Inhibitory effects of arbutin on melanin biosynthesis of α-melanocyte stimulating hormone-induced hyperpigmentation in cultured brownish guinea pig skin tissues

Toxicological profiling and diuretic potential of arbutin via aldosterone synthase gene inhibition

AIMS

Arbutin (ARB), a natural polyphenol isolated from the bearberry plant Arctostaphylos uva-ursi, has been studied for its diverse pharmacological activities including anti-diabetic, cardioprotective and anti-inflammatory effects. This study aimed to evaluate arbutin's diuretic activity, focusing on its impact on aldosterone synthase gene expression and its toxicity profile.

MATERIAL AND METHODS

Acute toxicity was assessed using single doses ranging from 500 to 9000 mg/kg and sub-acute toxicity with doses of 375 and 750 mg/kg over 14 days. To evaluate acute diuretic activity, ARB was administered in three doses (25, 50 and 75 mg/kg i.p) alongside standard groups, furosemide (FUR) 10 mg/kg i.p and Spironolactone (SPIR) 25 mg/kg i.p. In sub-acute diuretic study, treatment was administered for seven days, followed by blood collection and adrenal dissection for gene expression analysis.

KEY FINDINGS

Acute toxicity studies revealed that ARB is well-tolerated up to 7000 mg/kg with no significant changes in organ and body weight. However, sub-acute studies showed minor changes in leukocyte count, alkaline phosphatase (ALP), alanine aminotransferase (ALT) and triglycerides (TGs) at high doses while histopathological evaluations revealed no severe organ damage. The diuretic index and electrolyte analysis confirmed the potential of ARB as diuretic and saluretic with reduced risk of hyperuricemia and hyperkalemia. Gene expression studies showed non-selective downregulation of aldosterone synthase gene (CYP11B2) and 11β-hydroxylase (CYP11B1). While the effects on 17α-hydroxylase (CYP17A1) were less pronounced than SPIR, indicating fewer possible anti-androgenic effects.

SIGNIFICANCE

Our findings suggest that ARB is a promising diuretic agent with a favorable safety profile.

α-arbutin prevents UVA-induced skin photodamage via alleviating DNA damage and collagen degradation in NIH-3T3 cells

Ultraviolet radiation (UV) causes certain side effects to the skin, and their accumulation to a certain extent can lead to accelerated aging of the skin. Recent studies suggest that α-arbutin may be useful in various disorders such as hyperpigmentation disorders, wound healing, and antioxidant activity. However, the role of α-arbutin in skin photodamage is unclear. In this study, under UVA-induced photodamage conditions, α-arbutin treated mouse skin fibroblasts (NIH-3T3) can repair DNA damage and resist apoptosis by reducing the production of reactive oxygen species (ROS) and increasing the phosphorylation of glycogen synthase kinase 3 beta (GSK3β) to orchestra AKT/GSK3β pathway. Meanwhile, α-arbutin can also regulate collagen metabolism and facilitate the replenishment of collagen by targeting the phosphorylation of SMAD3 to mediate the TGFβ/SMAD pathway in NIH-3T3. In conclusion, we found that α-arbutin can mitigate the detrimental effects of skin photodamage induced by UVA irradiation, and provides a theoretical basis for the use of α-arbutin in the treatment of skin photodamage.

Giant Centella asiatica, a novel cultivar rich in madecassoside and asiaticoside, suppresses α‑melanocyte‑stimulating hormone‑induced melanogenesis through MC1R binding

The present study investigated the anti‑melanogenesis effects of Giant Centella asiatica (GCA), a new cultivator of Centella asiatica (CA) cataloged by the Korea Forest Service in 2022, and compared its efficacy with that of traditional CA. GCA has a high yield per unit area and enhanced antioxidant properties. The anti‑melanogenic effects of GCA were investigated using B16F10 melanoma cells and a 3D human skin‑equivalent model. Key molecular mechanisms were elucidated through western blotting, cAMP assays and molecular docking studies. Focus was addressed on the effect of GCA on skin whitening by comparing the ability of a GCA extract to inhibit melanin production in B16F10 melanoma cells and a 3D human skin‑equivalent model to that of CA. The results showed that the GCA extracts more effectively reduced melanin production, which was attributed to their higher content of two active components, madecassoside and asiaticoside. Further investigation revealed that GCA primarily inhibited melanogenesis through the PKA‑cAMP response element‑binding (CREB)‑microphthalmia‑associated transcription factor (MITF) axis, a key regulatory pathway in melanin synthesis. Notably, the present study, to the best of our knowledge, is the first to demonstrate that madecassoside and asiaticoside, the two principal compounds in GCA, directly bound to MC1R, which contributed to the significant skin‑whitening effects. Moreover, GCA reduced melanin production in a 3D human skin‑equivalent model, showing efficacy within a complex skin environment. These results demonstrated the superior effectiveness of GCA to that of CA for skin anti‑melanogenesis, indicating its potential as a promising natural material for targeting pigmentation disorders.

Hydrolyzed cow colostrum extract (BCFM) inhibits alpha-MSH-induced melanogenesis in B16F1 cells via regulation of the MC1R-cAMP signaling pathway

Cow colostrum is the first milk produced after birth and is a rich natural source of nutrients, immunoglobulins, peptides, and growth factors. The bioconversion of milk and whey changes the immobilization and biochemical characterization. However, the cellular mechanism and the anti-melanin synthesis effects of hydrolyzed cow colostrum extract (BCFM) in alpha-MSH-induced B16F1 cells have not been examined. In this study, we investigated the anti-melanogenesis mechanism by examining the effects of BCFM in alpha-MSH-induced B16F1 cells. Cells were treated with BCFM in the presence or absence of alpha-MSH and co-cultured for 24, 48, and 72 h. The treatment of B16F1 cells with alpha-MSH resulted in the darkening of the color of the cells and induction of melanin synthesis. In addition, the expression levels of MC1R and cAMP, as well as phosphorylation levels of CREB and PKA, were increased by alpha-MSH treatment. However, concomitant treatment with BCFM resulted in a significant decrease in these factors and phosphorylated MITF. At the same time, the expressive amount of TRP-1 and tyrosinase was also decreased in B16F1 cells. These results demonstrate the potential of BCFM for the prevention of melanogenesis progression via the regulation of the MC1R-cAMP signaling pathway in alpha-MSH-induced B16F1 cells. The administration of BCFM suppressed the expression of TRP-1 and/or tyrosinase by regulating the CREB/MITF signaling pathways in the B16F1 cells. We propose that hydrolyzed cow colostrum extract (BCFM) is suitable for use as a novel active agent for skin whitening or pharmaceutical applications.

Liposome preparation of alpha-arbutin: stability and toxicity assessment using mouse B16F10 melanoma cells

Melanoma is the most aggressive type of skin cancer, with few therapeutic alternatives following metastasis development. In recent years, drug delivery-associated nanotechnology has shown promising targeted results with diminished adverse effects compared to conventional treatments. This study aimed to (1) examine the effects of plant-derived α-arbutin, a natural compound and (2) compare these findings with bioactively developed liposomes containing α-arbutin utilizing the B16-F10 murine melanoma cell line as a model. Liposomes were obtained through reversed-phase evaporation by applying a spray dryer to assess their stability. The following biologic assays were measured cytotoxicity/antiproliferative (MTT, Neutral Red, and dsDNA PicoGreen). In addition, the levels of melanin and purinergic enzymes were also measured. The production of reactive oxygen species (ROS) and nitric oxide (NO) was determined as a measure of oxidative state. Treatment with nano-liposome containing alpha-arbutin induced a significant 68.4% cytotoxicity, similar to the positive control, in the B16-F10 murine melanoma cell line at 72 hr. Further, arbutin and liposomes containing alpha-arbutin increased levels of ROS and nitrite formation at 72 hr at the highest concentration (100 and 300 µg/ml) of treatments. Arbutin and liposomes containing alpha-arbutin reduced melanin levels at all tested concentrations. In addition, arbutin and alpha-arbutin containing liposomes lowered nucleotides (AMP, ADP, and ATP) and nucleoside (adenosine) levels in melanoma cells. Evidence suggests that α-arbutin containing liposome can be considered as an alternative immunosuppressive agent stimulated in melanoma treatment.

Wnt/β-catenin signaling pathway: proteins' roles in osteoporosis and cancer diseases and the regulatory effects of natural compounds on osteoporosis

Osteoblasts are mainly derived from mesenchymal stem cells in the bone marrow. These stem cells can differentiate into osteoblasts, which have the functions of secreting bone matrix, promoting bone formation, and participating in bone remodeling. The abnormality of osteoblasts can cause a variety of bone-related diseases, including osteoporosis, delayed fracture healing, and skeletal deformities. In recent years, with the side effects caused by the application of PTH drugs, biphosphonate drugs, and calmodulin drugs, people have carried out more in-depth research on the mechanism of osteoblast differentiation, and are actively looking for natural compounds for the treatment of osteoporosis. The Wnt/β-catenin signaling pathway is considered to be one of the important pathways of osteoblast differentiation, and has become an important target for the treatment of osteoporosis. The Wnt/β-catenin signaling pathway, whether its activation is enhanced or its expression is weakened, will cause a variety of diseases including tumors. This review will summarize the effect of Wnt/β-catenin signaling pathway on osteoblast differentiation and the correlation between the related proteins in the pathway and human diseases. At the same time, the latest research progress of natural compounds targeting Wnt/β-catenin signaling pathway against osteoporosis is summarized.

Oxidative Stress, Inflammation, and Altered Lymphocyte E-NTPDase Are Implicated in Acute Dyslipidemia in Rats: Protective Role of Arbutin

BACKGROUND/OBJECTIVES

Dyslipidemia is frequently linked to various disorders, and its clinical relevance is now recognized. The role of inflammation and oxidative stress (OS) in dyslipidemia has been acknowledged. This study assessed the potential of arbutin (ARB) to prevent dyslipidemia and its associated OS and inflammation in rats with acute hyperlipidemia.

METHODS

Rats received ARB orally for 14 days and a single intraperitoneal injection of poloxamer-407 on day 15.

RESULTS

Poloxamer-407 elevated circulating cholesterol (CHOL), triglycerides (TG), very low-density lipoprotein (vLDL), and LDL, and reduced high-density lipoprotein (HDL)-C and lipoprotein lipase (LPL). ARB ameliorated the circulating lipids and LPL, and suppressed 3-hydroxy-3-methylglutaryl CoA reductase (HMGCR) in rat liver and in vitro. Fatty acid synthase (FAS) in rat liver and its in vitro activity were suppressed by ARB, which also upregulated the LDL receptor (LDL-R) and ABCA1, and had no effect on ABCG5 and ABCG8 mRNA. ARB ameliorated liver malondialdehyde and nitric oxide and enhanced antioxidants in rats with dyslipidemia. Liver NF-κB p65 and blood inflammatory cytokines were increased in dyslipidemic rats, effects that were reversed by ARB. Moreover, ARB effectively suppressed lymphocyte E-NTPDase and E-ADA activities in dyslipidemic rats. The biochemical findings were supported by in silico data showing the affinity of ARB to bind LDL-R PCSK9 binding domain, HMGCR, FAS, and E-NTPDase.

CONCLUSIONS

ARB possessed anti-dyslipidemia, anti-inflammatory, and antioxidant effects mediated via the modulation of CHOL and TG synthesis, LPL, lymphocyte E-NTPDase and E-ADA, and cytokine release in rats. Thus, ARB could be an effective agent to attenuate dyslipidemia and its associated OS and inflammation, pending further studies as well as clinical trials.

GROWTH REGULATING FACTOR 7-mediated arbutin metabolism enhances rice salt tolerance

Salt stress is an environmental factor that limits plant growth and crop production. With the rapid expansion of salinized arable land worldwide, investigating the molecular mechanisms underlying the salt stress response in plants is urgently needed. Here, we report that GROWTH REGULATING FACTOR 7 (OsGRF7) promotes salt tolerance by regulating arbutin (hydroquinone-β-D-glucopyranoside) metabolism in rice (Oryza sativa). Overexpression of OsGRF7 increased arbutin content, and exogenous arbutin application rescued the salt-sensitive phenotype of OsGRF7 knockdown and knockout plants. OsGRF7 directly promoted the expression of the arbutin biosynthesis genes URIDINE DIPHOSPHATE GLYCOSYLTRANSFERASE 1 (OsUGT1) and OsUGT5, and knockout of OsUGT1 or OsUGT5 reduced rice arbutin content, salt tolerance, and grain size. Furthermore, OsGRF7 degradation through its interaction with F-BOX AND OTHER DOMAINS CONTAINING PROTEIN 13 reduced rice salinity tolerance and grain size. These findings highlight an underexplored role of OsGRF7 in modulating rice arbutin metabolism, salt stress response, and grain size, as well as its broad potential use in rice breeding.

Antioxidant and Antimelanogenic Activities of Lactobacillus kunkeei NCHBL-003 Isolated from Honeybees

Excessive reactive oxygen species production can detrimentally impact skin cell physiology, resulting in cell growth arrest, melanogenesis, and aging. Recent clinical studies have found that lactic acid bacteria have a special effect directly or indirectly on skin organs, but the exact mechanism has not been elucidated. In this study, we investigated the mechanisms underlying the antioxidant protective effect and the inhibitory effect on melanin synthesis of Lactobacillus kunkeei culture supernatant (CSK), isolated from Apis mellifera Linnaeus (the Western honeybee). CSK exhibited notable efficacy in promoting cell migration and wound healing under oxidative stress, surpassing the performance of other strains. CSK pretreatment significantly upregulated the expression of Nrf2/HO-1 (nuclear factor erythroid 2-related factor 2/heme oxygenase-1), a key player in cellular defenses against oxidative stress, relative to the control H2O2-treated cells. The DCF-DA (dichloro-dihydro-fluorescein diacetate) assay results confirmed that CSK's ability to enhance Nrf2 and HO-1 expression aligns with its robust ability to remove H2O2-induced reactive oxygen species. Furthermore, CSK upregulated MAPK (mitogen-activated protein kinase) phosphorylation, an upstream signal for HO-1 expression, and MAPK inhibitors compromised the wound-healing effect of CSK. Additionally, CSK exhibited inhibitory effects on melanin synthesis, downregulating melanogenesis-related genes in B16F10 cells. Thus, the present study demonstrated that CSK exhibited antioxidant effects by activating the Nrf2/HO-1 pathway through MAPK phosphorylation, thereby restoring cell migration and demonstrating inhibitory effects on melanin production. These findings emphasize the antioxidant and antimelanogenic potential of CSK, suggesting its potential use as a therapeutic agent, promoting wound healing, and as an active ingredient in skin-lightening cosmetics.

Characterization of a novel sucrose phosphorylase from Paenibacillus elgii and its use in biosynthesis of α-arbutin

α-Arbutin, a naturally occurring glycosylated derivative of hydroquinone (HQ), effectively inhibits melanin biosynthesis in epidermal cells. It is widely recognized as a fourth-generation whitening agent within the cosmetic industry. Currently, enzymatic catalysis is universally deemed the safest and most efficient method for α-arbutin synthesis. Sucrose phosphorylase (SPase), one of the most frequently employed glycosyltransferases, has been extensively reported for α-arbutin synthesis. In this study, a previously reported SPase known for its effectiveness in synthesizing α-arbutin, was used as a probe sequence to identify a novel SPase from Paenibacillus elgii (PeSP) in the protein database. The sequence similarity between PeSP and the probe was 39.71%, indicating a degree of novelty. Subsequently, the gene encoding PeSP was coexpressed with the molecular chaperone pG-Tf2 in Escherichia coli, significantly improving PeSP's solubility. Following this, PeSP was characterized and employed for α-arbutin biosynthesis. The specific activity of co-expressed PeSP reached 169.72 U/mg, exhibited optimal activity at 35℃ and pH 7.0, with a half-life of 3.6 h under the condition of 35℃. PeSP demonstrated excellent stability at pH 6.5-8.5 and sensitivity to high concentrations of metal ions. The kinetic parameters Km and kcat/Km were determined to be 14.50 mM and 9.79 min- 1·mM- 1, respectively.The reaction conditions for α-arbutin biosynthesis using recombinant PeSP were optimized, resulting in a maximum α-arbutin concentration of 52.60 g/L and a HQ conversion rate of 60.9%. The optimal conditions were achieved at 30℃ and pH 7.0 with 200 U/mL of PeSP, and by combining sucrose and hydroquinone at a molar ratio of 5:1 for a duration of 25 h.

Topical Application of No-Ozone Cold Plasma in Combination with Vitamin C Reduced Skin Redness and Pigmentation of UV-Irradiated Mice

Ultraviolet (UV) is the main cause of sunburn on the skin as it induces erythema and accelerates pigmentation. Vitamin C is one of the most frequently used compounds to reduce UV-induced skin pigmentation, but it has limitations in absorption through the skin. In this study, we tested whether a no-ozone cold plasma (NCP) treatment can improve UV-irradiated skin by helping the action of Vitamin C. For this, among five groups of HRM-2 hairless mice, four groups of mice were subjected to UVB irradiation, and three groups of UVB-treated mice were treated with NCP, Vitamin C, and NCP + Vitamin C, respectively. For evaluating the effect of each treatment, the melanin and erythema index was measured during animal experiments. Histological changes were monitored by performing H&E and MTS and IHC against tyrosinase and melanin. As a result, the naturally recovered mice showed a 28-point decrease in the melanin index, whereas a decrease of around 88, 74.3, and 106 points was detected in NCP-, Vitamin C-, and NCP + vitamin C-treated mice, respectively. Likewise, only a 39-point reduction in the erythema index was monitored in naturally recovered mice, but the NCP-, vitamin C-, and NCP + vitamin C-treated mice showed a 87.3-, 77-, and 111-point reduction, respectively. Interestingly, the skin tissues of the mice treated with NCP in combination with Vitamin C mostly recovered from UVB-induced damage. Altogether, this study elucidated the beneficial effect of the treatment of NCP in combination with Vitamin C on the UVB-irradiated skin, which might be helpful for treating sunburn on the skin.

Fabrication of polyvinyl pyrrolidone-K90/Eudragit RL100-based dissolving microneedle patches loaded with alpha-arbutin and resveratrol for skin depigmentation

Alpha-arbutin (AA) and resveratrol (Res) are widely used in skin-lightening products. However, current topical formulations have minimal skin-lightening effects due to the low absorption and poor solubility of these active compounds. This study investigated the efficacy and safety of using dissolving microneedle (DMN) patches to improve the delivery of AA and Res for skin depigmentation. The DMN patches (F0-F3) fabricated from polyvinyl pyrrolidone-K90 (PVP-K90)/Eudragit RL100 blends successfully penetrated excised porcine skin and showed sufficient mechanical strength to resist compression forces. Loading DMNs with 10% AA and 2% Res at a ratio of 5 : 1 (F3) resulted in a synergistic interaction between the drugs with desirable dissolving ability, drug loading, and stability. Furthermore, both in vitro and in vivo studies revealed that the use of F3 DMN patches successfully enhanced the intradermal delivery of AA and Res over a 24 h period, with the delivered amount being higher (∼2.6 times) than that provided by a cream formulation (P < 0.05). After removing the DMN patches, the mice's skin was spontaneously and completely resealed within 12 h. In clinical studies, F3 DMN patches slightly decreased the melanin index of the participants without causing skin irritation or erythema at any time during the 24 h period when the patches were applied (P < 0.05). Moreover, application of the patches for 24 h was not found to affect skin hydration, transepidermal water loss, or skin elasticity. Therefore, AA/Res-loaded DMN patches could offer a promising approach for the effective local delivery of cosmetic agents for skin depigmentation.

Recombinant Lignin Peroxidase with Superior Thermal Stability and Melanin Decolorization Efficiency in a Typical Human Skin-Mimicking Environment

Recently, the desire for a safe and effective method for skin whitening has been growing in the cosmetics industry. Commonly used tyrosinase-inhibiting chemical reagents exhibit side effects. Thus, recent studies have focused on performing melanin decolorization with enzymes as an alternative due to the low toxicity of enzymes and their ability to decolorize melanin selectively. Herein, 10 different isozymes were expressed as recombinant lignin peroxidases (LiPs) from Phanerochaete chrysosporium (PcLiPs), and PcLiP isozyme 4 (PcLiP04) was selected due to its high stability and activity at pH 5.5 and 37 °C, which is close to human skin conditions. In vitro melanin decolorization results indicated that PcLiP04 exhibited at least 2.9-fold higher efficiency than that of well-known lignin peroxidase (PcLiP01) in a typical human skin-mimicking environment. The interaction force between melanin films measured by a surface forces apparatus (SFA) revealed that the decolorization of melanin by PcLiP04 harbors a disrupted structure, possibly interrupting π-π stacking and/or hydrogen bonds. In addition, a 3D reconstructed human pigmented epidermis skin model showed a decrease in melanin area to 59.8% using PcLiP04, which suggests that PcLiP04 exhibits a strong potential for skin whitening.

Engineered production of bioactive polyphenolic O-glycosides

Polyphenolic compounds (such as quercetin and resveratrol) possess potential medicinal values due to their various bioactivities, but poor water solubility hinders their health benefits to humankind. Glycosylation is a well-known post-modification method to biosynthesize natural product glycosides with improved hydrophilicity. Glycosylation has profound effects on decreasing toxicity, increasing bioavailability and stability, together with changing bioactivity of polyphenolic compounds. Therefore, polyphenolic glycosides can be used as food additives, therapeutics, and nutraceuticals. Engineered biosynthesis provides an environmentally friendly and cost-effective approach to generate polyphenolic glycosides through the use of various glycosyltransferases (GTs) and sugar biosynthetic enzymes. GTs transfer the sugar moieties from nucleotide-activated diphosphate sugar (NDP-sugar) donors to sugar acceptors such as polyphenolic compounds. In this review, we systematically review and summarize the representative polyphenolic O-glycosides with various bioactivities and their engineered biosynthesis in microbes with different biotechnological strategies. We also review the major routes towards NDP-sugar formation in microbes, which is significant for producing unusual or novel glycosides. Finally, we discuss the trends in NDP-sugar based glycosylation research to promote the development of prodrugs that positively impact human health and wellness.

Arbutin ameliorates hyperglycemia, dyslipidemia and oxidative stress and modulates adipocytokines and PPARγ in high-fat diet/streptozotocin-induced diabetic rats

Arbutin is a glycosylated hydroquinone with antioxidant and anti-hyperglycemia effects. However, its beneficial effects in type 2 diabetes (T2D) were not clarified. This study evaluated the effect of arbutin on hyperglycemia, dyslipidemia, insulin resistance, oxidative stress, and inflammatory response in T2D. Rats induced by high fat diet and streptozotocin were treated with arbutin (25 and 50 mg/kg for 4 weeks). Diabetic rats exhibited glucose intolerance, elevated HbA1c%, reduced insulin, and high HOMA-IR. Liver glycogen and hexokinase activity were decreased in T2D rats while glucose-6-phosphatase (G6Pase), fructose-1,6- biphosphatase (FBPase), and glycogen phosphorylase were upregulated. Circulating and hepatic cholesterol and triglycerides and serum transaminases were elevated in T2D rats. Arbutin ameliorated hyperglycemia, dyslipidemia, insulin deficiency and resistance, and liver glycogen and alleviated the activity of carbohydrate-metabolizing enzymes. Both doses of arbutin decreased serum transaminases and resistin, and liver lipids, TNF-α, IL-6, malondialdehyde and nitric oxide, downregulated liver resistin and fatty acid synthase, and increased serum and liver adiponectin, and liver reduced glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT). These effects were associated with the upregulation of hepatic PPARγ. Arbutin inhibited α-glucosidase in vitro and in silico investigations revealed the ability of arbutin to bind PPARγ, hexokinase, and α-glucosidase. In conclusion, arbutin effectively ameliorated glucose intolerance, insulin resistance, dyslipidemia, inflammation, and oxidative stress, and modulated carbohydrate-metabolizing enzymes, antioxidants, adipokines and PPARγ in T2D in rats.

Efficient Whole-Cell Biotransformation for α-Arbutin Production through the Engineering of Sucrose Phosphorylase Combined with Engineered Cell Modification

α-Arbutin is extensively used in cosmetic industries. The lack of highly active enzymes and the cytotoxicity of hydroquinone limit the biosynthesis of α-arbutin. In this study, a whole-cell biocatalytic approach based on enzyme engineering and engineered cell modification was identified as effective in enhancing α-arbutin production. First, a sucrose phosphorylase (SPase) mutant with higher enzyme activity was obtained by experimental screening. Next, to avoid the oxidation of hydroquinone, we established an anaerobic process to improve the robustness of the cells by knocking out lytC, sdpC, and skfA in Bacillus subtilis and overcoming the inhibitory effect of a high concentration of hydroquinone. Finally, the engineered strain was used for biotransformation in a 5 L fermenter with batch feeding for 24 h. The final yield of α-arbutin achieved was 129.6 g/L, which may provide a basis for the large-scale industrial production of α-arbutin.

Screening and Evaluation of Dermo-Cosmetic Activities of the Invasive Plant Species Polygonum cuspidatum

Polygonum cuspidatum (P. cuspidatum) is among the world's most problematic invasive plant species with negative ecological, socio-economic and security consequences. Management operations in areas invaded systematically generate a large quantity of plant waste, most often without outlets. Using this plant material could constitute a new alternative treatment for sustainable management. P. cuspidatum is well known to have numerous biological properties, containing notably stilbenes, quinones, flavonoids and phenolic acids. The present work proposes a reliable strategy using powerful techniques for the screening and the evaluation of the dermo-cosmetic potential of its aerial parts (AP) and root parts (RP). To the best of our knowledge, only antioxidant and anti-tyrosinase activities were previously evaluated on P. cuspidatum among the targets studied (superoxide dismutase, hyaluronidase, elastase, collagenase and tyrosinase). The results revealed strong antioxidant and anti-collagenase activities, moderate anti-hyaluronidase activity, while weak anti-elastase and anti-tyrosinase activities were observed for ethanolic extracts. Different standards selected and screened on the same targets made it possible to correlate the observed residual activities of produced extracts of P. cuspidatum from Savoie Mont Blanc and their chemical compositions. A structure-activity study was thus conducted on main molecular families, widely represented in the genus Polygonum.

Natural products in cosmetics

The global cosmetics market reached US$500 billion in 2017 and is expected to exceed US$800 billion by 2023, at around a 7% annual growth rate. The cosmetics industry is emerging as one of the fastest-growing industries of the past decade. Data shows that the Chinese cosmetics market was US$60 billion in 2021. It is expected to be the world's number one consumer cosmetics market by 2050, with a size of approximately US$450 billion. The influence of social media and the internet has raised awareness of the risks associated with the usage of many chemicals in cosmetics and the health benefits of natural products derived from plants and other natural resources. As a result, the cosmetic industry is now paying more attention to natural products. The present review focus on the possible applications of natural products from various biological sources in skin care cosmetics, including topical care products, fragrances, moisturizers, UV protective, and anti-wrinkle products. In addition, the mechanisms of targets for evaluation of active ingredients in cosmetics and the possible benefits of these bioactive compounds in rejuvenation and health, and their potential role in cosmetics are also discussed.

Skin-Whitening and Antiwrinkle Proprieties of Maackia amurensis Methanolic Extract Lead Compounds

(1) Background: This study aimed to investigate the feasibility of using Maackia amurensis branch extract as a cosmetic ingredient with skin-whitening and antiwrinkle effects. (2) Methods: The skin-whitening effect of M. amurensis branch extract was confirmed by investigating α-melanocyte-stimulating hormone (α-MSH)-induced melanin synthesis and melanogenic protein expression in B16F1 cells. The antiwrinkle effect of M. amurensis branch extract was verified by assessing matrix metalloproteinase (MMP)-1 expression and soluble collagen content in CCD-986sk cells. The major compounds in M. amurensis branch extract were identified through isolation and characterization and confirmed by high-performance liquid chromatography analysis. (3) Results: M. amurensis branch extract significantly inhibited α-MSH-induced melanin synthesis by 49%, 42%, and 18% at 50, 37.5, and 25 μg/mL concentrations, respectively, compared with the negative control (NC). M. amurensis branch extract also significantly reduced the expression of the microphthalmia-associated transcription factor, tyrosinase-related protein (TRP)-1, TRP-2, and tyrosinase in B16F1 cells. Furthermore, M. amurensis branch extracts decreased ultraviolet A-induced MMP-1 expression and increased soluble collagen synthesis in CCD-986sk cells. In addition, the major compounds present in M. amurensis branch extract were found to be formononetin, genistein, trans-resveratrol, piceatannol, and tectoridin. (4) Conclusions: M. amurensis branch extract has skin-whitening and antiwrinkle properties. Therefore, it can be used as an ingredient in functional cosmetics with skin-whitening and antiwrinkle effects.

Antioxidant Capacity of Potentilla paradoxa Nutt. and Its Beneficial Effects Related to Anti-Aging in HaCaT and B16F10 Cells

Skin aging is a natural process influenced by intrinsic and extrinsic factors, and many skin anti-aging strategies have been developed. Plants from the genus Potentilla has been used in Europe and Asia to treat various diseases. Potentilla paradoxa Nutt. has been used as a traditional medicinal herb in China and has recently been shown to have anti-inflammatory effects. Despite the biological and pharmacological potential of Potentilla paradoxa Nutt., its skin anti-aging effects remain unclear. Therefore, this study evaluated the free radical scavenging, moisturizing, anti-melanogenic, and wound-healing effects of an ethanol extract of Potentilla paradoxa Nutt. (Pp-EE). Pp-EE was found to contain phenolics and flavonoids and exhibits in vitro antioxidant activities. α-Linolenic acid was found to be a major component of Pp-EE on gas chromatography-mass spectrometry. Pp-EE promoted the expression of hyaluronic acid (HA) synthesis-related enzymes and suppressed the expression of HA degradation-related enzymes in keratinocytes, so it may increase skin hydration. Pp-EE also showed inhibitory effects on the production and secretion of melanin in melanocytes. In a scratch assay, Pp-EE improved skin wound healing. Taken together, Pp-EE has several effects that may delay skin aging, suggesting its potential benefits as a natural ingredient in cosmetic or pharmaceutical products.

Kojic Acid Showed Consistent Inhibitory Activity on Tyrosinase from Mushroom and in Cultured B16F10 Cells Compared with Arbutins

Kojic acid, β-arbutin, α-arbutin, and deoxyarbutin have been reported as tyrosinase inhibitors in many articles, but some contradictions exist in their differing results. In order to provide some explanations for these contradictions and to find the most suitable compound as a positive control for screening potential tyrosinase inhibitors, the activity and inhibition type of the aforementioned compounds on monophenolase and diphenolase of mushroom tyrosinase (MTYR) were studied. Their effects on B16F10 cells melanin content, tyrosinase (BTYR) activity, and cell viability were also exposed. Results indicated that α-arbutin competitively inhibited monophenolase activity, whereas they uncompetitively activated diphenolase activity of MTYR. β-arbutin noncompetitively and competitively inhibited monophenolase activity at high molarity (4000 µM) and moderate molarity (250–1000 µM) respectively, whereas it activated the diphenolase activity of MTYR. Deoxyarbutin competitively inhibited diphenolase activity, but could not inhibit monophenolase activity and only extended the lag time. Kojic acid competitively inhibited monophenolase activity and competitive–noncompetitive mixed-type inhibited diphenolase activity of MTYR. In a cellular experiment, deoxyarbutin effectively inhibited BTYR activity and reduced melanin content, but it also potently decreased cell viability. α-arbutin and β-arbutin dose-dependently inhibited BTYR activity, reduced melanin content, and increased cell viability. Kojic acid did not affect cell viability at 43.8–700 µM, but inhibited BTYR activity and reduced melanin content in a dose-dependent manner. Therefore, kojic acid was considered as the most suitable positive control among these four compounds, because it could inhibit both monophenolase and diphenolase activity of MTYR and reduce intercellular melanin content by inhibiting BTYR activity without cytotoxicity. Some explanations for the contradictions in the reported articles were provided.

Mitigative Effects of PFF-A Isolated from Ecklonia cava on Pigmentation in a Zebrafish Model and Melanogenesis in B16F10 Cells

Melanin synthesis is a defense mechanism that prevents skin damage, but excessive accumulation of melanin occurs in the skin in various reactions such as pigmentation, lentigines, and freckles. Although anti-melanogenic effects have been demonstrated for various naturally occurring marine products that inhibit and control tyrosinase activity, most studies have not been extended to in vivo applications. Phlorofucofuroeckol-A (PFF-A, 12.5-100 µM) isolated from Ecklonia cava has previously been shown to have tyrosinase-mitigative effects in B16F10 cells, but it has not been evaluated in an in vivo model, and its underlying mechanism for anti-melanogenic effects has not been studied. In the present study, we evaluated the safety and efficacy of PFF-A for anti-melanogenic effects in an in vivo model. We selected low doses of PFF-A (1.5-15 nM) and investigated their mitigative effects on pigmentation stimulated by α-MSH in vivo and their related-mechanism in an in vitro model. The findings suggest that low-dose PFF-A derived from E. cava suppresses pigmentation in vivo and melanogenesis in vitro. Therefore, this study presents the possibility that PFF-A could be utilized as a new anti-melanogenic agent in the cosmeceutical industries.

Radioprotective Mechanisms of Arbutin: A Systematic Review

PURPOSE

Efforts to produce radioprotective agents of high potential are appropriate strategies for overcoming possible IR toxicity in organisms. The present research aims to evaluate the signaling pathways and mechanisms through which arbutin exerts radioprotective effects on organisms.

METHODS

The databases of PubMed, Web of Sciences, Google Scholar, and Scopus were searched to find studies that reported radioprotective effects for arbutin. Besides, the data were searched within the time period from 2010 to 2020.

RESULTS

Five research articles met our criteria, which were included in the analysis based on their relevance to the topic. The present systematic review provides conclusions about various mechanisms and pathways through which arbutin induces radioprotection.

CONCLUSIONS

Based on the relevant studies, various mechanisms can be proposed for inducing radioprotective effects by arbutin, including inhibition of oxidative stress, apoptosis, and inflammation.

Potential radioprotective properties of arbutin against ionising radiation on human leukocytes in vitro

Arbutin is a simple phenolic glucoside biosynthesised in many plant families. Some of the everyday foods that contain arbutin are species of the genus Origanum, peaches, cereal products, coffee and tea and Arctostaphyllos uva ursi L. leaves. Arbutin possesses various beneficial effects in the organism, and was confirmed effective in the treatment of urinary tract infections as well as in preventing skin hyperpigmentation. It shows antioxidant and anti-inflammatory properties, and antitumor activity. The aim of this study was to explore potential radioprotective properties of arbutin in concentrations of 11.4 μg/mL, 57 μg/mL, 200 μg/mL and 400 μg/mL administered as a pre-treatment for one hour before exposing human leukocytes to ionising radiation at a therapeutic dose of 2 Gy. The alkaline comet assay was used to establish the levels of primary DNA damage, and cytokinesis-block micronucleus (CBMN) cytome assay to determine the level of cytogenetic damage. None of the tested concentrations of single arbutin showed genotoxic and cytotoxic effects. Even at the lowest tested concentration, 11.4 μg/mL, arbutin demonstrated remarkable potential for radioprotection in vitro, observed both at the level of primary DNA damage, and using CBMN cytome assay. The best dose reduction compared with amifostine was observed after pre-treatment with the highest concentration of arbutin, corresponding to 400 μg/mL. Promising results obtained on the leukocyte model speak in favour of extending similar experiments on other cell and animal models.

Arbutin as a Skin Depigmenting Agent with Antimelanogenic and Antioxidant Properties

Arbutin is a compound of hydroquinone and D-glucose, and it has been over 30 years since there have been serious studies on the skin lightening action of this substance. In the meantime, there have been debates and validation studies about the mechanism of action of this substance as well as its skin lightening efficacy and safety. Several analogs or derivatives of arbutin have been developed and studied for their melanin synthesis inhibitory action. Formulations have been developed to improve the stability, transdermal delivery, and release of arbutin, and device usage to promote skin absorption has been developed. Substances that inhibit melanin synthesis synergistically with arbutin have been explored. The skin lightening efficacy of arbutin alone or in combination with other active ingredients has been clinically evaluated. Combined therapy with arbutin and laser could give enhanced depigmenting efficacy. The use of arbutin causes dermatitis rarely, and caution is recommended for the use of arbutin-containing products, especially from the viewpoint that hydroquinone may be generated during product use. Studies on the antioxidant properties of arbutin are emerging, and these antioxidant properties are proposed to contribute to the skin depigmenting action of arbutin. It is hoped that this review will help to understand the pros and cons of arbutin as a cosmetic ingredient, and will lead to future research directions for developing advanced skin lightening and protecting cosmetic products.

Arbutin ameliorates glucocorticoid-induced osteoporosis through activating autophagy in osteoblasts

Chronic long-term glucocorticoid use causes osteoporosis partly by interrupting osteoblast homeostasis and exacerbating bone loss. Arbutin, a natural hydroquinone glycoside, has been reported to have biological activities related to the differentiation of osteoblasts and osteoclasts. However, the role and underlying mechanism of arbutin in glucocorticoid-induced osteoporosis are elusive. In this study, we demonstrated that arbutin administration ameliorated osteoporotic disorders in glucocorticoid dexamethasone (Dex)-induced mouse model, including attenuating the loss of bone mass and trabecular microstructure, promoting bone formation, suppressing bone resorption, and activating autophagy in bone tissues. Furthermore, Dex-stimulated mouse osteoblastic MC3T3-E1 cells were treated with arbutin. Arbutin treatment rescued Dex-induced repression of osteoblast differentiation and mineralization, the downregulation of osteogenic gene expression, reduced autophagic marker expression, and decreased autophagic puncta formation. The application of autophagy inhibitor 3-MA decreased autophagy, differentiation, and mineralization of MC3T3-E1 cells triggered by arbutin. Taken together, our findings suggest that arbutin treatment fends off glucocorticoid-induced osteoporosis, partly through promoting differentiation and mineralization of osteoblasts by autophagy activation.

A comprehensive review of the therapeutic potential of α-arbutin

Cosmetic dermatology preparations such as bleaching agents are ingredients with skin-related biological activities for increasing and improving skin beauty. The possibility of controlling skin hyperpigmentation disorders is one of the most important research goals in cosmetic preparations. Recently, cosmetics containing herbal and botanical ingredients have attracted many interests for consumers of cosmetic products because these preparations are found safer than other preparations with synthetic components. However, high-quality trial studies in larger samples are needed to confirm safety and clinical efficacy of phytotherapeutic agents with high therapeutic index. Arbutin (p-hydroxyphenyl-β-d-glucopyranoside) is a bioactive hydrophilic polyphenol with two isomers including alpha-arbutin (4-hydroxyphenyl-α-glucopyranoside) and β-arbutin (4-hydroxyphenyl-β-glucopyranoside). It is used as a medicinal plant in phytopharmacy. Studies have shown that alpha-arbutin is 10 times more effective than natural arbutin. A comparison of IC50 values showed that α-arbutin (with concentration 2.0 mM) has a more potent inhibitory activity on human tyrosinase against natural arbutin (with higher concentration than 30 mM). A review of recent studies showed that arbutin could be beneficial in treatment of various diseases such as hyperpigmentation disorders, types of cancers, central nervous system disorders, osteoporosis, diabetes, etc. This study was designed to describe the therapeutic efficiencies of arbutin.

Arbutin suppresses osteosarcoma progression via miR-338-3p/MTHFD1L and inactivation of the AKT/mTOR pathway

Arbutin, a glycoside extracted from the plant Arctostaphylos uva‐ursi, has been previously reported to possess antioxidant, anti‐inflammatory and anticancer effects. Here, we investigated whether arbutin affects the proliferation of the cells of the osteosarcoma (OS) cell lines MG‐63 and SW1353. Arbutin suppressed OS cell viability in a dose‐ and time‐dependent manner, as shown by Cell Counting Kit‐8 assay. Furthermore, arbutin exposure decreased the protein levels of MTHFD1L, CCND1 and phosphorylated‐protein kinase B (AKT)/phosphorylated‐mammalian target of rapamycin (mTOR). Potential upstream miRNAs of MTHFD1L were predicted using TargetScan, PICTAR5, miRanda and miRWalk. We performed luciferase activity assays to show that miR‐338‐3p directly targets and negatively regulates the expression of MTHFD1L. Knockdown of miR‐338‐3p promoted cell invasion, migration and proliferation in arbutin‐treated OS cells via MTHFD1L. In summary, our data suggest that arbutin inhibits OS cell proliferation, migration and invasion via miR‐338‐3p/MTHFD1L and by inactivating the AKT/mTOR pathway.

Bergenia Genus: Traditional Uses, Phytochemistry and Pharmacology

Bergenia (Saxifragaceae) genus is native to central Asia and encompasses 32 known species. Among these, nine are of pharmacological relevance. In the Indian system of traditional medicine (Ayurveda), "Pashanabheda" (stone breaker) is an elite drug formulation obtained from the rhizomes of B. ligulata. Bergenia species also possess several other biological activities like diuretic, antidiabetic, antitussive, insecticidal, anti-inflammatory, antipyretic, anti-bradykinin, antiviral, antibacterial, antimalarial, hepatoprotective, antiulcer, anticancer, antioxidant, antiobesity, and adaptogenic. This review provides explicit information on the traditional uses, phytochemistry, and pharmacological significance of the genus Bergenia. The extant literature concerned was systematically collected from various databases, weblinks, blogs, books, and theses to select 174 references for detailed analysis. To date, 152 chemical constituents have been identified and characterized from the genus Bergenia that belong to the chemical classes of polyphenols, phenolic-glycosides, lactones, quinones, sterols, tannins, terpenes, and others. B. crassifolia alone possesses 104 bioactive compounds. Meticulous pharmacological and phytochemical studies on Bergenia species and its conservation could yield more reliable compounds and products of pharmacological significance for better healthcare.

Enzymatic decolorization of melanin by lignin peroxidase from Phanerochaete chrysosporium

Skin darkening results as a consequence of the accumulation of skin pigment melanin. To combat this, the amplitude of skin lightening agents are commercially available, most of which inhibit melanin synthesis. Decolorization of melanin is an alternative method of skin lightening. In this study, we show that lignin peroxidase (LiP), an extracellular enzyme purified from Phanerochaete chrysosporium NK-1 isolated from a forest soil can effectively degrade and decolorize melanin in vitro. Decolorization conditions including pH, temperature, incubation time, enzyme concentration, and mediator addition were investigated to optimize the reaction conditions. The results indicate that pH 3, 40 °C, 15 IU/ml, and 10 h incubation were the optimal conditions for the decolorization of the melanin. The use of the mediator, veratryl alcohol was also found effective to enhance the efficacy of the melanin decolonization, with up to 92% decolorization. The scanning electron microscopy results showed void spaces on the treated melanin granules as compared to the untreated sample, indicating the degradation of melanin. Changes in the fingerprint region of the melanin were observed. Between wavenumbers 1500–500 cm⁻¹, for example, the presence of new peaks in the treated melanin at 1513, 1464, and 1139 cm⁻¹ CH₂, CH₃ bend and C–O–C stretch represented structural changes. A new peak at 2144 cm⁻¹ (alkynyl C≡C stretch) was also detected in the decolorized melanin. The cytotoxicity study has shown that the treated melanin and LiP have low cytotoxic effects; however, the mediator of veratryl alcohol could result in high mortality which suggests that its use should be meticulously tested in formulating health and skincare products. The findings of the study suggest that LiP produced by Phanerochaete chrysosporium has the potential to be used in the medical and cosmetic industries, particularly for the development of biobased cosmetic whitening agents.

New class of alkynyl glycoside analogues as tyrosinase inhibitors

A new series of alkynyl glycoside analogues were designed and synthesized from cheap and a commercially available sugar by introduction of various alkynyl and alkyl groups at C-1 and C-6 positions of the sugar ring. The inhibitory abilities of alkynyl glycosides were investigated in vitro on mushroom tyrosinase for the catalysis of l-Tyrosine and l-DOPA as substrates and comparing with arbutin and kojic acid. Non-terminal alkyne compound 2d showed excellent tyrosinase inhibitory activity (IC₅₀ 54.0 μM) against l-Tyrosine comparable to arbutin (IC₅₀ 1.46 mM) while 2b exhibited potent activities (IC₅₀ 34.3 μM) against L-DOPA higher than kojic acid (IC₅₀ 0.11 mM) and arbutin (IC₅₀ 13.3 mM). Kinetic studies revealed that compound 2d was a non-competitive inhibitor with the best Ki value of 21 μM and formed an irreversible receptor complex with mushroom tyrosinase. The SARs results showed that the type of alkyne and alkyl groups at position C-6 on sugar and the stereoisomer played an important role in determining their inhibitory activities. The potent activity of alkynyl glycosides identified in this study highlight the importance of this scaffold and these compounds are very modestly potent to the development of new class for tyrosinase inhibitor.

Bergenia pacumbis from Nepal, an astonishing enzymes inhibitor

BACKGROUND

The Bergenia species are perennial herbs native to central Asia, and one of the most promising medicinal plants of the family Saxifragaceae which are popularly known as 'Pashanbheda'. The aim of this study was to evaluate antioxidant and α-amylase, α-glucosidase, lipase, tyrosinase, elastase, and cholinesterases inhibition potential of Bergenia pacumbis of Nepali origin collected from the Karnali region of Nepal.

METHODS

The sequential crude extracts were made in hexane, ethyl acetate, methanol, and water. Antioxidant activities were analyzed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay. The α-amylase, α-glucosidase, lipase, tyrosinase, elastase, acetylcholinesterase, and butyrylcholinesterase inhibition were analyzed by the 3,5-Dinitrosalicylic acid (DNSA), p-Nitrophenyl-α-D-glucopyranoside (p-NPG), 4-nitrophenyl butyrate (p-NPB), l-3,4-dihydroxyphenylalanine (L-DOPA), N-Succinyl-Ala-Ala-p-nitroanilide (AAAPVN), acetylthiocholine, and butyrylcholine as a respective substrate. The major metabolites were identified by high performance liquid chromatography with electron spray ionization- quadrupole time-of-flight mass spectrometry (HPLC-ESI-QTOF-MS) profiling.

RESULTS

Our results revealed the great antioxidant ability of crude extract of B. pacumbis in ethyl acetate extract against both DPPH (IC50 = 30.14 ± 0.14 μg/mL) and ABTS (IC50 = 17.38 ± 1.12 μg/mL). However, the crude methanol extract of B. pacumbis showed the comparable enzymes inhibitions with standard drugs; α-amylase (IC50 = 14.03 ± 0.04 μg/mL), α-glucosidase (IC50 = 0.29 ± 0.00 μg/mL), lipase (IC50 = 67.26 ± 0.17 μg/mL), tyrosinase (IC50 = 58.25 ± 1.63 μg/mL), elastase (IC50 = 74.00 ± 3.03 μg/mL), acetylcholinesterase (IC50 = 31.52 ± 0.58 μg/mL), and butyrylcholinesterase (IC50 = 11.69 ± 0.14 μg/mL). On the basis of HPLC-ESI-QTOF-MS profiling of metabolites, we identified major compounds such as Bergenin, Catechin, Arbutin, Gallic acid, Protocatechuic acid, Syringic acid, Hyperoside, Afzelechin, Methyl gallate, Paashaanolactone, Astilbin, Quercetin, Kaempferol-7-O-glucoside, Diosmetin, Phloretin, and Morin in methanol extract which has reported beneficial bioactivities.

CONCLUSION

Our study provides a plethora of scientific evidence that the crude extracts of B. pacumbis from Nepalese origin in different extracting solvents have shown significant potential on inhibiting free radicals as well as enzymes involved in digestion, skin related problems, and neurological disorders compared with the commercially available drugs.

Melanogenesis-inhibitory activities of limonoids and tricyclic diterpenoids from Azadirachta indica

The chemical constituents of the roots and bark of Azadirachta indica were investigated, leading to the isolation of six tricyclic diterpenoids and four limonoids including a new compound, azadirachtin J (4). The structures were elucidated on the basis of NMR spectroscopic techniques, mass spectrometry as well as comparison with the literature. Furthermore, melanogenesis-inhibitory activities of the isolated compounds were evaluated. As a result, compounds 1-3 and 10 exhibited superior inhibitory activities against melanogenesis with no, or almost no, toxicity to the cells (86.5-105.1% cell viability). Western blot analysis showed that compounds 1 and 3 exhibited melanogenesis inhibitory activities in α-MSH-stimulated B16 melanoma cells due to, at least in part, inhibition of the expression of MITF, followed by a decrease in the expression of tyrosinase, TRP-1, and TRP-2. Compounds 1 and 3 exhibited tyrosinase inhibitory activities (IC₅₀ values of 44.86 μM and 69.85 μM respectively). Docking results confirm that the active inhibitors strongly interact with tyrosinase residues.

Anti-melanogenic effects of epigallocatechin-3-gallate (EGCG), epicatechin-3-gallate (ECG) and gallocatechin-3-gallate (GCG) via down-regulation of cAMP/CREB /MITF signaling pathway in B16F10 melanoma cells

Tea catechins, the main bioactive polyphenols in green tea, are well known for their health promoting effects. Previous studies have shown that gallocatechin-3-gallate (GCG), epigallocatechin-3-gallate (EGCG) and epicatechin-3-gallate (ECG) exerted strong inhibitory effects on mushroom tyrosinase activity in vitro, whilst EGCG inhibited melanogenesis in vivo, yet the underlying mechanisms are not entirely clear. In this study, we (i) evaluated and compared the inhibitory effects of the main tea catechins (GCG, EGCG, and ECG) on melanogenesis in B16F10 melanoma cells, and (ii) explain the underlying mechanisms. The results showed that the tea catechins significantly suppressed tyrosinase activity and melanin synthesis in B16F10 cells, where the effects of ECG > EGCG > GCG. Interestingly, the inhibitory effects of the catechins were stronger than those of arbutin (AT), a well-known depigmenting agent. Moreover, GCG, EGCG, and ECG regulated the melanogenesis of B16F10 cells through the cAMP/CREB/MITF pathway. These results revealed catechins could be used as anti-melanogenic agents to protect cells from abnormal melanogenesis.

p-Hydroxybenzoic Acid β-d-Glucosyl Ester and Cimidahurinine with Antimelanogenesis and Antioxidant Effects from Pyracantha angustifolia via Bioactivity-Guided Fractionation

This study evaluated bioactivity-guided fractionation as a means to identify therapeutic phytochemicals from Pyracantha angustifolia that can attenuate melanogenesis and oxidation. Seven compounds with inhibitory effects on melanin production and tyrosinase (TYR) activity, and ABTS and DPPH radical-scavenging activities, which have not been reported as whitening materials, were isolated from the n-butanol fraction from P. angustifolia leaves (PAL). Among the seven compounds, p-hydroxybenzoic acid β-d-glucosylester (HG), and cimidahurinine (CH) had strong inhibitory effects on melanin production and TYR activity, as well as ABTS and DPPH radical-scavenging activities. Western blot analysis showed that HG and CH suppressed tyrosinase-related protein (TYRP)-1 and TYRP-2 expression. Moreover, HG and CH inhibited reactive oxygen species (ROS) generation in tert-butyl hydroperoxide (t-BHP)-treated B16F10 cells. These results suggest that P. angustifolia containing active compounds, such as HG and CH, is a potent therapeutic candidate for the development of hypopigmenting agents.

Triterpene-farnesyl hydroquinone conjugates from Ganoderma calidophilum

Two new lanostane-type triterpenoids characterized with farnesyl hydroquinone moieties, ganocalidoins A (1) and B (2), were isolated from the fruiting body of Ganoderma calidophilum, together with two known tripterpenes (3-4). The structures of compounds 1 and 2 were determined by extensive spectroscopic data including HRESIMS, 1D and 2D NMR. Ganocalidoins A and B showed anti-oxidant capacity with IC₅₀ values of 38.7 ± 2.8 and 34.2 ± 1.8 μM, respectively. The compounds did not show tyrosinase inhibition activity.

The in vitro and in vivo depigmenting activity of Coenzyme Q10 through the down-regulation of α-MSH signaling pathways and induction of Nrf2/ARE-mediated antioxidant genes in UVA-irradiated skin keratinocytes

Coenzyme CoQ10 (CoQ10), a ubiquinone compound, has been reported to inhibit tyrosinase activity and melanin production in melanoma B16F10 cells. However, the molecular mechanism underlying this inhibitory effect is poorly understood. In this paper we aimed to investigate the molecular mechanisms involved in the anti-melanogenic activity of CoQ10 (1-2 μM) in UVA (5 J/cm²)-irradiated keratinocyte HaCaT cells and α-MSH stimulated B16-F10 cells. It was observed that CoQ10 suppressed p53/POMC, α-MSH production as well as inhibited ROS generation in UVA-irradiated keratinocyte HaCaT cells. CoQ10 down-regulated the melanin synthesis in α-MSH-stimulated B16-F10 cells by suppressing the MITF expression by down regulating the cAMP mediated CREB signaling cascades. Furthermore, in vivo evidence demonstrated the inhibitory effect of CoQ10 on endogenous pigmentation in zebrafish. Increased nuclear Nrf2 translocation accompanied by the induction of HO-1 and γ-GCLC genes were observed in CoQ10 treated keratinocyte HaCaT cells. Notably, silencing of Nrf2 (siRNA transfection) significantly diminished CoQ10-mediated anti-melanogenic activity, as evidenced by impaired antioxidant HO-1 gene, uncontrolled ROS generation, and α-MSH production following UVA irradiation. To conclude, CoQ10 is an effective de-pigmention or skin-whitening agent and could be used in cosmetics for topical application.

Arbutin promotes MC3T3‑E1 mouse osteoblast precursor cell proliferation and differentiation via the Wnt/β‑catenin signaling pathway

Arbutin is a natural compound extracted from various plants, including bearberry leaves, that exerts multiple effects including skin whitening, anti‑inflammatory and oxidative stress‑protective properties. However, the effects of arbutin on osteoblasts remain unknown. The aim of the present study was to investigate the function and the mechanisms of arbutin on the proliferation and differentiation of MC3T3‑E1 mouse osteoblast precursor cells in vitro. The proliferation of MC3T3‑E1 cells treated with arbutin was assessed using a Cell Counting Kit‑8 assay and a 5‑ethynyl‑2'‑deoxyuridine labeling assay. Additionally, cell cycle and apoptosis were examined using flow cytometry analysis. The effects of arbutin on osteoblast differentiation were investigated using alkaline phosphatase (ALP) staining and by examining the mRNA expression levels of collagen type I α1 chain (COL1A1), bone γ‑carboxyglutamate protein (BGLAP) and Sp7 transcription factor (SP7). To further investigate the molecular mechanism underlying arbutin function in promoting osteogenesis, the mRNA and protein expression levels of runt‑related transcription factor 2 (RUNX2) and β‑catenin were analyzed by reverse transcription‑quantitative polymerase chain reaction and western blotting. Arbutin significantly promoted MC3T3‑E1 cell proliferation and increased the ratio of cells in S‑phase. Treatment with arbutin increased ALP activity and the mRNA expression levels of COL1A1, BGLAP and SP7 in MC3T3‑E1 cells. Furthermore, the protein and the mRNA expression levels of RUNX2 and β‑catenin increased significantly following treatment with arbutin. Collectively, the present findings suggested that arbutin was able to promote proliferation and differentiation of MC3T3‑E1 cells via the Wnt/β‑catenin signaling pathway.

Discovery of new depigmenting compounds and their efficacy to treat hyperpigmentation: Evidence from in vitro study

Human skin pigmentation is a result of constitutive and facultative pigmentation. Facultative pigmentation is frequently stimulated by UV radiation, pharmacologic drugs, and hormones whereby leads to the development of abnormal skin hyperpigmentation. To date, many state-of-art depigmenting compounds have been studied using in vitro model to treat hyperpigmentation problems for cosmetic dermatological applications; little attention has been made to compare the effectiveness of these depigmenting compounds and their mode of actions. In this present article, new and recent depigmenting compounds, their melanogenic pathway targets, and modes of action are reviewed. This article compares the effectiveness of these new depigmenting compounds to modulate several melanogenesis-regulatory enzymes and proteins such as tyrosinase (TYR), TYR-related protein-1 (TRP1), TYR-related protein-2 (TRP2), microphthalmia-associated transcription factor (MITF), extracellular signal-regulated kinase (ERK) and N-terminal kinases (JNK) and mitogen-activated protein kinase p38 (p38 MAPK). Other evidences from in vitro assays such as inhibition on melanosomal transfer, proteasomes, nitric oxide, and inflammation-induced melanogenesis are also highlighted. This article also reviews analytical techniques in different assays performed using in vitro model as well as their advantages and limitations. This article also provides an insight on recent finding and re-examination of some protocols as well as their effectiveness and reliability in the evaluation of depigmenting compounds. Evidence and support from related patents are also incorporated in this present article to give an overview on current patented technology, latest trends, and intellectual values of some depigmenting compounds and protocols, which are rarely highlighted in the literatures.

Oxidative Stress-Protective and Anti-Melanogenic Effects of Loliolide and Ethanol Extract from Fresh Water Green Algae, Prasiola japonica

Loliolide is a monoterpenoid hydroxylactone found in many algae, including fresh water green algae, Prasiola japonica. To date, loliolide and compounds in P. japonica have not been studied systematically with respect to skin pharmacology. In this study, we investigated oxidative stress-protective and anti-melanogenic effects of loliolide and P. japonica ethanol extract (Pj-EE), known to contain loliolide, in human keratinocyte (HaCaT) cells and mouse melanoma (B16F10) cells. Loliolide suppressed the transcription of genes encoding matrix metalloproteinases (MMPS), which were induced in HaCaT cells by hydrogen peroxide (H₂O₂) treatment. Loliolide and Pj-EE not only reduced the melanin secretion and content in B16F10 cells but also increased the expression of the antioxidant proteins nuclear factor (erythroid-derived 2)-like 2 (NRF2) and heme oxygenase-1 (HO-1) in HaCaT cells subjected to H₂O₂ treatment. Furthermore, loliolide and Pj-EE decreased expression of the anti-melanogenic protein microphthalmia-associated transcription factor (MITF) and tyrosinase in B16F10 cells subjected to α-melanocyte-stimulating hormone (α-MSH) treatment. Our findings demonstrate that loliolide and Pj-EE have antioxidant and anti-melanogenic effects on skin.