Cosmetic applications of glucitol-core containing gallotannins from a proprietary phenolic-enriched red maple (Acer rubrum) leaves extract: inhibition of melanogenesis via down-regulation of tyrosinase and melanogenic gene expression in B16F10 melanoma cells

Synthesis, in silico modelling, and in vitro biological evaluation of substituted pyrazole derivatives as potential anti-skin cancer, anti-tyrosinase, and antioxidant agents

Twenty-five azole compounds (P1-P25) were synthesised using regioselective base-metal catalysed and microwave-assisted approaches, fully characterised by high-resolution mass spectrometry (HRMS), nuclear magnetic resonance (NMR), and infrared spectra (IR) analyses, and evaluated for anticancer, anti-tyrosinase, and anti-oxidant activities in silico and in vitro. P25 exhibited potent anticancer activity against cells of four skin cancer (SC) lines, with selectivity for melanoma (A375, SK-Mel-28) or non-melanoma (A431, SCC-12) SC cells over non-cancerous HaCaT-keratinocytes. Clonogenic, scratch-wound, and immunoblotting assay data were consistent with anti-proliferative results, expression profiling therewith implicating intrinsic and extrinsic apoptosis activation. In a mushroom tyrosinase inhibition assay, P14 was most potent among the compounds (half-maximal inhibitory concentration where 50% of cells are dead, IC50 15.9 μM), with activity greater than arbutin and kojic acid. Also, P6 exhibited noteworthy free radical-scavenging activity. Furthermore, in silico docking and absorption, distribution, metabolism, excretion, and toxicity (ADMET) simulations predicted prominent-phenotypic actives to engage diverse cancer/hyperpigmentation-related targets with relatively high affinities. Altogether, promising early-stage hits were identified - some with multiple activities - warranting further hit-to-lead optimisation chemistry with further biological evaluations, towards identifying new skin-cancer and skin-pigmentation renormalising agents.

Searching for Natural Plants with Antimelanogenesis and Antityrosinase Properties for Cosmeceutical or Nutricosmetics Applications: A Systematic Review

Excessive UV radiation (UVR) exposure has been shown in studies to be a major risk factor for most melanomas, causing premature skin aging as well as immune system suppression due to the increased production of hydrogen peroxide (H2O2) and other reactive oxygen species (ROS) during the melanogenesis process. Although several compounds with antioxidant and antityrosinase activities are widely used in the cosmetic industry, like kojic acid, hydroquinone, ascorbic acid, and arbutin, their use has been limited due to their adverse effects on the skin and cytotoxic issues. Recently, attempts have been made to develop new natural skin-lightening products by using plant extracts that are less toxic and exhibit numerous biological properties with great market demand. In this study, information on the depigmentation effects of various natural plant species was gathered from the SCOPUS database according to the PRISMA guidelines. A total of 414 records were retrieved, and finally, 76 articles were included in the qualitative synthesis by fulfilling all the inclusion criteria. In this review, we discuss the extraction methods and biological assays of 75 highly potential plant species, including the olive, yuzu, longan, and lotus. We concluded that the use of natural plants as skin-whitening agents is highly effective as there is a significant correlation between the content of polyphenolic compounds, antimelanogenesis, antityrosinase, and antioxidant activities. However, it is worth noting that the use of extraction methods or types of solvents is very important in determining the biological activities of plants.

Bioactive Molecules from Myrianthus arboreus, Acer rubrum, and Picea mariana Forest Resources

Forest trees are the world's most important renewable natural resources in terms of their dominance among other biomasses and the diversity of molecules that they produce. Forest tree extractives include terpenes and polyphenols, widely recognized for their biological activity. These molecules are found in forest by-products, such as bark, buds, leaves, and knots, commonly ignored in forestry decisions. The present literature review focuses on in vitro experimental bioactivity from the phytochemicals of Myrianthus arboreus, Acer rubrum, and Picea mariana forest resources and by-products with potential for further nutraceutical, cosmeceutical, and pharmaceutical development. Although these forest extracts function as antioxidants in vitro and may act on signaling pathways involved in diabetes, psoriasis, inflammation, and skin aging, much still remains to be investigated before using them as therapeutic candidates, cosmetics, or functional foods. Traditional forest management systems focused on wood must evolve towards a holistic approach, allowing the use of these extractives for developing new value-added products.

What Is Authentic Maple Water? A Twelve-Month Shelf-Life Study of the Chemical Composition of Maple Water and Its Biological Activities

Maple water (maple sap) products are produced from sap tapped directly from maple trees, but there is confusion and lack of industry consensus and consumer knowledge as to what constitutes 'authentic' maple water. With an immense potential for growth in the multi-billion dollar functional beverage market, the market promotion of maple water products hinges on establishing standards of identity (SI), which are currently lacking. Herein, we aim to provide publishable SI and compositional chemistry findings of maple water. The chemical composition (including polyphenols, sugars, amino acids, and organic acids) of a pasteurized maple water was monitored over a 12-month (at 0, 4, 8, and 12 months) shelf-life. Furthermore, LC-MS/MS and molecular networking-based methods were developed to identify the phytochemical profile of a maple water extract (MWX) and to compare it to a previously chemically characterized phenolic-enriched maple syrup extract (MSX). Both MSX and MWX have similar phytochemical profiles and chemical characteristics. In addition, MSX and MWX showed moderate antioxidant capacity (in free radical scavenging and anti-tyrosinase assays) and anti-inflammatory effects (in soluble epoxide hydrolase and cyclooxygenase-2 inhibition assays). Our findings provide critical information on the SI and stability (in chemical composition) of maple water, which will help define, authenticate, and distinguish it from other functional beverages, thereby positioning the maple industry for promotion and growth in this market sector.

Standardized Pomegranate (Pomella®) and Red Maple (Maplifa®) Extracts and Their Phenolics Protect Type I Collagen by the Inhibition of Matrix Metalloproteinases, Collagenase, and Collagen Cross-Linking

Phenolics enriched pomegranate fruit (Pomella®) and red maple leaf (Maplifa®) extracts and their major phenolic constituents have demonstrated beneficial skin effects through the protection of human skin keratinocytes from oxidative-stress-induced damage. However, their mechanisms of protection of cutaneous collagen are still unclear. Herein, the collagen protective effects of Pomella® and Maplifa®, and their major bioactive phytochemicals, namely, punicalagin (PA) and ginnalin A (GA), respectively, were evaluated using enzymatic assays including collagenase, anti-glycation and cell-based models as well as computational methods. The importance of the modulatory effects was validated at the protein level for type I collagen and matrix metalloproteinases (MMPs) using human-skin-derived keratinocytes. The synergistic collagenase inhibitory effects upon combinations of Pomella® + Maplifa® and PA + GA at a combination ratio of 1:2 and 1:1, respectively, were evaluated using their combination index (CI; a well-established assessment of synergism). Pomella® (50-400 µg/mL), Maplifa® (100-800 µg/mL), PA (50-400 µM), and GA (50-400 µM) dose-dependently inhibited collagenase activity by 26.3-86.3%, 25.7-94.0%, 26.2-94.0%, and 12.0-98.0%, respectively. The CI of the anti-collagenase activity of Pomella® and Maplifa® ranged from 0.53-0.90, while that of PA and GA (12.5/12.5 and 25/25 µM) ranged from 0.66 and 0.69, respectively, suggesting a synergistic inhibitory effect. Interestingly, in the cell-based assays by Western blotting, Pomella® and Maplifa® reduced the protein expression levels of collagen degradation enzymes (MMPs), while simultaneously increasing that of type I collagen in epidermoid carcinoma A431 cells. This is the first report to show that these extracts exert synergistic collagen protective effects. Taken together, these findings provide molecular insights into the usefulness of Pomella® and Maplifa® or their phenolics as bioactive ingredients for skin care products to slow down aging and enhance skin tone.

The Modulation of Melanogenesis in B16 Cells Upon Treatment with Plant Extracts and Isolated Plant Compounds

Plants are a rich source of secondary metabolites that exhibit numerous desired properties. The compounds may influence the biology of melanocytes, pigment cells that produce melanin, by modulating numerous signaling pathways, including cAMP/PKA, MAPKs and PI3K/AKT. Its downstream target is microphthalmia-associated transcription factor, responsible for the expression of the tyrosinase enzyme, which plays a major role in melanogenesis. Therefore, this literature review aims to provide insights related to melanogenesis modulation mechanisms of plant extracts and isolated plant compounds in B16 cells. Database searches were conducted using online-based library search instruments from 2012 to 2022, such as NCBI-PubMed and Google Scholar. Upregulation or downregulation of signaling pathways by phytochemicals can influence skin hypo- and hyperpigmentation by changing the level of melanin production, which may pose a significant cosmetic issue. Therefore, plant extracts or isolated plant compounds may be used in the therapy of pigmentation disorders.

Melanins as Sustainable Resources for Advanced Biotechnological Applications

Melanins are a class of biopolymers that are widespread in nature and have diverse origins, chemical compositions, and functions. Their chemical, electrical, optical, and paramagnetic properties offer opportunities for applications in materials science, particularly for medical and technical uses. This review focuses on the application of analytical techniques to study melanins in multidisciplinary contexts with a view to their use as sustainable resources for advanced biotechnological applications, and how these may facilitate the achievement of the United Nations Sustainable Development Goals.

High Glucose and Hypoxia-Mediated Damage to Human Brain Microvessel Endothelial Cells Induces an Altered, Pro-Inflammatory Phenotype in BV-2 Microglia In Vitro

Diabetes is strongly linked to the development of Alzheimer’s disease (AD), though the mechanisms for this enhanced risk are unclear. Because vascular inflammation is a consistent feature of both diabetes and AD, the cerebral microcirculation could be a key target for the effects of diabetes in the brain. The goal of this study is to explore whether brain endothelial cells, injured by diabetes-related insults, glucose and hypoxia, can affect inflammatory and activation processes in microglia in vitro. Human brain microvascular endothelial cells (HBMVECs) were either treated with 5 mM glucose (control), 30 mM glucose (high glucose), exposed to hypoxia, or exposed to hypoxia plus high glucose. HBMVEC-conditioned medium was then used to treat BV-2 microglia. Alterations in microglia phenotype were assessed through measurement of nitric oxide (NO), cytokine production, microglial activation state markers, and microglial phagocytosis. HBMVECs were injured by exposure to glucose and/or hypoxia, as assessed by release of LDH, interleukin (IL)-1β, and reactive oxygen species (ROS). HBMVECs injured by glucose and hypoxia induced increases in microglial production of NO, tumor necrosis factor-α (TNFα) and matrix metalloproteinase (MMP)-9. Injured HBMVECs significantly increased microglial expression of CD11c and CLEC7A, and decreased expression of the homeostatic marker P2RY12. Finally, bead uptake by BV-2 cells, an index of phagocytic ability, was elevated by conditioned media from injured HBMVECs. The demonstration that injury to brain endothelial cells by diabetic-associated insults, glucose and hypoxia, promotes microglial inflammation supports the idea that the cerebral microcirculation is a critical locus for the deleterious effects of diabetes in the AD brain.

Thymocid®, a Standardized Black Cumin (Nigella sativa) Seed Extract, Modulates Collagen Cross-Linking, Collagenase and Elastase Activities, and Melanogenesis in Murine B16F10 Melanoma Cells

Black cumin (Nigella sativa) seed extract has been shown to improve dermatological conditions, yet its beneficial effects for skin are not fully elucidated. Herein, Thymocid®, a chemically standardized black cumin seed extract, was investigated for its cosmeceutical potential including anti-aging properties associated with modulation of glycation, collagen cross-linking, and collagenase and elastase activities, as well as antimelanogenic effect in murine melanoma B16F10 cells. Thymocid® (50, 100, and 300 µg/mL) inhibited the formation of advanced glycation end-products (by 16.7-70.7%), collagen cross-linking (by 45.1-93.3%), collagenase activity (by 10.4-92.4%), and elastases activities (type I and III by 25.3-75.4% and 36.0-91.1%, respectively). In addition, Thymocid® (2.5-20 µg/mL) decreased melanin content in B16F10 cells by 42.5-61.6% and reduced cellular tyrosinase activity by 20.9% (at 20 µg/mL). Furthermore, Thymocid® (20 µg/mL for 72 h) markedly suppressed the mRNA expression levels of melanogenesis-related genes including microphthalmia-associated transcription factor (MITF), tyrosinase-related protein 1 (TYRP1), and TYRP2 to 78.9%, 0.3%, and 0.2%, respectively. Thymocid® (10 µg/mL) also suppressed the protein expression levels of MITF (by 15.2%) and TYRP1 (by 97.7%). Findings from this study support the anti-aging and antimelanogenic potential of Thymocid® as a bioactive cosmeceutical ingredient for skin care products.

Cytoprotective effects of a proprietary red maple leaf extract and its major polyphenol, ginnalin A, against hydrogen peroxide and methylglyoxal induced oxidative stress in human keratinocytes

Phytochemicals from functional foods are common ingredients in dietary supplements and cosmetic products for anti-skin aging effects due to their antioxidant activities. A proprietary red maple (Acer rubrum) leaf extract (Maplifa™) and its major phenolic compound, ginnalin A (GA), have been reported to show antioxidant, anti-melanogenesis, and anti-glycation effects but their protective effects against oxidative stress in human skin cells remain unknown. Herein, we investigated the cytoprotective effects of Maplifa™ and GA against hydrogen peroxide (H2O2) and methylglyoxal (MGO)-induced oxidative stress in human keratinocytes (HaCaT cells). H2O2 and MGO (both at 400 μM) induced toxicity in HaCaT cells and reduced their viability to 59.2 and 61.6%, respectively. Treatment of Maplifa™ (50 μg mL-1) and GA (50 μM) increased the viability of H2O2- and MGO-treated cells by 22.0 and 15.5%, respectively. Maplifa™ and GA also showed cytoprotective effects by reducing H2O2-induced apoptosis in HaCaT cells by 8.0 and 7.2%, respectively. The anti-apoptotic effect of Maplifa™ was further supported by the decreased levels of apoptosis associated enzymes including caspases-3/7 and -8 in HaCaT cells by 49.5 and 19.0%, respectively. In addition, Maplifa™ (50 μg mL-1) and GA (50 μM) reduced H2O2- and MGO-induced reactive oxygen species (ROS) by 84.1 and 56.8%, respectively. Furthermore, flow cytometry analysis showed that Maplifa™ and GA reduced MGO-induced total cellular ROS production while increasing mitochondria-derived ROS production in HaCaT cells. The cytoprotective effects of Maplifa™ and GA in human keratinocytes support their potential utilization for cosmetic and/or dermatological applications.

Chamaejasmin B Decreases Malignant Characteristics of Mouse Melanoma B16F0 and B16F10 Cells

Chamaejasmin B (CHB), a natural biflavone isolated from Stellera chamaejasme L., has been reported to exhibit anti-cancer properties; however, its effect in melanoma cells is not clear. Here, we aimed to investigate the anticancer effect of CHB in mouse melanoma B16F0 and B16F10 cells. We found that CHB significantly suppressed cell proliferation and promoted cell cycle arrest at G0/G1 phase in B16F0 cells; it also induced cell differentiation and increased melanin content by increasing tyrosinase (TYR) activity and mRNA levels of melanogenesis-related genes in B16F0 cells. Meanwhile, wound closure, invasion, and migration of B16F0 and B16F10 cells were dramatically inhibited. Moreover, CHB significantly increased ROS levels and decreased ΔΨm, resulting in B16F0 and B16F10 cell apoptosis. Finally, in vivo studies showed that CHB inhibited tumor growth and induced tumor apoptosis in a mouse xenograft model of murine melanoma B16F0 and B16F10 cells. Overall, CHB decreases malignant characteristics and may be a promising therapeutic agent for malignant melanoma cells via multiple signaling pathways.

Ginnalin A Inhibits Aggregation, Reverses Fibrillogenesis, and Alleviates Cytotoxicity of Amyloid β(1-42)

Aggregation of misfolded amyloid beta (Aβ) peptides into neurotoxic oligomers and fibrils has been implicated as a key event in the etiopathogenesis of Alzheimer's disease (AD). Ginnalin A (GA), a polyphenolic compound isolated from the red maple (Acer rubrum), has been found to possess anticancer, antiglycation, and antioxidation properties. Using thioflavin T (ThT) fluorescence, surface plasmon resonance (SPR), and atomic force microscopy (AFM), we demonstrate that GA can also effectively inhibit Aβ aggregation by primarily binding to Aβ monomers in a dose-dependent manner. Furthermore, GA can bind to multiple sites of Aβ aggregates to disassemble preformed fibrils and convert them into small aggregates. Circular dichroism (CD) spectra showed that these small aggregates are much less abundant in β-sheets, while cell viability assay confirms that they are essentially innocuous. Molecular dynamics (MD) simulations revealed that GA preferentially contacts with the C- and N-terminal β-sheets and the U-turn region of Aβ(1-42) oligomers through hydrophobic interactions and hydrogen bonding. Compared with other natural compounds that have shown promise in anti-Aβ fibrillogenesis and ameliorating Aβ-induced cytotoxicity, GA is unique in that it exhibits a more efficient inhibition of Aβ aggregation at the very early stage through its strong interaction with Aβ monomers and exerts its inhibitory effect at a lower dosage.

Metabolite Profiling of Two Maple-Derived Products Using Dereplication Based on High-Performance Liquid Chromatography-Diode Array Detector-Electrospray Ionization-Time-of-Flight-Mass Spectrometry: Sugar Maple Bark and Bud Hot-Water Extracts

Recent studies about hot-water extracts from sugar maple (Acer saccharum Marsh.) bark and buds demonstrated that they contain high amounts of phenolic structures that may be used as antioxidant food additives. However, the detailed chemical composition of these maple-derived extracts has yet to be determined. By performing high-performance liquid chromatography-diode array detector-high-resolution mass spectrometry (HPLC-DAD-HRMS)-based dereplication, we were able to spike and classify almost 100 metabolites in each hot-water extract. The sugar maple bark hot-water extract is rich in simple phenolic compounds and phenylpropanoid derivatives, while bud extract contains predominantly flavonoids, benzoic acids, and their complex derivatives (condensed and hydrolyzable tannins). Among those chemical structures, we tentatively identified 69 phenolic compounds potentially reported for the first time in the genus Acer. Considering the growing commercial demand in natural products, the phenolic fingerprints of sugar maple bark and bud hot-water extracts will help in promoting these two maple-derived products as new sources of bioactive compounds in the food, nutraceutical, and cosmetic industries.

The study of inhibitory effects and mechanism of carboxylate chitooligomer on melanin, prepared by laccase/TEMPO system

A carboxylate chitooligomer (C-COS) containing carboxyl groups attached to chitooligomer (COS) molecules has been prepared by laccase/2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) system, which is a green-chemistry method. Several experiments were designed to evaluate inhibition effects on melanin and mechanisms of C-COS. The results indicated that C-COS exhibited more distinct anti-melanogenic effects compared to COS. C-COS inhibits melanin production with tyrosine (Tyr) and DOPA as the substrate of melanin formation, and the inhibition rates are, respectively, 89.07% and 84.45%, which reach 1.4-2 times those of COS. UV-vis spectroscopy was used to elucidate the interaction mechanism between C-COS and tyrosinase (TYR). It is C-COS chelating with metal Cu ions in tyrosinase (TYR) that decreases the enzyme activity. Half-maximal inhibitory concentrations (IC₅₀) of C-COS were calculated as 13.49 and 4.07 mg/mL for monophenolase (cresolase) and diphenolase (catecholase), respectively.

Synthesis and tyrosinase inhibitory activities of 4-oxobutanoate derivatives of carvacrol and thymol

Carvacrol (1) and thymol (2) were converted to their alkyl 4-oxobutanoate derivatives (7-20) in three steps, and evaluated for tyrosinase inhibitory activity. The compounds showed structure-dependent activity, with all alkyl 4-oxobutanoates, except 7 and 20, showing better inhibitory activity than the precursor 4-oxobutanoic acids (5 and 6). In general, thymol derivatives exhibited a higher percent inhibitory activity than carvacrol derivatives at 500 μM. Derivatives containing three-carbon and four-carbon alkyl groups gave the strongest activity (carvacrol derivatives 9-12, IC₅₀ = 128.8-244.1 μM; thymol derivatives 16-19, IC₅₀ = 102.3-191.4 μM).

Ultra-fast liquid chromatography coupled with electrospray ionization time-of-flight mass spectrometry for the rapid phenolic profiling of red maple (Acer rubrum) leaves

The red maple (Acer rubrum) species is economically important to North America because of its sap, which is used to produce maple syrup. In addition, various other red maple plant parts, including leaves, were used as a traditional medicine by the Native Americans. Currently, red maple leaves are being used for nutraceutical and cosmetic applications but there are no published analytical methods for comprehensive phytochemical characterization of this material. Herein, a rapid and sensitive method using liquid chromatography with electrospray ionization time-of-flight tandem mass spectrometry was developed to characterize the phenolics in a methanol extract of red maple leaves and a proprietary phenolic-enriched red maple leaves extract (Maplifa™). Time-of-flight mass spectrometry and tandem mass spectrometry experiments led to the identification of 106 phenolic compounds in red maples leaves with the vast majority of these compounds also detected in Maplifa™. The compounds included 68 gallotannins, 25 flavonoids, gallic acid, quinic acid, catechin, epicatechin, and nine other gallic acid derivatives among which 11 are potentially new and 75 are being reported from red maple for the first time. The developed method to characterize red maple leaves phenolics is rapid and highly sensitive and could aid in future standardization and quality control of this botanical ingredient.

Evaluation of Polyphenol Anthocyanin-Enriched Extracts of Blackberry, Black Raspberry, Blueberry, Cranberry, Red Raspberry, and Strawberry for Free Radical Scavenging, Reactive Carbonyl Species Trapping, Anti-Glycation, Anti-β-Amyloid Aggregation, and Microglial Neuroprotective Effects

Glycation is associated with several neurodegenerative disorders, including Alzheimer’s disease (AD), where it potentiates the aggregation and toxicity of proteins such as β-amyloid (Aβ). Published studies support the anti-glycation and neuroprotective effects of several polyphenol-rich fruits, including berries, which are rich in anthocyanins. Herein, blackberry, black raspberry, blueberry, cranberry, red raspberry, and strawberry extracts were evaluated for: (1) total phenolic and anthocyanins contents, (2) free radical (DPPH) scavenging and reactive carbonyl species (methylglyoxal; MGO) trapping, (3) anti-glycation (using BSA-fructose and BSA-MGO models), (4) anti-Aβ aggregation (using thermal- and MGO-induced fibrillation models), and, (5) murine microglia (BV-2) neuroprotective properties. Berry crude extracts (CE) were fractionated to yield anthocyanins-free (ACF) and anthocyanins-enriched (ACE) extracts. The berry ACEs (at 100 μg/mL) showed superior free radical scavenging, reactive carbonyl species trapping, and anti-glycation effects compared to their respective ACFs. The berry ACEs (at 100 μg/mL) inhibited both thermal- and MGO-induced Aβ fibrillation. In addition, the berry ACEs (at 20 μg/mL) reduced H₂O₂-induced reactive oxygen species production, and lipopolysaccharide-induced nitric oxide species in BV-2 microglia as well as decreased H₂O₂-induced cytotoxicity and caspase-3/7 activity in BV-2 microglia. The free radical scavenging, reactive carbonyl trapping, anti-glycation, anti-Aβ fibrillation, and microglial neuroprotective effects of these berry extracts warrant further in vivo studies to evaluate their potential neuroprotective effects against AD.

Inhibitory effects of Stichopus japonicus extract on melanogenesis of mouse cells via ERK phosphorylation

Stichopus japonicus has been used as a folk medicine and as an ingredient in traditional food in East Asian countries. In recent years, the bioactive compounds found in S. japonicus have been reported to possess efficacy in wound healing and may be of potential use in the cosmeceutical, pharmaceutical and biomedical industries. Although the components and their functions require further investigation, S. japonicus extracts exhibit anti-inflammatory properties, and may be used for cancer prevention and treatment. Although several reports have examined different aspects of S. japonicus, the effects of S. japonicus extract on melanogenesis in the skin has not been reported to date. Therefore the present study aimed to investigate the effects of S. japonicus extract on melanogenesis. Treatment with a mixture of S. japonicus extracts (MSCE) reduced melanin synthesis and tyrosinase (TYR) activity in mouse melanocyte cells lines, B16F10 and Melan-A. In addition, MSCE treatment reduced the protein expression levels of TYR, tyrosinase-related protein-1 and tyrosinase-related protein-2. The reduced protein levels may be the result of decreased microphthalmia-associated transcription factor (MITF) expression, which is an important regulator of melanogenesis. The reduced expression level of MITF was associated with delayed phosphorylation of extracellular signal-regulated kinase (ERK) induced by MSCE treatment. A specific MEK inhibitor, PD98059, significantly blocked MSCE-mediated inhibition of melanin synthesis. In conclusion, these results indicate that MSCE may be useful as a potential skin-whitening compound in the skin medical industry.