7,3',4'-Trihydroxyisoflavone, a Metabolite of the Soy Isoflavone Daidzein, Suppresses α-Melanocyte-Stimulating Hormone-Induced Melanogenesis by Targeting Melanocortin 1 Receptor.

7,3',4'-Trihydroxyisoflavone (7,3',4'-THIF) is a metabolite of daidzein which is a representative isoflavone found in soybean. Recent studies suggested that 7,3',4'-THIF exerts a hypopigmentary effect in B16F10 cells, however, its underlying molecular mechanisms and specific target protein remain unknown. Here, we found that 7,3',4'-THIF, but not daidzein, inhibited α-melanocyte-stimulating hormone (MSH)-induced intracellular and extracellular melanin production in B16F10 cells by directly targeting melanocortin 1 receptor (MC1R). Western blot data showed that 7,3',4'-THIF inhibited α-MSH-induced tyrosinase, tyrosinase-related protein-1 (TYRP-1), and tyrosinase-related protein-2 (TYRP-2) expressions through the inhibition of Microphthalmia-associated transcription factor (MITF) expression and cAMP response element-binding (CREB) phosphorylation. 7,3',4'-THIF also inhibited α-MSH-induced dephosphorylation of AKT and phosphorylation of p38 and cAMP-dependent protein kinase (PKA). cAMP and Pull-down assays indicated that 7,3',4'-THIF strongly inhibited forskolin-induced intracellular cAMP production and bound MC1R directly by competing with α-MSH. Moreover, 7,3',4'-THIF inhibited α-MSH-induced intracellular melanin production in human epidermal melanocytes (HEMs). Collectively, these results demonstrate that 7,3',4'-THIF targets MC1R, resulting in the suppression of melanin production, suggesting a protective role for 7,3',4'-THIF against melanogenesis.

Ginsenoside F1 attenuates hyperpigmentation in B16F10 melanoma cells by inducing dendrite retraction and activating Rho signalling.

Ginsenoside F1 (GF1) is a metabolite produced by hydrolysis of the ginsenoside Re and Rg1 in Panax ginseng. According to various studies, high amounts of ginseng components are absorbed in the metabolized form, which are key constituents responsible for the biological effects of P. ginseng. Recently, GF1 was reported to have beneficial effects on skin. However, there has not been a sound understanding of its antimelanogenic effect and underlying molecular mechanisms. In this study, GF1 reduced α-melanocyte-stimulating hormone-induced melanin secretion in B16F10 cell culture media by 60%. However, it did not suppress intracellular melanin levels, tyrosinase activity and expression. Immunofluorescence assay showed that GF1 had no effect on melanosome transport, but significantly induced dendrite retraction. Pull-down assay demonstrated that GF1 primarily modulates the Rho family GTPases resulting in dendrite retraction. Collectively, these data suggest that GF1 could act as a potent skin-whitening agent.

The daidzein metabolite, 6,7,4'-Trihydroxyisoflavone, is a novel inhibitor of PKCα in suppressing solar UV-induced matrix metalloproteinase 1.

Soy isoflavone is an attractive source of functional cosmetic materials with anti-wrinkle, whitening and skin hydration effects. After consumption, the majority of soy isoflavones are converted to their metabolites in the human gastrointestinal tract. To understand the physiological impact of soy isoflavone on the human body, it is necessary to evaluate and address the biological function of its metabolites. In this study, we investigated the effect of 6,7,4'-trihydroxyisoflavone (6,7,4'-THIF), a major metabolite of daidzein, against solar UV (sUV)-induced matrix metalloproteinases (MMPs) in normal human dermal fibroblasts. MMPs play a critical role in the degradation of collagen in skin, thereby accelerating the aging process of skin. The mitogen-activated protein/extracellular signal-regulated kinase (MEK)/extracellular signal-regulated kinase (ERK), mitogen-activated protein kinase (MKK)3/6/p38 and MKK4/c-Jun N-terminal kinases (JNK) signaling pathways are known to modulate MMP-1 function, and their activation by sUV was significantly reduced by 6,7,4'-THIF pretreatment. Our results also indicated that the enzyme activity of protein kinase C (PKC)α, an upstream regulator of MKKs signaling, is suppressed by 6,7,4'-THIF using the in vitro kinase assay. Furthermore, the direct interaction between 6,7,4'-THIF and endogenous PKCα was confirmed using the pull-down assay. Not only sUV-induced MMP-1 expression, but also sUV-induced signaling pathway activation were decreased in PKCα knockdown cells. Overall, we elucidated the inhibitory effect of 6,7,4'-THIF on sUV-induced MMPs and suggest PKCα as its direct molecular target.

Role of epidermal γδ T-cell-derived interleukin 13 in the skin-whitening effect of Ginsenoside F1.

Ginsenoside F1 (GF1) is a metabolite of ginsenoside Rg1. Although GF1 has several benefits for skin physiology, the effect of GF1 on skin pigmentation has not been reported. We found that a cream containing 0.1% GF1 showed a significant whitening effect on artificially tanned human skin after 8 weeks of application. However, GF1 did not inhibit mRNA expression of tyrosinase or dopachrome tautomerase (DCT) in normal human epidermal melanocytes (NHEMs) or cocultured NHEMs/normal human epidermal keratinocytes. Interestingly, GF1 enhanced production of interleukin 13 (IL-13) from human epidermal γδ T cells. IL-13 significantly reduced the mRNA expression and protein amount of both tyrosinase and DCT and reduced melanin synthesis activities in NHEMs, resulting in visible brightening of NHEM pellet. These results suggest that enhancement of IL-13 production by GF1 from epidermal γδ T cells might play a role in the skin-whitening effect of GF1 via the suppression of tyrosinase and DCT.

Determination and comparison of seed oil triacylglycerol composition of various soybeans (Glycine max (L.)) using ¹H-NMR spectroscopy.

Seed oil triacylglycerol (TAG) composition of 32 soybean varieties were determined and compared using ¹H-NMR. The contents of linolenic (Ln), linoleic (L), and oleic (O) ranged from 10.7% to 19.3%, 37.4%-50.1%, and 15.7%-34.1%, respectively. As is evident, linoleic acid was the major fatty acid of soybean oil. Compositional differences among the varieties were observed. Natural oils containing unsaturated groups have been regarded as important nutrient and cosmetic ingredients because of their various biological activities. The TAG profiles of the soy bean oils could be useful for distinguishing the origin of seeds and controlling the quality of soybean oils. To the best of our knowledge, this is the first study in which the TAG composition of various soybean oils has been analyzed using the ¹H-NMR method.

Compound K induces expression of hyaluronan synthase 2 gene in transformed human keratinocytes and increases hyaluronan in hairless mouse skin.

Ginsenosides, the major active ingredients of ginseng, have a variety of biomedical efficacies such as anti-aging, anti-oxidation, and anti-inflammatory activities. To understand the effects of compound K (20-O-beta-D-glucopyranosyl-20(S)-protopanaxadiol), one of the major metabolites of ginsenosides, on the skin, we assessed the expression levels of about 100 transcripts in compound K-treated HaCaT cells using cDNA microarray analysis. One gene up-regulated by compound K was hyaluronan synthase2 (HAS2). Semi-quantitative RT-PCR showed that compound K increased HAS2 mRNA in time- and dose-dependent manners. ELISA and immunocytochemistry using hyaluronan (HA)-binding protein showed that compound K effectively increased HA production in HaCaT cells. Finally, treatment of compound K on hairless mouse skin increased the amount of HA in the epidermis and papillary dermis. Our study suggests that topical application of compound K might prevent or improve the deteriorations, such as xerosis and wrinkles, partly ascribed to the age-dependent decrease of the HA content in human skin.