Inhibitory Effects of Coumarin Derivatives on Tyrosinase

In this study, a series of coumarin derivatives were synthesized and their inhibitory effects on the activity of mushroom tyrosinase were evaluated. As a result of measuring the inhibition of tyrosinase activity of these derivatives, the compounds 3e (1.05 μM), 3f (0.83 μM), 3h (0.85 μM), 3i (1.05 μM), and 3k (0.67 μM) of the geranyloxycoumarin derivatives were highly active at a concentration of 0.8%. The geranyloxycoumarin derivatives exhibited better activity than the hydroxycoumarin derivatives. Among the geranyloxycoumarin derivatives, compound 3k was two times more active than arbutin, a positive control, at a concentration of 0.4%. The above results suggest that geranyloxycoumarin derivatives have great potential for application as functional cosmetic ingredients with tyrosinase-inhibiting activity.     

Identification of Mushroom and Murine Tyrosinase Inhibitors from Achillea biebersteinii Afan. Extract

Growing scientific evidence indicates that Achillea biebersteinii is a valuable source of active ingredients with potential cosmetic applications. However, the data on its composition and pharmacological properties are still insufficient. This study aims to optimize the extraction procedure of the plant material, evaluate its phytochemical composition, and compare anti-tyrosinase potential of A. biebersteinii extracts obtained by various methods. In order to identify compounds responsible for the tyrosinase inhibitory activity of A. biebersteinii, the most active anti-tyrosinase extract was fractionated by column chromatography. The fractions were examined for their skin lightening potential by mushroom and murine tyrosinase inhibitory assays and melanin release assay. HPLC-ESI-Q-TOF-MS/MS analysis of the total extract revealed the presence of several phenolic acids, flavonoids, flavonoid glucosides, and carboxylic acid. Among them, fraxetin-8-O-glucoside, quercetin-O-glucopyranose, schaftoside/isoschaftoside, gmelinin B, 1,3-dicaffeoylquinic acid (1,3-DCQA), and ferulic acid were found in the fractions with the highest skin lightening potential. Based on obtained qualitative and quantitative analysis of the fractions, it was assumed that the caffeoylquinic acid derivatives and dicaffeoylquinic acid derivatives are more likely responsible for mushroom tyrosinase inhibitory activity of A. biebersteinii extracts and fractions. Ferulic acid was proposed as the most active murine tyrosinase inhibitor, responsible also for the reduced melanin release from B16F10 murine melanoma cells.     

The Photophysics and Photochemistry of Melanin- Like Nanomaterials Depend on Morphology and Structure

Melanin-like nanomaterials have found application in a large variety of high economic and social impact fields as medicine, energy conversion and storage, photothermal catalysis and environmental remediation. These materials have been used mostly for their optical and electronic properties, but also for their high biocompatibility and simplicity and versatility of preparation. Beside this, their chemistry is complex and it yields structures with different molecular weight and composition ranging from oligomers, to polymers as well as nanoparticles (NP). The comprehension of the correlation of the different compositions and morphologies to the optical properties of melanin is still incomplete and challenging, even if it is fundamental also from a technological point of view. In this minireview we focus on scientific papers, mostly recent ones, that indeed examine the link between composition and structural feature and photophysical and photochemical properties proposing this approach as a general one for future research.     

Detection and quantitation of a pheomelanin component in melanin pigments using pyrolysis–gas chromatography/tandem mass spectrometry system with multiple reaction monitoring mode

Here, we describe the reliable method for the detection and quantitation of a pheomelanin component in melanin pigments. Synthetic melanins with various contents of pheomelanin‐type structural units were thermally degraded, and the multiple reaction monitoring mode was applied to detect the pheomelanin markers in the pyrolysates by GC/MS/MS. The method allowed the specific detection and quantitation of a pheomelanin component in melanin with the incorporation of pheomelanin‐type units as low as 0.05%. Considering highly universal character of the pheomelanin markers, the method could be applied for structural studies of natural melanin pigments being mixtures of eumelanin and pheomelanin. Copyright © 2012 John Wiley & Sons, Ltd.     

Optimization of Ultrasound-Assisted Cellulase Extraction from Nymphaea hybrid Flower and Biological Activities: Antioxidant Activity,Protective Effect against ROS Oxidative Damage in HaCaT Cells and Inhibition of Melanin Production in B16 Cells

In this study, ultrasonic-assisted cellulase extraction (UCE) was applied to extract flavonoids and polyphenols from the Nymphaea hybrid flower. The extraction conditions were optimized using the response surface method (RSM) coupled with a Box-Behnken design. The crude extract of Nymphaea hybrid (NHE) was further purified using AB-8 macroporous resins, and the purified extract (NHEP) was characterized by FTIR and HPLC. In vitro activity determination by chemical method showed that NHEP displayed strong free radical scavenging abilities against the DPPH and ABTS radicals, good reduction power, and hyaluronidase inhibition. The cell viability by CCK-8 assays showed that NHEP had no significant cytotoxicity for B16 and HaCaT cells when the concentration was below 100 μg/mL and 120 μg/mL, respectively. NHEP with a concentration of 20–160 μg/mL can more effectively reduce the ROS level in H₂O₂ damaged HaCaT cells compared with 10 μg/mL of VC. The 40 μg/mL of NHEP had similar activity against intracellular melanin production in the B16 melanoma cells compared with 20 μg/mL Kojic acid. Good activities of antioxidation, whitening and protective effect against H₂O₂-induced oxidative damage promote the potential for NHEP as a functional raw material in the field of cosmetics and medicine.     

正交试验优化基因工程菌(E.Coli/p WSY)产黑色素培养基的组成

用正交试验优化了基因工程菌（Ｅ．ｃｏｌｉ／ｐ ＷＳＹ）产黑色素培养基的组成。配方为：蛋白胨１％、葡萄糖０．２％、硫酸铵０．５％、磷酸氢二钾０．７％、磷酸二氢钾０．３％、氯化钠０．５％，硫酸镁０．０１％，为实现微生物发酵法大规模生产黑色素提供了重要数据。     

Melanin‐Containing Films: Growth from Dopamine Solutions versus Layer‐by‐Layer Deposition

Films formed by oxidation of dopamine are of interest for functionalisation of solid–liquid interfaces owing to their versatility. However, the ability to modulate the properties of such films, for example, permeability to ionic species and the absorption coefficient, is urgently needed. Indeed, melanin films produced by oxidation of dopamine absorb strongly over the whole UV/Vis part of the electromagnetic spectrum and are impermeable to anions even for a film thickness as low as a few nanometers. Herein we combine oxidation of dopamine to produce a solution containing dopamine–melanin particles and their alternating deposition with poly(diallyldimethylammonium chloride) to produce films which have nearly the same morphology as pure dopamine–melanin films but are less compact, more transparent and more permeable to ferrocyanide anions.     

Isolation and Properties of Melanin in Fine Yak Hair

Melanin granules were isolated from fine yak hair by means of protein enzyme and hydrochloric acid.Resultsof SEM investigation and amino acid analysis were usedto study the physical and chemical properties of melaningranules.The solubility of melanin granules in differentchemical solutions was also studied.     

Time-resolved photoluminescence study of excited states in nanostructured melanin

Abstract

Time resolved emission spectra (TRES), 3D maps of photoluminescence excitation-emission (PLE maps), 3D maps of TRES, and kinetics of photoluminescence (PL) spectra of natural and synthetic melanin, as well as melanin composites with surfactant, sodium dodecyl benzenesulfonate, have been studied. The kinetics of PL and TRES for the melanin and the composites were investigated at low temperatures that allowed to discuss melanin’s intermolecular complexation, nano-aggregation and formation of charge transfer states. Particularly, the radiation of Frenkel excitons from fragments of different degrees of conjugation that are the parts of molecular nanodisks of melanin is observed. Furthermore, charge transfer excitons (CT-excitons) can be formed and observed at both room and helium temperatures. Some bands in the PL spectra of melanin, depending on temperature, behave like excimer radiation. The studies are aiming to understand the electronic properties of various melanins, particularly natural ones.     

Theoretical Exploring of a Molecular Mechanism for Melanin Inhibitory Activity of Calycosin in Zebrafish

Tyrosinase is an oxidase that is the rate-limiting enzyme for controlling the production of melanin in the human body. Overproduction of melanin can lead to a variety of skin disorders. Calycosin is an isoflavone from Astragali Radix, which is a traditional Chinese medicine that exhibits several pharmacological activities including skin whitening. In our study, the inhibitory effect of calycosin on melanin production is confirmed in a zebrafish in vivo model by comparing with hydroquinone, kojic acid, and arbutin, known as tyrosinase inhibitors. Moreover, the inhibitory kinetics of calycosin on tyrosinase and their binding mechanisms are determined using molecular docking techniques, molecular dynamic simulations, and free energy analysis. The results indicate that calycosin has an obvious inhibitory effect on zebrafish pigmentation at the concentration of 7.5 μM, 15 μM, and 30 μM. The IC₅₀ of calycosin is 30.35 μM, which is lower than hydroquinone (37.35 μM), kojic acid (6.51 × 10³ μM), and arbutin (3.67 × 10⁴ μM). Furthermore, all the results of molecular docking, molecular dynamics simulations, and free energy analysis suggest that calycosin can directly bind to the active site of tyrosinase with very good binding affinity. The study indicates that the combination of computer molecular modeling and zebrafish in vivo assay would be feasible in confirming the result of the in vitro test and illustrating the target-binding information.