Hypopigmenting agents: an updated review on biological, chemical and clinical aspects

Characterization of tyrosinase inhibitory constituents from the aerial parts of Humulus japonicus using LC-MS/MS coupled online assay

In the screening of natural products for the development as cosmetic ingredients, the EtOAc-soluble fraction of Humulus japonicus showed tyrosinase inhibitory activity. HPLC-MS/MS coupled online tyrosinase assay of EtOAc-soluble fraction of H. japonicus characterized the twenty-eight constituents including two unknown ones and their tyrosinase inhibitory activity. Fractionation of H. japonicus using various chromatographic techniques yielded thirty-eight compounds. The chemical structures of isolated compounds were identified by spectroscopic analysis. As characterized by HPLC-MS/MS analysis, we isolated twenty-four predicted compounds and further identified two unknown ones, named humulusides A (1) and B (2). Additional ten compounds were also identified by purification. Tyrosinase inhibitory activity of isolated compounds were evaluated, which was closely correlated with the results from HPLC-MS/MS coupled online tyrosinase assay. Consistent with predicted data, two major compounds, trans-N-coumaroyltyramine (14) and cis-N-coumaroyltyramine (15) showed tyrosinase inhibition with IC₅₀ values of 40.6 and 36.4 μM. Taken together, H. japonicus is suggested as whitening ingredient in cosmetic products. In addition, HPLC-MS/MS coupled tyrosinase assay is powerful tool for predicting active compounds with short time and limited amounts, although identification of new compounds and verification of predicted data are also needs to be demonstrated by further experiment.

Skin whitening agents: medicinal chemistry perspective of tyrosinase inhibitors

Melanogenesis is a process to synthesize melanin, which is a primary responsible for the pigmentation of human skin, eye and hair. Although numerous enzymatic catalyzed and chemical reactions are involved in melanogenesis process, the enzymes such as tyrosinase and tyrosinase-related protein-1 (TRP-1) and TRP-2 played a major role in melanin synthesis. Specifically, tyrosinase is a key enzyme, which catalyzes a rate-limiting step of the melanin synthesis, and the downregulation of tyrosinase is the most prominent approach for the development of melanogenesis inhibitors. Therefore, numerous inhibitors that target tyrosinase have been developed in recent years. The review focuses on the recent discovery of tyrosinase inhibitors that are directly involved in the inhibition of tyrosinase catalytic activity and functionality from all sources, including laboratory synthetic methods, natural products, virtual screening and structure-based molecular docking studies.

Potential biomedical applications of marine algae

Functional components extracted from algal biomass are widely used as dietary and health supplements with a variety of applications in food science and technology. In contrast, the applications of algae in dermal-related products have received much less attention, despite that algae also possess high potential for the uses in anti-infection, anti-aging, skin-whitening, and skin tumor treatments. This review, therefore, focuses on integrating studies on algae pertinent to human skin care, health and therapy. The active compounds in algae related to human skin treatments are mentioned and the possible mechanisms involved are described. The main purpose of this review is to identify serviceable algae functions in skin treatments to facilitate practical applications in this high-potential area.

Glandular hair constituents of Mallotus philippinensis Muell. fruit act as tyrosinase inhibitors: Insights from enzyme kinetics and simulation study

The glandular hair extracts from the fruit rind of Mallotus philippinensis Muell. is employed to treat various skin infections, however the anti-tyrosinase activity remains unknown. Hence the present study inspected on the anti-melanogenic activity of M. philippinensis constituents. Lineweaver Burk plot revealed mixed inhibition for Rottlerin; non-competitive type of inhibition for mallotophilippen A and B respectively. Thermodynamic studies resulted in static quenching forming ground state complex with higher binding constant temperature dependently. Fluorescence and circular dichroism study implicated conformational change in secondary and tertiary structure of tyrosinase. Molecular docking suggests rottlerin has high binding affinity to the active site pocket of tyrosinase. Simulation study further proved that the compactness of inhibitor with tyrosinase by hydrogen bonding influenced the stability of the enzyme. Depigmentation efficacy is further proved in Aspergillus niger spores. Thus our findings delineate that rottlerin could be utilized as a depigmentation agent in food pharmaceutical and agricultural industries.

Melanogenesis in uveal melanoma cells: Effect of argan oil

The mechanisms underlying cutaneous melanogenesis have been widely studied; however, very little is known about uveal melanogenesis. Melanin is normally produced by uveal melanocytes and gives the color to the iris. A derangement from this normal production may occur, for instance, by iatrogenic events, such as glaucoma therapy with prostaglandins that may enhance cutaneous and iris pigmentation. In this study, we investigated the mechanisms that regulate uveal melanogenesis in human uveal melanoma cells (92.1) and murine cutaneous melanoma cells (B16-F1). In the first part of the study, we compared the effects of known cutaneous pigmenting agents on the B16-F1 and 92.1 cells, showing an opposite response of the two cell lines. Subsequently, using argan oil, a known depigmenting agent for murine cutaneous melanoma cells, on 92.1 cells, we found that in these cells, it also functioned as an inhibitor of melanogenesis and tyrosinase expression. From a molecular perspective, treatment of the 92.1 cells with argan oil decreased melanogenesis-associated transcription factor (MITF) gene expression by inducing MITF phosphorylation at Ser73, thus leading to MITF ubiquitination and disposal. It also led to the downregulation of the extracellular signal-regulated kinase (ERK)1/2 and Akt pathways, also known to be involved in cutaneous melanogenesis, although with an opposing function. Taken together, our data indicate that: ⅰ) some differences exist in the regulation of melanogenesis between cutaneous and uveal melanoma cells; and ⅱ) argan oil exerts a depigmenting effect on 92.1 cells through its action on the ERK1/2 and Akt pathways.

Betaine reduces cellular melanin content via suppression of microphthalmia-associated transcription factor in B16-F1 murine melanocytes

Long-term topical skin care by traditional anti-melanogenic agents can raise several safety concerns. An understanding of the molecular mechanisms of active compounds on melanogenesis is, therefore, necessary to address pigmentation issues. Here we revealed that stimulation with 1 mM betaine, an abundant component in rice bran, significantly reduced 21% of intracellular melanin content by suppressing tyrosinase activity and microphthalmia-associated transcription factor (MITF) expression in B16-F1 murine melanocytes. The expression of MITF was suppressed at both mRNA and protein levels by 43 and 44%, respectively. Subsequently, the betaine-stimulated melanocytes showed inhibition of PKA-CREB signaling axis but activation of extracellular-signal-regulated kinase and AKT-GSK3β signaling pathways. This inhibition and activation led to downregulation of MITF expression at both the transcriptional and post-translational levels to suppress melanin synthesis. These findings collectively suggested that betaine is a potential anti-melanogenic compound for functional foods and cosmetics.

Potent anti-melanogenic activity and favorable toxicity profile of selected 4-phenyl hydroxycoumarins in the zebrafish model and the computational molecular modeling studies

7-Hydroxy-4-phenylcoumarin (7C) and 5,7-dihydroxy-4-phenylcoumarin (5,7C) have been evaluated as potential anti-melanogenic agents in the zebrafish (Danio rerio) model in comparison to commercially utilized depigmenting agents hydroquinone and kojic acid. 7C and 5,7C decreased the body pigmentation at 5 µg/mL, while did not affect the embryos development and survival at doses ≤50 µg/mL and ≤25 µg/mL. Unlike hydroquinone and kojic acid, 4-phenyl hydroxycoumarins were no melanocytotoxic, showed no cardiotoxic side effects, neither caused neutropenia in zebrafish embryos, suggesting these compounds may present novel skin-whitening agents with improved pharmacological properties. Inhibition of tyrosinase was identified as the possible mode of anti-melanogenic action. Molecular docking studies using the homology model of human tyrosinase as well as adenylate cyclase revealed excellent correlation with experimentally obtained results.

Protocatechuic Acid from Pear Inhibits Melanogenesis in Melanoma Cells

Despite the critical role of melanin in the protection of skin against UV radiation, excess production of melanin can lead to hyperpigmentation and skin cancer. Pear fruits are often used in traditional medicine for the treatment of melasma; therefore, we investigated the effects of pear extract (PE) and its component, protocatechuic acid (PCA), on melanogenesis in mouse melanoma cells. We found that PE and PCA significantly suppressed melanin content and cellular tyrosinase activity through a decrease in the expression of melanogenic enzymes and microphthalmia-associated transcription factor (Mitf) in α-melanocyte stimulating hormone-stimulated mouse melanoma cells. Moreover, PCA decreased cyclic adenosine monophosphate (cAMP) levels and cAMP-responsive element-binding protein phosphorylation, which downregulated Mitf promoter activation and subsequently mediated the inhibition of melanogenesis. These results suggested that pear may be an effective skin lightening agent that targets either a tyrosinase activity or a melanogenic pathway.

2-S-Lipoylcaffeic Acid, a Natural Product-Based Entry to Tyrosinase Inhibition via Catechol Manipulation

Conjugation of naturally occurring catecholic compounds with thiols is a versatile and facile entry to a broad range of bioinspired multifunctional compounds for diverse applications in biomedicine and materials science. We report herein the inhibition properties of the caffeic acid- dihydrolipoic acid S-conjugate, 2-S-lipoylcaffeic acid (LC), on mushroom tyrosinase. Half maximum inhibitory concentration (IC₅₀) values of 3.22 ± 0.02 and 2.0 ± 0.1 µM were determined for the catecholase and cresolase activity of the enzyme, respectively, indicating a greater efficiency of LC compared to the parent caffeic acid and the standard inhibitor kojic acid. Analysis of the Lineweaver–Burk plot suggested a mixed-type inhibition mechanism. LC proved to be non-toxic on human keratinocytes (HaCaT) at concentrations up to 30 µM. These results would point to LC as a novel prototype of melanogenesis regulators for the treatment of pigmentary disorders.

Antimelanogenic Efficacy of Melasolv (3,4,5-Trimethoxycinnamate Thymol Ester) in Melanocytes and Three-Dimensional Human Skin Equivalent

BACKGROUND/AIMS

Excessive melanogenesis often causes unaesthetic hyperpigmentation. In a previous report, our group introduced a newly synthesized depigmentary agent, Melasolv™ (3,4,5-trimethoxycinnamate thymol ester). In this study, we demonstrated the significant whitening efficacy of Melasolv using various melanocytes and human skin equivalents as in vitro experimental systems.

METHODS

The depigmentary effect of Melasolv was tested in melan-a cells (immortalized normal murine melanocytes), α-melanocyte-stimulating hormone (α-MSH)-stimulated B16 murine melanoma cells, primary normal human melanocytes (NHMs), and human skin equivalent (MelanoDerm). The whitening efficacy of Melasolv was further demonstrated by photography, time-lapse microscopy, Fontana-Masson (F&M) staining, and 2-photon microscopy.

RESULTS

Melasolv significantly inhibited melanogenesis in the melan-a and α-MSH-stimulated B16 cells. In human systems, Melasolv also clearly showed a whitening effect in NHMs and human skin equivalent, reflecting a decrease in melanin content. F&M staining and 2-photon microscopy revealed that Melasolv suppressed melanin transfer into multiple epidermal layers from melanocytes as well as melanin synthesis in human skin equivalent.

CONCLUSION

Our study showed that Melasolv clearly exerts a whitening effect on various melanocytes and human skin equivalent. These results suggest the possibility that Melasolv can be used as a depigmentary agent to treat pigmentary disorders as well as an active ingredient in cosmetics to increase whitening efficacy.

Inhibition of tyrosinase by 4H-chromene analogs: Synthesis, kinetic studies, and computational analysis

Inhibition of mushroom tyrosinase was observed with synthetic dihydropyrano[3,2-b]chromenediones. Among them, DHPC04 displayed the most potent tyrosinase inhibitory activity with a K_i value of 4 μm, comparable to the reference standard inhibitor kojic acid. A kinetic study suggested that these synthetic heterocyclic compounds behave as competitive inhibitors for the L-DOPA binding site of the enzyme. Furthermore, molecular modeling provided important insight into the mechanism of binding interactions with the tyrosinase copper active site.

Oleoylethanolamide inhibits α-melanocyte stimulating hormone-stimulated melanogenesis via ERK, Akt and CREB signaling pathways in B16 melanoma cells

The present study aimed to examine the potential inhibitory activity of oleoylethanolamide (OEA) on α-melanocyte stimulating hormone (α-MSH)-stimulated melanogenesis and the molecular mechanism(s) involved in the process in B16 mouse melanoma cells. Our data demonstrated that OEA markedly inhibited melanin synthesis and tyrosinase activity in α-MSH-stimulated B16 cells. In addition, the expression of melanogenesis-related proteins, such as melanocortin-1 receptor (MC1R), microphthalmia-associated transcription factor (MITF), tyrosinase-related protein-1 (TRP-1) and tyrosinase, was suppressed in a concentration-dependent manner by OEA. In addition, OEA may suppress melanogenesis through a peroxisome proliferator-activated receptor α (PPARα)-independent pathway. Moreover, OEA activated ERK, Akt, p38 pathways and inhibits CREB pathway in α-MSH-stimulated B16 cells. The specific ERK inhibitor PD98059 partly blocked OEA-inhibited melanin synthesis and tyrosinase activity and partly abrogated the OEA-suppressed expression of melanogenic proteins. Furthermore, OEA presented remarkable inhibition on the body pigmentation in the zebrafish model system. Our findings demonstrated that OEA is an effective inhibitor of hyperpigmentation through activation of ERK, Akt and p38 pathways, inhibition of the CREB pathway, and subsequent down-regulation of MITF, TRP-1 and tyrosinase production.

Proteomics and metabolomics-driven pathway reconstruction of mung bean for nutraceutical evaluation

Mung bean is a legume crop which has a various health-promoting effects. Although rich flavonoids are reported to be responsible for its biological activities, little is known about other nutrients that may potentiate the activities. To obtain information on mung bean nutritional properties, gel-free/label-free proteomic analysis and metabolomic profiling were combined. Pathway reconstruction detected that amino acid metabolism is more active in flesh. Coat contained wider variety of lipids and phenolic acids/flavonoids than flesh. Among the compounds detected in coat, sphingolipids, arachidonic acid, and prostaglandin E2 are compounds which are related to immune response induction. Furthermore, identification of prostaglandin F2α added scientific support to empirical validity of mung bean usage. The abundance of bioactive compounds such as naringenin, which can be metabolized into vitexin, varied among cultivars. These results suggest that lipids together with flavonoids might be potential responsible compounds for biological activity of mung bean coat and flesh.

Applications of Panax ginseng leaves-mediated gold nanoparticles in cosmetics relation to antioxidant, moisture retention, and whitening effect on B16BL6 cells

Background

Bioactive compounds in plant extracts are able to reduce metal ions to nanoparticles through the process of green synthesis. Panax ginseng is an oriental medicinal herb and an adaptogen which has been historically used to cure various diseases. In addition, the P. ginseng leaves-mediated gold nanoparticles are the value-added novel materials. Its potential as a cosmetic ingredient is still unexplored. The aim of this study was to evaluate the antioxidant, moisture retention and whitening properties of gold nanoparticles (PgAuNPs) in cosmetic applications.

Methods

Cell-free experiments were performed to evaluate PgAuNP's antioxidant and moisture retention properties and inhibition activity on mushroom tyrosinase. Furthermore, in vitro cell cytotoxicity was evaluated using normal human dermal fibroblast and murine B16BL6 melanoma cells (B16) after treatment with increasing concentrations of PgAuNPs for 24 h, 48 h, and 72 h. Finally, in vitro cell assays on B16 cells were performed to evaluate the whitening effect of PgAuNPs through reduction of cellular melanin content and tyrosinase activity.

Results

In vitro DPPH radical scavenging assay results revealed that PgAuNPs exhibited antioxidant activity in a dose-dependent manner. PgAuNPs exhibited moisture retention capacity and effectively inhibited mushroom tyrosinase. In addition, 3-(4,5-dimethyl-thiazol-2yl)-2,5-diphenyl tetrazolium bromide results revealed that PgAuNPs were not toxic to human dermal fibroblast and B16 cells; in addition, they significantly reduced melanin content, tyrosinase activity, and mRNA expression of melanogenesis-associated transcription factor and tyrosinase in B16 cells.

Conclusion

Our study is the first report to provide evidence supporting that P. ginseng leaves-capped gold nanoparticles could be used as multifunctional ingredients in cosmetics.

Anti-Melanogenic Properties of Greek Plants. A Novel Depigmenting Agent from Morus alba Wood

In therapeutic interventions associated with melanin hyperpigmentation, tyrosinase is regarded as a target enzyme as it catalyzes the rate-limiting steps in mammalian melanogenesis. Since many known agents have been proven to be toxic, there has been increasing impetus to identify alternative tyrosinase inhibitors, especially from natural sources. In this study, we investigated 900 extracts from Greek plants for potential tyrosinase inhibitive properties. Among the five most potent extracts, the methanol extract of Morus alba wood (MAM) demonstrated a significant reduction in intracellular tyrosinase and melanin content in B16F10 melanoma cells. Bioassay-guided isolation led to the acquisition of twelve compounds: oxyresveratrol (1), kuwanon C (2), mulberroside A (3), resorcinol (4), dihydrooxyresveratol (5), trans-dihydromorin (6), 2,4,3′-trihydroxydihydrostilbene (7), kuwanon H (8), 2,4-dihydroxybenzaldehyde (9), morusin (10), moracin M (11) and kuwanon G (12). Among these, 2,4,3′-trihydroxydihydrostilbene (7) is isolated for the first time from Morus alba and constitutes a novel potent tyrosinase inhibitor (IC₅₀ 0.8 ± 0.15). We report here for the first time dihydrooxyresveratrol (5) as a potent natural tyrosinase inhibitor (IC₅₀ 0.3 ± 0.05). Computational docking analysis indicated the binding modes of six tyrosinase inhibitors with the aminoacids of the active centre of tyrosinase. Finally, we found both MAM extract and compounds 1, 6 and 7 to significantly suppress in vivo melanogenesis during zebrafish embryogenesis.

Melanogenesis inhibition activity of floralginsenoside A from Panax ginseng berry

Background

Panax ginseng is a traditional herb used for medicinal purposes in eastern Asia. P. ginseng contains various ginsenosides with pharmacological effects. In this study, floralginsenoside A (FGA), ginsenoside Rd (GRD), and ginsenoside Re (GRE) were purified from P. ginseng berry.

Methods

Chemical structures of FGA, GRD, and GRE were determined based on spectroscopic methods, including fast atom bombardment mass spectroscopy, ID-nuclear magnetic resonance, and infrared spectroscopy. Inhibitory activities of these compounds on melanogenesis were studied by measuring the expression of protein and melanin content in the melan-a cell line. This inhibitory activity was confirmed by observing pigmentation and tyrosinase activities of zebrafish.

Results

GRD, GRE, and FGA were not cytotoxic at concentrations less than 20μM, 80μM, and 160μM in melan-a cells, respectively. GRD, GRE, and FGA inhibited melanin biosynthesis in melan-a cells by 15.2%, 22.9%, and 23.9% at 20μM, 80μM, and 160μM, respectively. FGA was observed to display the most potent inhibitory effect. In addition, FGA decreased microphthalmia-associated transcription factor protein expression in a dose-dependent manner. Moreover, FGA induced extracellular signal-regulated kinase phosphorylation level in melan-a cells. In addition, melanin pigment content and tyrosinase activity in zebrafish treated with FGA at160μM were reduced.

Conclusion

FGA showed the most potent inhibition of melanogenesis in both in vitro and in vivo studies. This study suggests that FGA purified from P. ginseng may be an effective melanogenesis inhibitor.

Pharmacoinformatics exploration of polyphenol oxidases leading to novel inhibitors by virtual screening and molecular dynamic simulation study

Polyphenol oxidases (PPOs)/tyrosinases are metal-dependent enzymes and known as important targets for melanogenesis. Although considerable attempts have been conducted to control the melanin-associated diseases by using various inhibitors. However, the exploration of the best anti-melanin inhibitor without side effect still remains a challenge in drug discovery. In present study, protein structure prediction, ligand-based pharmacophore modeling, virtual screening, molecular docking and dynamic simulation study were used to screen the strong novel inhibitor to cure melanogenesis. The 3D structures of PPO1 and PPO2 were built through homology modeling, while the 3D crystal structures of PPO3 and PPO4 were retrieved from PDB. Pharmacophore modeling was performed using LigandScout 3.1 software and top five models were selected to screen the libraries (2601 of Aurora and 727, 842 of ZINC). Top 10 hit compounds (C1-10) were short-listed having strong binding affinities for PPO1-4. Drug and synthetic accessibility (SA) scores along with absorption, distribution, metabolism, excretion and toxicity (ADMET) assessment were employed to scrutinize the best lead hit. C4 (name) hit showed the best predicted SA score (5.75), ADMET properties and drug-likeness behavior among the short-listed compounds. Furthermore, docking simulations were performed to check the binding affinity of C1-C10 compounds against target proteins (PPOs). The binding affinity values of complex between C4 and PPOs were higher than those of other complexes (-11.70, -12.1, -9.90 and -11.20kcal/mol with PPO1, PPO2, PPO3, or PPO4, respectively). From comparative docking energy and binding analyses, PPO2 may be considered as better target for melanogenesis than others. The potential binding modes of C4, C8 and C10 against PPO2 were explored using molecular dynamics simulations. The root mean square deviation and fluctuation (RMSD/RMSF) graphs results depict the significance of C4 over the other compounds. Overall, bioactivity and ligand efficiency profiles suggested that the proposed hit may be more effective inhibitors for melanogenesis.

Recent Advances in Effect-directed Enzyme Assays based on Thin-layer Chromatography

Thin-layer chromatography (TLC) together with its more modern form high-performance thin-layer chromatography (HPTLC) is a rapid and cost effective analytical tool with a long tradition in quality control of medicinal plants, extracts and natural products. Separated compounds are fixed on the solid silica phase to form a compound library. Through direct coupling of visualisable enzyme reactions on the TLC plate, this compound library can also be used for activity screening. Such TLC-based bioautographic enzyme and enzyme inhibition assays complement first stage development activity screening assays. They provide not only phytochemical results by chromatographic separation, but also additional information about the activity of constituents or fractions in multi-compound mixtures, and thus can reveal and distinguish artefacts generated by certain compound classes. This review summarises recently introduced TLC bioautographic enzyme assays as well as advances in already existing procedures. Bioautographic enzyme and enzyme inhibitory assays offer a rapid, high-throughput method for screening of secondary metabolite profiles for potential enzyme and enzyme inhibitory activities. Copyright © 2017 John Wiley & Sons, Ltd.

Biodegradable Kojic Acid-Based Polymers: Controlled Delivery of Bioactives for Melanogenesis Inhibition

Kojic acid (KA) is a naturally occurring fungal metabolite that is utilized as a skin-lightener and antibrowning agent owing to its potent tyrosinase inhibition activity. While efficacious, KA's inclination to undergo pH-mediated, thermal-, and photodegradation reduces its efficacy, necessitating stabilizing vehicles. To minimize degradation, poly(carbonate-esters) and polyesters comprised of KA and natural diacids were prepared via solution polymerization methods. In vitro hydrolytic degradation analyses revealed KA release was drastically influenced by polymer backbone composition (e.g., poly(carbonate-ester) vs polyester), linker molecule (aliphatic vs heteroatom-containing), and release conditions (physiological vs skin). Tyrosinase inhibition assays demonstrated that aliphatic KA dienols, the major degradation product under skin conditions, were more potent then KA itself. All dienols were found to be less toxic than KA at all tested concentrations. Additionally, the most lipophilic dienols were statistically more effective than KA at inhibiting melanin biosynthesis in cells. These KA-based polymer systems deliver KA analogues with improved efficacy and cytocompatible profiles, making them ideal candidates for sustained topical treatments in both medical and personal care products.

Antimelanogenic, Antioxidant and Antiproliferative Effects of Antrodia camphorata Fruiting Bodies on B16-F0 Melanoma Cells

Antrodia camphorata is a fungus that is endemic to Taiwan, and its fruiting body has been used as a folk medicine for the prevention or treatment of diverse diseases. The present study is aimed at investigating the antimelanogenesis and antioxidation effect of the ethanolic extract of Antrodia camphorata fruiting body (EE-AC), as well as its antiproliferation effects in B16-F0 melanoma cells. Regarding antimelanogenic effects, EE-AC had effective cupric ions reducing capacity and expressed more potent inhibitory effect than kojic acid on mushroom tyrosinase activity. Moreover, EE-AC significantly inhibited cellular tyrosinase activity and the melanin content in B16-F0 cells at 12.5 μg/mL concentration without cell toxicities. Regarding antioxidant effects, EE-AC exhibited potent DPPH radical- and SOD-like-scavenging activities. Regarding antiproliferative effects, EE-AC exhibited a selective cytotoxic effect and markedly inhibited the migration ability of B16-F0 cells. EE-AC increased the population of B16-F0 cells at sub-G1 phase of the cell cycle. EE-AC also caused the increase of early apoptotic cells and chromatin condensation, which indicated the apoptotic effects in B16-F0 cells. We demonstrated that EE-AC possessed antimelanogenic, antioxidant and anti-skin cancer actions. The results would contribute to the development and application of cosmetics, healthy food and pharmaceuticals.

N-(4-methoxyphenyl) caffeamide-induced melanogenesis inhibition mechanisms

Background

The derivative of caffeamide exhibits antioxidant and antityrosinase activity. The activity and mechanism of N-(4-methoxyphenyl) caffeamide (K36E) on melanogenesis was investigated.

Methods

B16F0 cells were treated with various concentrations of K36E; the melanin contents and related signal transduction were studied. Western blotting assay was applied to determine the protein expression, and spectrophotometry was performed to identify the tyrosinase activity and melanin content.

Results

Our results indicated that K36E reduced α-melanocyte-stimulating hormone (α-MSH)-induced melanin content and tyrosinase activity in B16F0 cells. In addition, K36E inhibited the expression of phospho-cyclic adenosine monophosphate (cAMP)-response element-binding protein, microphthalmia-associated transcription factor (MITF), tyrosinase, and tyrosinase-related protein-1 (TRP-1). K36E activated the phosphorylation of protein kinase B (AKT) and glycogen synthase kinase 3 beta (GSK3β), leading to the inhibition of MITF transcription activity. K36E attenuated α-MSH induced cAMP pathways, contributing to hypopigmentation.

Conclusions

K36E regulated melanin synthesis through reducing the expression of downstream proteins including p-CREB, p-AKT, p-GSK3β, tyrosinase, and TRP-1, and activated the transcription factor, MITF. K36E may have the potential to be developed as a skin whitening agent.

The depigmenting effect of natural resorcinol type polyphenols Kuwanon O and Sanggenon T from the roots of morus australis

ETHNOPHARMACOLOGICAL RELEVANCE

Morus australis, one of the major Morus species growing in East Asia, is rich in phenolic compounds. The extract of M. australis has been used as skin whitening components for a long period. The action mechanisms of its principal constituents are still unclear. This study aims to evaluate the skin lightening effects of phenolic compounds extracted from the root of M. australis in different melanocyte systems and artificial skin models.

MATERIALS AND METHODS

The depigmenting effect of resorcinol type polyphenols (RTPs) from the root extract of M. australis was evaluated in murine b16 and melan-a cell lines using a combined sulforhodamine B assay. Tyrosinase activity and the expression of melanogenesis proteins were evaluated for the mechanism study. The artificial skin model is used as a replacement of the animal test.

RESULTS

Only Kuwanon O and Sanggenon T were found to have significant depigmenting effects in both murine b16 and melan-a cell lines. Their depigmenting mechanisms are slightly different in the two cell systems. In b16 cells, Kuwanon O and Sanggenon T, together with the other two RTPs, induced post-transcriptional degradations of MITF without suppressing its mRNA expression, leading to significant decreases of TRP-1 and TRP-2 production. While in melan-a cells, the levels of tyrosinase families were suppressed via MITF downregulation at both transcription and translation level by RTPs, with Kuwanon O inducing the greatest suppression. Further evaluations in artificial skin model demonstrated the outstanding depigmenting effects of Kuwanon O and Sanggenon T.

CONCLUSIONS

Kuwanon O and Sanggenon T from M.australis root extract are two potential skin whitening ingredients. To screen resorcinol flavonone derivatives with an isoprenyl group in the Diels-Alder substituent might be an option for the search of potent hypopigmenting agents from plants.

Rare ginsenoside Ia synthesized from F1 by cloning and overexpression of the UDP-glycosyltransferase gene from Bacillus subtilis: synthesis, characterization, and in vitro melanogenesis inhibition activity in BL6B16 cells

Background

Ginsenoside F1 has been described to possess skin-whitening effects on humans. We aimed to synthesize a new ginsenoside derivative from F1 and investigate its cytotoxicity and melanogenesis inhibitory activity in B16BL6 cells using recombinant glycosyltransferase enzyme. Glycosylation has the advantage of synthesizing rare chemical compounds from common compounds with great ease.

Methods

UDP-glycosyltransferase (BSGT1) gene from Bacillus subtilis was selected for cloning. The recombinant glycosyltransferase enzyme was purified, characterized, and utilized to enzymatically transform F1 into its derivative. The new product was characterized by NMR techniques and evaluated by MTT, melanin count, and tyrosinase inhibition assay.

Results

The new derivative was identified as (20S)-3β,6α,12β,20-tetrahydroxydammar-24-ene-20-O-β-D-glucopyranosyl-3-O-β-D-glucopyranoside (ginsenoside Ia), which possesses an additional glucose linked into the C-3 position of substrate F1. Ia had been previously reported; however, no in vitro biological activity was further examined. This study focused on the mass production of arduous ginsenoside Ia from accessible F1 and its inhibitory effect of melanogenesis in B16BL6 cells. Ia showed greater inhibition of melanin and tyrosinase at 100 μmol/L than F1 and arbutin. These results suggested that Ia decreased cellular melanin synthesis in B16BL6 cells through downregulation of tyrosinase activity.

Conclusion

To our knowledge, this is the first study to report on the mass production of rare ginsenoside Ia from F1 using recombinant UDP-glycosyltransferase isolated from B. subtillis and its superior melanogenesis inhibitory activity in B16BL6 cells as compared to its precursor. In brief, ginsenoside Ia can be applied for further study in cosmetics.

Synthesis and biological evaluation of novel hydroxybenzaldehyde-based kojic acid analogues as inhibitors of mushroom tyrosinase

Two series of novel kojic acid analogues (4a-j) and (5a-d) were designed and synthesized, and their mushroom tyrosinase inhibitory activities was evaluated. The result indicated that all the synthesized derivatives exhibited excellent tyrosinase inhibitory properties having IC₅₀ values in the range of 1.35±2.15-17.50±2.75μM, whereas standard inhibitor kojic acid have IC₅₀ values 20.00±1.08μM. Specifically, 5-phenyl-3-[5-hydroxy-4-pyrone-2-yl-methylmercap-to]-4-(2,4-dihydroxyl-benzylamino)-1,2,4-triazole (4f) exhibited the most potent tyrosinase inhibitory activity with IC₅₀ value of 1.35±2.15μM. The kinetic studies of the compound (4f) demonstrated that the inhibitory effects of the compound on the tyrosinase were belonging to competitive inhibitors. Meanwhile, the structure-activity relationship was discussed.

Anti-Melanogenic Activity of Gagunin D, a Highly Oxygenated Diterpenoid from the Marine Sponge Phorbas sp., via Modulating Tyrosinase Expression and Degradation

Tyrosinase is the rate-limiting enzyme critical for melanin synthesis and controls pigmentation in the skin. The inhibition of tyrosinase is currently the most common approach for the development of skin-whitening cosmetics. Gagunin D (GD), a highly oxygenated diterpenoid isolated from the marine sponge Phorbas sp., has exhibited cytotoxicity toward human leukemia cells. However, the effect of GD on normal cells and the molecular mechanisms remain to be elucidated. In the present study, we identified for the first time the anti-melanogenic activity of GD and its precise underlying mechanisms in mouse melan-a cells. GD significantly inhibited melanin synthesis in the melan-a cells and a reconstructed human skin model. Further analysis revealed that GD suppressed the expression of tyrosinase and increased the rate of tyrosinase degradation. GD also inhibited tyrosinase enzymatic activity. In addition, GD effectively suppressed the expression of proteins associated with melanosome transfer. These findings suggest that GD is a potential candidate for cosmetic formulations due to its multi-functional properties.

Rice Bran Protein as a Potent Source of Antimelanogenic Peptides with Tyrosinase Inhibitory Activity

Rice (Oryza sativa) is consumed as a staple food globally, and rice bran, the byproduct, is an unused biomass that is ultimately discarded as waste. Thus, in the present study, a technique for producing tyrosinase inhibitory peptides from rice bran protein (RBP) was developed. Simultaneous treatment of RBP with chymotrypsin and trypsin produced numerous peptides. Subsequently, six tyrosinase inhibitory peptides were isolated from the hydrolysate fractions in a multistep purification protocol, and their amino acid sequences were determined. Three of these peptides had a C-terminal tyrosine residue and exhibited significant inhibitory effects against tyrosinase-mediated monophenolase reactions. Furthermore, peptide CT-2 (Leu-Gln-Pro-Ser-His-Tyr) potently inhibited melanogenesis in mouse B16 melanoma cells without causing cytotoxicity, suggesting the potential of CT-2 as an agent for melanin-related skin disorder treatment. The present data indicate that RBP is a potent source of tyrosinase inhibitory peptides and that simultaneous treatment of RBP with chymotrypsin and trypsin efficiently produces these peptides.

The unravelling of the complex pattern of tyrosinase inhibition

Tyrosinases are responsible for melanin formation in all life domains. Tyrosinase inhibitors are used for the prevention of severe skin diseases, in skin-whitening creams and to avoid fruit browning, however continued use of many such inhibitors is considered unsafe. In this study we provide conclusive evidence of the inhibition mechanism of two well studied tyrosinase inhibitors, KA (kojic acid) and HQ (hydroquinone), which are extensively used in hyperpigmentation treatment. KA is reported in the literature with contradicting inhibition mechanisms, while HQ is described as both a tyrosinase inhibitor and a substrate. By visualization of KA and HQ in the active site of TyrBm crystals, together with molecular modeling, binding constant analysis and kinetic experiments, we have elucidated their mechanisms of inhibition, which was ambiguous for both inhibitors. We confirm that while KA acts as a mixed inhibitor, HQ can act both as a TyrBm substrate and as an inhibitor.

Downregulation of melanogenesis: drug discovery and therapeutic options

Melanin, primarily responsible in humans for hair, eye and skin pigmentation, is produced by melanocytes through a process called melanogenesis. However, the abnormal accumulation of melanin causes dermatological problems such as café-au-lait macules ephelides (freckles), solar lentigo (age spots) and melasma, as well as cancer and vitiligo. Hence the regulation of melanogenesis is very important for treating hyperpigmentary disorders. Numerous antimelanogenic agents that target tyrosinase activity and/or stability, melanosome maturation, transfer and trafficking, or melanogenesis-related signaling pathways have been developed. This article reviews recent advances in research and development of human tyrosinase and melanogenesis-related signaling pathway inhibitors. Attempts have been made to provide a complete description of the mechanism of action of inhibitors on various melanogenesis signaling pathways.

Extracts of Morus nigra L. Leaves Standardized in Chlorogenic Acid, Rutin and Isoquercitrin: Tyrosinase Inhibition and Cytotoxicity

Melanogenesis is a process responsible for melanin production, which is stored in melanocytes containing tyrosinase. Inhibition of this enzyme is a target in the cosmetics industry, since it controls undesirable skin conditions such as hyperpigmentation due to the overproduction of melanin. Species of the Morus genus are known for the beneficial uses offered in different parts of its plants, including tyrosinase inhibition. Thus, this project aimed to study the inhibitory activity of tyrosinase by extracts from Morus nigra leaves as well as the characterization of its chromatographic profile and cytotoxicity in order to become a new therapeutic option from a natural source. M. nigra leaves were collected, pulverized, equally divided into five batches and the standardized extract was obtained by passive maceration. There was no significant difference between batches for total solids content, yield and moisture content, which shows good reproducibility of the extraction process. Tyrosinase enzymatic activity was determined for each batch, providing the percentage of enzyme inhibition and IC₅₀ values obtained by constructing dose-response curves and compared to kojic acid, a well-known tyrosinase inhibitor. High inhibition of tyrosinase activity was observed (above 90% at 15.625 μg/mL). The obtained IC₅₀ values ranged from 5.00 μg/mL ± 0.23 to 8.49 μg/mL ± 0.59 and were compared to kojic acid (3.37 μg/mL ± 0.65). High Performance Liquid Chromatography analysis revealed the presence of chlorogenic acid, rutin and, its major compound, isoquercitrin. The chromatographic method employed was validated according to ICH guidelines and the extract was standardized using these polyphenols as markers. Cytotoxicity, assessed by MTT assay, was not observed on murine melanomas, human keratinocytes and mouse fibroblasts in tyrosinase IC₅₀ values. This study demonstrated the potential of M. nigra leaf extract as a promising whitening agent of natural source against skin hyperpigmentation.

Characterization of a New Flavone and Tyrosinase Inhibition Constituents from the Twigs of Morus alba L

The twigs of Morus alba L. were found to show strong tyrosinase inhibition activity, and the responsible active components in the extract were further investigated in this study. A flavone, named morusone (1), and sixteen known compounds 2–17 were isolated from M. alba twigs and their structures were identified by interpretation of the corresponding ESI-MS and NMR spectral data. In the tyrosinase inhibitory test, the compounds steppogenin (IC₅₀ 0.98 ± 0.01 µM), 2,4,2′,4′-tetrahydroxychalcone (IC₅₀ 0.07 ± 0.02 µM), morachalcone A (IC₅₀ 0.08 ± 0.02 µM), oxyresveratrol (IC₅₀ 0.10 ± 0.01 µM), and moracin M (8.00 ± 0.22 µM) exhibited significant tyrosinase inhibition activities, much stronger than that of the positive control kojic acid. These results suggest that M. alba twig extract should served as a good source of natural tyrosinase inhibitors for use in foods as antibrowning agents or in cosmetics as skin-whitening agents.

Antimelanogenic effects of luteolin 7-sulfate isolated from Phyllospadix iwatensis Makino

BACKGROUND

Abnormal deposition of melanin may cause an aesthetic skin problem; therefore, the control of unwanted excessive melanin synthesis is the major goal of cosmetic research.

OBJECTIVES

To identify novel tyrosinase (TYR) inhibitors from marine plants and examine their cellular antimelanogenic effects.

METHODS

The extracts of 50 marine plants endemic to Korea were screened against human TYR. Active constituents were then isolated from the selected plant extracts that showed potential and their chemical structures elucidated. Furthermore, their antimelanogenic effects were examined using murine melanoma B16/F10 cells and human epidermal melanocytes (HEM).

RESULTS

Among the tested extracts, that of Phyllospadix iwatensis Makino exhibited the strongest human TYR inhibitory activity. The active constituents were purified from the butanol fraction of the P. iwatensis extract and identified as hispidulin 7-sulfate and luteolin 7-sulfate. Luteolin 7-sulfate inhibited human TYR more strongly than hispidulin 7-sulfate, luteolin, hispidulin and arbutin. Furthermore, luteolin 7-sulfate showed lower cytotoxicity than luteolin in both B16/F10 cells and HEM. Luteolin 7-sulfate attenuated cellular melanin synthesis more effectively in B16/F10 cells and HEM stimulated by α-melanocyte-stimulating hormone and l-tyrosine than arbutin.

CONCLUSIONS

This study demonstrates that luteolin 7-sulfate isolated from P. iwatensis is a human TYR inhibitor with advantageous antimelanogenic properties, and would be useful for development as a therapeutic agent for the control of unwanted skin pigmentation.

Novel synthetic kojic acid-methimazole derivatives inhibit mushroom tyrosinase and melanogenesis

In this study, two kojic acid-methimazole (2-mercapto-1-methylimidazole, MMI, 1) derivatives, 5-hydroxy-2-{[(1-methyl-1H-imidazol-2-yl)thio]methyl}-4H-pyran-4-one (compound 4) and 5-methoxy-2-{[(1-methyl-1H-imidazol-2-yl)thio]methyl}-4H-pyran-4-one (compound 5), were synthesized to examine their inhibitory kinetics on mushroom tyrosinase. Compound 4 exhibited a potent inhibitory effect on monophenolase activity in a dose-dependent manner, with an IC₅₀ value of 0.03 mM. On diphenolase activity, compound 4 exhibited a less inhibitory effect (IC₅₀ = 1.29 mM) but was stronger than kojic acid (IC₅₀ = 1.80 mM). Kinetic analysis indicated that compound 4 was both as a noncompetitive monophenolase and diphenolase inhibitor. By contrast, compound 5 exhibited no inhibitory effects on mushroom tyrosinase activity. The IC₅₀ value of compound 4 for the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity was 4.09 mM, being much higher than the IC₅₀ of compound 4 for inhibiting the tyrosinase activity. The results indicated that the antioxidant activity of compound 4 may be partly related to the potent inhibitory effect on mushroom tyrosinase. Compound 4 also exerted a potent inhibitory effect on intracellular melanin formation in B16/F10 murine melanoma cells, and caused no cytotoxicity. Furthermore, compound 4 induced no adverse effects on the Hen's egg test-chorioallantoic membrane (HET-CAM).

Melanins and melanogenesis: from pigment cells to human health and technological applications

During the past decade, melanins and melanogenesis have attracted growing interest for a broad range of biomedical and technological applications. The burst of polydopamine-based multifunctional coatings in materials science is just one example, and the list may be expanded to include melanin thin films for organic electronics and bioelectronics, drug delivery systems, functional nanoparticles and biointerfaces, sunscreens, environmental remediation devices. Despite considerable advances, applied research on melanins and melanogenesis is still far from being mature. A closer intersectoral interaction between research centers is essential to raise the interests and increase the awareness of the biomedical, biomaterials science and hi-tech sectors of the manifold opportunities offered by pigment cells and related metabolic pathways. Starting from a survey of biological roles and functions, the present review aims at providing an interdisciplinary perspective of melanin pigments and related pathway with a view to showing how it is possible to translate current knowledge about physical and chemical properties and control mechanisms into new bioinspired solutions for biomedical, dermocosmetic, and technological applications.

Effects of topical application of B-Resorcinol and Glycyrrhetinic acid monotherapy and in combination with fractional CO2 laser treatment for benign hand hyperpigmentation treatment

BACKGROUND

Hand solar lentigines are frequent benign lesions of elderly population, requiring longtime treatments with topical agents or laser to lighten.

AIMS

The aim of this study was to evaluate and compare the efficacy of CO₂ fractional laser photothermolysis followed by topical application of B-Resorcinol and Glycyrrhetinic acid vs. only topical B-Resorcinol and Glycyrrhetinic acid application for hand solar lentigines treatment.

METHODS

Hand solar lentigines of eleven volunteers were divided into two groups: Group A spots received CO₂ fractional laser photothermolysis followed by 4 weeks topical application of B-Resorcinol and Glycyrrhetinic acid, and Group B spots received only 4 weeks topical treatments. All hands were photographed, and hand solar lentigines scanned with dermatoscope at the beginning of the study (T₀ ), 1 month after laser treatment (T₁ ), and at the end of the study (T₂ ) to document spots dimensions and color. A blinded dermatologist evaluated dermoscopic T₀ and T₂ images. The considered variables were assessed for significance by the nonparametric Mann-Whitney U-test.

RESULTS

In all volunteers, investigators and blinded dermatologist's evaluation hand solar lentigines features improved, with no statistical differences in the two groups.

CONCLUSION

Topical application of B-Resorcinol and Glycyrrhetinic acid is effective to lighten hand solar lentigines after 4 weeks of treatment, with or without a previous fractional laser photothermolysis.

Bioactive properties and potentials cosmeceutical applications of phlorotannins isolated from brown seaweeds: A review

Currently, natural ingredients are becoming more attractive for the industries such as functional food, nutraceuticals, cosmeceutical and pharmaceutical industries as people starting to believe naturally occurring compounds are safer to humans than artificial compounds. Seaweeds are one of the most interesting organisms found in oceans around the earth, which are carrying great ecological importance and contribute to increase the biodiversity of ecosystems where they were originated and habitat. Within last few decades, discovery of secondary metabolites with biological activities from seaweeds has been significantly increased. Further, the unique secondary metabolites isolated from seaweeds including polysaccharides, carotenoids and polyphenols possess range of bioactive properties that make them potential ingredient for many industrial applications. Among those groups of compounds phlorotannins isolated from brown seaweeds have shown interesting bioactive properties including anti-cancer, anti-inflammation, anti-oxidant, anti-allergic, anti-wrinkling and hair growth promotion properties. Moreover, these properties associated with phlorotannins make them an ideal compounds to use as a functional ingredient in cosmeceutical products. Up to now no report has been reviewed about discuss properties of phlorotannins related to the cosmeceutical application. In the present review primary attention is given to the collect scientific data published about bioactive properties of brown algal phlorotannins related to the cosmeceutical industry.