Discovery of anti-melanogenic components in persimmon (Diospyros kaki) leaf using LC-MS/MS-MN, AlphaFold2-enabled virtual screening and biological validation.

Persimmon (Diospyros kaki) leaf is widely used as a tea substitute in East Asia, offering potential health benefits. Although studies have highlighted their effects on hyperpigmentation disorders, the active components remain unidentified. This study introduces a novel approach combining LC-MS/MS-based molecular networking with AlphaFold2-enabled virtual screening to expedite the identification of bioactive components in persimmon leaf. A total of 105 compounds were identified by MS/MS analysis. Further, virtual screening identified five flavonoids with potential anti-melanogenic properties. Bioassays confirmed myricetin, quercetin, and kaempferol inhibited melanogenesis in human melanocytes in a dose-dependent manner. Biolayer interferometry assays revealed strong binding affinity between these flavonols and hsTYR, with KD values of 23.26 ± 11.77 for myricetin, 12.43 ± 0.37 for quercetin, and 14.99 ± 3.80 µM for kaempferol. Molecular dynamics simulations provided insights into the binding interactions of these flavonols with hsTYR, particularly highlighting the essential role of the 3-OH group on the C-ring. This study elucidates the bioactive components responsible for the anti-melanogenic effects of persimmon leaf, supporting their use in product development.

Anti-Melanogenic Activity of Undecylprodigiosin, a Red Pigment Isolated from a Marine Streptomyces sp. SNA-077.

Bioassay and HPLC-UV guided fractionations of the crude extract of marine-derived Streptomyces sp. SNA-077 have led to the isolation of a red pigment, undecylprodigiosin (1). The chemical structure of undecylprodigiosin (1) was revealed by the interpretation of NMR and mass spectroscopic (MS) data. Further, anti-melanogenic effects of undecylprodigiosin (1) were investigated. First, the melanin contents of undecylprodigiosin (1)-treated B16 cells were evaluated. Furthermore, undecylprodigiosin (1) significantly inhibited the key enzymes involved in melanogenesis, including tyrosinase, tyrosinase related protein-1 (TYRP-1), and dopachrome tautomerase (DCT). The mRNA and protein expression levels of Microphthalmia-associated transcriptian factor (MiTF), a critical transcription factor for tyrosinase gene expression, were also suppressed by undecylprodigiosin (1) treatment in B16 analyses. Collectively, our results suggest for the first time that undecylprodigiosin (1), a potent component isolated from an extract of marine Streptomyces sp. SNA-077, critically exerts the anti-melanogenic ability for melanin synthesis.

Antioxidant and Anti-Melanogenesis Effects of Teucrium chamaedrys L. Cell Suspension Extract and Its Main Phenylethanoid Glycoside in B16-F10 Cells.

Teucrium chamaedrys L. is a typical European-Mediterranean species of the genus Teucrium. Among the phenolic compounds belonging to phenylethanoid glycosides (PGs), teucrioside (TS) is only found in this species, and it was previously demonstrated to be produced by in vitro-elicited cell cultures at levels higher than those found in leaves. However, T. chamaedrys cell suspension extracts (Cell-Ex) and pure TS have not been investigated yet for any biological effects. In this study, we evaluated the antioxidant and anti-melanogenesis activity of both Cell-Ex and TS in B16-F10 mouse melanoma cells. The results showed that Cell-Ex inhibited the reactive oxygen species formation evoked in B16-F10 cells by tert-butyl hydroperoxide and 5 J/cm2 of UVA, as well as the melanin increase stimulated by α-MSH or 20 J/cm2 of UVA. In parallel, a TS concentration equivalent to that present in Cell-Ex recorded the same biological effect profile, suggesting the main contribution of TS to the antioxidant and anti-melanogenic properties of Cell-Ex. Both Cell-Ex and TS also modulated the melanogenesis pathway through their ability to inhibit the tyrosinase activity both in a cell-free system and in B16-F10 cells stimulated by α-MSH. These results support the potential cosmeceutical use of Cell-Ex for protection against photooxidative damage and hyperpigmentation.

Characterizing Nanoparticle Isolated by Yam Bean (Pachyrhizus erosus) as a Potential Agent for Nanocosmetics: An in vitro and in vivo Approaches.

BACKGROUND: This study investigated the potential of Plant-Derived Exosome-Like Nanoparticles (PDENs) as cosmeceutical nanocarriers for treating skin problems, such as scar removal, face rejuvenation, anti-aging, and anti-pigmentation. OBJECTIVE: Researchers isolated PDENs from Yam Bean (Pachyrhizus erosus) using PEG-based precipitation, gradual filtration, and various centrifugations at low temperatures. Followed by in vitro and in vivo studies using HDF cells and Zebrafish. METHODS: The morphology of the YB-PDENs was determined using TEM analysis, they had a spherical shape with diameters of 236,83 ± 9,27nm according to PSA. The study found that YB-PDENs were stable in aquabidest at 4°C for one month of storage and had ~-26,5 mV of Zeta Potential. The concentration of YB-PDENs was measured using the BCA Assay, and internalization of YB-PDENs to HDF cells was observed using a Confocal Laser Scanning Microscope labelled with PKH67. RESULT: As for cytotoxicity, after 24 and 72 hours of incubation with YB-PDENs, the viability of HDF cells remained more than 80%. The study also examined cell migration using the Scratch Assay and found that at 2,5 µg/mL, YB-PDENs had better migration results than other concentrations. Immunocytochemistry showed that collagen expression was higher after 14 days of incubation with YB-PDENs, and melanocytes in zebrafish decreased at each concentration compared with controls. CONCLUSION: In conclusion, this study is the first to extract and describe PDENs from Yam Bean (Pachyrhizus erosus), with YB-PDENs having a promising anti-melanogenic effect in skin treatment. This study highlights the potential of YB-PDENs as a promising alternative to depigmentation and skin whitening treatments.

2,4,6-Triphenyl-1-hexene, an Anti-Melanogenic Compound from Marine-Derived Bacillus sp. APmarine135.

Although melanin protects against ultraviolet radiation, its overproduction causes freckles and senile lentigines. Recently, various biological effects of metabolites derived from marine microorganisms have been highlighted due to their potential for biological and pharmacological applications. In this study, we discovered the anti-melanogenic effect of Bacillus sp. APmarine135 and verified the skin-whitening effect. Fractions of APmarine135 showed the melanin synthesis inhibition effect in B16 melanoma cells, and 2,4,6-triphenyl-1-hexene was identified as an active compound. The melanogenic capacity of 2,4,6-triphenyl-1-hexene (1) was investigated by assessing the intracellular melanin content in B16 cells. Treatment with 5 ppm of 2,4,6-triphenyl-1-hexene (1) for 72 h suppressed the α-melanocyte-stimulating hormone (α-MSH)-induced intracellular melanin increase to the same level as in the untreated control group. Additionally, 2,4,6-triphenyl-1-hexene (1) treatment suppressed the activity of tyrosinase, the rate-limiting enzyme for melanogenesis. Moreover, 2,4,6-triphenyl-1-hexene (1) treatment downregulated tyrosinase, Tyrp-1, and Tyrp-2 expression by inhibiting the microphthalmia-associated transcription factor (MITF). Furthermore, 2,4,6-triphenyl-1-hexene (1) treatment decreased the melanin content in the three-dimensional (3D) human-pigmented epidermis model MelanoDerm and exerted skin-whitening effects. Mechanistically, 2,4,6-triphenyl-1-hexene (1) exerted anti-melanogenic effects by suppressing tyrosinase, Tyrp-1, and Tyrp-2 expression and activities via inhibition of the MITF. Collectively, these findings suggest that 2,4,6-triphenyl-1-hexene (1) is a promising anti-melanogenic agent in the cosmetic industry.

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.

Biological Activity of Fermented Plant Extracts for Potential Dermal Applications.

Fermented plant extracts (FPEs) are functional liquids formed as a result of the fermentation of fresh plants by microorganisms, mainly bacteria and fungi. The appropriate selection of plants, microorganism strains, and conditions under which the fermentation process is carried out is very important in terms of obtaining a suitable matrix of biologically active compounds with different biological properties. The purpose of this review is to provide verified data on the current knowledge acquired regarding the biological activity of FPEs for cosmetic use and dermal applications. The antioxidant, antimicrobial, anti-inflammatory, anti-melanogenic, and wound-healing activity of FPEs, as well as their potential dermal applications, will be described.

In Vitro and In Vivo Biological Evaluation of Indole-thiazolidine-2,4-dione Derivatives as Tyrosinase Inhibitors.

Tyrosinase is an important rate-limiting enzyme in melanin biosynthesis. To find potential tyrosinase inhibitors with anti-melanogenic activity, a series of indole-thiazolidine-2,4-dione derivatives 5a~5z were synthesized by incorporating indole with thiazolidine-2,4-dione into one compound and assayed for their biological activities. All compounds displayed tyrosinase inhibitory activities and 5w had the highest anti-tyrosinase inhibitory activity with an IC50 value of 11.2 µM. Inhibition kinetics revealed 5w as a mixed-type tyrosinase inhibitor. Fluorescence quenching results indicated that 5w quenched tyrosinase fluorescence in a static process. CD spectra and 3D fluorescence spectra results suggested that the binding of 5w with tyrosinase could change the conformation and microenvironment of tyrosinase. Molecular docking also represented the binding between 5w and tyrosinase. Moreover, 5w could inhibit tyrosinase activity and melanogenesis both in B16F10 cells and the zebrafish model. Therefore, compound 5w could serve as a tyrosinase inhibitor with anti-melanogenic activity.

Anti-Melanogenic Effects of Lilium lancifolium Root Extract via Downregulation of PKA/CREB and MAPK/CREB Signaling Pathways in B16F10 Cells.

Hyperpigmentation disorders causing emotional distress require the topical use of depigmenting agents of natural origin. In this study, the anti-melanogenic effects of the Lilium lancifolium root extract (LRE) were investigated in B16F10 cells. Consequently, a non-cytotoxic concentration of the extract reduced intracellular melanin content and tyrosinase activity in a dose-dependent manner, correlating with the diminished expression of core melanogenic enzymes within cells. LRE treatment also inhibited cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB)/microphthalmia-associated transcription factor signaling, which regulates the expression of tyrosinase-related genes. Upon examining these findings from a molecular mechanism perspective, LRE treatment suppressed the phosphorylation of protein kinase A (PKA), p38, and extracellular signal-related kinase (ERK), which are upstream regulators of CREB. In addition, L-phenylalanine and regaloside A, specifically identified within the LRE using liquid chromatography-mass spectrometry, exhibited inhibitory effects on melanin production. Collectively, these results imply that LRE potentially suppresses cAMP-mediated melanogenesis by downregulating PKA/CREB and mitogen-activated protein kinase (MAPK)/CREB signaling pathways. Therefore, it can be employed as a novel therapeutic ingredient of natural origin to ameliorate hyperpigmentation disorders.

Molecular Docking and Dynamics Simulations of Ammi visnaga L. Constituents as Antimelanogenic, Anti-Inflammatory and Anticoagulant Agents.

In this study, anti-melanogenic, anti-inflammatory and anti-coagulant potentials of eighteen selected constituents of Ammi visnaga L. were investigated by Induced Fit Docking (IFD) and molecular dynamic simulation with Schrödinger software. The binding free energies of the selected natural compounds were computed by means of ΔG MM-GBSA studies. Anti-melanogetic activity of the constituent against agaricus bisporus tyrosinase, Priestia megaterium tyrosinase and Homo sapiens tyrosinase were evaluated. The result showed that apiumetin had more negative binding free energy against three tyrosinase enzymes than cognate ligands, tropolone and kojic acid. Docking analysis was also performed to predict the constituents with anti-inflammatory activity against human Tumor necrosis factor, Cyclooxygenase-2, Prostaglandin D2 11-ketoreductase AKR1C3 and Prostaglandin reductase PTGR2. The results showed that pyranocoumarins (visnadin, dihydrosamidin, samidin) have more negative binding free energy against Cyclooxygenase-2 and Prostaglandin D2 11-ketoreductase receptors than cognate drugs, rofecoxib and indomethacin. In addition, docking analysis shows that pyranocoumarins, apiumetin and cimifugin have more negative binding free energy against Vitamin K epoxide reductase than S-warfarin drug, predicting that they have anticoagulant activity. Furthermore, the constituents and their cognate drugs were subjected to 100 ns MD Simulation to predict their stability at the active sites of the enzymes.

Anti-Melanogenic and Antioxidant Activity of Bifidobacterium longum Strain ZJ1 Extracts, Isolated from a Chinese Centenarian.

Melanin produced by melanocytes protects our skin against ultraviolet (UV) radiation-induced cell damage and oxidative stress. Melanin overproduction by hyperactivated melanocytes is the direct cause of skin hyperpigmentary disorders, such as freckles and melasma. Exploring natural whitening agents without the concern of toxicity has been highly desired. In this study, we focused on a Bifidobacterium longum strain, ZJ1, isolated from a Chinese centenarian, and we evaluated the anti-melanogenic activity of the distinctive extracts of ZJ1. Our results demonstrated that whole lysate (WL) and bacterial lysate (BL) of ZJ1 ferments efficiently reduce α-melanocyte-stimulating hormone (α-MSH)-induced melanin production in B16-F10 cells as well as the melanin content in zebrafish embryos. BL and WL downregulate melanogenesis-related gene expression and indirectly inhibit intracellular tyrosinase activity. Furthermore, they both showed antioxidant activity in a menadione-induced zebrafish embryo model. Our results suggest that ZJ1 fermentation lysates have application potential as therapeutic reagents for hyperpigmentary disorders and whitening agents for cosmetics.

Histone Deacetylase Inhibitor, Sodium Butyrate-Induced Metabolic Modulation in Platycodon grandiflorus Roots Enhances Anti-Melanogenic Properties.

While the status of histone acetylation is a critical regulator of chromatin's structure with a significant impact on plant physiology, our understanding of epigenetic regulation in the biosynthesis of active compounds in plants is limited. In this study, Platycodon grandiflorus was treated with sodium butyrate (NaB), a histone deacetylase inhibitor, to investigate the influence of histone acetylation on secondary metabolism. Its treatment with NaB increased the acetylation of histone H3 at lysine 9, 14, and 27 and enhanced the anti-melanogenic properties of P. grandiflorus roots. Through transcriptome and differentially expressed gene analyses, we found that NaB influenced the expression of genes that were involved in both primary and secondary metabolic pathways. In addition, NaB treatment caused the accumulation of polyphenolic compounds, including dihydroquercetin, gallic acid, and 2,4-dihydroxybenzoic acid. The NaB-induced transcriptional activation of genes in the phenylpropanoid biosynthetic pathway influenced the anti-melanogenic properties of P. grandiflorus roots. Overall, these findings suggest the potential of an epigenomic approach to enhance the medicinal qualities of medicinal plants.

Inhibitory Effects of Polyphenol- and Flavonoid-Enriched Rice Seed Extract on Melanogenesis in Melan-a Cells via MAPK Signaling-Mediated MITF Downregulation.

Melanin production is an important process that prevents the host skin from harmful ultraviolet radiation; however, an overproduction of melanin results in skin diseases. In the present study, we determined the antioxidative and anti-melanogenic activities of polyphenol- and flavonoid-enriched rice seed extracts in melan-a cells. The polyphenol and flavonoid content of Hopum (HP) and Sebok (SB) rice seed extracts was measured. The antioxidant capacity was determined using the ABTS radical scavenging method. SB contained high amounts of polyphenols and flavonoids, which significantly increased antioxidative activity compared with HP. Various concentrations of these extracts were evaluated in a cytotoxicity using melan-a cells. At 100 µg/mL, there was no significant difference for all treatments compared with untreated cells. Therefore, 100 µg/mL was selected as a concentration for the further experiments. SB significantly suppressed the phosphorylation/activation of p-38 MAPK, increased the expression of phosphorylated ERK 1/2 and Akt, and downregulated the microphthalmia-associated transcription factor (MITF). This resulted in decreased levels of tyrosinase and tyrosinase-related protein-1 and -2. These results indicate the potential of polyphenol- and flavonoid-enriched rice seed as a treatment for hyperpigmentation.

ANTIAGE-DB: A Database and Server for the Prediction of Anti-Aging Compounds Targeting Elastase, Hyaluronidase, and Tyrosinase.

Natural products bear a multivariate biochemical profile with antioxidant, anti-inflammatory, antibacterial, and antitumoral properties. Along with their natural sources, they have been widely used both as anti-aging and anti-melanogenic agents due to their effective contribution in the elimination of reactive oxygen species (ROS) caused by oxidative stress. Their anti-aging activity is mainly related to their capacity of inhibiting enzymes like Human Neutrophil Elastase (HNE), Hyaluronidase (Hyal) and Tyrosinase (Tyr). Herein, we accumulated literature information (covering the period 1965-2020) on the inhibitory activity of natural products and their natural sources towards these enzymes. To navigate this information, we developed a database and server termed ANTIAGE-DB that allows the prediction of the anti-aging potential of target compounds. The server operates in two axes. First a comparison of compounds by shape similarity can be performed against our curated database of natural products whose inhibitory potential has been established in the literature. In addition, inverse virtual screening can be performed for a chosen molecule against the three targeted enzymes. The server is open access, and a detailed report with the prediction results is emailed to the user. ANTIAGE-DB could enable researchers to explore the chemical space of natural based products, but is not limited to, as anti-aging compounds and can predict their anti-aging potential. ANTIAGE-DB is accessed online.

Design, Synthesis, and in Vitro Evaluation of 4-(4-Hydroxyphenyl)piperazine-Based Compounds Targeting Tyrosinase.

Melanin biosynthesis is enzymatically regulated by tyrosinase (TYR, EC 1.14.18.1), which is efficiently inhibited by natural and synthetic phenols, demonstrating potential therapeutic application for the treatment of several human diseases. Herein we report the inhibitory effects of a series of (4-(4-hydroxyphenyl)piperazin-1-yl)arylmethanone derivatives, that were designed, synthesised and assayed against TYR from Agaricus bisporus (AbTYR). The best inhibitory activity was predominantly found for compounds bearing selected hydrophobic ortho-substituents on the aroyl moiety (IC50 values in the range of 1.5-4.6 µM). They proved to be more potent than the reference compound kojic acid (IC50 =17.8 µM) and displayed competitive mechanism of inhibition of diphenolase activity of AbTYR. Docking simulation predicted their binding mode into the catalytic cavities of AbTYR and the modelled human TYR. In addition, these compounds displayed antioxidant activity combined with no cytotoxicity in MTT tests. Notably, the best inhibitor affected tyrosinase activity in α-MSH-stimulated B16F10 cells, thus demonstrating anti-melanogenic activity.

Catechin-7-O-α-L-rhamnopyranoside can reduce α-MSH-induced melanogenesis in B16F10 melanoma cells through competitive inhibition of tyrosinase.

Although melanogenesis is a defense mechanism against ultraviolet (UV)-induced skin damage, abnormally excessive melanin production causes pigmentation disorders. Tyrosinase, as a key factor for melanin synthesis, plays an important role in inducing skin pigmentation. Therefore, the inhibition of tyrosinase is crucial in preventing skin pigmentation in the cosmetics and medicine fields. However, the majority of well-known tyrosinase inhibitors have been discontinued due to toxic effects on the skin or lack of selectivity and/or stability. In this study, we evaluated possible anti-melanogenic effects of catechin-7-O-α-L-rhamnopyranoside (C7R) isolated from the stem bark of Ulmus parvifolia, to discover a new tyrosinase inhibitor that has both safety and stability. When C7R was pretreated in B16F10 melanoma cells stimulated by α-melanocyte-stimulating hormone, this compound reduced melanin accumulation and murine tyrosinase activity. In line with these results, C7R inhibits tyrosinase purified from a mushroom in vitro like kojic acid and arbutin. Furthermore, C7R exhibited a competitive inhibition on a Lineweaver-Burk plot. Next, the underlying mechanisms of the C7R-mediated tyrosinase inhibitory effect were sought through docking simulation and pharmacophore analysis between tyrosinase residues and C7R. The results of these analyses showed that C7R had binding energy of -14.5kcal/mol, and indicated that C7R interacts with tyrosinase through an aromatic ring and various hydrophobic and hydrogen bonds. Together, our results suggest that C7R can be applied as a novel natural anti-melanogenic agent that inhibits tyrosinase.

Enzymatic Biosynthesis of Simple Phenolic Glycosides as Potential Anti-Melanogenic Antioxidants.

Simple phenolics (SPs) and their glycosides have recently gained much attention as functional skin-care resources for their anti-melanogenic and antioxidant activities. Enzymatic glycosylation of SP aglycone make it feasible to create SP glycosides with updated bioactive potentials. Herein, a glycosyltransferase (GT)-encoding gene was cloned from the fosmid libraries of Streptomyces tenjimariensis ATCC 31603 using GT-specific degenerate PCR followed by in silico analyses. The recombinant StSPGT was able to flexibly catalyze the transfer of two glycosyl moieties towards two SP acceptors, (hydroxyphenyl-2-propanol [HPP2] and hydroxyphenyl-3-propanol [HPP3]), generating stereospecific α-anomeric glycosides as follows: HPP2-O-α-glucoside, HPP2-O-α-2″-deoxyglucoside, HPP3-O-α-glucoside and HPP3-O-α-2″-deoxyglucoside. This enzyme seems not only to prefer UDP-glucose and HPP2 as a favorable glycosyl donor and acceptor, respectively but also differentiates the positional difference of the hydroxyl function as acceptor catalytic sites. Paired in vitro and in vivo antioxidant assays represented SPs and their corresponding glycosides as convincing antioxidants in a time- and concentration-dependent manner by scavenging DPPH radicals and intracellular ROS. Even compared to the conventional agents, HPP2 and glycoside analogs displayed improved tyrosinase inhibitory activity in vitro and still suppressed in vivo melanogenesis. Both HPP2 glycosides are further likely to exert the best inhibitory activity against elastase, eventually highlighting these glycosides with enhanced anti-melanogenic and antioxidant activities as promising anti-wrinkle hits.

Dimethyl Itaconate Reduces α-MSH-Induced Pigmentation via Modulation of AKT and p38 MAPK Signaling Pathways in B16F10 Mouse Melanoma Cells.

Dimethyl itaconate (DMI) exhibits an anti-inflammatory effect. Activation of nuclear factor erythroid 2-related factor 2 (NRF2) is implicated in the inhibition of melanogenesis. Therefore, DMI and itaconic acid (ITA), classified as NRF2 activators, have potential uses in hyperpigmentation reduction. The activity of cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB), an important transcription factor for MITF gene promoter, is regulated by glycogen synthase kinase 3ß (GSK3ß) and protein kinase A (PKA). Here, we investigated the inhibitory effect of ITA and DMI on alpha-melanocyte-stimulating hormone (α-MSH)-induced MITF expression and the modulatory role of protein kinase B (AKT) and GSK3ß in melanogenesis in B16F10 mouse melanoma cells. These cells were incubated with α-MSH alone or in combination with ITA or DMI. Proteins were visualized and quantified using immunoblotting and densitometry. Compared to ITA, DMI treatment exhibited a better inhibitory effect on the α-MSH-induced expression of melanogenic proteins such as MITF. Our data indicate that DMI exerts its anti-melanogenic effect via modulation of the p38 mitogen-activated protein kinase (MAPK) and AKT signaling pathways. In conclusion, DMI may be an effective therapeutic agent for both inflammation and hyperpigmentation.

8-Methoxybutin inhibits α-MSH induced melanogenesis and proliferation of skin melanoma by suppression of the transactivation activity of microphthalmia-associated transcription factor.

Microphthalmia-associated transcription factor (MITF) is highly expressed in melanocytes and is the main regulator of melanogenesis and melanocyte cell fate. Although MITF is important for the differentiation and development of melanocytes, it is also considered an oncogene of skin melanoma. Based on these findings, MITF could be an attractive therapeutic target for skin cancer intervention. This study identified 8-methoxybutin as an inhibitor of MITF and investigated the underlying mechanism. 8-Methoxybutin inhibited α-MSH-induced melanogenesis in murine melanoma cells (B16F10) and skin melanoma proliferation by reducing melanogenic gene expression via blockade of the transactivation activity of MITF. In silico docking analysis and pull-down analysis suggested that 8-methoxybutin binds to the DNA-binding domain of MITF and further inhibits its binding to the E-box in the promoter of target genes, including tyrosinase. In addition, 8-methoxybutin suppressed growth of skin melanoma in a xenograft mouse model. These results indicate that 8-methoxybutin has potential as a therapeutic agent for hyperpigmentation disorder and skin cancer. SIGNIFICANCE STATEMENT: 8-Methoxybutin inhibits MITF transactivation activity resulting suppression of melanogenesis and skin melanoma growth.

Deoxyvasicinone with Anti-Melanogenic Activity from Marine-Derived Streptomyces sp. CNQ-617.

The tricyclic quinazoline alkaloid deoxyvasicinone (DOV, 1) was isolated from a marine-derived Streptomyces sp. CNQ-617, and its anti-melanogenic effects were investigated. Deoxyvasicinone was shown to decrease the melanin content of B16F10 and MNT-1 cells that have been stimulated by α-melanocyte-stimulating hormone (α-MSH). In addition, microscopic images of the cells showed that deoxyvasicinone attenuated melanocyte activation. Although, deoxyvasicinone did not directly inhibit tyrosinase (TYR) enzymatic activity, real-time PCR showed that it inhibited the mRNA expression of TYR, tyrosinase-related protein 1 (TRP-1), and tyrosinase-related protein 2 (TRP-2). In the artificial 3D pigmented skin model MelanodermTM, deoxyvasicinone brightened the skin significantly, as confirmed by histological examination. In conclusion, this study demonstrated that the marine microbial natural product deoxyvascinone has an anti-melanogenic effect through downregulation of melanogenic enzymes.