Tyrosinase Activity Research Articles

Preparation of Ethosome Gel with Total Flavonoids from Vernonia anthelmintica (L.) Willd. for the Treatment of Vitiligo

Vernonia anthelmintica (L.) Willd. is a traditional medicinal herb in Chinese medicine, extensively used by various ethnic groups due to the numerous advantages derived from its total flavonoids. These benefits encompass anti-inflammatory and antioxidant effects, and the promotion of melanin production, showcasing its significant efficacy in addressing vitiligo. To improve transdermal absorption and enhance the antioxidant effectiveness of the treatment, ethosome containing total flavonoids were prepared utilizing the ultrasound injection technique. The resulting ethosome was then carefully mixed with 0.7% Carbomer 934 gel in equal parts, yielding a gel concentration of 0.302 mg/g. This formulation produced small, consistent ethosome that exhibited high encapsulation efficiency and notable stability. In vitro analyses demonstrated sustained release characteristics of the gel and considerable therapeutic effectiveness against vitiligo resulting from hydroquinone exposure. Histological examinations performed through hematoxylin and eosin (H&E) staining of mouse skin revealed increased melanin production and increased activities of tyrosinase (TYR), cholinesterase (CHE), and mouse monoamine oxidase (MAO), while levels of superoxide dismutase (SOD) and malondialdehyde (MDA) were reduced. These findings underscore the promising effectiveness of this treatment strategy and validate the efficacy of the dosage form.

Salt Stress Enhanced Bioactivity of Quinoa Leaf Extracts: An In Vitro and In Silico Study of Acetylcholinesterase and Tyrosinase Inhibition for Sustainable Drug Development

Background: Quinoa is recognized for its nutritional and pharmacological properties. This study aims to investigate the impact of salt stress induced by varying concentrations of sodium chloride (NaCl) on the production of phenolic compounds and their biological activities in different quinoa accessions. Method: Leaves from three quinoa accessions (Q4, Q24, and Q45) cultivated under increasing NaCl treatments were subjected to chemical analysis using ethanol and water extract. The concentrations of various phenolic compounds, including polyphenols, tannins, anthocyanins, and flavonoids, were quantified. HPLC-DAD-ESI-MS/MS was employed to identify the major compounds in the water extract. Additionally, antioxidants (ABTS and FRAP), anti-tyrosinase, and anti-acetylcholinesterase effects were assessed using in vitro and in silico approaches. Results: NaCl treatment significantly increased the levels of phenolic compounds across all quinoa accessions. The Q45 accession exhibited the highest accumulation of these compounds, particularly in the aqueous extracts at the 200 mM NaCl concentration. Increases were observed in flavonoids (144%), anthocyanins (125%), tannins (89%), and total polyphenols (65%) relative to controls. HPLC-DAD-ESI-MS/MS analysis corroborated these findings, showing that the main compounds also increased with higher NaCl concentrations. Furthermore, the biological efficacy tests revealed that the IC50 values for both tyrosinase and acetylcholinesterase activities decreased with greater salt stress, indicating enhanced enzyme inhibition. The antioxidant activity of these extracts also showed a significant increase as the salt stress levels rose. Conclusions: Salt stress not only promotes the production of bioactive phenolic compounds in quinoa leaves but also enhances their inhibitory effects on key enzymes associated with neurodegenerative and pigmentary disorders. These findings suggest that quinoa may serve as a valuable resource for therapeutic applications, particularly under increased salinity conditions.

Inhibition of Melanin Synthesis and Inflammation by Exosomes Derived from Leuconostoc mesenteroides DB-14 Isolated from Camellia japonica Flower.

Leuconostoc mesenteroides is a lactic acid bacteria found in fermented products. In our previous study, L. mesenteroides was isolated from Camellia japonica flowers, and its acid tolerance and antibacterial properties were thoroughly investigated. This study focuses on the inhibition of melanin synthesis and inflammation of exosomes derived from L. mesenteroides. Moreover, L. mesenteroides exosomes (DB-14 exosome) exhibited significant inhibitory effects on inflammation and melanogenesis. At concentrations of 4.44 × 108, 8.88 × 108, and 1.78 × 109 particles/ml, the exosomes reduced nitric oxide and prostaglandin E2 activity while maintaining the growth of RAW 264.7 macrophages. In addition, proinflammatory cytokines, such as interleukin (IL)-1β, IL-6, and tumor necrosis factor alpha, were rarely expressed, and western blot revealed that L. mesenteroides DB-14 derived exosomes inhibited inducible nitric oxide synthase and cyclooxygenase-2 expression. Moreover, the exosomes had no toxic effects on B16F10 melanoma cells at concentrations of 1.78 × 109, 3.55 × 109, and 7.10 × 109 particles/ml, and they suppressed melanogenesis by reducing tyrosinase activity. Furthermore, western blot analysis demonstrated that microphthalmia-associated transcription factor (MITF), tyrosinase, tyrosinase related protein (TRP)-1, and TRP-2 were evidently reduced, ultimately repressing melanin production. Moreover, MITF expression was inhibited by reduced mitogen-activated protein kinase and protein kinase B phosphorylation levels. Overall, this study proves the efficacy of the novel DB-14 exosome as a strong lightening and anti-inflammatory agent.

Electrosynthesis of Mussel-inspired Adhesive Polymers as a Novel Class of Transient Enzyme Stabilizers.

Multifunctional ortho-quinones are required for the formation of thiol-catechol-connectivities (TCC) but can be delicate to handle. We present the electrochemical oxidation of the dipeptide DiDOPA, achieving up to 92 % conversion efficiency of the catechols to ortho-quinones. Graphite and stainless steel could be employed as cost-efficient electrodes. The electrochemical activation yields quinone-solutions, which are free of undesired reactive compounds and eliminates the challenging step of isolating the reactive quinones. The DiDOPA quinones were employed in polyaddition reactions with multi-thiols, forming oligomers that functioned as transient enzyme stabilizers (TES). These TCC-TES-additives improved the thermal stability and the activity of tyrosinase in heat stress assays.

Palmitoyl copper peptide and acetyl tyrosine complex enhances melanin production in both A375 and B16 cell lines

Copper peptide, a low molecular weight peptide composed of glycyl-L-histidyl-L-lysine-copper, possesses anti-aging, anti-inflammatory, and wound healing properties. In this study, we investigated the effects of a combination agent CP-AcT, composed of palmitoyl copper peptide (pal-GHK-Cu) and acetyl tyrosine (N-Acetyl-L-tyrosine), on melanin production in the human malignant melanoma cell line A375 and the mouse melanoma cell line B16. Firstly, the cytotoxicity of CP-AcT at various concentrations (0-8 μg/mL) on HaCat, HFF, A375, and B16 cells was evaluated. Subsequently, the effects of the CP-AcT on tyrosinase activity both extracellular and intracellularly, as well as on melanin production in two melanoma cell lines, were evaluated under conditions that did not compromise cell viability. Additionally, quantitative gene plex (QGP) combined with branched DNA (bDNA) technology was used to analyze the effects of CP-AcT on the expression of melanin-related genes in A375 cells, with a focus on five specific genes. Finally, the effects of the CP-AcT on the expression of three proteins involved in the biosynthesis pathway of melanin: tyrosinase (TYR), dopachrome tautomerase (DCT), and endothelin 3 (EDN3) were analyzed. The results indicate that the complex CP-AcT effectively promotes melanin production in both types of melanoma cells.

Structural and mechanistic insights into the anti-tyrosinase, anti-melanogenesis, and anti-browning effect of proanthocyanidins from seed coats of Acer truncatum Bunge

Acer truncatum is a multifunctional tree species with broad applications in ornamental, healthy drink, and seed oil. In the present study, proanthocyanidins were isolated from the seed coats of A. truncatum, which were largely discarded as industrial wastes in seed oil production. Meanwhile, structural features, effects and mechanisms of anti-tyrosinase, anti-melanogenesis, and anti-browning of A. truncatum seed coat proanthocyanidins (ASPs) were systematically investigated. The joint application of FT-IR, MALDI-TOF-MS, hiolysis-coupled reverse-phase LC-ESI-MS, together with normal-phase LC confirmed that ASPs were predominately constituted by procyanidins with a mean polymerization degree of 12.09. Furthermore, ASPs powerfully inhibited both monophenolase and diphenolase activities of tyrosinase, and the inhibition of diphenolase was proved to be reversible and competitive−uncompetitive mixed type. Analyses of fluorescence quenching, UV spectra, and copper-ion chelation indicated that ASPs could inhibit tyrosinase in varied stages, and molecular docking and dynamic simulation further revealed the interaction mode between ASPs and tyrosinase. Cell assays further suggested that ASPs exhibited a strong inhibition against intracellular tyrosinase activity and melanin production through suppressing the expression of tyrosinase and microphthalmia transcription factor (MITF) at transcription level and caused apoptosis in B16F10 cells at higher concentrations. Antioxidant and anti-browning studies demonstrated that ASPs possessed high capacities of antioxidant, and potently suppress the browning of fresh-cut potatoes. Therefore, this study confirmed that seed coats of Acer truncatum is a potential natural source of tyrosinase, melanogenesis, and browning inhibitor, which provided a theoretical basis for the utilization of ASPs in the cosmetics, pharmaceutical, and food industries.

Emerging Roles of Dermal Fibroblasts in Hyperpigmentation and Hypopigmentation: A Review.

Skin pigmentation disorders may increase patients' psychological burdens. Consequently, they are increasingly attracting attention. Dermal fibroblasts have been shown to regulate pigmentation by secreting soluble factors. This study aimed to summarize recent findings on the effects of dermal fibroblasts on hyperpigmentation and hypopigmentation, enabling the discovery of new therapeutic targets. PubMed was searched for literature on fibroblast factors, hyperpigmentation, and hypopigmentation, and a comprehensive summary and analysis were performed. Fibroblasts secrete both cytokines that promote pigmentation, including stem cell factor (SCF) and keratinocyte growth factor (KGF), and small amounts of those that inhibit pigmentation, such as Dickkopf1 (DKK1) and transforming growth factor (TGF)-β. Fibroblast-derived extracellular matrix (ECM) can also affect melanocyte tyrosinase activity and the transfer of melanosomes. In hyperpigmentation disorders, such as melasma and solar lentigines, the secretion of pigmentation-promoting factors increases, and the activity of key enzymes in melanin production is elevated. In hypopigmentation disorders, including vitiligo, the secretion of melanogenic factors decreases while the factors that inhibit pigmentation increase. Fibroblasts may serve as a new therapeutic target, providing new insights to precisely treat pigmentary disorders. Fibroblasts synthesize and secrete various cytokines and proteins that modify melanin synthesis and transfer through different signaling pathways, playing prominent roles in pigmentary skin disorders, such as photoaging, melasma, solar lentigo, and vitiligo.

Unfolded protein response modulates Tyrosinase levels and melanin production during melanogenesis.

Melanocytes protect the body from ultraviolet radiation by synthesizing melanin. Tyrosinase, a key enzyme in melanin production, accumulates in the endoplasmic reticulum (ER) during melanin synthesis, potentially causing ER stress. However, regulating ER function for melanin synthesis has been less studied than controlling Tyrosinase activity. This study investigates the regulatory mechanisms of melanin production, focusing on ER stress and the ER stress-induced response. B16 mouse melanoma cells induced to undergo melanogenesis were treated with unfolded protein response (UPR) inhibitors or chemical chaperones, and their effects on melanogenesis were analyzed. During melanogenesis in B16 cells stimulated by alpha-melanocyte-stimulating hormone (α-MSH), ER stress and UPR activation occurred, accompanied by increased Tyrosinase protein. Reducing IRE1 and ATF6 branch activity lowered melanin levels, while chemical chaperone treatment restored melanin production and increased Tyrosinase levels. UPR activation, linked to elevated Tyrosinase levels, influences melanin production during melanogenesis. Modulating UPR can regulate melanin synthesis and provides a potential new approach for treating pigmentation disorders.

Anilino-1,4-naphthoquinones as potent mushroom tyrosinase inhibitors: in vitro and in silico studies

Tyrosinase, a pivotal enzyme in melanin synthesis, is a primary target for the development of depigmenting agents. In this work, in vitro and in silico techniques were employed to identify novel tyrosinase inhibitors from a set of 12 anilino-1,4-naphthoquinone derivatives. Results from the mushroom tyrosinase activity assay indicated that, among the 12 derivatives, three compounds (1, 5, and 10) demonstrated the most significant inhibitory activity against mushroom tyrosinase, surpassing the effectiveness of the kojic acid. Molecular docking revealed that all studied derivatives interacted with copper ions and amino acid residues at the enzyme active site. Molecular dynamics simulations provided insights into the stability of enzyme–inhibitor complexes, in which compounds 1, 5, and particularly 10 displayed greater stability, atomic contacts, and structural compactness than kojic acid. Drug likeness prediction further strengthens the potential of anilino-1,4-naphthoquinones as promising candidates for the development of novel tyrosinase inhibitors for the treatment of hyperpigmentation disorders.

LC-MS/MS Analysis and Biological Activities of Different Parts of Ziziphora capitate L.

The Ziziphora species, classified under the Lamiaceae family, have a strong aromatic property. Ziziphora species have been used in folk medicine as sedative, gastric, aphrodisiac, bloating, and degassing. In the current study, the phenolic and flavanoid content of ethanol extracts of Ziziphora capitata L. species of flower, leaf, branch, mixed, and root parts was determined by the LC-MS/MS device. In addition, the antioxidant and cytotoxic activities of the extracts, as well as their inhibitory effects on enzymes (antihypertensive, AchE (acetylcholinesterase), BchE (butyrylcholinesterase), elastase, tyrosinase, collagenase and urease), were determined. The LC-MS/MS results showed that quinic acid (25578, 5842, 25171, 14055, 10597 µg g-1, respectively) was found in higher amounts in flower, leaf, branch, mixed, and root extracts of Z. capitata species compared to other components. Additionally, rosmarinic acid (17097 µg g-1), cynaroside (8432), and hesperidin (8067) were found to be major components. It was observed that the flower extract of the species exhibited strong antioxidant activity (IC50: 37.18±1.36 µg mL-1, 9.89±0.45, A0.5:16.27±0.02, respectively) in DPPH, ABTS and CUPRAC methods. It was concluded that the leaf extract of Z. capitata species had a strong cytotoxic effect on HT-29 (colon cancer cell line) (viability %: 9.26±0.69). It was observed that the root part of the species exhibited higher activity in butyrylcholinesterase (BChE) enzyme inhibition activity (inhibition %: 40.56±0.88) than other parts. It was determined that Z. capitata extracts did not show acetylcholinesterase, urease, tyrosinase, elastase, collagenase, and antihypertensive enzyme activity or showed low activity. As a result, it is thought that the flower extract of the Z. capitata species has better results in terms of the examined parameters, whereas the leaf extract needs to be subjected to more detailed in vitro and in vivo research conducted to be used in the pharmaceutical industry as a result of its cytotoxic effect against colon cancer cell lines.

Human Tyrosinase Displayed on the Surface of Chinese Hamster Ovary Cells for Ligand Fishing of Tyrosinase Inhibitors from Medicinal Plants

Ligand fishing is a promising strategy for the screening of active ingredients from complex natural products. In this work, human tyrosinase (hTYR) was displayed on the surface of Chinese hamster ovary (CHO) cells for the first time; it was then used as bait to develop a new method for ligand fishing. The localization of hTYR on the CHO cell surface was verified by an enzyme activity test and fluorescence microscopy. The displayed tyrosinase (CHO@hTYR) maintained relatively stable enzymatic activity (82.59 ± 2.70%) within 7 days. Furthermore, it can be reused for fishing five times. Guided by the proposed ligand fishing method, four tyrosinase inhibitors, including 4-methoxy-5-methyl coumarin (1), cupressuflavone (2), amentoflavone (3), and 3,4-dimethoxy-5-methyl coumarin (4), were isolated from Alhagi sparsifolia, and the active fraction with low polarity was isolated from Coffea arabica; these two medicinal plants possess skin-lightening potential. All the isolated tyrosinase inhibitors significantly reduced the intracellular tyrosinase activity and melanin level in B16 cells enhanced by α-MSH. Meanwhile, the active fraction (100 μg/mL) from C. arabica exhibited stronger inhibitory effects than the positive controls (α-arbutin and kojic acid) by recovering them to the normal levels. This work demonstrated the promising application of the cell surface display in the field of ligand fishing and is helpful in unveiling the chemical basis of the skin-lightening effect of A. sparsifolia and C. arabica.

Antioxidant, Anti-α-Glucosidase, Anti-Tyrosinase, and Anti-Acetylcholinesterase Components from Stem of Rhamnus formosana with Molecular Docking Study

Rhamnus formosana is a creeping evergreen shrub endemic to Taiwan. In traditional medicine, Rhamnaceae plants are used as herbal remedies for conditions such as itching, difficulty urinating, and constipation. This study explores the inhibitory effects of various solvent extracts and bioactive components of R. formosana on α-glucosidase, tyrosinase, acetylcholinesterase (AChE), and antioxidant activity. The 100 °C water extract exhibited strong antioxidant activity in DPPH, ABTS, superoxide, and FRAP assays. The methanol extract demonstrated the highest α-glucosidase inhibitory effect, while the ethanol extract displayed potent AChE inhibition and the acetone extract showed the most potential tyrosinase inhibitory activity among the extracts. Five main biocomponents were isolated and evaluated for their bioactivities. Among them, kaempferol (1) and quercetin (2) exhibited notable antioxidant activity in DPPH and ABTS assays. Particularly, kaempferol (1) performed the best α-glucosidase inhibitory effect, physcion (5) showed the strongest AChE inhibition, and quercetin (2) demonstrated the most potential for tyrosinase inhibitory activity. Further molecular docking studies revealed that there may be stronger binding mechanisms between bioactive components and target enzymes (including α-glucosidase, acetylcholinesterase, and tyrosinase) than the positive control. These findings suggest that bioactive extracts and compounds from the stems of R. formosana may have potential as natural antioxidant, anti-α-glucosidase, anti-AChE, and anti-tyrosinase drug candidates or dietary supplements for the management of oxidative stress-related conditions, including hyperglycemia, pigmentation disorders, and neurodegenerative diseases.

Diversity, Extracellular Enzyme Activity and Growth Promoting Potential of Fungal Isolates from the Roots of Coleus aromaticus Benth.

ABSTRACT: Coleus aromaticus Benth. a member of Lamiaceae family is a herbaceous plant with numerous medicinal properties. The present study was aimed at the isolation, characterization, extracellular enzyme activity and growth promoting ability of endophytic fungi from the roots of C. aromaticus collected from different parts of Palakkad, Kerala, India. A total of nine cultures grouped into five morphotypes including one non-sporulating taxa mostly belonging to Ascomycota were isolated. Their colonization rate and diversity index was determined. Extracellular enzyme activity and plant growth promotion studies were also carried out. Amylase activity was exhibited by all isolates, while none of them showed tyrosinase, protease, or laccase activity. Among the isolates, Fusarium sp. exhibited significant root and shoot length promotion in Vigna radiata seedlings, and its identification was confirmed through sequence analysis as Fusarium solani. The results indicated that the endophytic association has a positive role in promoting plant growth and revealed diverse mycoflora in the roots of Coleus aromaticus with various biological activities, highlighting the potential for further research into endophytes and their metabolites as a promising field.

10(E)-Pentadecenoic Acid Inhibits Melanogenesis Partly Through Suppressing the Intracellular MITF/Tyrosinase Axis.

Melanogenesis, the biological process responsible for melanin synthesis, plays a crucial role in determining skin and hair color, photoprotection, and serving as a biomarker in various diseases. While various factors regulate melanogenesis, the role of fatty acids in this process remains underexplored. This study investigated the anti-melanogenic properties of 10(E)-pentadecenoic acid (10E-PDA) through both in silico and in vitro analyses. SwissSimilarity was utilized to predict the functional properties of 10E-PDA by comparing it with structurally similar lipids known to exhibit anti-melanogenic effects. Subsequent in vitro experiments demonstrated that 10E-PDA significantly reduced melanin production and intracellular tyrosinase activity in α-MSH (melanocyte-stimulating hormone)-stimulated B16F10 melanoma cells without exhibiting significant cytotoxicity at concentrations up to 15 μM. Further mechanistic studies revealed that 10E-PDA inhibited the nuclear translocation of microphthalmia-associated transcription factor (MITF), consistent with the decrease observed in p-MITF protein levels. It also decreased the mRNA levels of tyrosinase-related proteins (TRP-1, TRP-2) and tyrosinase, while reducing the protein levels of TRP-1 and tyrosinase, but not TRP-2. These findings suggest that 10E-PDA exerts its anti-melanogenic effects by modulating the MITF/tyrosinase axis, presenting potential therapeutic implications for skin pigmentation disorders.

Development of a human tyrosinase activity inhibition assay using human melanoma cell lysate.

Tyrosinase (TYR) inhibitors are required to treat skin hyperpigmentation. Currently live cell-based TYR assays and mushroom TYR in vitro assays are the common methods used to screen for TYR inhibitors. However, these methods are either time consuming and expensive or are not human TYR (hsTYR) specific. Here, we describe a simple hsTYR assay using cell lysate prepared from pigmented human melanoma cell lines that takes less than 3 hours to complete after collecting cell pellets. We confirmed the assay is species specific by using a known hsTYR inhibitor, kojic acid, as a positive control, while arbutin, which inhibits mushroom TYR, but not hsTYR, was not effective. This assay is a simple method to confirm hsTYR inhibition before conducting follow-up studies in live biological models.

Valorization of Hom Thong Banana Peel (Musa sp., AAA Group) as an Anti-Melanogenic Agent Through Inhibition of Pigmentary Genes and Molecular Docking Study.

Prolonged and unprotected exposure to the environment explicitly influences the development of hyperpigmented lesions. The enzyme tyrosinase (TYR) is a key target for regulating melanin synthesis. Several bioactive compounds derived from plant extracts have been found to possess potent anti-melanogenesis properties against TYR. In particular, the potential of banana peels from various varieties has garnered interest due to their application in skin hyperpigmentation treatment. A molecular docking study demonstrated interactions between rosmarinic acid, which is predominantly found in all Hom Thong peel extracts, and the active site of TYR (PDB ID: 2Y9X) at residues HIS263, VAL283, SER282, and MET280, with the lowest binding energy of -5.05 kcal/mol, showing the strongest interaction. Additionally, Hom Thong banana peels are rich in phenolic compounds that could inhibit melanin content and tyrosinase activity in both human and mouse melanoma cells. These effects may be attributed to the suppression of gene expression related to melanogenesis, including the regulator gene MITF and pigmentary genes TYR, TRP-1, and DCT, indicating effects comparable to those of the standard treatment groups with arbutin and kojic acid. Our findings indicated the potential of Hom Thong peel extracts as anti-melanogenic agents.

P69 Modelling epidermal melanocyte behaviour during plaque psoriasis progression and resolution

Abstract Melanocytes in human epidermis reside in the basal layer in a ratio of 1 melanocyte to ∼10 keratinocytes. In healthy epidermis, melanocytes neither divide nor undergo apoptosis. In psoriasis, the 1:10 ratio is maintained despite significant keratinocyte hyperplasia, suggesting an increase in melanocyte numbers. We investigated whether melanocyte numbers change in active psoriasis plaques and after plaque resolution upon treatment with biologics, and via the impact of psoriasis-related cytokines on melanogenesis in primary normal melanocytes in vitro. Immunohistochemistry (IHC) with MITF (melanocyte marker) and Ki67 (proliferation marker) on lesional and non-lesional samples (n = 11) at baseline and after 12 weeks of treatment assessed melanocyte proliferation. Melanocyte number/mm of basal layer and melanocyte/keratinocyte ratio were estimated by analysis on ImageJ. The TUNEL-assay and IHC staining with pro-apoptotic marker, Cleaved Caspase 3, and anti-apoptotic marker, BCL-2 were performed on lesional and non-lesional samples (n = 5) at baseline and after 4 and 12 weeks of treatment to determine if melanocytes undergo apoptosis upon treatment with biologics. Primary normal human melanocytes were treated with proinflammatory cytokines (IL-17, TNF-α, IL-22, and IL-23) to assess their influence on melanogenesis via immunocytochemistry (ICC) and Western blot (WB) analysis. Proliferating melanocytes were detected in non-lesional and lesional samples and in resolving plaques after treatment but not in healthy control epidermis. Melanocyte number/mm of the basal layer was significantly higher in non-lesional compared with both lesional sections and healthy controls (P < 0.0001), suggesting melanocyte expansion occurs prior to psoriasis plaque establishment. Twelve weeks after treatment, melanocyte numbers in lesional and non-lesional samples were still significantly higher than controls (P < 0.05) despite the reduction in keratinocyte numbers. The TUNEL-assay and Cleaved Caspase 3 staining did not detect evidence of melanocyte apoptosis. ICC and WB analysis of treated primary melanocytes revealed that TNF-α decreases the activity of the rate-limiting melanogenesis enzyme tyrosinase and down-regulates TRP1 both when this cytokine was used alone and in combination with the other cytokines. This study shows early melanocyte dysregulation supporting a role for melanocytes in psoriasis pathogenesis perhaps via an ADAMSTL5-initiated inflammation. The higher melanocyte numbers are retained even after treatment, and we were unable to detect melanocyte deletion/apoptosis despite a reduction in keratinocyte number. We show the direct inhibitory impact of psoriasis-associated cytokines on melanogenesis. This raises intriguing questions as to the nature of melanocyte proliferation in this benign inflammatory skin disease and suggests that such ectopic melanocytic proliferation in the epidermis may not be a harbinger of malignancy risk.

Preparation and Characterization of Nanostructured Lipid Carriers (NLCs) Containing Glycyrrhiza glabra Extract for the Treatment of Skin Hyperpigmentation.

This study aimed to prepare, characterize, and in vitro and in vivo evaluate a novel nanostructured lipid carriers (NLCs) formulation containing two fractions of Glycyrrhiza glabra L. (licorice) extract for the treatment of hyperpigmentation. Two fractions, one enriched with glabridin (FEG) and the other enriched with liquiritin (FEL), were obtained by partitioning the methanol (MeOH) extract of licorice roots with ethyl acetate (EtOAc) and partitioning the EtOAc fraction with butanol (n-BuOH) and water. The quantities of glabridin (Glab) and liquiritin (LQ) in the fractions were determined by high-performance liquid chromatography (HPLC). FEG and FEL were loaded in different NLC formulations, and surface characterization and long-term stability were studied using Dynamic Light Scattering (DLS). The best formulation was chosen for further surface characterization, including Transmission Electron Microscopy (TEM), Differential Scanning Calorimetry (DSC), and Fouriertransform infrared (FTIR) spectroscopy. Moreover, entrapment efficiency percentage (EE%), in vitro drug release, in vivo skin penetration, cytotoxicity on B16F10 melanoma cells, effect on melanin production, and anti- tyrosinase activity were tested for the selected formulation. Based on HPLC results, FEG contained 34.501 mg/g of Glab, and FEL contained 31.714 mg/g of LQ. Among 20 different formulations, NLC 20 (LG-NLCs) showed desirable DLS results with a Z-average size of 185.3 ± 1.08 nm, polydispersity index (PDI) of 0.229 ± 0.35, and zeta potential of -16.2 ± 1.13 mV. It indicated good spherical shape, high EE% (79.01% for Glab and 69.27% for LQ), two-stage release pattern (an initial burst release followed by sustained release), efficient in vivo skin penetration, and strong anti-tyrosinase activity. LG-NLCs had acceptable physiochemical stability for up to 9 months and were non-cytotoxic. The LG-NLC formulation has revealed desirable surface characterization, good physiochemical stability, efficient drug release pattern and in vivo penetration, and high EE%. Therefore, it can be a suitable nanosystem for the delivery of licorice extract in the treatment of hyperpigmentation.

Inhibitory effects of phenylpropionamides from the hemp seed husk on tyrosinase

Tyrosinase is an enzyme involved in melanin production. To identify inhibitors of this enzyme in natural products, extracts and fractions of hemp seed husk were screened for tyrosinase inhibition. Phenylpropionamides 1–9, which were isolated from the ethyl acetate fraction, had inhibitory effects; compounds 3 and 4 had the greatest inhibitory effects. Cannabisin A (3) was a non-competitive and cannabisin B (4) was a competitive inhibitor. The binding site and interaction on tyrosinase of each inhibitor were calculated by computational chemistry. Potential inhibitor 3 decreased the melanin content and tyrosinase activity in B16F10 melanoma cells. Therefore, cannabisin A (3) has potential as a tyrosinase inhibitor.

Tanshinone Alleviates UVA-induced Melanogenesis in Melanocytes via the Nrf2-regulated Antioxidant Defense Signaling Pathway.

As a complex of natural plant compounds, tanshinone is renowned for its remarkable antioxidant properties. However, the potential impact of tanshinone on melanocyte pigmentation regulation has yet to be elucidated. This study aimed to explore the protective effects of tanshinone I (T-I) and dihydrotanshinone (DHT) on melanogenesis by modulating nuclear factor E2-related factor 2 (Nrf2) signaling and antioxidant defenses in human epidermal melanocyte (HEM) cells. HEM cells and Nrf2 knockdown HEM cells were subjected to ultraviolet A (UVA) and treated with T-I and/or DHT. Then, the anti-melanogenic properties of T-I and DHT were examined by assessing tyrosinase activity, melanogenesis-related proteins, and melanin content in UVA-irradiated HEM cells. Furthermore, the antioxidant activities of T-I and DHT were evaluated by assessing oxidant formation and modulation of Nrf2-related antioxidant defenses, including reactive oxygen species (ROS), glutathione (GSH) content, and the activity and expression of antioxidant enzymes, such as catalase (CAT), heme oxygenase-1 (HO-1), and superoxide dismutase (SOD). Our findings revealed that T-I and DHT diminished melanogenesis in UVAirradiated HEM cells, activated Nrf2-antioxidant response element signaling, and enhanced antioxidant defenses in the irradiated cells. Furthermore, Nrf2 knockdown by shRNA abolished the anti-melanogenesis effects of T-I and DHT on HEM cells against oxidative damage. These results suggest that T-I and DHT inhibit UVA-induced melanogenesis in HEM cells, possibly through redox mechanisms involving Nrf2 signaling activation and increased antioxidant defenses. This indicates that T-I and DHT have potential as whitening agents in cosmetics and medical treatments for hyperpigmentation disorders.