Advances in Biomedical Functions of Natural Whitening Substances in the Treatment of Skin Pigmentation Diseases

The molecular mechanisms underlying optical isomer arbutin permeating the skin: The molecular interaction between arbutin and skin components

Arbutin, a typical optical isomer, has garnered widespread acclaim in the whitening cosmetics for its favorable efficacy and safety. However, the molecular mechanisms underlying α-arbutin and β-arbutin permeating across the skin have not elucidated clearly yet. Herein we aimed to unveil how α-arbutin and β-arbutin interacted with keratin or SC lipids, further demonstrating their relationship with their drug permeability. We found that α-arbutin displayed significantly higher drug accumulation into the porcine skin than β-arbutin within 24 h through in vitro permeation test. Moreover, α-arbutin predominantly induced the alternations of secondary structure of amide II during the drug permeation, which was favorable for α-arbutin permeation. On the contrary, β-arbutin exhibited an observable effect on the stretching vibration of SC lipids, possessing a significantly stronger mixing energy, binding energy and compatibility with ceramide (Cer) than that of α-arbutin, which ultimately restricted its permeation. Interestingly, free fatty acids and ceramides of the SC lipids specifically utilized its oxygen atom of carboxyl group to dock the arbutin molecules, enhancing their affinity with β-arbutin, as confirmed by molecular simulation and 13Carbon Nuclear Magnetic Resonance. Nevertheless, a favorable compatibility between α-arbutin and keratin was observed. It was emphasized that the distinct spatial configuration and opposite optical rotation of arbutin was the leading factor impacting the intermolecular force between arbutin and the SC, and resulted in a diverse drug permeation. In cellular and in vivo skin pharmacokinetic studies, α-arbutin also possessed a higher cellular uptake and topical bioavailability than β-arbutin. This study revealed the transdermal permeation mechanisms of optical isomer arbutin at the molecular levels, providing methodological reference for the investigations of permeation behaviors of other isomers with similar spatial configuration.

In Vitro In Silico Screening Strategy and Mechanism of Novel Tyrosinase Inhibitory Peptides from Nacre of Hyriopsis cumingii

For thousands of years, pearl and nacre powders have been important traditional Chinese medicines known for their skin whitening effects. To prepare the enzymatic hydrolysates of Hyriopsis cumingii nacre powder (NP-HCH), complex enzymatic hydrolysis by pineapple protease and of neutral protease was carried out after the powder was pre-treated with a high-temperature and high-pressure method. The peptides were identified using LC-MS/MS and picked out through molecular docking and molecular dynamics simulations. Subsequently, the tyrosinase inhibitory and antioxidant properties of novel tyrosinase inhibitory peptides were investigated in vitro. In addition, the enzymatic activity of tyrosinase in B16F10 cells as well as melanin content and antioxidant enzyme levels were also examined. The results showed that a tyosinase inhibitory peptide (Tyr-Pro-Asn-Pro-Tyr, YPNPY) with an efficient IC50 value of 0.545 ± 0.028 mM was identified. The in vitro interaction results showed that YPNPY is a reversible competitive inhibitor of tyrosinase, suggesting that it binds to the free enzyme. The B16F10 cell whitening test revealed that YPNPY can reduce the melanin content of B16F10 cells by directly inhibiting the activity of intracellular tyrosinase. Additionally, it indirectly affects melanin production by acting as an antioxidant. These results suggest that YPNPY could be widely used as a tyrosinase inhibitor in whitening foods and drugs.

Germacrone, isolated from Curcuma wenyujin, inhibits melanin synthesis through the regulation of the MAPK signaling pathway

Abnormal melanin synthesis causes hyperpigmentation disorders, such as chloasma, freckles, and melanoma, which are highly multiple and prevalent. There were few reports on the anti-melanogenic effect of Curcuma wenyujin Y.H. Chen et C. Ling, and the bioactive compound has not been elucidated as well. The study aims to investigate the anti-melanogenic effect of C. wenyujin, and identify the bioactive compound, and further explore its underlying mechanism. Our results showed that the Petroleum ether fraction extracted from C. wenyujin rhizome had a significant anti-melanogenic effect, and germacrone isolated from it was confirmed as the major bioactive compound. To our data, germacrone significantly inhibited tyrosinase (TYR) activity, reduced melanosome synthesis, reduced dendrites formation of B16F10 cells, and melanosome transport to keratinocytes. Moreover, germacrone effectively decreased the hyperpigmentation in zebrafish and the skin of guinea pigs in vivo. Western-blot analysis showed that germacrone down-regulated the expression of TYR, TRP-1, TRP-2, Rab27a, Cdc42, and MITF proteins via the activation of the MAPK signaling pathway. Taken together, germacrone is an effective bioactive compound for melanogenesis inhibition. Our studies suggest that germacrone may be considered a potential candidate for skin whitening.

In Silico Identification and Molecular Mechanism of Novel Tyrosinase Inhibitory Peptides Derived from Nacre of Pinctada martensii

Pearl and nacre powders have been valuable traditional Chinese medicines with whitening properties for thousands of years. We utilized a high-temperature and high-pressure method along with compound enzyme digestion to prepare the enzymatic hydrolysates of nacre powder of Pinctada martensii (NP-PMH). The peptides were identified using LC-MS/MS and screened through molecular docking and molecular dynamics simulations. The interactions between peptides and tyrosinase were elucidated through enzyme kinetics, circular dichroism spectropolarimetry, and isothermal titration calorimetry. Additionally, their inhibitory effects on B16F10 cells were explored. The results showed that a tyrosinase-inhibitory peptide (Ala-His-Tyr-Tyr-Asp, AHYYD) was identified, which inhibited tyrosinase with an IC50 value of 2.012 ± 0.088 mM. The results of the in vitro interactions showed that AHYYD exhibited a mixed-type inhibition of tyrosinase and also led to a more compact enzyme structure. The binding reactions of AHYYD with tyrosinase were spontaneous, leading to the formation of a new set of binding sites on the tyrosinase. The B16F10 cell-whitening assay revealed that AHYYD could reduce the melanin content of the cells by directly inhibiting the activity of intracellular tyrosinase. Additionally, it indirectly affects melanin production by acting as an antioxidant. These results suggest that AHYYD could be widely used as a tyrosinase inhibitor in whitening foods and pharmaceuticals.

Mechanism, Formulation, and Efficacy Evaluation of Natural Products for Skin Pigmentation Treatment

Skin pigmentation typically arises from the excessive secretion and accumulation of melanin, resulting in a darker complexion compared to normal skin. Currently, the local application of chemical drugs is a first-line strategy for pigmentation disorders, but the safety and efficacy of drugs still cannot meet clinical treatment needs. For long-term and safe medication, researchers have paid attention to natural products with higher biocompatibility. This article begins by examining the pathogenesis and treatment approaches of skin pigmentation diseases and summarizes the research progress and mechanism of natural products with lightening or whitening effects that are clinically common or experimentally proven. Moreover, we outline the novel formulations of natural products in treating pigmentation disorders, including liposomes, nanoparticles, microemulsions, microneedles, and tocosomes. Finally, the pharmacodynamic evaluation methods in the study of pigmentation disorder were first systematically analyzed. In brief, this review aims to collect natural products for skin pigmentation treatment and investigate their formulation design and efficacy evaluation to provide insights for the development of new products for this complex skin disease.

Exploring the potential of white birch sap: A natural alternative to traditional skin whitening agents with reduced side effects

Common tyrosinase (TYR) inhibitors used in cosmetics, such as hydroquinone, kojic acid, and arbutin, can cause side effects including erythema, skin peeling, and dryness. Therefore, the development of natural whitening agents that offer excellent permeability, minimal irritation, and high safety has become a primary focus in the field of TYR inhibitors. In this study, we demonstrate that White birch sap (WBS), within a safe concentration range, effectively reduces TYR activity and melanin content in both B16F10 mouse melanoma cells and zebrafish larvae. Importantly, WBS exhibits minimal irritation to neutrophils in fluorescent zebrafish and does not affect the behavior of adult zebrafish. Furthermore, WBS downregulates the gene expression levels of microphthalmia-associated transcription factor, TYR, tyrosinase-related protein-1, and tyrosinase-related protein-2 in B16F10 cells. In conclusion, our research confirms that WBS, a naturally derived substance, offers high safety and mild effects, making it a promising candidate for a skin-whitening agent.

Comparative Studies on the Photoreactivity, Efficacy, and Safety of Depigmenting Agents

Depigmenting products are increasingly used to counteract skin hyperpigmentation and related psychosocial issues. This study aimed to compare different depigmenting agents-4-butylresorcinol; bakuchiol; tranexamic acid; ascorbyl glucoside; α-arbutin; and ascorbic acid-for photoreactivity; tyrosinase inhibition; and safety. Photoreactivity was assessed using the Reactive Oxygen Species assay. In vitro tyrosinase inhibition was compared, and cell viability was assessed in B-16V melanocytes to evaluate safety. Results showed 4-butylresorcinol, ascorbyl glucoside, and α-arbutin are non-photoreactive, while for ascorbic acid and bakuchiol it was not possible to reach conclusive results due to the lack of specificity of the ROS assay. 4-Butylresorcinol, acting as a competitive inhibitor, displayed potent tyrosinase inhibition, followed by ascorbic acid and bakuchiol. Both 4-butylresorcinol and bakuchiol reduced cell viability in a concentration-dependent manner. The insights obtained in this work support the development of depigmenting products by providing useful scientific guidance on the photostability, tyrosinase inhibitory efficacy, and skin safety of depigmenting agents.

In Vitro and In Vivo Antimelanogenesis Effects of Leaf Essential Oil from Agathis dammara

Agathis species are widely distributed around Southeast Asia, Australasia, South Pacific islands, and etc. Traditionally, Agathis species have been used as the folk medicines, the common ethnopharmacological uses of Agathis genus are the treatments of headache and myalgia. This study aims to investigate the chemical composition of Agathis dammara (Lamb.) Rich. leaf essential oil and to explore its antimelanogenesis effect. The chemical constituents of leaf essential oil are analyzed using gas chromatography-mass spectrometry (GC-MS), the major constituents of leaf essential oil are sesquiterpenoids. The major constituents are δ-cadinene (16.12%), followed by γ-gurjunene (15.57%), 16-kaurene (12.43%), β-caryophyllene (8.58%), germacrene D (8.53%), and γ-cadinene (5.33%). As for the in vitro antityrosinase activity, leaf essential oil inhibit the tyrosinase activity of mushroom when the substrate is 3,4-dihydroxyphenylalanine (L-DOPA). Leaf essential oil prevents tyrosinase from acting as diphenolase and catalyzing L-DOPA to dopaquinone, and converting into dark melanin pigments. A. dammara leaf essential oil also exhibits the in vivo antimelanogenesis effect, leaf essential oil reduces 43.48% of melanin formation in zebrafish embryos at the concentration of 50 μg/mL. Results reveal A. dammara leaf essential oil has the potential for developing the skin whitening drug and depigmentation ingredient for hyperpigmentary disorders.

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

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

The Effects of 2'-Hydroxy-3,6'-Dimethoxychalcone on Melanogenesis and Inflammation

In this study, we demonstrated that 2'-hydroxy-3,6'-dimethoxychalcone (3,6'-DMC) alleviated α-MSH-induced melanogenesis and lipopolysaccharides (LPS)-induced inflammation in mouse B16F10 and RAW 264.7 cells. In vitro analysis results showed that the melanin content and intracellular tyrosinase activity were significantly decreased by 3,6'-DMC, without cytotoxicity, via decreases in tyrosinase and the tyrosinase-related protein 1 (TRP-1) and TRP-2 melanogenic proteins, as well as the downregulation of microphthalmia-associated transcription factor (MITF) expression through the upregulation of the phosphorylation of extracellular-signal-regulated kinase (ERK), phosphoinositide 3-kinase (PI3K)/Akt, and glycogen synthase kinase-3β (GSK-3β)/catenin, and downregulation of the phosphorylation of p38, c-Jun N-terminal kinase (JNK), and protein kinase A (PKA). Furthermore, we investigated the effect of 3,6'-DMC on macrophage RAW264.7 cells with LPS stimulation. 3,6'-DMC significantly inhibited LPS-stimulated nitric oxide production. 3,6'-DMC also suppressed the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 on the protein level. In addition, 3,6'-DMC decreased the production of the tumor necrosis factor-α and interleukin-6. Successively, our mechanistic studies revealed that 3,6'-DMC also suppressed the LPS-induced phosphorylation of the inhibitor of IκBα, p38MAPK, ERK, and JNK. The Western blot assay results showed that 3,6'-DMC suppresses LPS-induced p65 translocation from cytosol to the nucleus. Finally, the topical applicability of 3,6'-DMC was tested through primary skin irritation, and it was found that 3,6'-DMC, at 5 and 10 μM concentrations, did not cause any adverse effects. Therefore, 3,6'-DMC may provide a potential candidate for preventing and treating melanogenic and inflammatory skin diseases.

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.

The Skin-Whitening and Antioxidant Effects of Protocatechuic Acid (PCA) Derivatives in Melanoma and Fibroblast Cell Lines

The skin is the most voluminous organ of the human body and is exposed to the outer environment. Such exposed skin suffers from the effects of various intrinsic and extrinsic aging factors. Skin aging is characterized by features such as wrinkling, loss of elasticity, and skin pigmentation. Skin pigmentation occurs in skin aging and is caused by hyper-melanogenesis and oxidative stress. Protocatechuic acid (PCA) is a natural secondary metabolite from a plant-based source widely used as a cosmetic ingredient. We chemically designed and synthesized PCA derivatives conjugated with alkyl esters to develop effective chemicals that have skin-whitening and antioxidant effects and enhance the pharmacological activities of PCA. We identified that melanin biosynthesis in B16 melanoma cells treated with alpha-melanocyte-stimulating hormone (α-MSH) is decreased by PCA derivatives. We also found that PCA derivatives effectively have antioxidant effects in HS68 fibroblast cells. In this study, we suggest that our PCA derivatives are potent ingredients for developing cosmetics with skin-whitening and antioxidant effects.

Epidermis-on-a-chip system to develop skin barrier and melanin mimicking model

In vitro skin models are rapidly developing and have been widely used in various fields as an alternative to traditional animal experiments. However, most traditional static skin models are constructed on Transwell plates without a dynamic three-dimensional (3D) culture microenvironment. Compared with native human and animal skin, such in vitro skin models are not completely biomimetic, especially regarding their thickness and permeability. Therefore, there is an urgent need to develop an automated biomimetic human microphysiological system (MPS), which can be used to construct in vitro skin models and improve bionic performance. In this work, we describe the development of a triple-well microfluidic-based epidermis-on-a-chip (EoC) system, possessing epidermis barrier and melanin-mimicking functions, as well as being semi-solid specimen friendly. The special design of our EoC system allows pasty and semi-solid substances to be effectively utilized in testing, as well as allowing for long-term culturing and imaging. The epidermis in this EoC system is well-differentiated, including basal, spinous, granular, and cornified layers with appropriate epidermis marker (e.g. keratin-10, keratin-14, involucrin, loricrin, and filaggrin) expression levels in corresponding layers. We further demonstrate that this organotypic chip can prevent permeation of over 99.83% of cascade blue (a 607 Da fluorescent molecule), and prednisone acetate (PA) was applied to test percutaneous penetration in the EoC. Finally, we tested the whitening effect of a cosmetic on the proposed EoC, thus demonstrating its efficacy. In summary, we developed a biomimetic EoC system for epidermis recreation, which could potentially serve as a useful tool for skin irritation, permeability, cosmetic evaluation, and drug safety tests.