Anti-Melanogenic Properties of Velutin and Its Analogs.

Velutin, one of the flavones contained in natural plants, has various beneficial activities, such as skin whitening, as well as anti-inflammatory, anti-allergic, antioxidant, and antimicrobial activities. However, the relationship between the structure of velutin and its anti-melanogenesis activity is not yet investigated. In this study, we obtained 12 velutin derivatives substituted at C5, C7, C3', and C4' of the flavone backbone with hydrogen, hydroxyl, and methoxy functionalities by chemical synthesis, to perform SAR analysis of velutin structural analogues. The SAR study revealed that the substitution of functional groups at C5, C7, C3', and C4' of the flavone backbone affects biological activities related to melanin synthesis. The coexistence of hydroxyl and methoxy at the C5 and C7 position is essential for inhibiting tyrosinase activity. However, 1,2-diol compounds substituted at C3' and C4' of flavone backbone induce apoptosis of melanoma cells. Further, substitution at C3' and C4' with methoxy or hydrogen is essential for inhibiting melanogenesis. Thus, this study would be helpful for the development of natural-derived functional materials to regulate melanin synthesis.

Iridium-Catalyzed Cyclative Indenylation and Dienylation through Sequential B(4)-C Bond Formation, Cyclization, and Elimination from o-Carboranes and Propargyl Alcohols.

Described herein is the first iridium-catalyzed cyclative indenylation through sequential B(4)-C and intramolecular C-C bond formation from o-carboranes and propargyl alcohols, leading to the formation of B(4)-indenylated o-carboranes with excellent regioselectivity via direct B-H activation. Moreover, the iridium-catalyzed regioselective 1,3-dienylation has been accessed through sequential B-H activation, dehydration, and decarboxylation, producing B(4)-dienylated o-carboranes.

Expansion of Azulenes as Nonbenzenoid Aromatic Compounds for C-H Activation: Rhodium- and Iridium-Catalyzed Oxidative Cyclization of Azulene Carboxylic Acids with Alkynes for the Synthesis of Azulenolactones and Benzoazulenes.

Rhodium-catalyzed oxidative [4 + 2] cyclization reactions through the C-H activation of azulene carboxylic acids as nonbenzenoid aromatic compounds with symmetrical and unsymmetrical alkynes were developed under aerobic conditions, which produced azulenolactone derivatives with a wide substrate scope and excellent functional group tolerance. Interestingly, azulenic acids in reaction with alkynes underwent iridium-catalyzed [2 + 2 + 2] cyclization accompanied by decarboxylation to afford tetra(aryl)-substituted benzoazulene derivatives. The reactivity order for C-H activation reaction is greater toward azulene-6-carboxylic acid, azulene-1-carboxylic acid, and azulene-2-carboxylic acid. For the first time, the expansion of azulenes having directing group as nonbenzenoid aromatic compounds for C-H activation was successful, indicating that nonbenzenoid aromatic compounds can be used as good substrates for the C-H activation reaction. Therefore, the research area of C-H activation will certainly expand to nonbenzenoid aromatic compounds in future.

Velutin, an Aglycone Extracted from Korean Mistletoe, with Improved Inhibitory Activity against Melanin Biosynthesis.

The abnormal regulation of melanin synthesis leads to a wide range of pigmentary disorders. Although various melanin biosynthesis inhibitors have been developed, their efficacy and long-term safety needs to be further improved, and thus the goal of this study is to develop promising natural compound inhibitors of melanin biosynthesis. Here, we obtained aglycone flavonoid extract through the microwave-assisted hydrolysis of glycoside extract from Korean mistletoe in acidic condition. The aglycone extract inhibited tyrosinase activity more efficiently with better antioxidant activity than glycoside extract in vitro. The microwave-assisted aglycone extract of mistletoe was further analyzed for in vivo activity, and the results showed the aglycone extract inhibited both early melanocyte development and melanin synthesis more efficiently in zebrafish embryo in a dose-dependent manner. Our in vivo toxicity assay quantitatively measured cell death in zebrafish embryos and showed that the microwave-assisted aglycone extract of mistletoe had no significant effect on cell death (p < 0.001), indicating that aglycone extract is more biocompatible than glycoside extract. Furthermore, our in vitro and in vivo analyses successfully identified and characterized velutin, an aglycone of a homoflavoyadorinin B glycoside, as a major inhibitory component in the microwave-assisted mistletoe extract. Ultimately, this study showed that the novel natural compound inhibitor velutin, which was generated through microwave-assisted extraction from mistletoe, improved the efficacy of melanin biosynthesis inhibition with little toxicity.

3D Visualization of Developmental Toxicity of 2,4,6-Trinitrotoluene in Zebrafish Embryogenesis Using Light-Sheet Microscopy.

Environmental contamination by trinitrotoluene is of global concern due to its widespread use in military ordnance and commercial explosives. Despite known long-term persistence in groundwater and soil, the toxicological profile of trinitrotoluene and other explosive wastes have not been systematically measured using in vivo biological assays. Zebrafish embryos are ideal model vertebrates for high-throughput toxicity screening and live in vivo imaging due to their small size and transparency during embryogenesis. Here, we used Single Plane Illumination Microscopy (SPIM)/light sheet microscopy to assess the developmental toxicity of explosive-contaminated water in zebrafish embryos and report 2,4,6-trinitrotoluene-associated developmental abnormalities, including defects in heart formation and circulation, in 3D. Levels of apoptotic cell death were higher in the actively developing tissues of trinitrotoluene-treated embryos than controls. Live 3D imaging of heart tube development at cellular resolution by light-sheet microscopy revealed trinitrotoluene-associated cardiac toxicity, including hypoplastic heart chamber formation and cardiac looping defects, while the real time PCR (polymerase chain reaction) quantitatively measured the molecular changes in the heart and blood development supporting the developmental defects at the molecular level. Identification of cellular toxicity in zebrafish using the state-of-the-art 3D imaging system could form the basis of a sensitive biosensor for environmental contaminants and be further valued by combining it with molecular analysis.

PKA regulates calcineurin function through the phosphorylation of RCAN1: identification of a novel phosphorylation site.

Calcineurin is a calcium/calmodulin-dependent phosphatase that has been implicated in T cell activation through the induction of nuclear factors of activated T cells (NFAT). We have previously suggested that endogenous regulator of calcineurin (RCAN1, also known as DSCR1) is targeted by protein kinase A (PKA) for the control of calcineurin activity. In the present study, we characterized the PKA-mediated phosphorylation site in RCAN1 by mass spectrometric analysis and revealed that PKA directly phosphorylated RCAN1 at the Ser 93. PKA-induced phosphorylation and the increase in the half-life of the RCAN1 protein were prevented by the substitution of Ser 93 with Ala (S93A). Furthermore, the PKA-mediated phosphorylation of RCAN1 at Ser 93 potentiated the inhibition of calcineurin-dependent pro-inflammatory cytokine gene expression by RCAN1. Our results suggest the presence of a novel phosphorylation site in RCAN1 and that its phosphorylation influences calcineurin-dependent inflammatory target gene expression.

Characterization of Phenethyl Cinnamamide Compounds from Hemp Seed and Determination of Their Melanogenesis Inhibitory Activity.

Hyperpigmentation is induced by the overactivation of tyrosinase, which is a rate-limiting enzyme in melanogenesis. The defatted extract of hemp (Cannabis sativa L.) seed is known to have inhibitory effects on melanogenesis; however, effective compounds in the extract have not been identified yet. In this study, three phenethyl cinnamamides present in hemp seed extract were prepared by purification and chemical synthesis and were assessed for their inhibitory effect on melanogenesis in B16F10 melanoma cells. A comparison of the anti-melanogenesis and anti-tyrosinase activity of hemp seed solvent fractions revealed that the ethyl acetate fraction possessed the greatest potential for suppressing melanogenesis in melanoma cells by decreasing tyrosinase activity. We tentatively identified 26 compounds in the ethyl acetate fraction by comparing spectroscopic data with the literature. Three phenethyl cinnamamides such as N-trans-caffeoyltyramine, N-trans-coumaroyltyramine, and N-trans-feruloyltyramine present abundantly in the ethyl acetate fraction were prepared and their anti-melanogenesis and anti-tyrosinase activities in melanoma cells were evaluated. We found that N-trans-caffeoyltyramine and N-trans-feruloyltyramine inhibited alpha melanocyte stimulating hormone (α-MSH)-induced melanogenesis without cytotoxicity, while N-trans-coumaroyltyramine inhibited melanogenesis with cytotoxicity. IC50 values of N-trans-caffeoyltyramine, N-trans-feruloyltyramine, and N-trans-coumaroyltyramine for inhibition of α-MSH-mediated tyrosinase activation were 0.8, 20.2, and 6.3 µM, respectively. Overall, N-trans-caffeoyltyramine possessed the strongest anti-melanogenesis activity among the three phenethyl cinnamamides evaluated. The inhibitory effect of N-trans-caffeoyltyramine was verified by determining the melanin content and tyrosinase activity in melanoma after treating the cells with synthetic compounds. Thus, N-trans-caffeoyltyramine isolated from hemp seed extract could be useful in cosmetics as a skin-whitening agent.

Mechanochemical Iridium(III)-Catalyzed B-Amidation of o-Carboranes with Dioxazolones.

Mechanochemistry was successfully applied to the functionalization of carboranes. The mechanochemical iridium(III)-catalyzed regioselective B(3)- and B(4)-amidation of unsubstituted o-carboranes with dioxazolones was developed. In addition, the mechanochemical iridium(III)-catalyzed regioselective B(4)-amidation of substituted o-carboranes was demonstrated. Because mechanochemical B-amidation proceeds smoothly without organic solvents or external heating, the present method is regarded as a sustainable and environmentally friendly surrogate for typical solvent-based reactions.

Preparation and Evaluation of Nanostructured Lipid Carrier for Topical Delivery of Velutin: Synthetic Tyrosinase Inhibitor.

The purpose of this study is to produce nanostructured lipid carrier (NLC) that can solubilize poorly water-soluble velutin and verify an improved tyrosinase synthesis inhibition. A solubility test for velutin was conducted. Cetyl palmitate and caprylic/capric triglyceride were selected as solubilizer. The lipid matrix was produced using the ultrasound dispersion method. The morphology and size distribution of the produced NLC was analyzed through scanning electron microscopy (SEM) and dynamic light scattering (DLS), and the release and tyrosinase inhibition of velutin was evaluated through the Franz diffusion cell method and tyrosinase inhibition assay. Lipid matrix nanoparticles showed an average size of approximately 250 nm and polydispersity of 0.2, and it was confirmed that the velutin incorporated within nanoparticles sustained release at a constant rate over 36 hours. Due to extremely low aqueous solubility, the tyrosinase synthesis inhibition of velutin suspension was 0%, and the value of velutin incorporated within the NLC formulation was greatly improved 56.5% (40 µg/mL). As a result, it was verified that lipid-based NLC nanoparticles are an efficient formulation for the topical delivery of poorly water-soluble flavonoids such as velutin.

Surface Activity and Emulsifying Effect of Non-Toxic Starch Nanocrystal.

The purpose of this study is to investigate the surface activity of starch nanocrystals (SNC), material derived from starch, and confirm their usefulness as a surfactant. In order to evaluate the surface activity, the surface tension change of suspended SNC solution via the Wilhelmy plate method was measured and the values were compared with various synthetic surfactants. The effect of SNC as emulsifier was evaluated on emulsion formation and physical stability. The surface tension of the SNC-dispersed solution was decreased while its concentration was increased. When the 5.0% (w/v) of SNC was added, the surface tension was decreased from 70.3 to 49.5 mN/m. It was confirmed that the physical stability of the emulsion prepared by adding the SNC was improved compared to that of surface inactivity material (PEG 400). The phase separation was observed within 1 hour after preparation of the emulsion containing PEG 400, but the emulsion containing SNC was stable for 5 hours or more. To summarize this study, SNC, a natural-derived and non-toxic material, exhibits sufficient surface activity, thereby confirming the possibility of being applied to the food and pharmaceutical industry.

Characterization of Caffeoylquinic Acids from Lepisorus thunbergianus and Their Melanogenesis Inhibitory Activity.

Hyperpigmentation resulting from the overactivation of tyrosinase leads to darker spots or patches on the human skin. Although these phenomena are harmless, there is still great demand for melanogenesis inhibitors to prevent hyperpigmentation by inhibiting the tyrosinase, a rate-limiting enzyme in melanogenesis. Although Lepisorus thunbergianus has been used in folk remedies as a diuretic and hemostatic agent, its effect on melanogenesis has not yet been reported. In this study, we prepared an L. thunbergianus extract and its solvent fractions and evaluated their biological activity against free radical and melanin synthesis. The extract of L. thunbergianus inhibited mushroom tyrosinase activity more efficiently than, and with similar antioxidant activity to, arbutin in vitro. Comparative evaluation of the anti-melanogenesis and anti-tyrosinase activity of L. thunbergianus solvent fractions demonstrated that, by inhibiting tyrosinase activity, the butanol fraction has the highest potential for the inhibition of melanogenesis in melanoma cells. We found by structural analysis using high-performance liquid chromatography (HPLC) and NMR spectroscopy that the major compounds in butanol fraction were three caffeoylquinic acid derivatives. The three derivatives had similar radical scavenging and anti-tyrosinase activities in vitro, while only 5-caffeoylquinic acid had an inhibitory effect on α-MSH-induced melanogenesis. The inhibitory effect of 5-caffeoylquinic acid was verified by the determination of the melanin content and tyrosinase activity in melanoma after treating the cells with a commercial compound. Further, we revealed that 5-caffeoylquinic acid inhibited melanogenesis by chelating a copper cation from a copper-tyrosinase complex. Thus, 5-caffeoylquinic acid or butanol fraction isolated from L. thunbergianus might be useful in cosmetics as a skin-whitening agent.

Sequential 1,3-N- to C- and 1,3-C- to C-Migration of Sulfonyl Groups through the Synthesis of 1,4-Diazepines from the Aza-[5 + 2] Cycloaddition of Indoloazomethine Ylides.

Described herein is the sequential 1,3-N- to C- and 1,3-C- to C-migration of sulfonyl groups through the synthesis of 1,4-diazepines from an operationally simple thermal aza-[5 + 2] cycloaddition reaction of indoloazomethine ylides with dialkyl acetylenedicarboxylates under mild conditions, leading to the formation of C-sulfonylated 1,4-diazepines.

Selective C-C bond formation from rhodium-catalyzed C-H activation reaction of 2-arylpyridines with 3-aryl-2H-azirines.

A novel method for the synthesis of acylmethyl-substituted 2-arylpyridine derivatives using 3-aryl-2H-azirines was developed by exploring a prototype reaction using DFT-calculations and carrying out targeted experiments guided by the calculated mechanism. 2H-Azirine was initially hypothesized to ring-open at the metal center to furnish familiar metal nitrene complexes that may undergo C-N coupling. Computational studies quickly revealed and prototype experimental work confirmed that neither the formation of the expected metal nitrene complexes nor the C-N coupling were viable. Instead, azirine ring-opening followed by C-C coupling was found to be much more favorable to give imines that readily underwent hydrolysis in aqueous conditions to form acylmethyl-substituted products. This new method was highly versatile and selective toward a wide range of substrates with high functional group tolerance. The utility of the new method is demonstrated by a convenient one-pot synthesis of biologically relevant heterocycles such as pyridoisoindole and pyridoisoqunolinone.

Efficient synthetic method of multisubstituted allenes from the reactions of allylindium reagents with 3 degree-propargyl alcohols.

An efficient synthetic method of tri- and tetra-substituted allenes having an allyl and methallyl group was developed by the reactions of allylindium reagents generated in situ from indium and allyl bromides with 3 degree-propargyl alcohols.

Inhibitory effects of 2-oxo-2H-chromen-4-yl 4-methylbenzenesulfonate on allergic inflammatory responses in rat basophilic leukemia cells.

Mast cells play crucial roles in the initiation of allergic inflammatory responses by releasing various mediators such as histamines, cytokines, and leukotrienes. In addition, signaling cascade pathways, such as the mitogen-activated protein kinase (MAPK) pathway, contribute to the regulation of mast cell degranulation. Accordingly, different research strategies have been pursued to develop anti-inflammatory and anti-allergic drugs by regulating these signaling pathways. The development of new drugs that inhibit mast cell degranulation may help in the treatment of allergies. In this study, we investigated the effects of coumarin derivatives on mast cell degranulation. The effect of coumarin derivatives on degranulation in rat basophilic leukemia (RBL)-2H3 cells was determined by a ß-hexosaminidase assay and histamine assay. A coumarin derivative 1 (C1), 2-oxo-2H-chromen-4-yl 4-methylbenzenesulfonate, inhibited degranulation in a dose-dependent manner and demonstrated maximum therapeutic effect when used at 25µM. Additionally, these compounds inhibited the phosphorylation of the extracellular signal-regulated kinase (ERK) pathway. Taken together, these results indicate that 2-oxo-2H-chromen-4-yl 4-methylbenzenesulfonate inhibits mast cell degranulation by suppressing the activation of the ERK pathway and this inhibitory effect suggests potential therapeutic strategies towards the prevention of allergic disorders.

Cinnamaldehyde derivatives inhibit degranulation and inflammatory mediator production in rat basophilic leukemia cells.

Mast cells play a critical role in allergic diseases. Therefore, development of new therapeutic agents that suppresses the activation of mast cells may help prevent or treat allergic diseases. Here, we investigated the anti-allergic effects of 4-chloro-cinnamaldehyde and 4-trifluoro-cinnamaldehyde in RBL-2H3 cells. ß-Hexosaminidase assays revealed that degranulation of RBL-2H3 cells was decreased following treatment with 60µM 4-chloro-cinnamaldehyde or 4-trifluoro-cinnamaldehyde. Moreover, quantitative real-time reverse transcription polymerase chain reaction showed that the relative expression levels of tumor necrosis factor-α, interleukin-4, and cyclooxygenase-2 mRNAs were decreased in RBL-2H3 cells treated with 4-chloro-cinnamaldehyde and 4-trifluoro-cinnamaldehyde in a concentration-dependent manner. Additionally, 4-chloro-cinnamaldehyde blocked the phosphorylation of MKKs and MAPKs. These data clearly suggested that 4-chloro-cinnamaldehyde and 4-trifluoro-cinnamaldehyde had inhibitory effects on the inflammatory responses of mast cells and may have potential as novel therapeutic agents for the prevention or treatment of allergic diseases.

Palladium-catalyzed inter- and intramolecular coupling reactions of aryl and vinyl halides mediated by indium.

Treatment of aryl and vinyl halides with 50 mol % of 100 mesh indium, 2.5 mol % of Pd-C, and 1.5 equiv of LiCl under mild conditions (DMF, 100 degrees C, 1-3 h) could produce coupling products efficiently in good to excellent yields in which the C(sp2)-C(sp2) bond was formed. This reagent worked equally well with both intermolecular and intramolecular coupling reactions, producing a variety of biaryls, 1,3-dienes, and cyclic compounds.

Regioselective allylgallation of terminal alkynes.

The reactions of terminal alkynes with allylgallium reagents generated in situ from gallium and allyl bromides gave the corresponding 1,4-dienes in good yield via Markovnikov addition in THF at 70 degrees C.

Pd-catalyzed carbonylative cross-coupling reactions by triorganoindiums: highly efficient transfer of organic groups attached to indium under atmospheric pressure.

[reaction: see text] A highly atom-efficient synthetic method of unsymmetrical ketones was developed by using trialkyl- and triarylindiums, which could be employed as effective cross-coupling partners in Pd-catalyzed carbonylative cross-coupling reactions with a variety of organic electrophiles. The present method produced unsymmetrical ketones and 1,4-diacylbenzenes in good yields with highly efficient transfer of almost all the organic groups attached to the indium under atmospheric pressure of CO gas in THF at 66 degrees C.

An efficient method for cyclopentene annulation onto alpha,beta-unsaturated ketones: W(CO)(5)(L)-catalyzed 5-endo-dig cyclization of 6-siloxy-5-en-1-ynes.

[reaction: see text] A highly efficient method for the cyclopentene annulation onto alpha,beta-unsaturated ketones is described. Indium-mediated 1,4-propargylation onto alpha,beta-unsaturated ketones in the presence of tert-butyldimethylsilyl triflate and dimethyl sulfide gives the 6-siloxy-5-en-1-yne derivatives, which undergo W(CO)(5)(L)-catalyzed 5-endo-dig cyclization to give the corresponding cyclopentene derivatives in good yield.