silico analysis showed that the main constituents, puerarin and daidzin, had excellent binding affinities for human tyrosinase. Collectively, our results suggest that the PLS extracts could be used as anti-pigmentation agents.

Schisandrin B inhibits α-melanocyte-stimulating hormone-induced melanogenesis in B16F10 cells via downregulation of MAPK and CREB signaling pathways

Schisandrin B (Sch B), a lignan compound in Schisandra, possesses antioxidant, anti-inflammatory, and antiobesity activities. The effect of Sch B on melanogenesis and molecular mechanisms are still unknown. Therefore, we aimed to investigate the antimelanogenic effects of Sch B on α-melanocyte-stimulating hormone-induced B16F10 cells and elucidate the underlying molecular mechanisms. We found that Sch B significantly suppressed melanin content and mushroom tyrosinase (TYR) activity. Sch B treatment decreased the expression of TYR, melanocyte-inducing transcription factor (MITF), tyrosinase-related protein (TRP) 1, and TRP2. Moreover, Sch B modulated the phosphorylation of p38, extracellular-regulated protein kinase, c-Jun N-terminal kinase, and cAMP-response element binding protein (CREB), implying that these pathways may be involved in suppressing melanogenesis. Furthermore, we found that Sch B decreased melanogenesis by downregulating MITF and melanogenic enzymes via MAPK and CREB pathways. Overall, these findings indicate that Sch B has the potential use in whitening.

Thiamidol containing treatment regimens in facial hyperpigmentation: An international multi-centre approach consisting of a double-blind, controlled, split-face study and of an open-label, real-world study

Objective

Tyrosinase is the rate‐limiting enzyme in melanogenesis. Thiamidol is the most potent inhibitor of human tyrosinase out of 50 000 tested compounds. In clinical studies, it was shown to improve facial hyperpigmentation, post‐inflammatory hyperpigmentation and age spots significantly. To identify the optimal number of daily Thiamidol applications, we conducted a split‐face study comparing the efficacy and tolerability of four‐times with two‐times daily application. Subsequently, we evaluated the efficacy and tolerability of a typical face care regimen containing Thiamidol in a real‐world study.

Methods

The split‐face study was double‐blind, randomized, controlled, including two Thiamidol containing products (serum and day care SPF 30). The serum was applied twice daily on one half of the face and the day care SPF30 twice‐daily on the whole face. The real‐world study was open‐label, observational, including three Thiamidol containing products (day care SPF 30 in the morning, serum and night care in the evening). In both studies, subjects with mild‐to‐moderate facial hyperpigmentation applied the products over 12 weeks. Assessments included clinical and subjective grading of hyperpigmentation, skin condition, hemi‐/modified MASI, chromameter and clinical photography.

Results

In the split‐face study (n = 34), hyperpigmentation, skin roughness and hMASI improved all significantly (P < 0.001) versus baseline, with first visible results after two weeks of twice‐daily application. The four‐times daily application led to significant improvement versus the two‐times daily application. In the real‐world study (n = 83), all evaluated parameters, including skin condition and chromametry (n = 30), improved significantly (P < 0.001) in comparison with baseline and the corresponding preceding visits. The subjects judged the cosmetic properties of the products positively. In both studies, the products were well tolerated.

Conclusion

Four‐times daily Thiamidol improves facial hyperpigmentation significantly more than two‐times daily and is well tolerated by the subjects. The real‐world study with a typical face care regimen containing Thiamidol shows improvement of facial hyperpigmentation and confirms tolerability. Furthermore, the data provide evidence for the suitability of this three‐product Thiamidol regimen for day‐to‐day life.

Collagenase and Tyrosinase Inhibitory Effect of Isolated Constituents from the Moss Polytrichum formosum

Mosses from the genus Polytrichum have been shown to contain rare benzonaphthoxanthenones compounds, and many of these have been reported to have important biological activities. In this study, extracts from Polytrichum formosum were analyzed in vitro for their inhibitory properties on collagenase and tyrosinase activity, two important cosmetic target enzymes involved respectively in skin aging and pigmentation. The 70% ethanol extract showed a dose-dependent inhibitory effect against collagenase (IC₅₀ = 4.65 mg/mL). The methanol extract showed a mild inhibitory effect of 44% against tyrosinase at 5.33 mg/mL. Both extracts were investigated to find the constituents having a specific affinity to the enzyme targets collagenase and tyrosinase. The known compounds ohioensin A (1), ohioensin C (3), and communin B (4), together with nor-ohioensin D (2), a new benzonaphthoxanthenone, were isolated from P. formosum. Their structures were determined by mass spectrometry and NMR spectroscopy. Compounds 1 (IC₅₀ = 71.99 µM) and 2 (IC₅₀ = 167.33 µM) showed inhibitory activity against collagenase. Compound 1 also exhibited inhibition of 30% against tyrosinase activity at 200 µM. The binding mode of the active compounds was theoretically generated by an in-silico approach against the 3D structures of collagenase and tyrosinase. These current results present the potential application from the moss P. formosum as a new natural source of collagenase and tyrosinase inhibitors.