Molecular mechanisms of flavonoids in melanin synthesis and the potential for the prevention and treatment of melanoma

Phytoflavonoids as alternative therapeutic effect for melanoma: Integrative Network pharmacology, molecular dynamics and drug-likeness profiling for lead discovery

Melanoma, an aggressive skin cancer, poses significant therapeutic challenges due to its resistance to conventional therapies and high metastatic potential. From this perspective, phytoflavonoids from different medicinal and aromatic plants gained attention due to their diverse multimodal anticancer effects with higher antioxidant and anti-inflammatory properties. This study explores phytoflavonoid potency against melanoma via a computer-aided drug design (CADD) platform. Using the core moiety of flavonoids (flavan), four most putative targets, such as cyclin-dependent kinases 1 and 5 (CDK1, CDK5), cell division cycles 25B and 225 C (CDC25B, and CDC225C), have been identified through a network pharmacology approach using TNMplot datasets (GenChip and RNA sequence). Further, 44 phytoflavonoids were selected from extensive literature, and molecular docking studies were carried out against four targets along with standard drugs using AutoDock 4.2 software. Subsequently, physicochemical, toxicity, pharmacokinetics, and drug-ability profiles of phytoflavonoids were predicted. Based on potency and drug-ability, we have selected 'CDK1-naringenin' with the standard drug complex, 'CDK1-dinaciclib,' for molecular dynamic simulation at 100 nanoseconds using GROMACS 2020 software. Based on potency (average docking score: 8.35 kcal/mol.), physicochemical properties (obeyed Lipinski rule of five), toxicity (class-IV), fifty percent lethal dose (2000 mg/kg), bioavailability (0.55), drug-likeness score (0.82), along with ideal pharmacokinetics profiles and higher protein-ligand stability, naringenin is considered as a potential and non-toxic anticancer candidate to be used for melanoma as alternative or complementary agent. The integrative and systematic analyses not only highlight the potential of phytoflavonoids but also select the potential lead from the library within limited resources to accelerate the current anticancer drug discovery process.

Methoxylated Chrysin and Quercetin as Potent Stimulators of Melanogenesis

Polymethoxyflavonoids (PMFs) from plants are known to exhibit melanogenic activity. Very little is known about their structure-activity relationships, and this was the aim of this study. Several series of alkoxy flavonoids were synthesized via semisynthetic and total synthetic pathways. Their structures were identified by NMR analyses, followed by evaluating their potency on the stimulation of melanogenesis using mouse B16F10 and human MNT-1 cells. Among more than twenty methoxylated flavonoids, 5,7-dimethoxychrysin (dimethoxylated chrysin, F1) and 3,3',4',5,7-pentamethoxyquercetin (pentamethoxylated quercetin, F21) appeared to be the most active melanogenic-stimulating compounds in a dose-dependent manner. Both compounds showed no effect on cell viability as determined by MTT assay. The structure-activity relationship study of PMFs revealed that the -OCH3 substituent at 5 and 7 positions of A-ring are the most important as melanogenic-stimulating part (e.g., 5,7-dimethoxychrysin, F1) followed by at 3' and 4' positions of B-ring, and at 3 positions of C-ring (e.g., 3,3',4',5,7-pentamethoxyquercetin, F21), Therefore, both natural methoxylated flavonoid derivatives of chrysin and quercetin have a potential to be developed further as melanogenic stimulators.

Effects of natural products on angiogenesis in melanoma

Melanoma is the most aggressive form of skin cancer and originates from genetic mutations in melanocytes. The disease is multifactorial, but its main cause is overexposure to UV radiation. Currently, available chemotherapy expresses little to no results, which may justify the extensive use of natural products to treat this cancer. In this study, we reviewed the inhibition of melanoma angiogenesis by natural products and its potential mechanisms using literature from PubMed, EMBASE, Web of Science, Ovid, ScienceDirect and China National Knowledge Infrastructure databases. According to summarizes 27 natural products including alkaloids, polyphenols, terpenoids, flavonoids, and steroids that effectively inhibit angiogenesis in melanoma. In addition to these there are 15 crude extracts that can be used as promising agents to inhibit angiogenesis, but their core components still deserve further investigation. There are current studies on melanoma angiogenesis involving oxidative stress, immune-inflammatory response, cell proliferation and migration and capillary formation. The above natural products can be involved in melanoma angiogenesis through core targets such as VE-cadherin, COX-2, iNOS, VEGF, bFGF, FGF2,MMP2,MMP9,IL-1β,IL-6 play a role in inhibiting melanoma angiogenesis. Effective excavation of natural products can not only clarify the mechanism of drug action and key targets, but also help to promote the preclinical research of natural products for melanoma treatment and further promote the development of new clinical drugs, which will bring the gospel to the vast number of patients who are deeply afflicted by melanoma.

Blocking the WNT/β-catenin pathway in cancer treatment:pharmacological targets and drug therapeutic potential

The WNT/β-catenin signaling pathway plays crucial roles in tumorigenesis and relapse, metastasis, drug resistance, and tumor stemness maintenance. In most tumors, the WNT/β-catenin signaling pathway is often aberrantly activated. The therapeutic usefulness of inhibition of WNT/β-catenin signaling has been reported to improve the efficiency of different cancer treatments and this inhibition of signaling has been carried out using different methods including pharmacological agents, short interfering RNA (siRNA), and antibodies. Here, we review the WNT-inhibitory effects of some FDA-approved drugs and natural products in cancer treatment and focus on recent progress of the WNT signaling inhibitors in improving the efficiency of chemotherapy, immunotherapy, gene therapy, and physical therapy. We also classified these FDA-approved drugs and natural products according to their structure and physicochemical properties, and introduced briefly their potential mechanisms of inhibiting the WNT signaling pathway. The review provides a comprehensive understanding of inhibitors of WNT/β-catenin pathway in various cancer therapeutics. This will benefit novel WNT inhibitor development and optimal clinical use of WNT signaling-related drugs in synergistic cancer therapy.

Optimizing ultrasound-assisted extraction of bioactive compounds from Canthium horridum blume leaves utilizing polyols: A study on skin-related activities

The focus on reducing organic solvent usage, owing to their negative environmental and health impacts, is driving a search for innovative green alternative solvents in academia and industry. Canthium horridum Blume (CH) exhibits many therapeutic activities, including antioxidant and anti-inflammatory efficacy. The objective of this study is to evaluate the optimal solvent concentration using a simplex-lattice design with an aqueous-polyols mixture and to optimize the parameters for extracting bioactive compounds and antioxidant activities from ultrasound-assisted extraction (UAE) of CH leaves through central composite design (CCD) in response surface methodology (RSM). This study examines the total phenolic content (TPC), antioxidant activities, comparison of different extraction conditions, identification of bioactive compounds, cell cytotoxicity, cellular antioxidant activity, and melanin content reduction efficacy of the extracts. According to the findings from the simplex-lattice model, the ideal solvent composition consisted of 32.57%w/w butylene glycol, 32.92%w/w glycerine, and 34.51%w/w water. Furthermore, based on the response model, optimal extraction conditions were identified as a 15-min extraction time and a solvent-to-sample ratio of 32.94:1. In comparison to alternative extraction methods, ultrasonic-assisted extraction using the aqueous-glycerine-butylene glycol (GB-UAE) extract resulted in notably elevated TPC and antioxidant responses (p < 0.05). Major antioxidant bioactive compounds included 4-(Butoxymethyl) phenol, 3-O-Caffeoyl-4-O-methylquinic acid, Quercetin 3-(2G-glucosylrutinoside), 2,4-Dihydroxybenzoic acid and other bioactive compounds. The GB-UAE extract revealed greater cell viability than UAE using ethanol (EtOH-UAE) extract in both cytotoxicity and cellular antioxidant assays at the same concentration. Additionally, it exhibited comparable melanin content reduction efficacy at a higher concentration compared to that of EtOH-UAE extract. The researcher anticipates that the current study will advance the utilization of an aqueous-polyols system for extracting bioactive compounds extending beyond CH leaves. Although the potential applications of CH leaves in cosmetics and pharmaceutical formulations have been identified, further comprehensive mechanistic and clinical studies are required to fully understand their effects.

Identification of active compounds in Vernonia anthelmintica (L.) willd by targeted metabolome MRM and kaempferol promotes HaCaT cell proliferation and reduces oxidative stress

Introduction: Vernonia anthelmintica (L.) Willd. is a traditional treatment for vitiligo in Xinjiang. However, its therapeutic mechanism remains unclear owing to its complex composition and limited research on its chemical profile. Methods: We employed a targeted metabolome approach, combining selective reaction monitoring/multiple response monitoring (SRM/MRM) with high-performance liquid chromatography and MRM mass spectrometry to quantitatively analyze the flavonoid constituents of Vernonia anthelmintica. We also used network pharmacology and molecular docking to identify potential vitiligo-linked compounds and targets of V. anthelmintica seeds. Additionally, we assessed HaCaT cell proliferation by AAPH-induced, alongside changes in SOD activity and MDA content, following treatment with V. anthelmintica components. Finally, flow cytometry was used to detect apoptosis and ROS levels. Results and Discussion: We identified 36 flavonoid compounds in V. anthelmintica seeds, with 14 compounds exhibiting druggability. AKT1, VEGFA, ESR1, PTGS2, and IL2 have been identified as key therapeutic target genes, with PI3K/AKT signaling being an important pathway. Notably, kaempferol, one of the identified compounds, exhibited high expression in network pharmacology analysis. Kaempferol exhibited a strong binding affinity to important targets. Further, kaempferol enhanced HaCaT cell viability, inhibited apoptosis, reduced MDA levels, suppressed ROS activity, and upregulated SOD activity, increase the expression of cellular antioxidant genes, including HO-1, GCLC, GCLM, Nrf2, NQO1 and Keap1, providing significant protection against oxidative stress damage in vitro. Here, we present the first comprehensive study integrating SRM/MRM approaches and network analysis to identify active flavonoid compounds within V. anthelmintica (L.) Willd. Moreover, we revealed that its active ingredient, kaempferol, offers protection against AAPH-induced damage in keratinocytes, highlighting its potential as a clinical resource.

Hispidulin: a promising anticancer agent and mechanistic breakthrough for targeted cancer therapy

Cancer is a complex disease characterized by dysregulated cell growth and division, posing significant challenges for effective treatment. Hispidulin, a flavonoid compound, has shown promising biological effects, particularly in the field of anticancer research. The main objective of this study is to investigate the anticancer properties of hispidulin and gain insight into its mechanistic targets in cancer cells. A comprehensive literature review was conducted to collect data on the anticancer effects of hispidulin. In vitro and in vivo studies were analyzed to identify the molecular targets and underlying mechanisms through which hispidulin exerts its anticancer activities. Hispidulin has shown significant effects on various aspects of cancer, including cell growth, proliferation, cell cycle regulation, angiogenesis, metastasis, and apoptosis. It has been observed to target both extrinsic and intrinsic apoptotic pathways, regulate cell cycle arrest, and modulate cancer progression pathways. The existing literature highlights the potential of hispidulin as a potent anticancer agent. Hispidulin exhibits promising potential as a therapeutic agent for cancer treatment. Its ability to induce apoptosis and modulate key molecular targets involved in cancer progression makes it a valuable candidate for further investigation. Additional pharmacological studies are needed to fully understand the specific targets and signaling pathways influenced by hispidulin in different types of cancer. Further research will contribute to the successful translation of hispidulin into clinical settings, allowing its utilization in conventional and advanced cancer therapies with improved therapeutic outcomes and reduced side effects.

Inhibition of α-melanocyte-stimulating hormone-induced melanogenesis and molecular mechanisms by polyphenol-enriched fraction of Tagetes erecta L. flower

BACKGROUND

The pursuit for safe and efficacious skin-whitening agents has prompted a dedicated exploration of plant-derived compounds. Notably, Tagetes erecta L. flowers have been used as a medicinal extract and possessed in vitro mushroom tyrosinase activity. However, whether polyphenol-enriched fraction extracted from T. erecta L. flowers (TE) regulates melanogenesis within cellular and animal models has not yet been investigated.

PURPOSE

This study aimed to investigate the effect of TE as a prospective inhibitor of melanogenesis.

METHODS

Through advanced UPLC-QTof/MS analysis, the components of TE were analyzed. Anti-melanogenic effects of TE were evaluated in α-melanocyte-stimulating hormone (α-MSH)-stimulated B16F10 melanoma cells by measuring cell viability assay, extracellular and intracellular melanin biosynthesis, cyclic adenosine monophosphate (cAMP) production, and melanogenesis-related gene and protein expression. Zebrafish larvae were employed for in vivo studies, assessing both heart rate and melanogenesis. Furthermore, molecular docking analyses were employed to predict the interaction between TE components and the melanocortin 1 receptor (MC1R). Direct binding activity of TE components to MC1R was compared with [Nle4, d-Phe7]-MSH (NDP-MSH).

RESULTS

TE was found to contain significant phenolic compounds such as patulitrin, quercetagetin, kaempferol, patuletin, and isorhamnetin. This study revealed that TE effectively inhibits melanin biosynthesis in both in vitro and in vivo models. This inhibition was attributed to interference of TE with the cAMP-cAMP response element-binding protein (CREB)-microphthalmia-associated transcription factor (MITF)-tyrosinase pathway, which plays a pivotal role in regulating melanogenesis. Importantly, TE exhibited the remarkable ability to curtail α-MSH-induced melanogenesis in zebrafish larvae without impacting heart rates. Molecular docking analyses predicted that the components of TE possibly interact with the melanocortin 1 receptor, suggesting their role as potential inhibitors of melanin biosynthesis. However, through the direct binding activity compared with NDP-MSH, any TE components did not directly bind to MC1R, suggesting that TE inhibits α-MSH-induced melanogenesis by inhibiting the cAMP-mediated intracellular signaling pathway. The assessment of anti-melanogenic activity, conducted both in vitro and in vivo, revealed that patulitrin and patuletin exhibited significant inhibitory effects on melanin formation, highlighting their potency as major contributors.

DISCUSSION

This investigation demonstrated the considerable potential of TE as a natural remedy endowed with remarkable anti-melanogenic properties. The demonstrated capacity of TE to attenuate melanin production by modulating the cAMP-CREB-MITF-tyrosinase pathway underscores its central role in management of disorders associated with excessive pigmentation. Importantly, the implications of these findings extend to the cosmetics industry, where TE emerges as a prospective and valuable ingredient for the formulation of skin-whitening products. The elucidated interactions between TE components and MC1R not only provide insight into a potential mechanism of action but also elevate the significance of this study. In summary, this study not only contributes to our comprehension of pigmentation-related conditions but also firmly establishes TE as a secure and natural strategy for the regulation of melanin production. The innovative aspects of TE propel it into the forefront of potential interventions, marking a noteworthy advancement in the pursuit of effective and safe solutions for pigmentation disorders.

Ceiba pentandra ethyl acetate extract improves doxorubicin antitumor outcomes against chemically induced liver cancer in rat model: a study supported by UHPLC-Q-TOF-MS/MS identification of the bioactive phytomolecules

Hepatocellular carcinoma (HCC) is a prevalent cancer worldwide. Late-stage detection, ineffective treatments, and tumor recurrence contribute to the low survival rate of the HCC. Conventional chemotherapeutic drugs, like doxorubicin (DOX), are associated with severe side effects, limited effectiveness, and tumor resistance. To improve therapeutic outcomes and minimize these drawbacks, combination therapy with natural drugs is being researched. Herein, we assessed the antitumor efficacy of Ceiba pentandra ethyl acetate extract alone and in combination with DOX against diethylnitrosamine (DENA)-induced HCC in rats. Our in vivo study significantly revealed improvement in the liver-function biochemical markers (ALT, AST, GGT, and ALP), the tumor marker (AFP-L3), and the histopathological features of the treated groups. A UHPLC-Q-TOF-MS/MS analysis of the Ceiba pentandra ethyl acetate extract enabled the identification of fifty phytomolecules. Among these are the dietary flavonoids known to have anticancer, anti-inflammatory, and antioxidant qualities: protocatechuic acid, procyanidin B2, epicatechin, rutin, quercitrin, quercetin, kaempferol, naringenin, and apigenin. Our findings highlight C. pentandra as an affordable source of phytochemicals with possible chemosensitizing effects, which could be an intriguing candidate for the development of liver cancer therapy, particularly in combination with chemotherapeutic drugs.

Recent Updates Regarding the Antiproliferative Activity of Galium verum Extracts on A375 Human Malignant Melanoma Cell Line

The biological activity of Galium verum herba was exerted on various tumor cell lines with incredible results, but their potential effect on malignant melanoma has not been established yet. Therefore, the current study was structured in two directions: (i) the investigation of the phytochemical profile of diethyl ether (GvDEE) and butanol (GvBuOH) extracts of G. verum L. and (ii) the evaluation of their biological profile on A375 human malignant melanoma cell line. The GvDEE extract showed an FT-IR profile different from the butanol one, with high antioxidant capacity (EC50 of GvDEE = 0.12 ± 0.03 mg/mL > EC50 of GvBuOH = 0.18 ± 0.05 mg/mL). The GvDEE extract also showed antimicrobial potential, especially against Gram-positive bacteria strains, compared to the butanol extract, which has no antimicrobial activity against any bacterial strain tested. The results regarding the antitumor potential showed that both extracts decreased A375 cell viability largely (69% at a dose of 55 µg/mL of the GvDEE extract). Moreover, both extracts induce nuclear fragmentation by forming apoptotic bodies and slight chromatin condensation, which is more intense for GvDEE. Considering the results, one can state that the Galium verum herba possesses antitumor effects on the A375 human malignant melanoma cell line, a promising phytocompound for the antitumor approach to skin cancer.

A Systematic Study of Yiqi Qubai Standard Decoction for Treating Vitiligo Based on UPLC-Q-TOF/MS Combined with Chemometrics, Molecular Docking, and Cellular and Zebrafish Assays

The Yiqi Qubai (YQ) formula is a hospital preparation for treating vitiligo in China that has had reliable efficacy for decades. The formula consists of four herbs; however, the extraction process to produce the formula is obsolete and the active ingredients and mechanisms remain unknown. Therefore, in this paper, fingerprints were combined with the chemometrics method to screen high-quality herbs for the preparation of the YQ standard decoction (YQD). Then, the YQD preparation procedure was optimized using response surface methodology. A total of 44 chemical constituents, as well as 36 absorption components (in rat plasma) of YQD, were identified via UPLC-Q-TOF/MS. Based on the ingredients, the quality control system of YQD was optimized by establishing the SPE-UPLC-Q-TOF/MS identification method and the HPLC quantification method. Network pharmacological analysis and molecular docking showed that carasinaurone, calycosin-7-O-β-d-glucoside, methylnissolin-3-O-glucoside, genkwanin, akebia saponin D, formononetin, akebia saponin B, and apigenin may be the key active components for treating vitiligo; the core targets associated with them were AKT1, MAPK1, and mTOR, whereas the related pathways were the PI3K-Akt, MAPK, and FoxO signaling pathways. Cellular assays showed that YQD could promote melanogenesis and tyrosinase activity, as well as the transcription and expression of tyrosinase-associated proteins (i.e., TRP-1) in B16F10 cells. In addition, YQD also increased extracellular tyrosinase activity. Further efficacy validation showed that YQD significantly promotes melanin production in zebrafish. These may be the mechanisms by which YQD improves the symptoms of vitiligo. This is the first systematic study of the YQ formula that has optimized the standard decoction preparation method and investigated the active ingredients, quality control, efficacy, and mechanisms of YQD. The results of this study lay the foundations for the clinical application and further development of the YQ formula.

Synthesis, in silico modelling, and in vitro biological evaluation of substituted pyrazole derivatives as potential anti-skin cancer, anti-tyrosinase, and antioxidant agents

Twenty-five azole compounds (P1-P25) were synthesised using regioselective base-metal catalysed and microwave-assisted approaches, fully characterised by high-resolution mass spectrometry (HRMS), nuclear magnetic resonance (NMR), and infrared spectra (IR) analyses, and evaluated for anticancer, anti-tyrosinase, and anti-oxidant activities in silico and in vitro. P25 exhibited potent anticancer activity against cells of four skin cancer (SC) lines, with selectivity for melanoma (A375, SK-Mel-28) or non-melanoma (A431, SCC-12) SC cells over non-cancerous HaCaT-keratinocytes. Clonogenic, scratch-wound, and immunoblotting assay data were consistent with anti-proliferative results, expression profiling therewith implicating intrinsic and extrinsic apoptosis activation. In a mushroom tyrosinase inhibition assay, P14 was most potent among the compounds (half-maximal inhibitory concentration where 50% of cells are dead, IC50 15.9 μM), with activity greater than arbutin and kojic acid. Also, P6 exhibited noteworthy free radical-scavenging activity. Furthermore, in silico docking and absorption, distribution, metabolism, excretion, and toxicity (ADMET) simulations predicted prominent-phenotypic actives to engage diverse cancer/hyperpigmentation-related targets with relatively high affinities. Altogether, promising early-stage hits were identified - some with multiple activities - warranting further hit-to-lead optimisation chemistry with further biological evaluations, towards identifying new skin-cancer and skin-pigmentation renormalising agents.

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.

Morin Hydrate Encapsulation and Release from Mesoporous Silica Nanoparticles for Melanoma Therapy

Melanoma incidence, a type of skin cancer, has been increasing worldwide. There is a strong need to develop new therapeutic strategies to improve melanoma treatment. Morin is a bioflavonoid with the potential for use in the treatment of cancer, including melanoma. However, therapeutic applications of morin are restrained owing to its low aqueous solubility and limited bioavailability. This work investigates morin hydrate (MH) encapsulation in mesoporous silica nanoparticles (MSNs) to enhance morin bioavailability and consequently increase the antitumor effects in melanoma cells. Spheroidal MSNs with a mean size of 56.3 ± 6.5 nm and a specific surface area of 816 m²/g were synthesized. MH was successfully loaded (MH-MSN) using the evaporation method, with a loading capacity of 28.3% and loading efficiency of 99.1%. In vitro release studies showed that morin release from MH-MSNs was enhanced at pH 5.2, indicating increased flavonoid solubility. The in vitro cytotoxicity of MH and MH-MSNs on human A375, MNT-1 and SK-MEL-28 melanoma cell lines was investigated. Exposure to MSNs did not affect the cell viability of any of the cell lines tested, suggesting that the nanoparticles are biocompatible. The effect of MH and MH-MSNs on reducing cell viability was time- and concentration-dependent in all melanoma cell lines. The A375 and SK-MEL-28 cell lines were slightly more sensitive than MNT-1 cells in both the MH and MH-MSN treatments. Our findings suggest that MH-MSNs are a promising delivery system for the treatment of melanoma.

Oxidative Stress in Melanoma: Beneficial Antioxidant and Pro-Oxidant Therapeutic Strategies

Cutaneous melanoma ranks as the fifth most common cancer in the United States and represents one of the deadliest forms of skin cancer. While recent advances in systemic targeted therapies and immunotherapies have positively impacted melanoma survival, the survival rate of stage IV melanoma remains at a meager 32%. Unfortunately, tumor resistance can impede the effectiveness of these treatments. Oxidative stress is a pivotal player in all stages of melanoma progression, with a somewhat paradoxical function that promotes tumor initiation but hinders vertical growth and metastasis in later disease. As melanoma progresses, it employs adaptive mechanisms to lessen oxidative stress in the tumor environment. Redox metabolic rewiring has been implicated in acquired resistance to BRAF/MEK inhibitors. A promising approach to enhance the response to therapy involves boosting intracellular ROS production using active biomolecules or targeting enzymes that regulate oxidative stress. The complex interplay between oxidative stress, redox homeostasis, and melanomagenesis can also be leveraged in a preventive context. The purpose of this review is to provide an overview of oxidative stress in melanoma, and how the antioxidant system may be manipulated in a therapeutic context for improved efficacy and survival.

Targeting Tyrosinase in Hyperpigmentation: Current Status, Limitations and Future Promises

Hyperpigmentation is a common and distressing dermatologic condition. Since tyrosinase (TYR) plays an essential role in melanogenesis, its inhibition is considered a logical approach along with other therapeutic methods to prevent the accumulation of melanin in the skin. Thus, TYR inhibitors are a tempting target as the medicinal and cosmetic active agents of hyperpigmentation disorder. Among TYR inhibitors, hydroquinone is a traditional lightening agent that is commonly used in clinical practice. However, despite good efficacy, prolonged use of hydroquinone is associated with side effects. To overcome these shortcomings, new approaches in targeting TYR and treating hyperpigmentation are desperately requiredessentialneeded. In line with this purpose, several non-hydroquinone lightening agents have been developed and suggested as hydroquinone alternatives. In addition to traditional approaches, nanomedicine and nanotheranostic platforms have been recently proposed in the treatment of hyperpigmentation. In this review, we discuss the available strategies for the management of hyperpigmentation with a focus on TYR inhibition. In addition, alternative treatment options to hydroquinone are discussed. Finally, we present nano-based strategies to improve the therapeutic effect of drugs prescribed to patients with skin disorders.

An updated overview of cyanidins for chemoprevention and cancer therapy

Anthocyanins are colored polyphenolic compounds that belong to the flavonoids family and are largely present in many vegetables and fruits. They have been used in traditional medicine in many cultures for a long time. The most common and abundant anthocyanins are those presenting an O-glycosylation at C-3 (C ring) of the flavonoid skeleton to form -O-β-glucoside derivatives. The present comprehensive review summarized recent data on the anticancer properties of cyanidings along with natural sources, phytochemical data, traditional medical applications, molecular mechanisms and recent nanostrategies to increase the bioavailability and anticancer effects of cyanidins. For this analysis, in vitro, in vivo and clinical studies published up to the year 2022 were sourced from scientific databases and search engines such as PubMed/Medline, Google scholar, Web of Science, Scopus, Wiley and TRIP database. Cyanidins' antitumor properties are exerted during different stages of carcinogenesis and are based on a wide variety of biological activities. The data gathered and discussed in this review allows for affirming that cyanidins have relevant anticancer activity in vitro, in vivo and clinical studies. Future research should focus on studies that bring new data on improving the bioavailability of anthocyanins and on conducting detailed translational pharmacological studies to accurately establish the effective anticancer dose in humans as well as the correct route of administration.

Design, Synthesis, and Biological Evaluation of Novel Hybrids Containing Dihydrochalcone as Tyrosinase Inhibitors to Treat Skin Hyperpigmentation

Excessive melanin deposition may lead to a series of skin disorders. The production of melanin is carried out by melanocytes, in which the enzyme tyrosinase performs a key role. In this work, we identified a series of novel tyrosinase inhibitor hybrids with a dihydrochalcone skeleton and resorcinol structure, which can inhibit tyrosinase activity and reduce the melanin content in the skin. Compound 11c possessed the most potent activity against tyrosinase, showing IC₅₀ values at nanomolar concentration ranges, along with significant antioxidant activity and low cytotoxicity. Furthermore, in vitro permeation tests, supported by HPLC analysis and 3D OrbiSIMS imaging visualization, revealed the excellent permeation of 11c. More importantly, compound 11c reduced the melanin content on UV-induced skin pigmentation in a guinea pig model in vivo. These results suggest that compound 11c may serve as a promising potent tyrosinase inhibitor for the development of a potential therapy to treat skin hyperpigmentation.

Quercetin 3-O-Galactoside Isolated from Limonium tetragonum Inhibits Melanogenesis by Regulating PKA/MITF Signaling and ERK Activation

Quercetin 3-O-galactoside (Q3G) is a common dietary flavanol that has been shown to possess several bioactivities, including anti-melanogenesis. However, how Q3G exerts its anti-melanogenic effect has not been studied. The current study, therefore aimed to investigate the anti-melanogenesis potential of Q3G and elucidate the underlying action mechanism in α-melanocyte-stimulating hormone (α-MSH)-induced hyperpigmentation model of B16F10 murine melanoma cells. Results showed that α-MSH stimulation significantly increased tyrosinase (TYR) and melanin production, which were significantly downregulated by Q3G treatment. The treatment with Q3G suppressed the transcriptional and protein expressions of melanogenesis-related enzymes TYR, tyrosinase related protein-1 (TRP-1), and TRP-2, along with the melanogenic transcription factor microphthalmia-associated transcription factor (MITF) in B16F10 cells. It was shown that Q3G downregulated MITF expression and suppressed its transcriptional activity by inhibiting the cAMP-dependent protein kinase A (PKA)-mediated activation of CREB and GSK3β. In addition, MAPK-regulated MITF activation signaling was also involved in the inhibition of melanin production by Q3G. The results suggest that the anti-melanogenic properties of Q3G rationalize further studies in vivo to confirm its action mechanism and consequent utilization as a cosmetic ingredient against hyperpigmentation.

Vitiligo and Mental Health: Natural Compounds' Usefulness

Vitiligo is an autoimmune dermatosis frequently associated with other comorbidities, such as mental health disorders. It is unclear if vitiligo triggers mental disorders or if mental disorders trigger vitiligo, but each one affects and worsen the other, if present at the same time. Both mental health disorders and vitiligo present a multifactorial pathogenesis and often require prolonged periods of therapy, sometimes with poor results. Given the possible link of common pathogenetic factors and the need of integrated therapies, the aim of this review is to look at natural compounds as possible supplements for both conditions. The results yielded show a possible role of these supplements in ameliorating both conditions, thus helping these patients to achieve a better quality of life and reduce the need for prolonged therapies. The limitations regarding the relative lack of in vivo studies, and the increasing need to lighten the burden of these chronic diseases, suggests that it is mandatory to proceed with further trials.

Pinostrobin Suppresses the α-Melanocyte-Stimulating Hormone-Induced Melanogenic Signaling Pathway

Pinostrobin is a dietary flavonoid found in several plants that possesses pharmacological properties, such as anti-cancer, anti-virus, antioxidant, anti-ulcer, and anti-aromatase effects. However, it is unclear if pinostrobin exerts anti-melanogenic properties and, if so, what the underlying molecular mechanisms comprise. Therefore, we, in this study, investigated whether pinostrobin inhibits melanin biosynthesis in vitro and in vivo, as well as the potential associated mechanism. Pinostrobin reduced mushroom tyrosinase activity in vitro in a concentration-dependent manner, with an IC₅₀ of 700 μM. Molecular docking simulations further revealed that pinostrobin forms a hydrogen bond, as well as other non-covalent interactions, between the C-type lectin-like fold and polyphenol oxidase chain, rather than the previously known copper-containing catalytic center. Additionally, pinostrobin significantly decreased α-melanocyte-stimulating hormone (α-MSH)-induced extracellular and intracellular melanin production, as well as tyrosinase activity, in B16F10 melanoma cells. More specifically, pinostrobin inhibited the α-MSH-induced melanin biosynthesis signaling pathway by suppressing the cAMP-CREB-MITF axis. In fact, pinostrobin also attenuated pigmentation in α-MSH-stimulated zebrafish larvae without causing cardiotoxicity. The findings suggest that pinostrobin effectively inhibits melanogenesis in vitro and in vivo via regulation of the cAMP-CREB-MITF axis.

In Vitro Antithrombotic, Antitumor and Antiangiogenic Activities of Green Tea Polyphenols and Its Main Constituent Epigallocatechin-3-gallate

The balance between embolic risk and bleeding represents a clinical challenge in cancer patient treatment, encouraging studies on adjuvant oncologic treatments. Thereby, this study evaluated the in vitro effect of green tea extract (GTE) and epigallocatechin-3-gallate (EGCG) on hemostasis modulation and the antineoplastic effect on melanoma cells (B16-F10) by applying platelet aggregation, angiogenesis and viability cell assays. The results displayed a significant platelet antiaggregant effect, corresponding to 50 and 80% for the extract and EGCG, respectively, compared to the negative control. Furthermore, both GTE and EGCG exhibited antitumor effects by reducing melanoma cell growth by 25 and 50%, respectively, verified by cellular apoptosis. Regarding angiogenesis, these substances inhibited blood vessel formation, reaching about 25% and 99% for GTE and EGCG at 100 μg/mL, respectively. Moreover, TNF-α cell stimulation evidenced VEGF and IL-8 secretion inhibition at 55 and 20% with GTE, while EGCG promoted an inhibition around 78% for both VEGF and IL-8. The results indicate the promising performance of GTE and EGCG as an option for treating cancer and its side effects. Nonetheless, further studies are required to elucidate their action mechanism on clotting, cell death and angiogenesis.

Drug Delivery Systems and Flavonoids: Current Knowledge in Melanoma Treatment and Future Perspectives

Melanoma is an aggressive form of skin cancer with a high prevalence in the population. An early diagnosis is crucial to cure this disease. Still, when this is not possible, combining potent pharmacological agents and effective drug delivery systems is essential to achieve optimal treatment and improve patients' quality of life. Nanotechnology application in biomedical sciences to encapsulate anticancer drugs, including flavonoids, in order to enhance therapeutic efficacy has attracted particular interest. Flavonoids have shown effectiveness against various types of cancers including in melanoma, but they show low aqueous solubility, low stability and very poor oral bioavailability. The utilization of novel drug delivery systems could increase flavonoid bioavailability, thereby potentiating its antitumor effects in melanoma. This review summarizes the potential of different flavonoids in melanoma treatment and the several nanosystems used to improve their biological activity, considering published information that reported improved biological and pharmacological properties of encapsulated flavonoids.

(+)-Magnolin Enhances Melanogenesis in Melanoma Cells and Three-Dimensional Human Skin Equivalent; Involvement of PKA and p38 MAPK Signaling Pathways

Magnoliae Flos is a traditional herbal medicine used to treat nasal congestion associated with headache, empyema, and allergic rhinitis. In our preliminary screening of crude drugs used in Japanese Kampo formulas for melanin synthesis, the methanol extract of Magnoliae Flos was found to exhibit strong melanin synthesis activity. However, there have been no studies evaluating the effects of Magnoliae Flos or its constituents on melanogenesis. The present study aimed to isolate the active compounds from Magnoliae Flos that activate melanin synthesis in melanoma cells and three-dimensional human skin equivalent, and to investigate the molecular mechanism underlying melanin induction. The methanol extract of Magnoliae Flos induced an increase of melanin content in both B16-F1 and HMV-II cells. A comparison of melanin induction by three fractions prepared from the extract showed that the ethyl acetate fraction markedly induced melanin synthesis. Bioassay-guided separation of the ethyl acetate fraction resulted in the isolation of seven lignans (1:  - 7: ). Among them, (+)-magnolin (5: ) strongly induced melanin synthesis and intracellular tyrosinase activity. Furthermore, the ethyl acetate fraction and 5: clearly induced melanin content in a three-dimensional human skin equivalent. Molecular analysis revealed that 5: triggered the protein expression of tyrosinase, tyrosinase-related protein-1, and tyrosinase-related protein-2. Further analysis of transcriptional factors and signaling pathways demonstrated that 5: induces the protein expression of tyrosinase, tyrosinase-related protein-1, and tyrosinase-related protein-2 activated by the protein kinase A- and p38 mitogen-activated protein kinase-dependent pathways, leading to cAMP-responsive element-binding protein phosphorylation and microphthalmia-associated transcription factor expression. These findings demonstrate the potential of 5: as a potent therapeutic agent for hypopigmentation.

CDK1 promotes the proliferation of melanocytes in Rex rabbits

BACKGROUND

The fur color constitutes one of the most important economic characteristics of fur animals and is determined by the content of melanin. A previous study has shown that the cyclin-dependent kinase 1 (CDK1) is a member of the protein kinase family, involved in forming the color of the fur in Rex rabbits. However, its effect on the melanocytes remains unclear.

OBJECTIVE

This study aimed to provide evidence for the role of CDK1 in melanogenesis.

METHODS

This study measured the expression of CDK1 in Rex rabbit skins of six coat colors using qRT-PCR. The CDK1-mediated regulation of the pigmentation-related genes and cyclin-dependent kinases were analyzed. The melanin content, proliferation, and apoptosis of the melanocytes were analyzed using the NaOH, CCK8, and Annexin V-FITC methods.

RESULTS

The CDK1 expression in the skin of the rex rabbits with different coat colors was found to be regular, and the expression level was found to be the highest in the skin of the black rex rabbits (P < 0.05). The overexpression/knockdown of CDK1 was found to significantly increase/decrease the melanin content in the melanocytes (P < 0.01). Besides, CDK1 was found to significantly promote the proliferation of the melanocyte and inhibit apoptosis (P < 0.01). Furthermore, the overexpression of CDK1 was found to significantly affect the expression of the other melanin-related genes like TYR, PMEL, DCT, as well as the mRNA expression of the cyclin-dependent kinases CDK4, CDK6, CDK8, CCNB1.

CONCLUSIONS

The results indicated that CDK1 can serve as a key gene regulating melanogenesis, melanocyte proliferation, and apoptosis, providing a new theoretical basis for studying the mechanism by which the different colors of the fur evolve in mammals.

Vegetable-derived indole enhances the melanoma-treating efficacy of chemotherapeutics

Food-drug interaction is an important but overlooked issue. For example, little is known concerning whether or not the chemotherapy of cancers is affected by the well-defined dietary chemicals such as 2-(indol-3-ylmethyl)-3,3'-diindolylmethane (LTr1) derived from daily consumed cruciferous vegetables. This work, inspired by the described melanogenesis reduction by certain indoles, presents that LTr1 mitigates the melanogenesis and thus potentiates the in vitro and in vivo anti-melanoma effectiveness of different chemotherapeutic agents including dacarbazine, vemurafenib, and sorafenib. In B16 melanoma cells, LTr1 was shown to inhibit the melanogenesis by acting towards the regulatory (R) subunit of protein kinase A (PRKAR1a) associated with the phosphorylation of cAMP-response element binding protein (CREB). This allows LTr1 to reduce the expression of melanogenesis-related enzymes such as tyrosinase (TYR), tyrosinase-related protein 1 (TYRP1), and tyrosinase-related protein 2 (TYRP2). Furthermore, LTr1 was addressed to bind to the aryl hydrocarbon receptor (AhR) and up-regulate the expression of CYP1A1 encoding cytochrome P450 1A1, leading to the escalation of reactive oxygen species (ROS) level. The increased ROS generation promotes the cysteine-to-cystine transformation to inhibit the pheomelanogenesis in melanomas. Collectively, the work identifies LTr1 as a new melanogenesis inhibitor that modulates the PKA/CREB/MITF and AhR/CYP1A1/ROS pathways, thereby providing a new option for (re)sensitizing melanomas to chemotherapeutics.

Depigmenting effect of banana stem and flower on melanocytes

Gingival repigmentation is an inevitable hindrance among different procedures accepted for gingival depigmentation. To overcome this, there is a need for the procedure that can delay the duration of reappearance of pigmentation. A number of studies using herbal extracts with antioxidant property shown to have anti melanogenic effect. In the present in - vitro study, we investigated the effect of banana stem and flower extracts on melanocytes, as Banana stem and flower are rich in polyphenols and flavonoids, which are potent antioxidants. The melanocytes were exposed to ethanolic extract of banana stem and flower at 2 concentrations (100 μgm, 150 μgm) for 72 h. The cellular melanin contents were measured using Bradford assay which depicted the reduction in the melanin content and Resazurin assay was used for assessment of cell viability showed no significant cytotoxic effect of banana stem and flower on the cells. The cells exposed to higher concentration (150 μgm) of banana stem and flower showed significant reduction in melanin content. Flower extract showed better reduction in the melanin content. Based on these results both banana flower and stem can be tried as potent gingival depigmenting agent.

Selected Flavonoids to Target Melanoma: A Perspective in Nanoengineering Delivery Systems

Melanoma is a complex type of cancer that depends on several metabolic factors, while the currently used therapies are not always effective and have unwanted side effects. In this review, the main factors involved in the etiology of cutaneous carcinoma are highlighted, together with the main genes and proteins that regulate cancer invasion and metastization. The role of five selected flavonoids, namely, apigenin, epigallocatechin-3-gallate, kaempferol, naringenin, and silybin, in the modulating receptor tyrosine kinase (RTK) and Wnt pathways is reported with their relevance in the future design of drugs to mitigate and/or treat melanoma. However, as phenolic compounds have some difficulties in reaching the target site, the encapsulation of these compounds in nanoparticles is a promising strategy to promote improved physicochemical stabilization of the bioactives and achieve greater bioavailability. Scientific evidence is given about the beneficial effects of loading these flavonoids into selected nanoparticles for further exploitation in the treatment of melanoma.

Epigallocatechin gallate triggers apoptosis by suppressing de novo lipogenesis in colorectal carcinoma cells

The de novo lipogenesis (DNL) pathway has been identified as a regulator of cancer progression and aggressiveness. Downregulation of key lipogenesis enzymes has been shown to activate apoptosis in cancerous cells. Epigallocatechin gallate (EGCG) inhibits cancer cell proliferation without causing cytotoxicity in healthy cells. The present study aimed to investigate the effects of EGCG on the promotion of apoptosis associated with the DNL pathway inhibition in cancer cells, both in vitro and in vivo. We observed that two colorectal cancer cell lines (HCT116 and HT-29) had a higher cytotoxic response to EGCG treatment than hepatocellular carcinoma cells, including HepG2 and HuH-7. EGCG treatment decreased cell viability and increased mitochondrial damage-triggered apoptosis in both HCT116 and HT-29 cancer cells. Additionally, we treated mice transplanted with HCT116 cells with 30 or 50 mg·kg-1 EGCG for 7 days to evaluate the apoptotic effects of EGCG treatment in a xenograft mouse model of cancer. We observed a decrease in intracellular fatty acid levels, which suggested that EGCG-induced apoptosis was associated with a decrease in fatty acid levels in cancer. Suppression of ATP synthesis by EGCG indicated that cell death induction in cancer cells could be mediated by shared components of the DNL and energy metabolism pathways. In addition, EGCG-induced apoptosis suppressed the expression of the phosphorylation protein kinase B and extracellular signal-regulated kinase 1/2 signaling proteins in tumors from xenografted mice. Cytotoxic effects in unaffected organs and tissues of the mouse xenograft model were absent upon EGCG treatment.

Continuous ZnO nanoparticle exposure induces melanoma-like skin lesions in epidermal barrier dysfunction model mice through anti-apoptotic effects mediated by the oxidative stress–activated NF-κB pathway

Background

Increasing interest in the hazardous properties of zinc oxide nanoparticles (ZnO NPs), commonly used as ultraviolet filters in sunscreen, has driven efforts to study the percutaneous application of ZnO NPs to diseased skin; however, in-depth studies of toxic effects on melanocytes under conditions of epidermal barrier dysfunction remain lacking.

Methods

Epidermal barrier dysfunction model mice were continuously exposed to a ZnO NP-containing suspension for 14 and 49 consecutive days in vivo. Melanoma-like change and molecular mechanisms were also verified in human epidermal melanocytes treated with 5.0 µg/ml ZnO NPs for 72 h in vitro.

Results

ZnO NP application for 14 and 49 consecutive days induced melanoma-like skin lesions, supported by pigmented appearance, markedly increased number of melanocytes in the epidermis and dermis, increased cells with irregular nuclei in the epidermis, recruited dendritic cells in the dermis and dysregulated expression of melanoma-associated gene Fkbp51, Trim63 and Tsp 1. ZnO NPs increased oxidative injury, inhibited apoptosis, and increased nuclear factor kappa B (NF-κB) p65 and Bcl-2 expression in melanocytes of skin with epidermal barrier dysfunction after continuously treated for 14 and 49 days. Exposure to 5.0 µg/ml ZnO NPs for 72 h increased cell viability, decreased apoptosis, and increased Fkbp51 expression in melanocytes, consistent with histological observations in vivo. The oxidative stress–mediated mechanism underlying the induction of anti-apoptotic effects was verified using the reactive oxygen species scavenger N-acetylcysteine.

Conclusions

The entry of ZnO NPs into the stratum basale of skin with epidermal barrier dysfunction resulted in melanoma-like skin lesions and an anti-apoptotic effect induced by oxidative stress, activating the NF-κB pathway in melanocytes.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01308-w.

Protective effect of hydroxygenkwanin against hair graying induced by X-ray irradiation and repetitive plucking

Hair graying in mice is caused by various injuries such as X-ray radiation and repeated plucking that ultimately damage melanocytes and their stem cells (melanocyte stem cells). In X-ray‒induced hair graying, injuries first manifest as a loss-of-niche function of hair follicular keratinocyte stem cells to maintain melanocyte stem cells. Thus, we hypothesized that hair follicular keratinocyte stem cells could be a practical target to prevent hair graying. In this study, we investigated the in vivo effect of the flavonoid hydroxygenkwanin, which has been shown to exert the best protection on human epidermal keratinocytes against in vitro X-ray‒induced cytological effects, using X-ray‒induced and repeated hair plucking‒induced hair graying mice models. We found that hydroxygenkwanin exerted a remarkable effect in preventing hair graying; however, when receptor Y kinase Kit-mutant mice were used, no prevention effect was observed. Therefore, we propose that Kit signaling might be involved in the hydroxygenkwanin-induced protective effect against hair graying.

HPLC-DAD phenolics screening and in vitro investigation of haemostatic, antidiabetic, antioxidant and photoprotective properties of Centaurea tougourensis Boiss. & Reut

Introduction

Traditional medicine has an important place in human history and this since antiquity. Indeed, during Egyptian and Chinese civilization era, many detailed manuscripts, describing the therapeutic effect of plants, were found which suggest that folk medicine is the basis of the actual medicine.

Objective

To investigate the phytochemical and pharmacological properties of the n-butanol (n-BuOH) and ethyl acetate (EA) extracts of the aerial part of Centaurea tougourensis.

Methods

The phytochemical evaluation was done based on HPLC-DAD approach. The antioxidant activity was determined by DPPH and cupric ion reducing antioxidant capacity (CUPRAC), while the hemostatic effect was performed using plasma recalcification time (PRT) method. The antidiabetic capacity was investigated by alpha-amylase inhibition assay and the photoprotective test was evaluated by the measurement of sun protection factor (SPF).

Results

13 phenolic compounds were identified in both extracts of C. tougourensis. These extracts showed antioxidant, haemostatic, antidiabetic and photoprotective properties with a dose-dependent manner. Amounts of n-BuOH activities were found higher, with a respective IC50 value of 0.72±0.07 μg/ml in DPPH assay, an A0.50 value lower than 3.125 μg/ml in CUPRAC assay besides a shortening rate percentage of coagulation (86.71%) in haemostatic assay, a moderate inhibition effect on alpha amylase activity with an IC50 value of (711.5±0.03 μg/ml) and a maximum sun protection factor of (56.035). These results were mostly found highly significant (p<0.001) when compared to respective standards.

Conclusion

This study demonstrated some pharmacological effects of C. tougourensis which suggests that our plant could be a good candidate to treat some illnesses related to oxidative stress, bleeding or skin cancer.

Nutrition and melanoma prevention

There has been considerable research in recent years on dietary factors and/or nutritional elements that might impact melanoma risk. A wide variety of dietary compounds have been studied, but only a selected group will be discussed in this review. Many have promising in vitro evidence supporting their potential, and some have been associated with decreased melanoma risk in epidemiologic studies; however, data from randomized controlled trials in humans are lacking. Future studies may be able to clarify the potential role of dietary components in melanoma risk reduction.

Kaempferol, the melanogenic component of Sanguisorba officinalis, enhances dendricity and melanosome maturation/transport in melanocytes

Kaempferol, a representative flavonoid constituent of Sanguisorba officinalis, promotes melanogenesis, but the underlying mechanisms remain unknown. Here, we evaluated the effects of kaempferol on melanocytes morphology and behavior and determined the mechanisms regulating kaempferol-induced pigmentation. We observed that kaempferol increased melanin contents and dendritic length and stimulated melanocyte migration both in vitro and vivo. It significantly enhanced the expression of microphthalmia-associated transcription factor (MITF) and downstream enzymes of melanin biosynthesis-tyrosinase (TYR), tyrosinase-related protein (TRP-1), and dopachrome tautomerase (DCT). It also induced melanosome maturation (increased stage III and IV melanosomes) and melanin transfer to dendritic tips; this was evidenced as follows: kaempferol-treated melanocytes exhibited the perimembranous accumulation of HMB45-positive melanosomes and increased the expression of Rab27A, RhoA, and Cdc42, which improved melanosome transport to perimembranous actin filaments. These results jointly indicated that kaempferol promotes melanogenesis and melanocyte growth. Additionally, kaempferol stimulated the phosphorylation of P38/ERK MAPK and downregulated p-PI3K, p-AKT, and p-P70s6K expression. Pre-incubation with P38 (SB203580) and ERK (PD98059) signaling inhibitors reversed the melanogenic and dendritic effects and MITF expression. PI3K/AKT inhibitor augmented kaempferol-induced melanin content and dendrite length. In summary, kaempferol regulated melanocytes' dendritic growth and melanosome quantity, maturation, and transport via P38/ERK MAPK and PI3K/AKT signaling pathways.

Grape Extract Promoted α-MSH-Induced Melanogenesis in B16F10 Melanoma Cells, Which Was Inverse to Resveratrol

Melanin is a natural pigment produced by cells to prevent damage caused by ultraviolet radiation. Previously, resveratrol was shown to reduce melanin synthesis. As a natural polyphenol with various biological activities, resveratrol occurs in a variety of beverages and plant foods, such as grapes. Therefore, we investigated whether grape extracts containing resveratrol also had the ability to regulate melanin synthesis. In this study, we used mouse B16F10 melanoma cells as a model for melanin synthesis with the melanogenesis-inducing α-melanocyte-stimulating hormone (α-MSH) as a positive control. Our results confirmed previous reports that resveratrol reduces melanin synthesis by reducing the activity of the rate-limiting enzyme tyrosinase. In contrast, the grape extract could not reduce melanin synthesis, and in fact promoted melanogenesis in the presence of α-MSH. The expression of genes related to melanin synthesis, such as tyrosinase, tyrosinase-related protein-1, tyrosinase-related protein-2, and microphthalmia-associated transcription factor, also supports these phenomena, which means that even in the presence of resveratrol, grape extract will strengthen the function of α-MSH in promoting melanin synthesis. Therefore, these results also provide a point of view for research on cosmetics.

Recent Advances in Phenolic Metabolites and Skin Cancer

Skin cancer represents any tumor development from the cutaneous structures within the epidermis, dermis or subcutaneous tissue, and is considered to be the most prevalent type of cancer. Compared to other types of cancer, skin cancer is proven to have a positive growth rate of prevalence and mortality. There are available various treatments, including chemotherapy, immunotherapy, radiotherapy and targeted therapy, but because of the multidrug resistance development, a low success has been registered. By this, the importance of studying naturally occurring compounds that are both safe and effective in the chemoprevention of skin cancer is emphasized. This review focuses on melanoma because it is the deadliest form of skin cancer, with a significantly increasing incidence in the last decades. As chemopreventive agents, we present polyphenols and their antioxidant activity, anti-inflammatory effect, their ability to balance the cell cycle and to induce apoptosis and their various other effects on skin melanoma. Besides chemoprevention, studies suggest that polyphenols can have treating abilities in some conditions. The limitations of using polyphenols are also pointed out, which are related to their poor bioavailability and stability, but as the technology is well developed, it is possible to augment the efficacy of polyphenols in the case of melanoma.

Epigenetic regulation of melanogenesis

Melanogenesis is a complex process in which melanin is synthesized in melanocytes and transported to keratinocytes, which involves multiple genes and signaling pathways. Epigenetics refers to the potential genetic changes that affect gene expression without involving changes in the original sequence of DNA nucleotides. DNA methylation regulates the expression of key genes such as tyrosinase (TYR), tyrosinase-related protein 1 (TYRP1), dopachrome tautomerase (DCT) and microphthalmia-associated transcription factor (MITF), as well as paracrine factors such as stem cell factor (SCF) and endothelin-1 (ET-1) in melanogenesis. Potential DNA methylation sites are present in the genes of melanogenesis-related signaling pathways such as "Wnt", "PI3K/Akt/CREB" and "MAPK". H3K27 acetylation is abundant in melanogenesis-related genes. Both the upstream activation and downstream regulation of MITF depend on histone acetyltransferase CBP/p300, and pH-induced H3K27 acetylation may be the amplifying mechanism of MITF's effect. HDAC1 and HDAC10 catalyze histone deacetylation of melanogenesis-related gene promoters. Chromatin remodelers SWI/SNF complex and ISWI complex use the energy of ATP hydrolysis to rearrange nucleosomes, while their active subunits BRG1, BRM and BPTF, act as activators and cofactors of MITF. MicroRNAs (miRNAs) can directly target a large number of melanogenesis-related genes, while long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) regulate melanogenesis in a variety of ways. Interactions exist among the epigenetic mechanisms of melanogenesis. For example, the methyl CpG binding domain protein 2 (MeCP2) links DNA methylation, histone deacetylation, and histone methylation. Epigenetic-based therapy provides novel opportunities for treating dermatoses that are caused by pigmentation disturbances. This review summarizes the epigenetic regulation mechanisms of melanogenesis, and examines the pathogenesis and treatment of epigenetics in pigmentation disorders.

Skin hyperpigmentation and its treatment with herbs: an alternative method

Background

With an increasing number of patients, those who are facing a lot of skin-related complaints, often referred to as skin of pigmentation patients, are on the rise. Among all the most common complaints in patients with skin of color is hyperpigmentation. So, there is need of herbal formulation for treatment of hyperpigmentation.

Main body

This review article addresses the different types of hyperpigmentation, causes, and its treatment with herbs for the management of the skin hyperpigmentation. As uneven pigmentation of skin or hyperpigmentation is a common skin condition, which occurs when the skin produces more melanin. This can make spots or patches of skin appear darker than surrounding areas. Some forms of hyperpigmentation with post-inflammatory, melasma, and sun spots are more likely to affect areas of face, arms, and legs due to sun exposure and injury. Although the availability of multiple treatments for the condition which leads to some adverse effects, hyperpigmentation continues to present skin care management challenges for dermatologists.

Conclusion

Some plants and phytoconstituents, e.g., Azadirachta indica, Glycyrrhiza glabra, Panax ginseng and genistein, ellagic acids, quercetin, are very useful in herbal cosmetic as anti-hyperpigmentry agents in cosmetic industries. Some of flavonoids and triterpenoids present in plants also show their effect as antioxidant and skin whitening agents. It is expected that this review will compile and improve the existing knowledge on the potential utilization of herbs for the treatment of skin hyperpigmentation.

The Role of Senescent Cells in Acquired Drug Resistance and Secondary Cancer in BRAFi-Treated Melanoma

BRAF is the most common gene mutated in malignant melanoma, and predominately it is a missense mutation of codon 600 in the kinase domain. This oncogenic BRAF missense mutation results in constitutive activation of the mitogen-activate protein kinase (MAPK) pro-survival pathway. Several BRAF inhibitors (BRAFi) have been developed to specifically inhibit BRAFV600 mutations that improve melanoma survival, but resistance and secondary cancer often occur. Causal mechanisms of BRAFi-induced secondary cancer and resistance have been identified through upregulation of MAPK and alternate pro-survival pathways. In addition, overriding of cellular senescence is observed throughout the progression of disease from benign nevi to malignant melanoma. In this review, we discuss melanoma BRAF mutations, the genetic mechanism of BRAFi resistance, and the evidence supporting the role of senescent cells in melanoma disease progression, drug resistance and secondary cancer. We further highlight the potential benefit of targeting senescent cells with senotherapeutics as adjuvant therapy in combating melanoma.

Berberine-photodynamic induced apoptosis by activating endoplasmic reticulum stress-autophagy pathway involving CHOP in human malignant melanoma cells

Malignant melanoma is a critical and aggressive skin tumor with a steeply rising incidence and a less favorable prognosis due to the lack of efficient treatment. Photodynamic therapy (PDT) is a new promising treatment for this tumor through photosensitizers-mediated oxidative cytotoxicity. In this study, we explored the role of berberine-mediated PDT (BBR-PDT) in the anti-proliferative effect on human malignant melanoma cells (MMCs). We found that there were significant differences between MMCs with BBR-PDT and MMCs with BBR or PDT only. Further research showed that BBR-PDT induced apoptosis via up-regulating the expression of cleaved caspase-3 protein. We also observed that LC3-related autophagy level was upregulated in MMCs with BBR-PDT. Besides, it was also found that BBR-PDT activated endoplasmic reticulum (ER) stress, involving a dramatic increase in reactive oxygen species (ROS). Interestingly, the knockdown of CHOP protein expression inhibited apoptosis, autophagy and ER stress levels caused by BBR-PDT, suggesting that CHOP protein may be related to apoptosis, autophagy and ER stress in MMCs with BBR-PDT. Collectively, our results indicated that BBR-PDT had an essential impact on MMCs' growth inhibition, and therefore may reveal the possibility of developing BBR-PDT into human malignant melanoma.

Depigmenting effect of Xanthohumol from hop extract in MNT-1 human melanoma cells and normal human melanocytes

Xanthohumol (XH) is the most abundant prenylated flavonoid found in the hop plant (Humulus lupulus L.) and has previously been shown to have depigmenting effects in B16F10 mouse melanoma cells; however, studies of its depigmenting efficacy in human melanocytes are still lacking. In this work, we explored the effects of XH on melanogenesis in MNT-1 human melanoma cells and normal human melanocytes from darkly-pigmented skin (HEM-DP). XH was screened for cytotoxicity over 48 h, and subsequently tested on melanogenesis in MNT-1 cells. XH was further tested in HEM-DP cells for melanin synthesis and melanosome export; dendricity was quantitated to assess effects on melanosome export. Melanosome degradation was studied in human keratinocytes (HaCaT). Our results showed that XH inhibited melanin synthesis in MNT-1 cells at 30 μM but increased intracellular tyrosinase activity without affecting ROS levels. In HEM-DP cells, XH robustly suppressed cellular tyrosinase activity at nontoxic concentrations (2.5–5 μM) without any effect on melanin synthesis. However, XH inhibited melanosome export by reducing dendrite number and total dendrite length. Further testing in HaCaT cells demonstrated that XH induced melanosome degradation at low micromolar concentrations without any cytotoxicity. In summary, our results demonstrate that XH at low micromolar concentrations might hold promise as a potent inhibitor of human pigmentation by primarily targeting melanin export and melanin degradation. Further studies to elucidate the signaling mechanisms of action of melanosome export inhibition by XH and in vivo efficacy are warranted.

•

Xanthohumol (XH) inhibited melanin synthesis in MNT-1 human melanoma cells.

•

XH did not inhibit melanin synthesis in primary human melanocytes but significantly suppressed both dendrite number and total dendrite length at low micromolar concentrations.

•

Reduction of melanosome export by reduction in dendricity was correlated with the inhibition of intracellular tyrosinase activity.

•

XH induced melanosome degradation in human keratinocytes.

•

XH is a candidate for skin-lightning which inhibits human melanogenesis by targeting later steps in melanogenesis.

Flavonoids nanoparticles in cancer: Treatment, prevention and clinical prospects

The conventional therapies for cancer have a major concern of poor accessibility to tumor tissues. Furthermore, the requirement of higher doses and non-selective nature of therapeutic are associated with a range of adverse drug reactions (ADRs). However, flavonoids are documented to be effective against various types of cancer, but they are not evaluated for their safety profile and tumor site-specific action. Low solubility, rapid metabolism and poor absorption of dietary flavonoids in gastrointestinal tract hinder their pharmacological potential. Some studies have also suggested that flavonoids may act as pro-oxidant in some cases and may interact with other therapeutic agents, especially through biotransformation. Nanocarriers can alter pharmacokinetics and pharmacodynamic profile of incorporating drug. Moreover, nanocarriers are designed for targeted drug delivery, improving the bioavailability of poorly water-soluble drugs, delivery of macromolecules to site of action within the cell, combining therapeutic agents with imaging techniques which may visualize the site of drug delivery and co-delivery of two or more drugs. Combining two or more anti-cancer agents can reduce ADRs and nanotechnology played a pivotal role in this regard. In vitro and in vivo studies have shown the potential of flavonoids nano-formulations, especially quercetin, naringenin, apigenin, catechins and fisetin in the prevention and treatment of several types of cancer. Similarly, clinical trials have been conducted using flavonoids alone or in combination, however, the nano-formulations effect still needs to be elucidated. This review focuses on the impact of flavonoids nano-formulations on the improvement of their bioavailability, therapeutic and safety profile and will open new insights in the field of drug discovery for cancer therapeutics.

Tyrosinase-mediated melanogenesis in melanoma cells: Array comparative genome hybridization integrating proteomics and bioinformatics studies

We investigated the tyrosinase-associated melanogenesis in melanoma cells by using OMICS techniques. We characterized the chromosome copy numbers, including Chr 11q21 where the tyrosinase gene is located, from several melanoma cell lines (TXM13, G361, and SK-MEL-28) by using array CGH. We revealed that 11q21 is stable in TXM13 cells, which is directly related to a spontaneous high melanin pigment production. Meanwhile, significant loss of copy number of 11q21 was found in G361 and SK-MEL-28. We further profiled the proteome of TXM13 cells by LC-ESI-MSMS and detected more than 900 proteins, then predicted 11 hub proteins (YWHAZ; HSP90AA1; HSPA5; HSPA1L; HSPA9; HSP90B1; HSPA1A; HSPA8; FKSG30; ACTB; DKFZp686DQ972) by using an interactomic algorithm. YWHAZ (25% interaction in the network) is thought to be a most important protein as a linking factor between tyrosinase-triggered melanogenesis and melanoma growth. Bioinformatic tools were further applied for revealing various physiologic mechanisms and functional classification. The results revealed clues for the spontaneous pigmentation capability of TXM13 cells, contrary to G361 and SK-MEL-28 cells, which commonly have depigmentation properties during subculture. Our study comparatively conducted the genome-wide screening and proteomic profiling integrated interactomics prediction for TXM13 cells and suggests new insights for studying both melanogenesis and melanoma.

Flavonoid-rich extracts from okra flowers exert antitumor activity in colorectal cancer through induction of mitochondrial dysfunction-associated apoptosis, senescence and autophagy

Okra flowers contain a higher content of total flavonoids than most other flowers; however little research has been conducted on their potential benefits, including antitumor activity. In this study, we extracted and purified flavonoids from okra flower (AFE), and aimed to evaluate the effect of AFE and its underlying mechanism on colorectal cancer (CRC) cell growth in vitro and in vivo. Here, we identify that AFE is a safe, natural antioxidant and exerts significant antitumor efficacy on the inhibition of CRC cell proliferation and metastasis as well as tumour growth in vivo. We further reveal that AFE inhibits CRC cell proliferation by inducing mitochondrial dysfunction, which results from the activation of p53 and induction of apoptosis and senescence, and inhibits autophagic degradation. Furthermore, AFE inhibited migration and invasion of CRC cells by regulating the balance of MMP2/TIMP2 and MMP9 expression levels. Of note, administration of AFE as a preventive agent achieves a more effective antitumor effect than the therapeutic agent in a xenograft mouse model. Our results reveal, for the first time, that AFE is a safe, natural antioxidant with significant antitumor efficacy, which has great potential in the application for CRC prevention and treatment.

Design, synthesis of Cinnamyl-paeonol derivatives with 1, 3-Dioxypropyl as link arm and screening of tyrosinase inhibition activity in vitro

This study aimed to obtain tyrosinase inhibitors for treating hyperpigmentation. A series of cinnamyl ester analogues were designed and synthesized with cinnamic acid (CA) and peaonol compounds. The safety, melanin content and inhibitory effects of all target compounds were evaluated. In the enzymatic activity test, the inhibitory rate of compounds 8, 13 and 14 had stronger inhibitory activity with the IC₅₀ values of 20.7 μM, 13.98 μM and 15.16 μM, respectively than the positive drug kojic acid (IC₅₀ with 30.83 μM). The cytotoxicity evaluation showed that compounds 13 and 14 have higher safety than the other compounds to the proliferation of B16F10 cells. The result of the melanocyte test supported that compound13 has stronger cellular tyrosinase inhibitory activity than kojic acid and arbutin at 100 μM and 200 μM. The enzyme kinetics mechanism revealed that compound 13 was a non-competitive inhibitor while compounds 8 and 14 were mixed inhibitors. For the experiments of melanin content and tyrosinase activity in the B16F10 melanona cells, the inhibition rates of compounds 8, 14 and 13 were with 19.62%, 20.59% and 23.83%, respectively. In addition, compound 13 revealed the highest inhibitory activity to tyrosinase in the melanocyte with inhibition rates of 23.83%, which was better than kojic acid and arbutin (19.21% and 20.45%) at the same concentration. In the anti-melanogenesis experiment, compounds 8 and 13 had better anti-melanin effects than kojic acid from 25 μM to 100 μM. In summary, the results indicated that compounds 8, 13 and 14 had better tyrosinase inhibitory activity and anti-melanogenesis activity. Especially, the compound 13 has potentiality to develop novel tyrosinase inhibitors and whitening agents. The docking studies results revealed that the functional group of compound 13 mostly depends on the phenolic hydroxyl moiety, and its hydroxyl group did not insert into the active site of tyrosinase, which was in agreement with the results of the kinetics study.

Anti-Melanogenic Effects of Ethanol Extracts of the Leaves and Roots of Patrinia villosa (Thunb.) Juss through Their Inhibition of CREB and Induction of ERK and Autophagy

Patrinia villosa (Thunb.) Juss is a traditional herb commonly used in East Asia including Korea, Japan, and China. It has been administered to reduce and treat inflammation in Donguibogam, Korea. The mechanism for its anti-inflammatory effects has already been reported. In this study, we confirmed the efficacy of Patrinia villosa (Thunb.) Juss ethanol extract (Pv-EE) for inducing autophagy and investigate its anti-melanogenic properties. Melanin secretion and content were investigated using cells from the melanoma cell line B16F10. Pv-EE inhibited melanin in melanogenesis induced by α-melanocyte-stimulating hormone (α-MSH). The mechanism of inhibition of Pv-EE was confirmed by suppressing the mRNA of microphthalmia-associated transcription factor (MITF), decreasing the phosphorylation level of CREB, and increasing the phosphorylation of ERK. Finally, it was confirmed that Pv-EE induces autophagy through the autophagy markers LC3B and p62, and that the anti-melanogenic effect of Pv-EE is inhibited by the autophagy inhibitor 3-methyl adenine (3-MA). These results suggest that Pv-EE may be used as a skin protectant due to its anti-melanin properties including autophagy.

Pectolinarigenin inhibits cell viability, migration and invasion and induces apoptosis via a ROS-mitochondrial apoptotic pathway in melanoma cells

Pectolinarigenin a plant secondary metabolite that has various biological effects, including the inhibition of melanogenesis and tumor growth. Melanoma has a high degree of malignancy, with rapid metastasis and severe drug resistance, explaining the need for new candidate drugs that inhibit tumor growth and metastasis. However, the pharmacological action and mechanism of pectolinarigenin on the growth and metastasis of melanoma remain elusive. Thus, the present study aimed to investigate the role of pectolinarigenin in melanoma cell proliferation, apoptosis, migration and invasion. Apoptotic and metastasis-associated proteins were analyzed using western blotting. The results demonstrated that pectolinarigenin treatment resulted in growth inhibition and apoptosis induction in melanoma cells, arising from the loss of mitochondrial transmembrane potential, reactive oxygen species and the altered expression of apoptosis-associated proteins. In addition, wound-healing and Transwell assays demonstrated the potential of pectolinarigenin to impair the migration and invasion of melanoma cells in accordance with the changes in the expression of the associated proteins. Therefore, the results of the present study suggested that pectolinarigenin may serve a pivotal role in promoting melanoma cell apoptosis and reducing metastasis, and may thus be a promising potential candidate for an anti-melanoma treatment strategy.