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

Eriodictyon angustifolium extract, but not Eriodictyon californicum extract, reduces human hair greying

OBJECTIVE

Yerba Santa (Eriodictyon angustifolium and Eriodictyon californicum) has been used for many years in traditional medicine. However, the effect of Yerba Santa on melanogenesis has not yet been investigated. We aimed to assess the biological effects of Yerba Santa on hair pigmentation.

METHODS

Yerba Santa extracts were assessed for their cytological effects following X-ray irradiation treatment and then tested directly for the prevention of human hair greying. Ultra-performance liquid chromatography (UPLC) was utilized to identify the individual extract components.

RESULTS

Eriodictyon angustifolium extract significantly increased melanin synthesis in the melanoma cell line through activation of the WNT/MITF/tyrosinase-signalling pathway. In contrast, E. californicum had no effect on melanin synthesis. E. angustifolium extract also demonstrated a protective effect against the damage induced by X-ray irradiation in human keratinocytes. Application of the extracts to subjects who had grey beards demonstrated a reduced number of grey beard hair per year specifically with the E. angustifolium extract. A significant decrease in grey head hair was also observed after application of E. angustifolium extract. Upregulation of gene expression related to melanin production and WNT signalling was observed after the application of E. angustifolium extract. Sterubin was the most abundant flavonoid detected by UPLC in E. angustifolium extract. In addition, sterubin showed the highest difference in terms of quantity, between E. angustifolium and E. californicum extract.

CONCLUSION

Eriodictyon angustifolium extract, which is abundant in sterubin, may be suitable as a potential cosmetic and medical agent for the prevention and improvement of hair greying.

Assessment of Antioxidants in Selected Plant Rootstocks

The service tree (Sorbus domestica) is a wild fruit tree with immense medicinal and industrial value. This study aimed at determining the four major groups of antioxidants (flavonoids, phenolic acids and aldehydes, catechin and procyanidin) in rootstocks of Crataegus laevigata (genotypes O-LE-14 and O-LE-21), Aronia melanocarpa (genotypes O-LE-14 and O-LE-21), Chaenomeles japonica (genotype O-LE-9) and Cydonia oblonga (BA 29) (genotypes O-LE-14 and O-LE-21). Hyperoside (Quercetin 3-D-galactoside) was the most abundant flavonoid compound, since its average content in the rootstocks of Crataegus laevigata (O-LE-21) was 180.68 ± 0.04 μg·g-1. Dihydrokaempherol was the least frequently found flavonoid compound, with an average concentration of 0.43 ± 0.01 μg·g-1 in all the rootstocks of plants considered in this study. Among the phenolic compounds, the most represented one was protocatechuic acid, with 955.92 ± 10.25 μg·g-1 in the rootstocks of Aronia melanocarpa (O-LE-14). On the other hand, the least represented p-Coumaric acid exhibited the average concentration of 0.34 ± 0.01 μg·g-1 in the plant rootstocks. Epicatechin was the most abundant catechin compound, with a content of 3196.37 ± 50.10 μg·g-1 in the rootstocks of Aronia melanocarpa (O-LE-14). The lowest represented catechin compound was epigallocatechin, with the average concentration of 0.95 ± 0.08 μg·g-1 in the screened plant rootstocks. From the procyanidin compounds, the most abundant one was procyanidin b2 in the rootstocks of Crataegus laevigata (O-LE-14), with a concentration of 5550.40 ± 99.56 μg·g-1. On the contrary, procyanidin a2, with an average concentration of 40.35 ± 1.61 μg·g-1, represented the least frequent procyanidin compound in all the plant rootstocks screened herein.

GSK-3β-Targeting Fisetin Promotes Melanogenesis in B16F10 Melanoma Cells and Zebrafish Larvae through β-Catenin Activation

Fisetin is found in many fruits and plants such as grapes and onions, and exerts anti-inflammatory, anti-proliferative, and anticancer activity. However, whether fisetin regulates melanogenesis has been rarely studied. Therefore, we evaluated the effects of fisetin on melanogenesis in B16F10 melanoma cell and zebrafish larvae. The current study revealed that fisetin slightly suppressed in vitro mushroom tyrosinase activity; however, molecular docking data showed that fisetin did not directly bind to mushroom tyrosinase. Unexpectedly, fisetin significantly increased intracellular and extracellular melanin production in B16F10 melanoma cells regardless of the presence or absence of α-melanocyte stimulating hormone (α-MSH). We also found that the expression of melanogenesis-related genes such as tyrosinase and microphthalmia-associated transcription factor (MITF), were highly increased 48 h after fisetin treatment. Pigmentation of zebrafish larvae by fisetin treatment also increased at the concentrations up to 200 µM and then slightly decreased at 400 µM, with no alteration in the heart rates. Molecular docking data also revealed that fisetin binds to glycogen synthase kinase-3β (GSK-3β). Therefore, we evaluated whether fisetin negatively regulated GSK-3β, which subsequently activates β-catenin, resulting in melanogenesis. As expected, fisetin increased the expression of β-catenin, which was subsequently translocated into the nucleus. In the functional assay, FH535, a Wnt/β-catenin inhibitor, significantly inhibited fisetin-mediated melanogenesis in zebrafish larvae. Our data suggested that fisetin inhibits GSK-3β, which activates β-catenin, resulting in melanogenesis through the revitalization of MITF and tyrosinase.

Metal complexes of flavonoids: their synthesis, characterization and enhanced antioxidant and anticancer activities

Flavonoids are polyphenolic compounds of natural origin. They are extensively studied within drug discovery programs due to their wide ranging biological activities such as antimicrobial, antioxidant, antitumor, neuroprotective and cardioprotective properties. The ability of flavonoids to coordinate with metal atoms has provided new leads for drug discovery programs, with better pharmacological activities and clinical profiles than the parent flavonoids. In this review, the enhanced antioxidant and anticancer activities of flavonoid metal complexes versus the parent flavonoids are discussed. Possible mechanisms of action for the metal complexes, such as DNA binding and apoptosis induction, are also presented alongside an overview of the synthesis of the metal complexes, and the different techniques used for their characterization.

Prediction of new targets and mechanisms for quercetin in the treatment of pancreatic cancer, colon cancer, and rectal cancer

Quercetin has been widely found to exhibit anticancer activity with low toxicity and prevalence in foods. Quercetin has been reported to inhibit digestive system cancers including pancreatic cancer (PAAD) and colon cancer (COAD), but rectal cancer (READ) has not been reported. The reported mechanisms and targets are divergent. In this study, new targets and mechanisms were predicted for the influence of quercetin on PAAD, COAD, and READ using bioinformatics methods. The results showed that quercetin may target CD36 and reduce the death rate caused by PAAD by enhancing the cell adhesion, mediating the uptake of fatty acids (FAs), regulating thrombospondin-1, and stimulating the immune response. Quercetin may lower the death rate from READ by targeting SLCO1B1 and producing enhanced effects from use of this compound, inhibiting cell growth, and inducing apoptosis in tumor cells. ACADS, ALDH3B2, UGT2A3, AMH, CDKN2A, FOSL1, CD36, CFL2, CYP3A4, and MAF were identified as targets for quercetin to reduce the death rate caused by COAD. Glutathione metabolism was mainly involved in the effect of quercetin on COAD, including the enhancement of the oxidation of fatty acids, the metabolism of anticancer medications, and the stiffness of cells, and the reduction of chemical carcinogenesis, the level of anti-Müllerian hormone, the proliferation of cancer cells and transcriptional misregulation, and mediation of the activity of glutathione transferases. The combined analyses of three databases can be referred to and used to seek medications and targets that can be applied to other diseases.

Role and Therapeutic Targeting of the PI3K/Akt/mTOR Signaling Pathway in Skin Cancer: A Review of Current Status and Future Trends on Natural and Synthetic Agents Therapy

The mammalian or mechanistic target of rapamycin (mTOR) and associated phosphatidyl-inositiol 3-kinase (PI3K)/protein kinase B (Akt) pathways regulate cell growth, differentiation, migration, and survival, as well as angiogenesis and metabolism. Dysregulation of these pathways is frequently associated with genetic/epigenetic alterations and predicts poor treatment outcomes in a variety of human cancers including cutaneous malignancies like melanoma and non-melanoma skin cancers. Recently, the enhanced understanding of the molecular and genetic basis of skin dysfunction in patients with skin cancers has provided a strong basis for the development of novel therapeutic strategies for these obdurate groups of skin cancers. This review summarizes recent advances in the roles of PI3K/Akt/mTOR and their targets in the development and progression of a broad spectrum of cutaneous cancers and discusses the current progress in preclinical and clinical studies for the development of PI3K/Akt/mTOR targeted therapies with nutraceuticals and synthetic small molecule inhibitors.

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.

Dietary compounds and cutaneous malignant melanoma: recent advances from a biological perspective

Cutaneous malignant melanoma is a heterogeneous disease, being the consequence of specific genetic alterations along several molecular pathways. Despite the increased knowledge about the biology and pathogenesis of melanoma, the incidence has grown markedly worldwide, making it extremely important to develop preventive measures. The beneficial role of correct nutrition and of some natural dietary compounds in preventing malignant melanoma has been widely demonstrated. This led to numerous studies investigating the role of several dietary attitudes, patterns, and supplements in the prevention of melanoma, and ongoing research investigates their impact in the clinical management and outcomes of patients diagnosed with the disease. This article is an overview of recent scientific advances regarding specific dietary compounds and their impact on melanoma development and treatment.

5, 7, 2', 4', 5'-Pentamethoxyflavanone regulates M1/M2 macrophage phenotype and protects the septic mice

Flavonoids have been reported to exert protective effect against many inflammatory diseases, while the underlying cellular mechanisms are still not completely known. In the present study, we explored the anti-inflammation activity of 5, 7, 2', 4', 5'-pentamethoxyflavanone (abbreviated as Pen.), a kind of polymethoxylated flavonoid, both in vitro and in vivo experiments. Pen. was showed no obvious toxicity in macrophages even at high dosage treatment. Our results indicated that Pen. significantly inhibited both mRNA and protein level of proinflammatory cytokines, IL-1β, IL-6, TNF-α and iNOS, which was characteristic expressed on M1 polarized macrophages. These effects of Pen. were further confirmed by diminished expression of CD11c, the M1 macrophage surface marker. Further researches showed that the mechanism was due to that Pen. downregulated the activity of p65, key transcription factor for M1 polarization. On the other hand, Pen. also enhanced M2 polarization with upregulation of anti-inflammatory factors and increase of M2 macrophage surface markers, which lead to the balance of M1 and M2 macrophages. Moreover, in vivo research verified that Pen. treatment alleviated LPS-induced sepsis in mice by increasing survival rate, decreasing inflammatory cytokines and improving lung tissue damage. In summary, our results suggested that Pen. modulated macrophage phenotype via suppressing p65 signal pathway to exert the anti-inflammation activity.

Luteolin 7-Sulfate Attenuates Melanin Synthesis through Inhibition of CREB- and MITF-Mediated Tyrosinase Expression

Antioxidants with antimelanogenic activity are potentially useful for the attenuation of skin hyperpigmentation disorders. In a previous study, luteolin 7-sulfate isolated from Phyllospadix iwatensis Makino, a marine plant, was shown to inhibit cellular melanin synthesis. The aim of the present study was to examine its action mechanism, focusing on the regulation of tyrosinase (TYR) expression in cells. Cell-based assay was undertaken using murine melanoma B16-F10 cells and primary human epidermal melanocytes (HEMs). Luteolin 7-sulfate showed lower toxicity compared to luteolin in B16-F10 cells. At the non-toxic concentration ranges, luteolin 7-sulfate attenuated melanin synthesis, stimulated by α-melanocyte-stimulating hormone or forskolin. Luteolin 7-sulfate attenuated forskolin-induced microphthalmia-associated transcription factor (MITF) and TYR expressions at the mRNA and protein levels in B16-F10 cells. It also attenuated the phosphorylation of cAMP-responsive element binding protein (CREB) stimulated by forskolin. Luteolin 7-sulfate also attenuated melanin synthesis in primary HEMs. This study demonstrates that luteolin 7-sulfate attenuates TYR gene expression through the intervention of a CREB- and MITF-mediated signaling pathway, leading to the decreased melanin synthesis.

Drying the leaves of Perilla frutescens increases their content of anticancer nutraceuticals

A regular intake of plant-derived bioactive agents has gained popularity because of the health benefits. Fresh leafy greens, however, normally have a low concentration of such bioactive agents. In this study, we found that drying markedly affected the accumulation of secondary metabolites and that dried leaves of Perilla frutescens L. (perilla) contained more anticancer flavonoids than fresh leaves. Drying is a major method of food preparation, particularly for plant-based foods, but the quality of the bioactive agents contained in the fresh and dried leaves of perilla has received only scant attention. Quantitative analysis of the concentrations of perillaldehyde, rosmarinic acid, apigenin, luteolin, 4-hydroxyphenyllactic acid, and 4-coumaric acid, some of which are known as nutraceuticals, revealed that the effect of drying significantly increased apigenin (28-fold) and luteolin (86-fold), but decreased rosmarinic acid in all leaf stages. We examined the positive effect on flavonoid levels on perilla leaves and confirmed that, by comparison with fresh perilla leaves, the dried leaves contained greater concentrations of anticancer flavonoids regardless of variety, form, or manner of cultivation. This indicates that drying can significantly increase the level of flavonoids in perilla leaves without a loss of flavor. Therefore, drying is a simple and effective method to improve the concentrations of bioactive agents, which increases the intake of beneficial substances derived from herbs and edible plants. This finding serves as a method for the supply of raw plant materials rich in bioactive agents that are suitable for labeling as edible nutraceuticals.

Chemoprevention agents for melanoma: A path forward into phase 3 clinical trials

Recent progress in the treatment of advanced melanoma has led to unprecedented improvements in overall survival and, as these new melanoma treatments have been developed and deployed in the clinic, much has been learned about the natural history of the disease. Now is the time to apply that knowledge toward the design and clinical evaluation of new chemoprevention agents. Melanoma chemoprevention has the potential to reduce dramatically both the morbidity and the high costs associated with treating patients who have metastatic disease. In this work, scientific and clinical melanoma experts from the national Melanoma Prevention Working Group, composed of National Cancer Trials Network investigators, discuss research aimed at discovering and developing (or repurposing) drugs and natural products for the prevention of melanoma and propose an updated pipeline for translating the most promising agents into the clinic. The mechanism of action, preclinical data, epidemiological evidence, and results from available clinical trials are discussed for each class of compounds. Selected keratinocyte carcinoma chemoprevention studies also are considered, and a rationale for their inclusion is presented. These data are summarized in a table that lists the type and level of evidence available for each class of agents. Also included in the discussion is an assessment of additional research necessary and the likelihood that a given compound may be a suitable candidate for a phase 3 clinical trial within the next 5 years.

Flavonoid Productivity Optimized for Green and Red Forms of Perilla frutescens via Environmental Control Technologies in Plant Factory

Perilla frutescens (Lamiaceae) is a dietary staple in Asia. It is an abundant source of flavonoids that are bioactively beneficial to human health and fitness. The current popularity of plant-based consumption is being driven by the healthful benefits of bioactive nutrition, and the concentration of bioactive agents found in raw plant materials is an important factor in the assessment of food quality. To test the feasibility of promoting flavonoid productivity in perilla plants via environmental treatment, plant factory technology was applied to perilla plant cultivation. Apigenin (AG) and luteolin (LT) are two of the most potent anticarcinogenic flavonoids in perilla, and these are also found in many vegetables and fruits. Quantitative analysis of AG and LT was conducted on plants cultivated under nine environmental forms of treatment imposed by three levels of light intensity (100, 200, and 300 µmol·m−2·s−1) combined with three levels of nutrient-solution concentration (1.0, 2.0, and 3.0 dS·m−1) for hydroculture. The contents of AG in green and red perilla plant were increased by high nutrient-solution levels under the same light intensity. In green perilla, the highest concentration of AG (8.50 µg·g−1) was obtained under treatment of the highest level of nutrient-solution (3.0 dS·m−1) and 200 µmol·m−2·s−1 of light intensity, whereas in red perilla, the highest concentration of AG (6.38 µg·g−1) was achieved from the highest levels of both of these forms of treatment (300 µmol·m−2·s−1 and 3.0 dS·m−1). The increase in AG content per plant between the lowest and the highest levels was recorded by 6.4-fold and 8.6-fold in green and red perilla, respectively. The behavior of LT concentration differed between green and red forms of perilla. LT concentration in red perilla was enhanced under nutrient deficiency (1.0 dS·m−1) and affected by light intensity. Different responses were observed in the accumulations of AG and LT in red and green perilla during treatments, and this phenomenon was discussed in terms of biosynthetic pathways that involve the expressions of phenylpropanoids and anthocyanins. The total yield of flavonoids (AG and LT) was improved with the optimization of those forms of treatment, with the best total yields: 33.9 mg·plant−1 in green Perilla; 10.0 mg·plant−1 in red perilla, and a 4.9-fold and a 5.4-fold increase was recorded in green and red perilla, respectively. This study revealed that flavone biosynthesis and accumulation in perilla plants could be optimized via environmental control technologies, and this approach could be applicable to leafy vegetables with bioactive nutrition to produce a stable industrial supply of high flavonoid content.

Novel Docosahexaenoic Acid Ester of Phloridzin Inhibits Proliferation and Triggers Apoptosis in an In Vitro Model of Skin Cancer

Skin cancer is among the most common cancer types accompanied by rapidly increasing incidence rates, thus making the development of more efficient therapeutic approaches a necessity. Recent studies have revealed the potential role of decosahexaenoic acid ester of phloridzin (PZDHA) in suppressing proliferation of liver, breast, and blood cancer cell lines. In the present study, we investigated the cytotoxic potential of PZDHA in an in vitro model of skin cancer consisting of melanoma (A375), epidermoid carcinoma (A431), and non-tumorigenic (HaCaT) cell lines. Decosahexaenoic acid ester of phloridzin led to increased cytotoxicity in all cell lines as revealed by cell viability assays. However, growth inhibition and induction of both apoptosis and necrosis was more evident in melanoma (A375) and epidermoid carcinoma (A431) cells, whereas non-tumorigenic keratinocytes (HaCaT) appeared to be more resistant as detected by flow cytometry. More specifically, PZDHA-induced cell cycle growth arrest at the G2/M phase in A375 and A431 cells in contrast to HaCaT cells, which were growth arrested at the G0/G1 phase. Elevated intracellular generation of reactive oxygen species ROS was detected in all cell lines. Overall, our findings support the potential of PZDHA as a novel therapeutic means against human skin cancer.

A Newly Authenticated Compound from Traditional Chinese Medicine Decoction Induces Melanogenesis in B16-F10 Cells by Increasing Tyrosinase Activity

Vitiligo is a kind of skin dysfunction on melanogenesis. The highly prevalent, chronic, and distinctive complexion changes on patients have imposed enormous psychic and economic burden on both individuals and society. Traditional Chinese Medicine (TCM) is a kind of precious source on chronic disease treatment, including skin dysfunctional diseases. In our previous study, a new compound named apigenin-7-butylene glucoside has been authenticated and purified from a prescription of Chinese traditional medicine formula which has been used clinically in vitiligo treatment. The aim of this work is to evaluate the effects of this compound on melanogenesis using melanoma cell B16-F10 in vitro. The results showed that apigenin-7-butylene glucoside had almost no cytotoxicity on B16-F10 cells within a lower dose of 5.0 μg ml⁻¹ and enhanced the melanin level to about 41% and tyrosinase activity to 1.32-fold when compared with controls. The compound showed minor cytotoxicity to B16-F10 cells at the higher concentration of 10 μg ml⁻¹ and 50 μg ml⁻¹, the inhibition rate was 8.4% and 11.8%, and the melanin level and tyrosinase activity showed a decreased trend because of the lower cell number at the higher concentrations. The results indicated that apigenin-7-butylene glucoside was safe to B16-F10 cells within a lower concentration, <5.0 μg ml⁻¹. Incubated with 5.0 ug ml⁻¹of apigenin-7-butylene glucoside for 48 hours, the mRNA and protein levels of Tyr, Trp-1, and Trp-2 genes were all increased except Mitf in B16-F10 cells. The stimulation of apigenin-7-butylene glucoside on melanogenesis of B16-F10 cells through Tyr, Trp-1, and Trp-2 pathway highlighted the potential usage of the compound in vitiligo treatment.

Characterization of sulfuretin as a depigmenting agent

Sulfuretin is a major flavonoid found in Rhus verniciflua and carries anti-oxidative and anti-inflammatory properties, but its potential use in the control of skin pigmentation is unknown. The purpose of the present study was to elucidate sulfuretin as a new active compound inhibiting melanogenesis and the underlying mechanism. The effects of sulfuretin on melanin production, tyrosinase activity, cAMP level, and MITF expression were examined in murine melanoma B16 cells challenged with forskolin or α-MSH. The inhibitory effect of sulfuretin on melanogenesis was further validated on neonatal human melanocytes. When tested in melanoma B16 cells treated with forskolin or α-MSH, sulfuretin inhibited the cellular melanogenesis. Sulfuretin also showed direct inhibitory effect on tyrosinase activity in vitro. In human primary melanocytes, the inhibitory effect of sulfuretin on melanin synthesis was also confirmed. Our current results support the depigmenting effect of sulfuretin and suggest a clinical strategy for using sulfuretin in the topical treatment of hyperpigmentation disorders.

Hydroalcoholic extract of Spartium junceum L. flowers inhibits growth and melanogenesis in B16-F10 cells by inducing senescence

BACKGROUND

Ultraviolet light exposure generates, in human tissues, radical species, which represent the main cause of photo-aging, DNA damage and skin cancer onset. On the other hand, Mediterranean plants, being continuously subjected to high solar radiation levels, are naturally adapted to take on this type of abiotic stress, thanks to the production of antioxidant secondary metabolites. For these reasons, several plant extracts were documented to be excellent antineoplastic drugs.

PURPOSE

We investigated the potential antitumor activity of the flower extract obtained by Spartium junceum L., a Mediterranean shrub, correlating it with the plant metabolic profile.

STUDY DESIGN

After selecting the best extraction method to obtain as more secondary metabolites as possible from S. junceum flowers, we characterized the extract metabolic content. Then, by in vitro analyses, the antioxidant profile and the antineoplastic activity on B16-F10 murine melanoma cell of our extract were investigated.

METHODS

Spectrophotometric assays, HPLC-DAD and GC-MS analyses provided us information about flower extract composition and antioxidant activity. MTT assay and Trypan Blue exclusion test were performed to assess the extract toxicity and the viability, after treatments, of B16-F10 cancer cells and of C2C12 murine myoblasts. In vitro experiments (i.e. cytofluorimetry, protein analysis and qPCR) allowed us to analyze the effect of the plant extract on B16-F10 cell redox state, melanogenesis and cell cycle. Senescence induction was investigated by using a specific kit.

RESULTS

We observed that the hydroalcoholic extract of S. junceum flowers (HFE) strongly inhibited B16-F10 murine melanoma cell proliferation, while just a feeble effect was observed on C2C12 murine myoblasts. Moreover, we found that HFE exerted a pro-oxidant activity on melanoma cells, inhibited melanogenesis and caused cell cycle arrest in G2/M phase, inducing senescence. These anti-cancer properties of HFE could be related to the rich metabolic profile of the extract that we characterized by HPLC-DAD and GC-MS analyses.

CONCLUSION

This evidence suggests that S. junceum phytocomplex can be used as a selective, nontoxic, economic and easily available anticancer drug.

Fisetin alleviates oxidative stress after traumatic brain injury via the Nrf2-ARE pathway

Fisetin, a natural flavonoid, has neuroprotection properties in many brain injury models. However, its role in traumatic brain injury (TBI) has not been fully explained. In the present study, we aimed to explore the neuroprotective effects of fisetin in a mouse model of TBI. We found that fisetin improved neurological function, reduced cerebral edema, attenuated brain lesion and ameliorated blood-brain barrier (BBB) disruption after TBI. Moreover, the up-regulation of malondialdehyde (MDA) and the activity of glutathione peroxidase (GPx) were reversed by fisetin treatment. Furthermore, administration of fisetin suppressed neuron cell death and apoptosis, increased the expression of B-cell lymphoma 2 (Bcl-2), while decreased the expression of Bcl-2-associated X protein (Bax) and caspase-3 after TBI. In addition, fisetin activated the nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway following TBI. However, fisetin only failed to suppress oxidative stress in Nrf2^-/- mice. In conclusion, our data provided the first evidence that fisetin played a critical role in neuroprotection after TBI partly through the activation of the Nrf2-ARE pathway.

Apigenin's anticancer properties and molecular mechanisms of action: Recent advances and future prospectives

Cancer is a major health concern and leading burden on economy worldwide. An increasing effort is devoted to isolation and development of plant-derived dietary components as effective chemo-preventive products. Phytochemical compounds from natural resources such as fruits and vegetables are responsible for decreasing the risk of certain cancers among the consuming populations. Apigenin, a flavonoid phytochemical found in many kinds of fruits and vegetables, has been shown to exert significant biological effects, such as anti-oxidant, anti-inflammatory and most particularly anti-neoplastic properties. This review is intended to summarize the most recent advances in the anti-proliferative and chemo-preventive effects of apigenin in different cancer models. Analysis of the data from the studied cancer models has revealed that apigenin exerts its anti-proliferative effects through multiple and complex pathways. This guided us to discover some controversial results about the exact role of certain molecular pathways such as autophagy in the anticancer effects of apigenin. Further, there were cumulative positive evidences supporting the involvement of certain pathways such as apoptosis, ROS and DNA damage and repair. Apigenin possesses a high potential to be used as a chemosensitizing agent through the up-regulation of DR5 pathway. According to these preclinical findings we recommend that further robust unbiased studies should consider the possible interactions between different molecular pathways.

Phytochemical-induced reactive oxygen species and endoplasmic reticulum stress-mediated apoptosis and differentiation in malignant melanoma cells

BACKGROUND

Phytochemicals are derived from plants, vegetables and daily products and exert chemopreventive effects. Malignant melanoma is highly metastatic, and melanoma patients can develop chemotherapeutic resistance against conventional melanoma therapies.

METHODS

In the present study, we investigated the anti-cancer effect of the phytochemicals kaempferol (Kaem), genistein (Gen), and 3'3-diindolylmethane (DIM) on melanoma cell viability. We also evaluated the altered expression of cell cycle-related genes. We verified the production of intracellular reactive oxygen species (ROS) and endoplasmic reticulum (ER) stress at both the protein and cellular level using a western blot, TUNEL assay, and Dihydrodichlorofluorescein diacetate (DCF-DA) assay.

RESULTS

Treatment of A375SM melanoma cells with phytochemicals resulted in inhibition of cell growth. Treatment with phytochemicals increased the gene expression of p21 and decreased the gene expression of cyclin E and/or cyclin B. The three phytochemicals activated the ROS-p38-p53 apoptotic pathway by increasing the level of phosphorylated p38 MAPK and p53, and they activated the ER stress-mediated apoptotic pathway by increasing the level of phosphorylated eIF2α and C/EBP homologous protein (CHOP). Both the ROS-p38-p53 and ER stress-mediated pathway induced the mitochondrial apoptotic pathway by attenuating Bcl-2 expression and upregulating BAX. Detection of morphological changes demonstrated that Kaem and Gen can induce differentiation in A375SM cell line.

CONCLUSION

These results indicate that phytochemicals are potentially useful in treatments for melanoma due to their ability to inhibit melanoma cell growth and division via the ROS and ER stress pathway.

Anti-melanogenesis and anti-tyrosinase properties of Pistacia atlantica subsp. mutica extracts on B16F10 murine melanoma cells

Pistacia atlantica (P. atlantica) subsp. mutica has been used in traditional medicine and is famous for its medicinal properties. The aim of this study was to evaluate the effect of methanol (MeOH), n-hexane, dichloromethane (CH₂Cl₂), n-butanol (BuOH), ethyl acetate (EtOAc), water extracts and essential oil of P. atlantica subsp. mutica on melanin synthesis and oxidative stress in B16F10 melanoma cell line. The B16F10 cells viability after treatment with increasing concentrations of different extracts of the plant (0.2-200 μg/mL) was measured using resazurin. Essential oil composition was identified by gas-chromatography-mass spectrometry (GC-MS) analysis and inhibitory effect on synthesis of melanin, mushroom tyrosinase activity, cellular tyrosinase, and oxidative stress were evaluated by the colorimetric and fluorometric methods. The data showed extracts at concentrations 0.2-200 μg/mL, did not show significant toxicity on melanoma cells but concentrations of 200 μg/mL of essential oil had cytotoxic effect. Pistacia atlantica subsp. mutica could inhibit the mushroom tyrosinase activity. Also the amount of melanin in B16F10 cells declined. In addition, the ability of P. atlantica subsp. mutica extracts in decreasing the amount of reactive oxygen species in melanoma cells revealed remarkable antioxidant activity. In addition, all concentrations of essential oil had no significant effect in this study. The melanogenesis inhibitory and antioxidant effects of P. atlantica subsp. mutica on B16F10 cells may suggest the potential whitening activity of the plant for using in dermatological skin care products and for prevention of skin aging in cosmetic industry.

Vacuolar H+-ATPases (V-ATPases) as therapeutic targets: a brief review and recent developments

Vacuolar H⁺-ATPases (V-ATPases) are multi-subunit enzymes that play housekeeping roles in eukaryotic cells by acidifying lysosomes, late endosomes, Golgi, and other membrane-bounded compartments. Beyond that, V-ATPases have specialized functions in certain cell types linked to diseases including osteoporosis and cancer. Efforts to identify strategies to develop inhibitors selective for V-ATPases that are involved in disease progression have been ongoing for more than two decades, but so far have not yielded a therapeutic agent that has been translated to the clinic. Recent basic science studies have identified unexpected roles for V-ATPases in nutrient and energy sensing, and renin/angiotensin signaling, which offer additional incentives for considering V-ATPases as therapeutic targets. This article briefly reviews efforts to utilize inhibitors of V-ATPases as drugs. Primary focus is on recent "rational" efforts to identify small molecule inhibitors of the V-ATPases that are selectively expressed in osteoclasts and cancer cells. Enoxacin and bis-enoxacin are two molecules that emerged from these efforts. These molecules block a binding interaction between V-ATPases and microfilaments that occurs in osteoclasts, but not most other cell types, which relates to the specialized function of V-ATPases in bone resorption. Enoxacin and bis-enoxacin have proven useful in the treatment of bone diseases and cancer in animal models and display therapeutic effects that are different, and perhaps better, than current drugs. These results provide evidence that agents targeting subsets of V-ATPases may prove useful in the clinic.

Characterization of tyrosinase inhibitory constituents from the aerial parts of Humulus japonicus using LC-MS/MS coupled online assay

In the screening of natural products for the development as cosmetic ingredients, the EtOAc-soluble fraction of Humulus japonicus showed tyrosinase inhibitory activity. HPLC-MS/MS coupled online tyrosinase assay of EtOAc-soluble fraction of H. japonicus characterized the twenty-eight constituents including two unknown ones and their tyrosinase inhibitory activity. Fractionation of H. japonicus using various chromatographic techniques yielded thirty-eight compounds. The chemical structures of isolated compounds were identified by spectroscopic analysis. As characterized by HPLC-MS/MS analysis, we isolated twenty-four predicted compounds and further identified two unknown ones, named humulusides A (1) and B (2). Additional ten compounds were also identified by purification. Tyrosinase inhibitory activity of isolated compounds were evaluated, which was closely correlated with the results from HPLC-MS/MS coupled online tyrosinase assay. Consistent with predicted data, two major compounds, trans-N-coumaroyltyramine (14) and cis-N-coumaroyltyramine (15) showed tyrosinase inhibition with IC₅₀ values of 40.6 and 36.4 μM. Taken together, H. japonicus is suggested as whitening ingredient in cosmetic products. In addition, HPLC-MS/MS coupled tyrosinase assay is powerful tool for predicting active compounds with short time and limited amounts, although identification of new compounds and verification of predicted data are also needs to be demonstrated by further experiment.

Hypopigmenting Effects of Brown Algae-Derived Phytochemicals: A Review on Molecular Mechanisms

There is a rapid increase in the demand for natural hypopigmenting agents from marine sources for cosmeceutical and pharmaceutical applications. Currently, marine macroalgae are considered as a safe and effective source of diverse bioactive compounds. Many research groups are exploring marine macroalgae to discover and characterize novel compounds for cosmeceutical, nutraceutical, and pharmaceutical applications. Many types of bioactive secondary metabolites from marine algae, including phlorotannins, sulfated polysaccharides, carotenoids, and meroterpenoids, have already been documented for their potential applications in the pharmaceutical industry. Among these metabolites, phlorotannins from brown algae have been widely screened for their pharmaceutical and hypopigmenting effects. Unfortunately, the majority of these articles did not have detailed investigations on molecular targets, which is critical to fulfilling the criteria for their cosmeceutical and pharmaceutical use. Very recently, a few meroterpenoids have been discovered from Sargassum sp., with the examination of their anti-melanogenic properties and mechanisms. Despite the scarcity of in vivo and clinical investigations of molecular mechanistic events of marine algae-derived hypopigmenting agents, identifying the therapeutic targets and their validation in humans has been a major challenge for future studies. In this review, we focused on available data representing molecular mechanisms underlying hypopigmenting properties of potential marine brown alga-derived compounds.

Apigenin inhibits renal cell carcinoma cell proliferation

Apigenin, a natural flavonoid found in vegetables and fruits, has antitumor activity in several cancer types. The present study evaluated the effects and mechanism of action of apigenin in renal cell carcinoma (RCC) cells. We found that apigenin suppressed ACHN, 786-0, and Caki-1 RCC cell proliferation in a dose- and time-dependent manner. A comet assay suggested that apigenin caused DNA damage in ACHN cells, especially at higher doses, and induced G2/M phase cell cycle arrest through ATM signal modulation. Small interfering RNA (siRNA)-mediated p53 knockdown showed that apigenin-induced apoptosis was likely p53 dependent. Apigenin anti-proliferative effects were confirmed in an ACHN cell xenograft mouse model. Apigenin treatment reduced tumor growth and volume in vivo, and immunohistochemical staining revealed lower Ki-67 indices in tumors derived from apigenin-treated mice. These findings suggest that apigenin exposure induces DNA damage, G2/M phase cell cycle arrest, p53 accumulation and apoptosis, which collectively suppress ACHN RCC cell proliferation in vitro and in vivo. Given its antitumor effects and low in vivo toxicity, apigenin is a highly promising agent for treatment of RCC.

Antimelanogenic Effect of Urolithin A and Urolithin B, the Colonic Metabolites of Ellagic Acid, in B16 Melanoma Cells

Antimelanogenic agents from natural sources have been widely investigated. Urolithin A (UA) and B (UB), the main gut microflora metabolites of dietary ellagic acid derivatives, have various bioactivities such as anti-inflammatory and antiaging effects. In this study, the metabolites were found to possess depigmentation efficacy by suppressing tyrosinase activity. Both UA and UB could attenuate melanogenesis in B16 melanoma cells to 55.1 ± 3.8 and 76.4 ± 17.4% of control at noncytotoxic dosage, 10 μM, respectively. UA showed comparable efficacy to positive control, 5 μM of kojic acid treatment (51.2 ± 7.8). RT-PCR results revealed that UA and UB inhibited melanin formation by affecting the catalytic activity of tyrosinase rather than its mRNA expression. Kinetics for UA and UB on tyrosinase activity revealed that their inhibition behavior toward cellular tyrosinase involved competitive inhibition. UA and UB may be potent tyrosinase inhibitors and they possess significant antimelanogenesis ability as novel skin-whitening ingredients.

Scutellaria baicalensis Georgi induces caspase-dependent apoptosis via mitogen activated protein kinase activation and the generation of reactive oxygen species signaling pathways in MCF-7 breast cancer cells

Scutellaria baicalensis Georgi extract (SBGE) is used in traditional herbal medicine and has also been used clinically to ameliorate the symptoms of various inflammatory diseases and cancer. In women, breast cancer is one of the most common diseases and numerous women succumb to it. The present study was undertaken to investigate the mechanism responsible for the SBGE‑induced apoptosis of MCF‑7 human breast cancer cells. SBGE was administered to cells at concentrations between 100 and 500 mg/ml, and cell viabilities were identified using an MTT assay. B‑cell lymphoma 2 (Bcl-2) and Bcl-2 X‑associated protein (Bax) family members were identified by western blotting, and the mRNA expression levels of the pro‑apoptosis genes Fas, Fas ligand (FasL) and tumor necrosis factor (TNF)‑α were assessed by reverse transcription‑polymerase chain reaction. It was identified that SBGE treatment for 24 h inhibited MCF‑7 proliferation and increased the sub‑G1 phase ratio. SBGE suppressed mitochondrial membrane potentials and SBGE‑induced apoptotic cell death was identified to be associated with downregulation of Bcl‑2, but upregulation of Bax. SBGE‑activated caspases 3 and 9, and increased reactive oxygen species generation. However, SBGE had no effect on the expression levels of Fas, FasL or TNF‑α. Furthermore, mitogen‑activated protein kinase and C‑Jun N‑terminal kinase inhibitors inhibited SBGE‑induced cell death. These results suggested that SBGE be considered as an agent for the treatment of breast cancer.

Effects of anthocyanins on the prevention and treatment of cancer

Anthocyanins are a class of water-soluble flavonoids, which show a range of pharmacological effects, such as prevention of cardiovascular disease, obesity control and antitumour activity. Their potential antitumour effects are reported to be based on a wide variety of biological activities including antioxidant; anti-inflammation; anti-mutagenesis; induction of differentiation; inhibiting proliferation by modulating signal transduction pathways, inducing cell cycle arrest and stimulating apoptosis or autophagy of cancer cells; anti-invasion; anti-metastasis; reversing drug resistance of cancer cells and increasing their sensitivity to chemotherapy. In this review, the latest progress on the anticancer activities of anthocyanins and the underlying molecular mechanisms is summarized using data from basic research in vitro and in vivo, from clinical trials and taking into account theory and practice.

LINKED ARTICLES

This article is part of a themed section on Principles of Pharmacological Research of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.11/issuetoc.

Hormonally active phytochemicals and vertebrate evolution

Living plants produce a diversity of chemicals that share structural and functional properties with vertebrate hormones. Wildlife species interact with these chemicals either through consumption of plant materials or aquatic exposure. Accumulating evidence shows that exposure to these hormonally active phytochemicals (HAPs) often has consequences for behavior, physiology, and fecundity. These fitness effects suggest there is potential for an evolutionary response by vertebrates to HAPs. Here, we explore the toxicological HAP-vertebrate relationship in an evolutionary framework and discuss the potential for vertebrates to adapt to or even co-opt the effects of plant-derived chemicals that influence fitness. We lay out several hypotheses about HAPs and provide a path forward to test whether plant-derived chemicals influence vertebrate reproduction and evolution. Studies of phytochemicals with direct impacts on vertebrate reproduction provide an obvious and compelling system for studying evolutionary toxicology. Furthermore, an understanding of whether animal populations evolve in response to HAPs could provide insightful context for the study of rapid evolution and how animals cope with chemical agents in the environment.

Baicalein Inhibits the Migration and Invasion of B16F10 Mouse Melanoma Cells through Inactivation of the PI3K/Akt Signaling Pathway

Baicalein, a natural flavonoid obtained from the rhizome of Scutellaria baicalensis Georgi, has been reported to have anticancer activities in several human cancer cell lines. However, its antimetastatic effects and associated mechanisms in melanoma cells have not been extensively studied. The current study examined the effects of baicalein on cell motility and anti-invasive activity using mouse melanoma B16F10 cells. Within the noncytotoxic concentration range, baicalein significantly inhibited the cell motility and invasiveness of B16F10 cells in a concentration-dependent manner. Baicalein also reduced the activity and expression of matrix metalloproteinase (MMP)-2 and -9; however, the levels of tissue inhibitor of metalloproteinase-1 and -2 were concomitantly increased. The inhibitory effects of baicalein on cell motility and invasiveness were found to be associated with its tightening of tight junction (TJ), which was demonstrated by an increase in transepithelial electrical resistance and downregulation of the claudin family of proteins. Additionally, treatment with baicalein markedly reduced the expression levels of lipopolysaccharide-induced phosphorylated Akt and the invasive activity in B16F10 cells. Taken together, these results suggest that baicalein inhibits B16F10 melanoma cell migration and invasion by reducing the expression of MMPs and tightening TJ through the suppression of claudin expression, possibly in association with a suppression of the phosphoinositide 3-kinase/Akt signaling pathway.

Apigenin in the regulation of cholesterol metabolism and protection of blood vessels

Hyperlipidemia is a major independent risk factor for atherosclerosis. Seeking natural compounds in medicinal plants capable of reducing blood fat and studying their mechanisms of action has been the focus of research in recent years. The aim of the present study was to analyze the mechanisms of apigenin in regulating cholesterol metabolism and protecting blood vessels, and to provide a theoretical basis for the clinical application of apigenin. The mouse model of hyperlipidemia was established to verify the efficacy of apigenin in improving hyperlipidemia and to observe the mechanism of action of apigenin in reducing cholesterol content. In vitro cell experiments were conducted to evaluate the role of apigenin in mediating reverse cholesterol transport. Additionally, H₂O₂-injured human umbilical venous endothelial cells (EA.hy926 cells) were used for further study on the roles of apigenin in resisting oxidization and protecting vascular endothelial cells. Apigenin significantly regulated blood fat, reduced animal weight, and reduced total cholesterol (P=0.024), triglyceride (P=0.031) and low-density lipoprotein cholesterol (P=0.014) in the serum of the high-fat diet mice. Apigenin improved the blood lipid metabolism of the hyper-lipidemia model mice. Body weight and serum cholesterol content increased abnormally (P=0.003) as a consequence of high-fat diet. Apigenin increased the activity of superoxide dismutase in EA.hy926 cells (P=0.043) and increased the amount of nitric oxide secreted by the cells (P=0.038). Apigenin also inhibited the proliferation of vascular smooth muscle cells in a dose-dependent manner (P=0.036). In conclusion, apigenin can regulate cholesterol metabolism in vivo and plays a role in reducing the level of blood fat by promoting cholesterol absorption and conversion, and accelerating reverse cholesterol transport. Apigenin also has a role in resisting oxidization and protecting blood vessels.

Apigenin alleviates STZ-induced diabetic cardiomyopathy

Apigenin is an important component of fruits and vegetables in human daily diets. Several cellular and animal models have been performed to demonstrate its anti-oxidant and anti-inflammatory bioactivities. However, the cardioprotective effects of apigenin in diabetic cardiomyopathy (DCM) remain unclear. In this study, we intended to explore the roles of apigenin in cardiac remodeling of DCM. Male C57BL/6 J mice were treated with streptozotocin (STZ, 50 mg/kg) for 5 consecutive days to induce DCM. The echocardiography and catheter-based measurements of hemodynamic parameters were performed to evaluate the cardiac function. Paraffin slices of harvested hearts were prepared for histological pathological analysis and TUNEL assay. Oxidative assay kits were used to detect Glutathione Peroxidase (GPx), Lipid Peroxidation Malondialdehyde (MDA), and Superoxide Dismutase (SOD). Western blot and real-time PCR were used for accessing the expressions of protein and mRNA. Diabetes mellitus exacerbated the cardiac dysfunction, fibrosis, and overaccumulation of 4-hydroxynonenal accompanying with down-regulation of Bcl2, GPx, and SOD, up-regulation of MDA, cleaved caspase3, and pro-apoptotic protein Bax, and contribution to the translocation of NF-κB. All these pathological changes could be effectively blunted by treatment of apigenin in vivo. Finally, H9c2 treated with high glucose or apigenin was used for further investigation of these effects in vitro; what is more, we also compared the effects between apigenin and Resveratrol in in vitro experiments. Our experiments have demonstrated that apigenin may be a potential drug for diabetic patients suffering from DCM.

SERS-Based Flavonoid Detection Using Ethylenediamine-β-Cyclodextrin as a Capturing Ligand

Ethylenediamine-modified β-cyclodextrin (Et-β-CD) was immobilized on aggregated silver nanoparticle (NP)-embedded silica NPs (SiO₂@Ag@Et-β-CD NPs) for the effective detection of flavonoids. Silica NPs were used as the template for embedding silver NPs to create hot spots and enhance surface-enhanced Raman scattering (SERS) signals. Et-β-CD was immobilized on Ag NPs to capture flavonoids via host-guest inclusion complex formation, as indicated by enhanced ultraviolet absorption spectra. The resulting SiO₂@Ag@Et-β-CD NPs were used as the SERS substrate for detecting flavonoids, such as hesperetin, naringenin, quercetin, and luteolin. In particular, luteolin was detected more strongly in the linear range 10-7 to 10-3 M than various organic molecules, namely ethylene glycol, β-estradiol, isopropyl alcohol, naphthalene, and toluene. In addition, the SERS signal for luteolin captured by the SiO₂@Ag@Et-β-CD NPs remained even after repeated washing. These results indicated that the SiO₂@Ag@Et-β-CD NPs can be used as a rapid, sensitive, and selective sensor for flavonoids.

Inhibitory effect of a genistein derivative on pigmentation of guinea pig skin

This study demonstrated the mechanisms of the inhibitory effects of GD against UVB-induced pigmentation in guinea pig skin.

Estrogen Receptor β in Melanoma: From Molecular Insights to Potential Clinical Utility

Cutaneous melanoma is an aggressive tumor; its incidence has been reported to increase fast in the past decades. Melanoma is a heterogeneous tumor, with most patients harboring mutations in the BRAF or NRAS oncogenes, leading to the overactivation of the MAPK/ERK and PI3K/Akt pathways. The current therapeutic approaches are based on therapies targeting mutated BRAF and the downstream pathway, and on monoclonal antibodies against the immune checkpoint blockade. However, treatment resistance and side effects are common events of these therapeutic strategies. Increasing evidence supports that melanoma is a hormone-related cancer. Melanoma incidence is higher in males than in females, and females have a significant survival advantage over men. Estrogens exert their effects through estrogen receptors (ERα and ERβ) that affect cancer growth in an opposite way: ERα is associated with a proliferative action and ERβ with an anticancer effect. ERβ is the predominant ER in melanoma, and its expression decreases in melanoma progression, supporting its role as a tumor suppressor. Thus, ERβ is now considered as an effective molecular target for melanoma treatment. 17β-estradiol was reported to inhibit melanoma cells proliferation; however, clinical trials did not provide the expected survival benefits. In vitro studies demonstrate that ERβ ligands inhibit the proliferation of melanoma cells harboring the NRAS (but not the BRAF) mutation, suggesting that ERβ activation might impair melanoma development through the inhibition of the PI3K/Akt pathway. These data suggest that ERβ agonists might be considered as an effective treatment strategy, in combination with MAPK inhibitors, for NRAS mutant melanomas. In an era of personalized medicine, pretreatment evaluation of the expression of ER isoforms together with the concurrent oncogenic mutations should be considered before selecting the most appropriate therapeutic intervention. Natural compounds that specifically bind to ERβ have been identified. These phytoestrogens decrease the proliferation of melanoma cells. Importantly, these effects are unrelated to the oncogenic mutations of melanomas, suggesting that, in addition to their ERβ activating function, these compounds might impair melanoma development through additional mechanisms. A better identification of the role of ERβ in melanoma development will help increase the therapeutic options for this aggressive pathology.