Up- or Downregulation of Melanin Synthesis Using Amino Acids, Peptides, and Their Analogs

Advancing the accuracy of tyrosinase inhibitory peptides prediction via a multiview feature fusion strategy

Tyrosinase plays a crucial role as an enzyme in the production of melanin, which is the pigment accountable for determining the color of the hair, eyes, and skin. Tyrosinase inhibitory peptides (TIPs), mainly designed to regulate the activity of the enzyme tyrosinase, are of interest in various domains, including cosmetics, dermatology, and pharmaceuticals, due to their potential applications in controlling skin pigmentation. To date, a few machine learning-based models have been proposed for predicting TIPs, but their predictive performance remains unsatisfactory. In this study, we propose an innovative computational approach, named TIPred-MVFF, to accurately predict TIPs using only sequence information. Firstly, we established an up-to-date and high-quality dataset by collecting samples from various sources. Secondly, we applied a multi-view feature fusion (MVFF) strategy to extract and explore probability and category information embedded in TIPs, employing several machine learning (ML) algorithms coupled with different commonly used sequence-based feature encodings. Then, we employed resampling approaches to address the class imbalance issue. Finally, to maximize the utility of each feature, we fused probability-based and sequence-based features, generating more informative feature that were used to develop the final prediction model. Based on the independent test, experimental results showed that TIPred-MVFF outperformed several conventional ML classifiers and existing methods in terms of prediction accuracy and robustness, achieving an accuracy of 0.937 and a Matthew's correlation coefficient of 0.847. This new computational approach is anticipated to aid community-wide efforts in rapidly and cost-effectively discovering novel peptides with strong tyrosinase inhibitory activities.

Peptide Design for Enhanced Anti-Melanogenesis: Optimizing Molecular Weight, Polarity, and Cyclization

Melanogenesis is a biochemical process that regulates skin pigmentation, which is crucial role in protecting against ultraviolet radiation. It is also associated with hyperpigmentation conditions such as melasma and age spots, which negatively impact aesthetics and self-confidence. Tyrosinase (TYR), a key enzyme in the melanogenesis pathway, catalyzes the biosynthesis of melanin in the skin. Inhibition of tyrosinase particularly by blocking its active site and preventing the binding of natural substrates such as tyrosine, can reduce melanin production, making it a promising therapeutic target for treating hyperpigmentation. Peptides have emerged as promising therapeutics to regulate melanogenesis by minimizing the side effects associated with conventional skin whitening therapeutics. This review is designed to offer a comprehensive analysis of current strategies in peptide design aimed at optimizing anti-melanogenic activity, by focusing on the role of molecular weight, polarity, and cyclization strategies in enhancing peptide efficacy and stability. It was found that optimal peptide size was within the range of 400-600 Da. The balance between hydrophilic and hydrophobic properties in peptides is crucial for effective TYR inhibition, as higher hydrophilicity enhances affinity for the TYR active site and stronger catalytic inhibition, while hydrophobicity can contribute through alternative mechanisms. Cyclization of peptides enhances their structural stability, serum resistance, and binding affinity while reducing toxicity. This process increases resistance to enzymatic degradation and improves target specificity by limiting conformational flexibility. Additionally, the rigidity and internal hydrogen bonding of cyclic peptides can aid in membrane permeability, making them more effective for therapeutic use. Peptide optimizations through size modification, polarity change, and cyclization strategies have been shown to be promising as reliable and safe agents for melanin inhibition. Future studies exploring specific amino acid in peptide chains are required to improve efficacy and potential clinical applications of these anti-melanogenic peptides as a hyperpigmentation treatment.

Rutin of Moringa oleifera as a potential inhibitor to Agaricus bisporus tyrosinase as revealed from the molecular dynamics of inhibition

Tyrosinase is a binuclear copper-containing enzyme that catalyzes the conversation of monophenols to diphenols via o-hydroxylation and then the oxidation of o-diphenols to o-quinones which is profoundly linked to eukaryotic melanin synthesis and fruits browning. The hyperpigmentation due to unusual tyrosinase activity has gained growing health concern. Plants and their metabolites are considered promising and effective sources for potent antityrosinase enzymes. Hence, searching for potent, specific tyrosinase inhibitor from different plant extracts is an alternative approach in regulating overproduction of tyrosinase. Among the tested extracts, the hydro-alcoholic extract of Moringa oleifera L. leaves displayed the potent anti-tyrosinase activity (IC50 = 98.93 µg/ml) in a dose-dependent manner using L-DOPA as substrate; however, the kojic acid showed IC50 of 88.92 µg/ml. The tyrosinase-diphenolase (TYR-Di) kinetic analysis revealed mixed inhibition type for the Ocimum basilicum L. and Artemisia annua L. extracts, while the Coriandrum sativum L. extract displayed a non-competitive type of inhibition. Interestingly, the extract of Moringa oleifera L. leaves exhibited a competitive inhibition, low inhibition constant of free enzyme ( K ii app ) value and no Pan-Assay Interfering Substances, hinting the presence of strong potent inhibitors. The major putative antityrosinase compound in the extract was resolved, and chemically identified as rutin based on various spectroscopic analyses using UV-Vis, FTIR, mass spectrometry, and 1H NMR. The in silico computational molecular docking has been performed using rutin and A. bisporus tyrosinase (PDB code: 2Y9X). The binding energy of the predicted interaction between tropolone native ligand, kojic acid, and rutin against 2Y9X was respectively - 5.28, - 4.69, and - 7.75 kcal/mol. The docking simulation results revealed the reliable binding of rutin to the amino acid residues (ASN260, HIS259, SER282) in the tyrosinase catalytic site. Based on the developed results, rutin extracted from M. oleifera L. leaves has the capability to be powerful anti-pigment agent with a potential application in cosmeceutical area. In vivo studies are required to unravel the safety and efficiency of rutin as antityrosinase compound.

Melanin-based plumage coloration and melanin content in organs in the barn owl

Although the evolutionary ecology of melanin pigments and melanin-based coloration has been studied in great details, particularly in birds, little is known about the function of melanin stored inside the body. In the barn owl Tyto alba, in which individuals vary in the degree of reddish pheomelanin-based coloration and in the size of black eumelanic feather spots, we measured the concentration in melanin pigments in seven organs. The eyes had by far the most melanin then the skin, pectoral muscle, heart, liver, trachea, and uropygial gland. The concentration in eumelanin was not necessarily correlated with the concentration in pheomelanin suggesting that their production can be regulated independently from each other. Redder barn owls had more pheomelanin in the skin and uropygial gland than white owls, while owls displaying larger black feather spots had more eumelanin in the skin than small-spotted owls. More data are required to evaluate whether melanin-based traits can evolve as an indirect response to selection exerted on melanin deposition in organs.

In vitro inhibitory effects on free radicals, pigmentation, and skin cancer cell proliferation from Dendrobium hybrid extract: A new plant source of active compounds

Orchidaceae are diverse plants whose bioactive compounds have various biological activities. New hybrids of Dendrobium have been generated to gain characteristics shared with their ancestors. Dendrobium Pearl Vera (designated as DH) is derived from parents used for dermatological treatments and cosmetics. However, the phytoconstituents and biological properties of DH have not been reported. The current study investigated extracts from DH plants using four solvents (water, methanol, ethanol, or 2-propanol). The propanolic extract (DH-P) contained the highest phenolic and flavonoid contents, along with a high scavenging performance for free radicals. In total, 25 tentative constituents in the DH-P matrix were identified, consisting of amino acids, nucleotides, and three types of secondary metabolites: furan, phenolics, and alkaloids. The DH-P inhibited human tyrosinase in vitro in a concentration-dependent manner of the phenolic content. Furthermore, there was no significant difference between DH-P with 10 μg/ml phenolic content and 0.75 mM kojic acid (a commercial whitening agent) on the inhibition of human tyrosinase. Incubation with DH-P containing at least 15 μg/ml phenolic content greatly inhibited the proliferation of human melanoma; however, the cell viability was not affected by the phenolic content at 5 μg/ml or less. The half-maximal inhibitory concentration (IC50) of the phenolic content in DH-P on melanoma viability was 12.90 ± 1.04 μg/ml. Melanin production in vivo by human melanoma incubated with 5 μg/ml phenolic content in DH-P was reduced significantly, compared to 2.5 μg/ml phenolic content in DH-P, 100 μg/ml arbutin, and in control. The identified components, including 5-hydroxymethyl-2-furaldehyde, salicylic acid, nicotinamide, acetophenone, cytidine, adenosine, proline, or valine, have been reported to be associated with depigmentation, antioxidant, and anticancer. This research revealed, for the first time, the tentative phytoconstituents of Dendrobium Pearl Vera and their biological activities, thus demonstrating the potential use of DH-P in dermal applications.

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

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

Anti-Inflammation and Anti-Melanogenic Effects of Maca Root Extracts Fermented Using Lactobacillus Strains

Maca is a well-known biennial herb with various physiological properties, such as antioxidant activity and immune response regulation. In this study, the antioxidant, anti-inflammatory, and anti-melanogenic effects of fermented maca root extracts were investigated. The fermentation was carried out using Lactobacillus strains, such as Lactiplantibacillus plantarum subsp. plantarum, Lacticaseibacillus rhamnosus, Lacticaseibacillus casei, and Lactobacillus gasseri. In RAW 264.7 cells, the non-fermented maca root extracts increased the secretion of nitric oxide (NO), an inflammatory mediator, in a dose-dependent manner. In contrast, the fermented extracts showed considerably lower NO secretion than the non-fermented extracts at concentrations of 5% and 10%. This indicates the effective anti-inflammatory effects of fermented maca. The fermented maca root extracts also inhibited tyrosinase activity, melanin synthesis, and melanogenesis by suppressing MITF-related mechanisms. These results show that fermented maca root extracts exhibit higher anti-inflammatory and anti-melanogenesis effects than non-fermented maca root extracts. Thus, maca root extracts fermented using Lactobacillus strains have the potential to be used as an effective cosmeceutical raw material.

Effect of Chicken Egg White-Derived Peptide and Hydrolysates on Abnormal Skin Pigmentation during Wound Recovery

Abnormal skin pigmentation commonly occurs during the wound healing process due to the overproduction of melanin. Chicken egg white (CEW) has long been used to improve skin health. Previous published works had found CEW proteins house bioactive peptides that inhibit tyrosinase, the key enzyme of melanogenesis. The current study aimed to evaluate the anti-pigmentation potential and mechanism of the CEW-derived peptide (GYSLGNWVCAAK) and hydrolysates (CEWH_mono and CEWH_di), using a cell-based model. All of these peptide and hydrolysates inhibited intracellular tyrosinase activity and melanin level up to 45.39 ± 1.31 and 70.01 ± 1.00%, respectively. GYSLGNWVCAAK and CEWH_di reduced intracellular cAMP levels by 13.38 ± 3.65 and 14.55 ± 2.82%, respectively; however, CEWH_mono did not affect cAMP level. Moreover, the hydrolysates downregulated the mRNA expression of melanogenesis-related genes, such as Mitf, Tyr, Trp-1 and Trp-2, but GYSLGNWVCAAK only suppressed Tyr gene expression. Downregulation of the genes may lower the catalytic activities and/or affect the structural stability of TYR, TRP-1 and TRP-2; thus, impeding melanogenesis to cause an anti-pigmentation effect in the cell. Outcomes from the current study could serve as the starting point to understand the underlying complex, multifaceted melanogenesis regulatory mechanism at the cellular level.

Anti-Melanogenesis Activity of Crocodile (Crocodylus siamensis) White Blood Cell Extract on Ultraviolet B-Irradiated Melanocytes

Ultraviolet (UV) radiation generates a range of biological effects in the skin, which includes premature skin aging, hyperpigmentation, and cancer. Therefore, the development of new effective agents for UV-related skin damage remains a challenge in the pharmaceutical industry. This study aims to test the inhibitory effect of crocodile white blood cell (cWBC) extract, a rich source of bioactive peptides, on ultraviolet B (UVB)-induced melanocyte pigmentation. The results showed that cWBC (6.25-400 μg/mL) could inhibit tyrosinase without adduct formation by 12.97 ± 4.20% on average. cWBC pretreatment (25-100 μg/mL) had no cytotoxicity and reduced intracellular melanin to 111.17 ± 5.20% compared with 124.87 ± 7.43 for UVB condition. The protective role of cWBC pretreatment against UVB was exhibited by the promotion of cell proliferation and the prevention of UVB-induced morphological change as observed from F actin staining. The decrease of microphthalmia-associated transcription factor expression levels after cWBC pretreatment might be a mechanism by which cWBC suppresses UVB-induced pigmentation. These results suggest that cWBC could be beneficial for the prevention of UVB-induced skin pigmentation.

Ultra-Performance Liquid Chromatography-Mass Spectrometry-Based Untargeted Metabolomics Reveals the Key Potential Biomarkers for Castor Meal-Induced Enteritis in Juvenile Hybrid Grouper (Epinephelus fuscoguttatus♀ × E. lanceolatus♂)

The intensification of aquaculture to help kerb global food security issues has led to the quest for more economical new protein-rich ingredients for the feed-based aquaculture since fishmeal (FM, the ingredient with the finest protein and lipid profile) is losing its acceptability due to high cost and demand. Although very high in protein, castor meal (CM), a by-product after oil-extraction, is disposed-off due to the high presence of toxins. Concurrently, the agro-industrial wastes’ consistent production and disposal are of utmost concern; however, having better nutritional profiles of these wastes can lead to their adoption. This study was conducted to identify potential biomarkers of CM-induced enteritis in juvenile hybrid-grouper (Epinephelus fuscoguttatus♀ × Epinephelus lanceolatus♂) using ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) alongside their growth and distal intestinal (DI) health evaluation. A total of 360 fish (initial weight = 9.13 ± 0.01g) were randomly assigned into three groups, namely, fish-meal (FM) (control), 4% CM (CM4), and 20% CM (CM20). After the 56-days feeding-trial, the DI tissues of FM, CM4, and CM20 groups were collected for metabolomics analysis. Principal components analysis and partial least-squares discriminant-analysis (PLS-DA, used to differentiate the CM20 and CM4, from the FM group with satisfactory explanation and predictive ability) were used to analyze the UPLC-MS data. The results revealed a significant improvement in the growth, DI immune responses and digestive enzyme activities, and DI histological examinations in the CM4 group than the others. Nonetheless, CM20 replacement caused DI physiological damage and enteritis in grouper as shown by AB-PAS staining and scanning electron microscopy examinations, respectively. The most influential metabolites in DI contents identified as the potential biomarkers in the positive and negative modes using the metabolomics UPLC-MS profiles were 28 which included five organoheterocyclic compounds, seven lipids, and lipid-like molecules, seven organic oxygen compounds, two benzenoids, five organic acids and derivatives, one phenylpropanoids and polyketides, and one from nucleosides, nucleotides, and analogues superclass. The present study identified a broad array of DI tissue metabolites that differed between FM and CM diets, which provides a valuable reference for further managing fish intestinal health issues. A replacement level of 4% is recommended based on the growth and immunity of fish.

Evaluation of TILI-2 as an Anti-Tyrosinase, Anti-Oxidative Agent and Its Role in Preventing Melanogenesis Using a Proteomics Approach

There is a desire to develop new molecules that can combat hyperpigmentation. To this end, the N-terminal cysteine-containing heptapeptide TILI-2 has shown promising preliminary results. In this work, the mechanism by which it works was evaluated using a series of biochemical assays focusing on known biochemical pathways, followed by LC-MS/MS proteomics to discover pathways that have not been considered before. We demonstrate that TILI-2 is a competitive inhibitor of tyrosinase’s monophenolase activity and it could potentially scavenge ABTS and DPPH radicals. It has a very low cytotoxicity up to 1400 µM against human fibroblast NFDH cells and macrophage-like RAW 264.7 cells. Our proteomics study revealed that another putative mechanism by which TILI-2 may reduce melanin production involves the disruption of the TGF-β signaling pathway in mouse B16F1 cells. This result suggests that TILI-2 has potential scope to be used as a depigmenting agent.

Combination of Glycinamide and Ascorbic Acid Synergistically Promotes Collagen Production and Wound Healing in Human Dermal Fibroblasts

The purpose of this study is to present a novel strategy to enhance collagen production in cells. To identify amino acid analogs with excellent collagen production-enhancing effects, human dermal fibroblasts (HDFs) were treated with 20 kinds of amidated amino acids and 20 kinds of free amino acids, individually at 1 mM. The results showed that glycinamide enhanced collagen production (secreted collagen level) most effectively. Glycine also enhanced collagen production to a lesser degree. However, other glycine derivatives, such as N-acetyl glycine, N-acetyl glycinamide, glycine methyl ester, glycine ethyl ester, and glycyl glycine, did not show such effects. Glycinamide increased type I and III collagen protein levels without affecting COL1A1 and COL3A1 mRNA levels, whereas transforming growth factor-β1 (TGF-β1, 10 ng mL−1) increased both mRNA and protein levels of collagens. Ascorbic acid (AA, 1 mM) increased COL1A1 and COL3A1 mRNA and collagen I protein levels. Unlike TGF-β1, AA and glycinamide did not increase the protein level of α-smooth muscle actin, a marker of differentiation of fibroblasts into myofibroblasts. The combination of AA and glycinamide synergistically enhanced collagen production and wound closure in HDFs to a level similar to that in cells treated with TGF-β1. AA derivatives, such as magnesium ascorbyl 3-phosphate (MAP), 3-O-ethyl ascorbic acid, ascorbyl 2-O-glucoside, and ascorbyl tetraisopalmitate, enhanced collagen production, and the mRNA and protein levels of collagens at 1 mM, and their effects were further enhanced when co-treated with glycinamide. Among AA derivatives, MAP had a similar effect to AA in enhancing wound closure, and its effect was further enhanced by glycinamide. Other AA derivatives had different effects on wound closure. This study provides a new strategy to enhance cell collagen production and wound healing using glycinamide in combination with AA.

Anti-Melanogenic and Antioxidant Effects of Cell-Free Supernatant from Lactobacillus gasseri BNR17

In recent years, there has been considerable interest in the use of cell-free supernatant of probiotics culture for nutritional and functional applications. In this study, we investigated the effect of the cell-free supernatant from Lactobacillus gasseri BNR17 (CFS) on anti-melanogenesis and reducing oxidative stress in B16-F10 murine melanoma cells and HaCaT human keratinocytes. Treatment with CFS significantly inhibited the production of extracellular and intracellular melanin without cytotoxicity during melanogenesis induced by the α-MSH in B16-F10 cells. The CFS dramatically reduced tyrosinase activity and the melanogenesis-related gene expression. Further, it showed antioxidative effects in a dose-dependent manner in DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) assays and significantly increased the mRNA levels of HO-1 and CAT in HaCaT cells. Furthermore, the CFS increased HO-1 and anti-oxidative-related gene expression during H2O2-induced oxidative stress in HaCaT cells. Together, this study suggests that the CFS reduces hyperpigmentation and inhibits oxidative stress, and thus can be used as a potential skincare product in the future.

Theoretical Studies of Cyanophycin Dipeptides as Inhibitors of Tyrosinases

The three-dimensional structure of tyrosinase has been crystallized from many species but not from Homo sapiens. Tyrosinase is a key enzyme in melanin biosynthesis, being an important target for melanoma and skin-whitening cosmetics. Several studies employed the structure of tyrosinase from Agaricus bisporus as a model enzyme. Recently, 98% of human genome proteins were elucidated by AlphaFold. Herein, the AlphaFold structure of human tyrosinase and the previous model were compared. Moreover, tyrosinase-related proteins 1 and 2 were included, along with inhibition studies employing kojic and cinnamic acids. Peptides are widely studied for their inhibitory activity of skin-related enzymes. Cyanophycin is an amino acid polymer produced by cyanobacteria and is built of aspartic acid and arginine; arginine can be also replaced by other amino acids. A new set of cyanophycin-derived dipeptides was evaluated as potential inhibitors. Aspartate–glutamate showed the strongest interaction and was chosen as a leading compound for future studies.

Metabolic Basis and Clinical Evidence for Skin Lightening Effects of Thiol Compounds

Melanin pigment is a major factor in determining the color of the skin, and its abnormal increase or decrease can cause serious pigmentation disorders. The melanin pigment of the skin is divided into light pheomelanin and dark eumelanin, and a big difference between them is whether they contain sulfur. Melanin synthesis starts from a common reaction in which tyrosine or dihydroxyphenylalanine (DOPA) is oxidized by tyrosinase (TYR) to produce dopaquinone (DQ). DQ is spontaneously converted to leukodopachrome and then oxidized to dopachrome, which enters the eumelanin synthesis pathway. When DQ reacts with cysteine, cysteinyl dopa is generated, which is oxidized to cysteinyl DQ and enters the pheomelanin synthesis pathway. Therefore, thiol compounds can influence the relative synthesis of eumelanin and pheomelanin. In addition, thiol compounds can inhibit enzymatic activity by binding to copper ions at the active site of TYR, and act as an antioxidant scavenging reactive oxygen species and free radicals or as a modulator of redox balance, thereby inhibiting overall melanin synthesis. This review will cover the metabolic aspects of thiol compounds, the role of thiol compounds in melanin synthesis, comparison of the antimelanogenic effects of various thiol compounds, and clinical trials on the skin lightening efficacy of thiol compounds. We hope that this review will help identify the advantages and disadvantages of various thiol compounds as modulators of skin pigmentation and contribute to the development of safer and more effective strategies for the treatment of pigmentation disorders.

Fraxinol Stimulates Melanogenesis in B16F10 Mouse Melanoma Cells through CREB/MITF Signaling

Melanin pigment produced in melanocytes plays a protective role against ultraviolet radiation. Selective destruction of melanocytes causes chronic depigmentation conditions such as vitiligo, for which there are very few specific medical treatments. Here, we found that fraxinol, a natural coumarin from Fraxinus plants, effectively stimulated melanogenesis. Treatment of B16-F10 cells with fraxinol increased the melanin content and tyrosinase activity in a concentration-dependent manner without causing cytotoxicity. Additionally, fraxinol enhanced the mRNA expression of melanogenic enzymes such as tyrosinase, tyrosinase-related protein-1, and tyrosinase-related protein-2. Fraxinol also increased the expression of microphthalmia-associated transcription factor at both mRNA and protein levels. Fraxinol upregulated the phosphorylation of cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB). Furthermore, H89, a cAMP-dependent protein kinase A inhibitor, decreased fraxinol-induced CREB phosphorylation and microphthalmia-associated transcription factor expression and significantly attenuated the fraxinol-induced melanin content and intracellular tyrosinase activity. These results suggest that fraxinol enhances melanogenesis via a protein kinase A-mediated mechanism, which may be useful for developing potent melanogenesis stimulators.

Mechanistic Basis and Clinical Evidence for the Applications of Nicotinamide (Niacinamide) to Control Skin Aging and Pigmentation

Vitamin B3 (nicotinic acid, niacin) deficiency causes the systemic disease pellagra, which leads to dermatitis, diarrhea, dementia, and possibly death depending on its severity and duration. Vitamin B3 is used in the synthesis of the NAD+ family of coenzymes, contributing to cellular energy metabolism and defense systems. Although nicotinamide (niacinamide) is primarily used as a nutritional supplement for vitamin B3, its pharmaceutical and cosmeceutical uses have been extensively explored. In this review, we discuss the biological activities and cosmeceutical properties of nicotinamide in consideration of its metabolic pathways. Supplementation of nicotinamide restores cellular NAD+ pool and mitochondrial energetics, attenuates oxidative stress and inflammatory response, enhances extracellular matrix and skin barrier, and inhibits the pigmentation process in the skin. Topical treatment of nicotinamide, alone or in combination with other active ingredients, reduces the progression of skin aging and hyperpigmentation in clinical trials. Topically applied nicotinamide is well tolerated by the skin. Currently, there is no convincing evidence that nicotinamide has specific molecular targets for controlling skin aging and pigmentation. This substance is presumed to contribute to maintaining skin homeostasis by regulating the redox status of cells along with various metabolites produced from it. Thus, it is suggested that nicotinamide will be useful as a cosmeceutical ingredient to attenuate skin aging and hyperpigmentation, especially in the elderly or patients with reduced NAD+ pool in the skin due to internal or external stressors.

Identification of L-Cysteinamide as a Potent Inhibitor of Tyrosinase-Mediated Dopachrome Formation and Eumelanin Synthesis

The purpose of this study is to identify amino acid derivatives with potent anti-eumelanogenic activity. First, we compared the effects of twenty different amidated amino acids on tyrosinase (TYR)-mediated dopachrome formation in vitro and melanin content in dark-pigmented human melanoma MNT-1 cells. The results showed that only L-cysteinamide inhibited TYR-mediated dopachrome formation in vitro and reduced the melanin content of cells. Next, the antimelanogenic effect of L-cysteinamide was compared to those of other thiol compounds (L-cysteine, N-acetyl L-cysteine, glutathione, L-cysteine ethyl ester, N-acetyl L-cysteinamide, and cysteamine) and positive controls with known antimelanogenic effects (kojic acid and β-arbutin). The results showed the unique properties of L-cysteinamide, which effectively reduces melanin content without causing cytotoxicity. L-Cysteinamide did not affect the mRNA and protein levels of TYR, tyrosinase-related protein 1, and dopachrome tautomerase in MNT-1 cells. L-Cysteinamide exhibited similar properties in normal human epidermal melanocytes (HEMs). Experiments using mushroom TYR suggest that L-cysteinamide at certain concentrations can inhibit eumelanin synthesis through a dual mechanism by inhibiting TYR-catalyzed dopaquinone synthesis and by diverting the synthesized dopaquinone to the formation of DOPA-cysteinamide conjugates rather than dopachrome. Finally, L-cysteinamide was shown to increase pheomelanin content while decreasing eumelanin and total melanin contents in MNT-1 cells. This study suggests that L-cysteinamide has an optimal structure that can effectively and safely inhibit eumelanin synthesis in MNT-1 cells and HEMs, and will be useful in controlling skin hyperpigmentation.

Promelanogenic Effects by an Annurca Apple-Based Natural Formulation in Human Primary Melanocytes

Introduction

Melanocytes are engaged in synthesis, transport, and release of pigments at the epidermal-melanin units in response to the finely regulated melanogenic pathway. A multifaceted combination of both intrinsic and extrinsic factors – from endocrine and paracrine dynamics to exogenous stimuli such as sunlight and xenobiotics – modulates expression and activity of proteins involved in pigmentation, including the rate-limiting enzyme tyrosinase. As well as playing critical physiological functions comprising skin photoprotection, melanins define hair and skin pigmentation which in turn have impacted considerably to human social communication since time immemorial. Additionally, numerous skin diseases based on pigmentation alterations can have serious public influence. While several melanogenesis inhibitors are already available, the number of melanin activators and tyrosinase stimulators as drug-like agents is still limited.

Methods

To explore the biological effects of an Annurca Apple-based nutraceutical preparation (AMS) on melanin production, experiments in cellular models of human skin were performed. Both primary cultures and co-cultures of epidermal melanocytes (HEMa) and follicular keratinocytes (HHFK) were used.

Results

We show that AMS, by now branded for its cutaneous beneficial effects, induces in total biocompatibility a significant promelanogenic effect in human primary melanocytes. In line, we found melanin cytosolic accumulation consistent with tyrosinase up-regulation.

Conclusion

Disposal of skin pigmenting agents would be attractive for the treatment of hypopigmentation disorders, to postpone skin photoaging or simply for fashion, so that discovery and development of melanogenesis stimulators, especially from natural sources, is nowadays a dynamic area of research.

Pharmacologic manipulation of skin pigmentation

Skin complexion is among the most recognizable phenotypes between individuals and is mainly determined by the amount and type of melanin pigment deposited in the epidermis. Persons with dark skin complexion have more of a brown/black pigment known as eumelanin in their epidermis whereas those with fair skin complexions have less. Epidermal eumelanin acts as a natural sunblock by preventing incoming UV photons from penetrating into the skin and therefore protects against UV mutagenesis. By understanding the signaling pathways and regulation of pigmentation, strategies can be developed to manipulate skin pigmentation to improve UV resistance and to diminish skin cancer risk.