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

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

Flavonoid Glycosides from Ziziphus jujuba var. inermis (Bunge) Rehder Seeds Inhibit α-Melanocyte-Stimulating Hormone-Mediated Melanogenesis.

Ziziphus jujuba extracts possess a broad spectrum of biological activities, such as antioxidant and anticancer activities in melanoma cancers. Nevertheless, the compounds contain high antioxidant capacities and anticancer activities in melanoma cells, shown to be effective in hyperpigmentation disorders, but whether flavonoid glycosides from Z. jujuba regulate anti-melanogenesis remains unclear. In this study, we evaluated the anti-melanogenic activity of five flavonoid glycosides from Z. jujuba var. inermis (Bunge) Rehder seeds, including jujuboside A (JUA), jujuboside B (JUB), epiceanothic acid (EPA), betulin (BTL), and 6'''-feruloylspinosin (FRS), in B16F10 melanoma cells and zebrafish larvae. According to our results, JUB, EPA, and FRS potently inhibited α-melanocyte-stimulating hormone (α-MSH)-induced melanogenesis and prevented hyperpigmentation in zebrafish larvae. In particular, under α-MSH-stimulated conditions, FRS most significantly inhibited α-MSH-induced intracellular and extracellular melanin content in B16F10 melanoma cells. Additionally, JUB, EPS, and FRS remarkably downregulated melanogenesis in α-MSH-treated zebrafish larvae, with no significant change in heart rate. Neither JUA nor BTA were effective in downregulating melanogenesis in B16F10 melanoma cells and zebrafish larvae. Furthermore, JUB, EPA, and FRS directly inhibited in vitro mushroom tyrosinase enzyme activity. JUB, EPA, and FRS also downregulated cyclic adenosine monophosphate (cAMP) levels and the phosphorylation of cAMP-response element-binding protein (CREB), and subsequent microphthalmia transcription factor (MITF) and tyrosinase expression. In conclusion, this study demonstrated that JUB, EPA, and FRS isolated from Z. jujuba var. inermis (Bunge) Rehder seeds exhibit potent anti-melanogenic properties by inhibition of the cAMP-CERB-MITF axis and consequent tyrosinase activity.

A Basic Domain-Derived Tripeptide Inhibits MITF Activity by Reducing its Binding to the Promoter of Target Genes.

The keratinocytes in UV-irradiated skin produce and secrete α-melanocyte-stimulating hormone. α-Melanocyte-stimulating hormone upregulates the expression of MITF in melanocytes through the cAMP‒protein kinase A‒CREB signaling pathway. Thereafter, MITF induces the expression of melanogenic genes, including the tyrosinase gene TYR and TYRP-1 and TYRP-2 genes, which leads to the synthesis and accumulation of melanin. In this study, we examined whether MITF basic region-derived tripeptides can bind to the DNA-binding domain of MITF and inhibit MITF-induced melanogenesis through the inhibition of MITF‒DNA binding. MITF-KGR, a representative MITF-derived tripeptide, suppressed the transcriptional activity of MITF by disrupting its binding to the promoter region of the target genes, which resulted in the inhibition of skin epidermis thickness and melanin synthesis in vivo and in vitro. Our results indicate that MITF-KGR exerts an inhibitory effect on melanogenesis by targeting MITF.

The anti-melanogenic effects of ellagic acid through induction of autophagy in melanocytes and suppression of UVA-activated α-MSH pathways via Nrf2 activation in keratinocytes.

Ellagic acid (EA) is a natural phenol antioxidant in different fruits, vegetables, and nuts. As a copper iron chelator from the tyrosinase enzyme's active site, EA was reported to inhibit melanogenesis in melanocytes. Here, we demonstrated the anti-melanogenic mechanisms of EA through autophagy induction in melanoma B16F10 cells and the role of Nrf2 and UVA (3 J/cm2)-activated α-melanocyte stimulating hormone (α-MSH) pathways in keratinocyte HaCaT cells. In vitro data showed that EA suppressed the tyrosinase activity and melanogenesis by suppressing cAMP-mediated CREB and MITF signaling mechanisms in α-MSH-stimulated B16F10 cells. ERK, JNK, and AKT pathways were involved in this EA-regulated MITF downregulation. Notably, EA induced autophagy in B16F10 cells was evidenced from increased LC3-II accumulation, p62/SQSTM1 activation, ATG4B downregulation, acidic vesicular organelle (AVO) formation, PI3K/AKT/mTOR inhibition, and Beclin-1/Bcl-2 dysregulation. Interestingly, 3-MA (an autophagy inhibitor) pretreatment or LC3 silencing (siRNA transfection) of B16F10 cells significantly reduced EA-induced anti-melanogenic activity. Besides this, in UVA-irradiated keratinocyte HaCaT cells, EA suppressed ROS production and α-MSH generation. Moreover, EA mediated the activation and nuclear translocation of Nrf2, leading to antioxidant γ-GCLC, HO-1, and NQO-1 protein expression in HaCaT cells. However, Nrf2 knockdown has significantly impaired this effect, and there was an uncontrolled ROS generation following UVA irradiation. JNK, PKC, and ROS pathways were involved in the activation of Nrf2 in HaCaT cells. In vivo experiments using the zebrafish model confirmed that EA inhibited tyrosinase activity and endogenous pigmentation. In conclusion, ellagic acid is an effective skin-whitening agent and might be used as a topical applicant.

Schisandrin B inhibits α-melanocyte-stimulating hormone-induced melanogenesis in B16F10 cells via downregulation of MAPK and CREB signaling pathways.

Schisandrin B (Sch B), a lignan compound in Schisandra, possesses antioxidant, anti-inflammatory, and antiobesity activities. The effect of Sch B on melanogenesis and molecular mechanisms are still unknown. Therefore, we aimed to investigate the antimelanogenic effects of Sch B on α-melanocyte-stimulating hormone-induced B16F10 cells and elucidate the underlying molecular mechanisms. We found that Sch B significantly suppressed melanin content and mushroom tyrosinase (TYR) activity. Sch B treatment decreased the expression of TYR, melanocyte-inducing transcription factor (MITF), tyrosinase-related protein (TRP) 1, and TRP2. Moreover, Sch B modulated the phosphorylation of p38, extracellular-regulated protein kinase, c-Jun N-terminal kinase, and cAMP-response element binding protein (CREB), implying that these pathways may be involved in suppressing melanogenesis. Furthermore, we found that Sch B decreased melanogenesis by downregulating MITF and melanogenic enzymes via MAPK and CREB pathways. Overall, these findings indicate that Sch B has the potential use in whitening.

Diphlorethohydroxycarmalol inhibits melanogenesis via protein kinase A/cAMP response element-binding protein and extracellular signal-regulated kinase-mediated microphthalmia-associated transcription factor downregulation in α-melanocyte stimulating hormone-stimulated B16F10 melanoma cells and zebrafish.

Diphlorethohydroxycarmalol (DPHC) is a marine polyphenolic compound derived from brown alga Ishige okamurae. A previously study has suggested that DPHC possesses strong mushroom tyrosinase inhibitory activity. However, the anti-melanogenesis effect of DPHC has not been reported at cellular level. The objective of the present study was to clarify the melanogenesis inhibitory effect of DPHC and its molecular mechanisms in murine melanoma cells (B16F10) and zebrafish model. DPHC significantly inhibited tyrosinase activity and melanin content dose-dependently in α-melanocyte stimulating hormone (α-MSH)-stimulated B16F10 cells. This polyphenolic compound also suppressed the expression of phosphorylation of cAMP response element-binding protein (CREB) by attenuating phosphorylation of cAMP-dependent protein kinase A, resulting in decreased MITF expression levels. Furthermore, DPHC downregulated MITF protein expression levels by promoting the phosphorylation of extracellular signal-regulated kinase. It also inhibited tyrosinase, tyrosinase-related protein 1 (TRP-1), and TRP-2 in α-MSH stimulated B16F10 cells. In in vivo studies using zebrafish, DPHC also markedly inhibited melanin synthesis in a dose-dependent manner. These results demonstrate that DPHC can effectively inhibit melanogenesis in melanoma cells in vitro and in zebrafish in vivo, suggesting that DPHC could be applied in fields of pharmaceutical and cosmeceuticals as a skin-whitening agent. Significance of study: The present study showed for the first time that DPHC could inhibit a-MSH-stimulated melanogenesis via PKA/CREB and ERK pathway in melanoma cells. It also could inhibit pigmentation in vivo in a zebrafish model. This evidence suggests that DPHC has potential as a skin whitening agent. Taken together, DPHC could be considered as a novel anti-melanogenic agent to be applied in cosmetic, food, and medical industry.

Seven traditional Chinese herbal extracts fermented by Lactobacillus rhamnosus provide anti-pigmentation effects by regulating the CREB/MITF/tyrosinase pathway.

Skin pigmentation is resulted from several processes, such as melanin synthesis transportation and abnormal melanin accumulation in keratinocytes. Various studies have suggested that seven traditional Chinese herbal extracts from Atractylodes macrocephala, Paeonia lactiflora, Bletilla striata, Poria cocos, Dictamnus dasycarpus, Ampelopsis japonica and Tribulus terrestris (which we collectively named ChiBai), show several protective effects toward skin-related diseases. Lactobacillus rhamnosus, a lactic acid bacterium, has been reported to treat skin inflammation and atopic dermatitis. In this study, the broth produced by the cofermentation of ChiBai with Lactobacillus rhamnosus was studied for its effects on skin pigmentation through in vitro and in vitro experiments. In the in vitro experiments, we found that the fermented broth of ChiBai (FB-ChiBai) suppressed alpha-melanocyte stimulating hormone (α-MSH)-induced melanogenesis in B16F0 murine melanoma cells without any cytotoxicity at a concentration of 0.5%. FB-ChiBai significantly attenuated melanin production, tyrosinase activities and melanogenesis-related signaling pathways. Treatment with FB-ChiBai also reduced the nuclear translocation and promoter binding activities of MITF. In the in vivo experiments, FB-ChiBai was topically applied to the dorsal skin of C57BL/6J nude mice and concurrently irradiated with UVB, three times a week for 8 weeks. The results indicated that FB-ChiBai alleviated UVB-induced hyperpigmentation by reducing epidermal hyperplasia and inhibiting the CREB/MITF/tyrosinase pathway. In conclusion, our data indicated that the anti-melanogenic effects of FB-ChiBai are mediated by the inhibition of CREB/MITF/tyrosinase signaling pathway. The findings suggest that FB-ChiBai can protect against UV-B irradiation and that it might be used as an agent in cosmetic products to protect against UVB-induced hyperpigmentation.

Synthesis of N-arylindazole-3-carboxamide and N-benzoylindazole derivatives and their evaluation against α-MSH-stimulated melanogenesis.

We have designed and synthesized twenty-six N-arylindazole-3-carboxamide (3a-p) and N-benzoylindazole (6a-j) derivatives to discover with excellent inhibition activities of α-MSH-stimulated melanogenesis. In the bio evaluation studies of these compounds, we discovered eighteen compounds, out of twenty-six exhibited more potent inhibition than the positive control arbutin. From the SAR studies, we identified 3k and 6g as lead compounds which displayed almost 5 and 9 times more potent inhibition of α-MSH-stimulated melanogenesis respectively than the reference arbutin. It is also evident the presence of electron withdrawing group at para position (R3) for the compounds (3a-p) and presence of +M group at ortho position (R5) for the compounds (6a-j) were crucial for their excellent inhibition activities of α-MSH-stimulated melanogenesis.

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

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

Anti-melanogenesis effect of dehydroglyasperin C through the downregulation of MITF via the reduction of intracellular cAMP and acceleration of ERK activation in B16F1 melanoma cells.

BACKGROUND: In mammals, UV radiation induces melanin synthesis in melanocyte for protecting their skin through the stimulation of α-melanocyte stimulating hormone (α-MSH) from keratinocytes. In this study, the inhibitory effects of dehydroglyasperin C (DGC), an useful component of Glycyrrhiza uralensis (G. uralensis), was investigated on melanogenesis induced by α-melanocyte stimulating hormone (α-MSH) and its mechanisms. METHODS: Melanogenesis suppression effect of DGC on α-MSH induced B16F1 melanoma cells. The cell viability was measured by MTT assay. Expression and phosphorylation of melanogeic protein were conducted using western blot. cAMP acceleration was measured by cAMP immunoassay kit. To investigate whitening mechanism, we used ERK inhibitor (PD98059). RESULTS: DGC decreased intra cellular tyrosinase (TYR) activity and expression of melanin synthesis related proteins (TYR and TRP-1) in a dose-dependent manner on α-MSH induced melanogenesis. In addition, DGC induced the downregulation of MITF (melanocyte-specific transcription factor) through suppression of cAMP-CREB pathway. Also, phosphorylation of extracellular signal regulated kinase (ERK) decreased MITF by DGC treatment. CONCLUSION: Therefore, DGC could be used as a whitening ingredient in skin and clinical usage against hyperpigmentation.

Inhibitors of Melanogenesis: An Updated Review.

Melanins are pigment molecules that determine the skin, eye, and hair color of the human subject to its amount, quality, and distribution. Melanocytes synthesize melanin and provide epidermal protection from various stimuli, such as harmful ultraviolet radiation, through the complex process called melanogenesis. However, serious dermatological problems occur when there is excessive production of melanin in different parts of the human body. These include freckles, melasma, senile lentigo, pigmented acne scars, and cancer. Therefore, controlling the production of melanin is an important approach for the treatment of pigmentation related disorderes. In this Perspective, we focus on the inhibitors of melanogenesis that directly/indirectly target a key enzyme tyrosinase as well as its associated signaling pathways.

Mansonone E from Mansonia gagei Inhibited α-MSH-Induced Melanogenesis in B16 Cells by Inhibiting CREB Expression and Phosphorylation in the PI3K/Akt Pathway.

Many natural products that inhibit melanogenesis, freckles, and hyperpigmentation have been selectively used in cosmetics because melanogenesis is linked to the multiple biogenesis cascades of melanin synthesis. However, some of these compounds have side effects that may result in their restriction in the future. We report here the isolation and structural elucidation of compounds extracted from Mansonia gagei and evaluate their activity on melanogenesis inhibition. We isolated five known compounds from M. gagei and identified them as mansonone E (1), mansorin I (2), populene F (3), mansonone G (4), and mansorin B (5). After evaluating the five compounds for cytotoxicity against B16 cells and inhibitory activity on α-melanocyte-stimulating hormone (α-MSH) induced melanogenesis, we determined that the cytotoxicity and melanogenesis-inhibitory effect of 1 were relatively low and high, respectively. Next, the effect of 1 on the expression of melanogenesis-related proteins was assessed; it was confirmed that 1 dose-dependently inhibited the expression levels of tyrosinase, tyrosinase-related protein 1 (TRP-1), TRP-2, cAMP response element binding protein (CREB), and microphthalmia-associated transcription factor (MITF) which were increased after stimulation by α-MSH. Furthermore, the effects of 1 on the phosphorylation levels of intracellular signaling pathway-related proteins were evaluated, and it was found that 1 dose-dependently rescued the phosphorylation of Akt and p38 mitogen-activated protein kinases (MAPK), which were up- or down-regulated after stimulation by α-MSH. In contrast, treatment with the phosphoinositide 3-kinase (PI3K)/Akt inhibitor wortmannin enhanced melanogenesis inhibition by mansonone E. Cumulatively, the data suggest that 1 suppresses α-MSH-induced melanogenesis in B16 cells by inhibiting both phosphorylation in the PI3K/Akt pathway and the expression of melanogenesis-related proteins.

Inhibitory effect of berberine from Coptidis rhizoma on melanin synthesis of murine malignant melanoma.

Berberine has abundant beneficial properties including anti-cancer effects. In the present study, we examined the inhibitory effect of berberine on α-melanocyte-stimulating hormone (α-MSH)-induced melanogenesis in B16F1 melanoma cells. The results showed that berberine decreased the expression of tyrosinase and microphthalmia-associated transcription factor (MITF) in a dose-dependent manner. In order to observe the potential target for the inhibitory effect of berberine, we examined the effect of berberine on TRP-1 and TRP-2. The results showed that berberine led to a reduction of TRP-1, while the change of TRP-2 was inconspicuous. In the end, we observed the specific effect of berberine on zebrafish skin pigmentation. Overall, the results suggested that berberine inhibits tyrosinase activity and melanin synthesis by attenuating the expression of tyrosinase and MITF. Therefore, these findings may contribute to the potential application of berberine in medicinal or cosmetic products.

Synthesis, biological evaluation, and metabolic stability of chlorogenic acid derivatives possessing thiazole as potent inhibitors of α-MSH-stimulated melanogenesis.

A series of catechol and dioxolane analogs containing thiazole CGA derivatives have been synthesized and evaluated for their inhibitory activity against α-MSH. The inhibitory activity was improved by replacing an α,ß-unsaturated carbonyl of previously reported caffeamides with thiazole motif. Surprisingly, compound 7d, one of the derivatives of dioxolane analogs, displayed the most potent inhibitory activity with an IC50 of 0.90µM. Further studies on metabolic stability and bioactivation potential were also accomplished.

Synthesis and biological evaluation of caffeic acid derivatives as potent inhibitors of α-MSH-stimulated melanogenesis.

We have disclosed our effort to develop caffeic acid derivatives as potent and non-toxic inhibitors of α-MSH-stimulated melanogenesis to treat pigmentation disorders and skin medication including a cosmetic skin-whitening agent. The SAR studies revealed that cyclohexyl ester and secondary amide derivatives of caffeic acid showed significant inhibitory activities.

Effect of Melanotan-II on Brain Fos Immunoreactivity and Oxytocin Neuronal Activity and Secretion in Rats.

Melanocortins stimulate the central oxytocin systems that are involved in regulating social behaviours. Alterations in central oxytocin have been linked to neurological disorders such as autism, and melanocortins have been proposed for therapeutic treatment. In the present study, we investigated how systemic administration of melanotan-II (MT-II), a melanocortin agonist, affects oxytocin neuronal activity and secretion in rats. The results obtained show that i.v., but not intranasal, administration of MT-II markedly induced Fos expression in magnocellular neurones of the supraoptic (SON) and paraventricular nuclei (PVN) of the hypothalamus, and this response was attenuated by prior i.c.v. administration of the melanocortin antagonist, SHU-9119. Electrophysiological recordings from identified magnocellular neurones of the SON showed that i.v. administration of MT-II increased the firing rate in oxytocin neurones but did not trigger somatodendritic oxytocin release within the SON as measured by microdialysis. Our data suggest that, after i.v., but not intranasal, administration of MT-II, the activity of magnocellular neurones of the SON is increased. Because previous studies showed that SON oxytocin neurones are inhibited in response to direct application of melanocortin agonists, the actions of i.v. MT-II are likely to be mediated at least partly indirectly, possibly by activation of inputs from the caudal brainstem, where MT-II also increased Fos expression.

The assessment of the effect of a cosmetic product brightening the skin of people with discolorations of different etiology.

BACKGROUND: Hyperpigmentations are disorders displayed with a change in the color of the skin, its strange shape, the lack of symmetry, and irregular placement. They appear no matter on the age, gender, and often as a congenital defect. Disorder connected with overproduction of melanin by pigmentary cells. The change of color is due to endogenous and exogenous cause. OBJECTIVES: The aim of this thesis was to conduct a research in vivo. This will allow to judge the effectiveness of the cosmetic product which brightens the skin with hyperpigmentation problems. The characteristics of dermocosmetics were tested on people with various etiology of hyperpigmentation. The aim of the research was to assess the effect of the active substances used daily on skin hyperpigmentation. METHODS: The tests were carried out on groups of patients with hyperpigmentations. The application of the pharmaceutical and the use of specific apparatus measurements were taken on every medical checkup. A survey was conducted to assess the changes in the face, neck, and neckline skin. The research was based on the apparatus analysis of the skin condition (MPA® , VISIA® ). RESULTS: Regular application of the pharmaceutical caused brightening of hyperpigmentations (P < 0.05). General improvement in skin condition was also observed - the increase in skin elasticity, smoothness, and the enhancement of hydration levels. CONCLUSIONS: Dermocosmetics for people with hyperpigmentation are an essential part of their medical treatment. In case of epidermal hyperpigmentation, the recipe of individually chosen and tested combination of ingredients enables us to reach satisfactory results.

Central vagal afferent endings mediate reduction of food intake by melanocortin-3/4 receptor agonist.

Injection of the melanocortin-3/4 receptor agonist melanotan-II (MTII) into the nucleus of the solitary tract (NTS) produces rapid and sustained reduction of food intake. Melanocortin-4 receptors (MC4Rs) are expressed by vagal afferent endings in the NTS, but it is not known whether these endings participate in MTII-induced reduction of food intake. In experiments described here, we evaluated the contribution of central vagal afferent endings in MTII-induced reduction of food intake. Examination of rat hindbrain sections revealed that neuronal processes expressing immunoreactivity for the endogenous MC4R agonist α-melanoctyte-stimulating hormone course parallel and wrap around anterogradely labeled vagal afferent endings in the NTS and thus are aptly positioned to activate vagal afferent MC4Rs. Furthermore, MTII and endogenous MC4R agonists increased protein kinase A (PKA)-catalyzed phosphorylation of synapsin I in vagal afferent endings, an effect known to increase synaptic strength by enhancing neurotransmitter release in other neural systems. Hindbrain injection of a PKA inhibitor, KT5720, significantly attenuated MTII-induced reduction of food intake and the increase in synapsin I phosphorylation. Finally, unilateral nodose ganglion removal, resulting in degeneration of vagal afferent endings in the ipsilateral NTS, abolished MTII-induced synapsin I phosphorylation ipsilateral to nodose ganglion removal. Moreover, reduction of food intake following MTII injection into the NTS ipsilateral to nodose ganglion removal was significantly attenuated, whereas the response to MTII was not diminished when injected into the contralateral NTS. Altogether, our results suggest that reduction of food intake following hindbrain MC4R activation is mediated by central vagal afferent endings.

Tyrosol and its analogues inhibit alpha-melanocyte-stimulating hormone induced melanogenesis.

Melanin is responsible for skin color and plays a major role in defending against harmful external factors such as ultraviolet (UV) irradiation. Tyrosinase is responsible for the critical steps of melanogenesis, including the rate-limiting step of tyrosine hydroxylation. The mechanisms of action of skin hypopigmenting agents are thought to be based on the ability of a given agent to inhibit the activity of tyrosinase and, hence, down regulate melanin synthesis. Tyrosol and its glycoside, salidroside, are active components of Rhodiola rosea, and in our preliminary study we found that Rhodiola rosea extract inhibited melanogenesis. In this study, we examined the effects of tyrosol and its analogues on melanin synthesis. We found that treatment of B16F0 cells to tyrosol (1), 4-hydroxyphenylacetic acid (5), 3-hydroxyphenylacetic acid (6), 2-hydroxyphenylacetic acid (7), or salidroside (11) resulted in a reduction in melanin content and inhibition of tyrosinase activity as well as its expression. Tyrosol (1), 4-hydroxyphenylacetic acid (5) and 2-hydroxyphenylacetic acid (7) suppressed MC1R expression. Tyrosol (1), 4-hydroxyphenylacetic acid (5), 3-hydroxyphenylacetic acid (6), and 2-hydroxyphenylacetic acid (7) inhibited α-MSH induced TRP-1 expression, but salidroside (11) did not. All the compounds did not affect MITF and TRP-2 expression. Furthermore, we found that the cell viability of tyrosol (1), 4-hydroxyphenylacetic acid (5), 3-hydroxyphenylacetic acid (6), and 2-hydroxyphenylacetic acid (7) at concentrations below 4 mM and salidroside (11) at concentrations below 0.5 mM were higher than 90%. The compounds exhibited metal-coordinating interactions with copper ion in molecular docking with tyrosinase. Our results suggest that tyrosol, 4-hydroxyphenylacetic acid, 3-hydroxyphenylacetic acid, 2-hydroxyphenylacetic acid, and salidroside are potential hypopigmenting agents.

Octaphlorethol A isolated from Ishige foliacea inhibits α-MSH-stimulated induced melanogenesis via ERK pathway in B16F10 melanoma cells.

In this study, the potent skin-whitening effects of Octaphlorethol A (OPA) isolated from Ishige foliacea was investigated through inhibitory effect of melanin synthesis and tyrosinase activity in alpha-melanocyte stimulating hormone (α-MSH) induced B16F10 melanoma cells. OPA markedly inhibited melanin synthesis and tyrosinase activity in a concentration-dependent manner. We also found that OPA decreased microphthalmia-associated transcription factor (MITF), tyrosinase, tyrosinase-related protein-1 and -2 (TRP-1 and TRP-2) protein expressions. Moreover, OPA reduces p38 MAPK protein levels and activates extracellular signal-regulated kinase (ERK) and c-jun N-terminal kinases (JNKs) protein expressions in B16F10 cells. A specific ERK inhibitor PD98059 significantly blocks OPA-inhibited melanin synthesis and tyrosinase activity, whereas a p38MAP and JNK inhibitor had no effect. These findings provide evidence demonstrating that the anti-melanogenic effect of OPA is mediated through the activation of ERK signal pathway in B16F10 cells. These results indicate that OPA has the potential to be used as a melanogenesis inhibitor in the food and cosmetics industry.