Inhibitory effects of 1,3-selenazol-4-one derivatives on mushroom tyrosinase

This study reports depigmenting potency of 1,3-selenazol-4-one derivatives, which would be based upon the finding of direct inhibition to mushroom tyrosinase. 1,3-Selenazol-4-one derivatives exhibited inhibitory effect on dopa oxidase activity of mushroom tyrosinase. In this study, inhibitory effects of six kinds of 1,3-selenazol-4-one derivatives (A, B, C, D, E and F) on mushroom tyrosinase were investigated. Compounds at a concentration of 500 microM exhibited 33.4-62.1% of inhibition on dopa oxidase activity of mushroom tyrosinase. Their inhibitory effects were higher than that of kojic acid (31.7%), a well known tyrosinase inhibitor. 2-(4-Methylphenyl)-1,3-selenazol-4-one (A) exhibited the strongest inhibitory effect among them dose-dependently and in competitive inhibition manner.     

Development of 5-[(3-aminopropyl)phosphinooxy]-2-(hydroxymethyl)-4H-pyran-4-one as a novel whitening agent

A stable derivative of kojic acid, 5-[(3-aminopropyl)phosphinooxy]-2-(hydroxymethyl)-4H-pyran-4-one (Kojyl-APPA), was synthesized in good yield. The effects of Kojyl-APPA on tyrosinase activity and melanin synthesis were investigated. Kojyl-APPA showed tyrosinase inhibition effect (30%) in situ, but not in vitro. Kojyl-APPA inhibited tyrosinase activity significantly at 24 h after treatment in normal human melanocytes. It means that Kojyl-APPA is not a direct inhibitor of tyrosinase itself, but it is converted to a potential inhibitor kojic acid enzymatically in cells. In addition, Kojyl-APPA decreased melanin content to 75% of control in melanoma cells and decreased neomelanin synthesis to 43% of control in normal human melanocytes. Its permeation through skin increased by about 8 times as compared with kojic acid.     

Potent inhibitory effects of N-aryl S-alkylthiocarbamate derivatives on the dopa oxidase activity of mushroom tyrosinase

This study reports the potent inhibitory effect of N-aryl S-alkylthiocarbamate derivatives on mushroom tyrosinase (MT) activity. N-Aryl S-alkylthiocarbamate derivatives were found to exhibit a potent inhibitory effect on the dopa (3,4-dihydroxyphenylalanine) oxidase activity of mushroom tyrosinase. Most of the N-aryl S-alkylthiocarbamate derivatives (compounds from A to J) exhibited higher inhibitory effects than kojic acid (IC50=318 microM), a well known tyrosinase inhibitor. Tyrosinase was the most inhibited by S-phenetyl N-phenylthiocarbamate (compound E, IC50=7.25 microM), and this inhibition was 44 times stronger than that of kojic acid. Compound E exhibited 95.0% of inhibition at 100 microM. A kinetic study of MT inhibition by compound E using the Lineweaver-Burk plots analysis was performed. And the kinetics profiles observed suggest that compound E competitively inhibits MT.     

Novel Anti-Melanogenic Compounds, (Z)-5-(Substituted Benzylidene)-4-thioxothiazolidin-2-one Derivatives: In Vitro and In Silico Insights

To confirm that the β-phenyl-α,β-unsaturated thiocarbonyl (PUSTC) scaffold, similar to the β-phenyl-α,β-unsaturated carbonyl (PUSC) scaffold, acts as a core inhibitory structure for tyrosinase, twelve (Z)-5-(substituted benzylidene)-4-thioxothiazolidin-2-one ((Z)-BTTZ) derivatives were designed and synthesized. Seven of the twelve derivatives showed stronger inhibitory activity than kojic acid against mushroom tyrosinase. Compound 2b (IC₅₀ = 0.47 ± 0.97 µM) exerted a 141-fold higher inhibitory potency than kojic acid. Kinetic studies’ results confirmed that compounds 2b and 2f are competitive tyrosinase inhibitors, which was supported by high binding affinities with the active site of tyrosinase by docking simulation. Docking results using a human tyrosinase homology model indicated that 2b and 2f might potently inhibit human tyrosinase. In vitro assays of 2b and 2f were conducted using B16F10 melanoma cells. Compounds 2b and 2f significantly and concentration-dependently inhibited intracellular melanin contents, and the anti-melanogenic effects of 2b at 10 µM and 2f at 25 µM were considerably greater than the inhibitory effect of kojic acid at 25 µM. Compounds 2b and 2f similarly inhibited cellular tyrosinase activity and melanin contents, indicating that the anti-melanogenic effects of both were due to tyrosinase inhibition. A strong binding affinity with the active site of tyrosinase and potent inhibitions of mushroom tyrosinase, cellular tyrosinase activity, and melanin generation in B16F10 cells indicates the PUSTC scaffold offers an attractive platform for the development of novel tyrosinase inhibitors.     

1-(2,4-dihydroxyphenyl)-3-(2,4-dimethoxy-3-methylphenyl)propane, a novel tyrosinase inhibitor with strong depigmenting effects

A series of diarylpropane compounds was isolated by screening a plant extract library for inhibitors of mushroom tyrosinase. The most potent compound, 1-(2,4-dihydroxyphenyl)-3-(2,4-dimethoxy-3-methylphenyl)propane (UP302: CAS# 869743-37-3), was found in the medicinal plant Dianella ensifolia. Synthetic and plant-derived versions of UP302 inhibited mushroom tyrosinase with similar potencies. UP302 inhibited mushroom tyrosinase with K(i)=0.3 microM, in a competitive and reversible fashion. UP302 was 22 times more potent than Kojic acid in inhibiting murine tyrosinase, with IC(50) values of 12 and 273 microM respectively. Experiments on mouse melanoma cells B16-F1 and on human primary melanocytes demonstrated that UP302 inhibits melanin formation with IC(50) values of 15 and 8 microM respectively. Long-term treatment of cultured melanocytes with up to 62 microM of UP302 revealed no detectable cytotoxicity. In a reconstructed skin model (MelanoDerm) topical application of 0.1% UP302 resulted in significant skin lightening and decrease of melanin production without effects on cell viability, melanocyte morphology or overall tissue histology. In conclusion, UP302 is a novel tyrosinase inhibitor that suppresses melanin production in both cultured melanocytes and reconstructed skin with high potency and without adverse side effects.     

Synthesis and Preliminary In Vitro Biological Evaluation of 5-Chloro-2-(Substituted Phenyl)Benzo[d]Thiazole Derivatives Designed As Novel Antimelanogenesis Agents

We describe the design, synthesis, and biological activities of 5-chloro-2-(substituted phenyl)benzo[d]thiazole derivatives as novel tyrosinase inhibitors. Among them, 4-(5-chloro-2,3-dihydrobenzo[d]thiazol-2-yl)-2,6-dimethoxyphenol (MHY884) and 2-bromo-4-(5-chloro-benzo[d]thiazol-2-yl)phenol (MHY966) showed inhibitory activity higher than or similar to kojic acid, against mushroom tyrosinase. Therefore, we carried out kinetic studies on the two compounds with potent tyrosinase inhibitory effects. Kinetic analysis of tyrosinase inhibition revealed that all of these compounds are competitive inhibitors. MHY884 and MHY966 effectively inhibited tyrosinase activity and reduced melanin levels in B16 cells treated with ??-melanocyte stimulating hormone (??-MSH). These data strongly suggest that the newly synthesized compounds MHY884 and MHY966 could suppress production of melanin via inhibition of tyrosinase activity.     

Methoxy-Substituted Tyramine Derivatives Synthesis,Computational Studies and Tyrosinase Inhibitory Kinetics

Targeting tyrosinase for melanogenesis disorders is an established strategy. Hydroxyl-substituted benzoic and cinnamic acid scaffolds were incorporated into new chemotypes that displayed in vitro inhibitory effects against mushroom and human tyrosinase for the purpose of identifying anti-melanogenic ingredients. The most active compound 2-((4-methoxyphenethyl)amino)-2-oxoethyl (E)-3-(2,4-dihydroxyphenyl) acrylate (Ph9), inhibited mushroom tyrosinase with an IC₅₀ of 0.059 nM, while 2-((4-methoxyphenethyl)amino)-2-oxoethyl cinnamate (Ph6) had an IC₅₀ of 2.1 nM compared to the positive control, kojic acid IC₅₀ 16700 nM. Results of human tyrosinase inhibitory activity in A375 human melanoma cells showed that compound (Ph9) and Ph6 exhibited 94.6% and 92.2% inhibitory activity respectively while the positive control kojic acid showed 72.9% inhibition. Enzyme kinetics reflected a mixed type of inhibition for inhibitor Ph9 (K_i 0.093 nM) and non-competitive inhibition for Ph6 (K_i 2.3 nM) revealed from Lineweaver–Burk plots. In silico docking studies with mushroom tyrosinase (PDB ID:2Y9X) predicted possible binding modes in the catalytic site for these active compounds. Ph9 displayed no PAINS (pan-assay interference compounds) alerts. Our results showed that compound Ph9 is a potential candidate for further development of tyrosinase inhibitors.     

Microwave-assisted synthesis and biological evaluation of new thiazolylhydrazone derivatives as tyrosinase inhibitors and antioxidants

In this work, we have synthesized a series of 2-thiazolylhydrazone derivatives ( 1–27 ) and investigated their biological activities as tyrosinase inhibitors and antioxidants. Some compounds showed potent tyrosinase inhibitory activities and 4-(2-(2-(1-(4-Aminophenyl)ethylidene)-hydrazinyl)thiazol-4-yl) phenol ( 26 ) showed more potent inhibitory effect than the standard tyrosinase inhibitor kojic acid (IC₅₀: 9.8 μM vs. 23.6 μM). Compounds 2 , 14 , and 26 exhibited high antioxidant activities in 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays. The structure–activity relationship (SAR) indicated that the substitutions of bromine, hydroxyl group, and amino groups cause great effect to the inhibition effect against tyrosinase. The mechanism and kinetic studies demonstrated that the inhibitory effect of compound 26 on the tyrosinase by acting as the reversible and uncompetitive inhibitor. Docking studies suggests that compound 26 interacts strongly with mushroom tyrosinase via hydrogen bonding.     

Depigmenting activity and low cytotoxicity of alkoxy benzoates or alkoxy cinnamte in cultured melanocytes

To obtain effective and safe topical depigmenting agents, we synthesized hydroxybenzoates, alkoxybenzoates, and 3,4,5-trimethoxycinnamate containing a thymol moiety and screened then for high-level inhibitory activity against melanin synthesis in cultured melanocytes. Eight compounds were tested for their depigmenting effect and cytotoxicity using a murine melanocyte cell line. We found that 3,4,5-trialkoxybenzoates and 3,4,5-trimethoxycinnamate, synthesized by conjugating 3,4,5-trialkoxybenzoic acids and 3,4,5-trimethoxycinnmic acid with thymol, showed a potent depigmenting effect and low cytotoxicity. Compound 4h, 5-methyl-2-(methylethyl)phenyl (2E)-3-(3,4,5-trimethoxyphenyl)prop-2-enoate, showed the most potent depigmenting effect (IC50=10 microM) with low cytotoxicity (IC50=200 microM).     

Biological activities of phenolic compounds isolated from galls of Terminalia chebula Retz. (Combretaceae)

The aqueous extract of galls from Terminalia chebula Retz. (Combretaceae) was fractionated on Diaion and refractionated on octadecyl silica column. Six phenolic compounds were isolated and identified as gallic acid (1), punicalagin (2), isoterchebulin (3), 1,3,6-tri-O-galloyl-β-D-glucopyranose (4), chebulagic acid (5) and chebulinic acid (6). All of the compounds showed stronger 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and melanin inhibitory activities than ascorbic acid, butylated hydroxytoluene, α-tocopherol, arbutin and kojic acid, the reference compounds. Gallic acid (1) exhibited inhibitory activity against nitric oxide production in lipopolysaccharide-activated macrophages. However, all isolated compounds exhibited less activity than the reference compounds in mushroom tyrosinase inhibition and human tumour cytotoxicity assays. This study has demonstrated that the phenolic compounds isolated from galls of T. chebula might contribute significantly due to their antioxidant and whitening activities.     

Enzymatic synthesis of kojic acid esters and their potential industrial applications

In this paper, enzymatic methods for the synthesis of 5-hydroxy-2-(hydroxymethyl)-4H-pyran-4-one (kojic acid) esters are reviewed. Important process parameters related to the synthesis of kojic acid esters such as the type of immobilized lipase, solvent, temperature, initial water activity, water content, pH, metal salts, enzyme loading, substrates mole ratio, and acyl donors are highlighted and discussed. The properties of kojic acid esters related to their solubility, stability, cytotoxicity, depigmenting activity, tyrosinase inhibitory, metal-chelating, anti-oxidant, and other biological activities are also highlighted. At present, kojic acid and its esters are widely used in cosmetic and skin health industries as skin whitening agents. The advantages and disadvantages of various kojic acid esters are compared and possible industrial applications of these derivatives are also discussed.     

Phenolic constituents from the heartwood of Artocapus altilis and their tyrosinase inhibitory activity

From the MeOH extract of the heartwood of Artocapus altilis, thirteen phenolic compounds have been isolated, namely curcumin (1), desmethoxycurcumin (2), retrodihydrochalcone (3), apigenin (4), tangeretin (5), nobiletin (6), O-methyldehydrodieugenol (7), dehydrodieugenol (8), beta-hydroxypropiovanillone (9), p-coumaric acid (10), p-hydroxybenzaldehyde (11), vanillin (12), and vanillic acid (13). This is the first report on the presence of these compounds in the heartwood of A. altilis. Compounds 1, 2, and 10 showed more potent tyrosinase inhibitory activities, with IC50 values ranging from 2.3 to 42.0 microM, than the positive control kojic acid (IC50, 44.6 microM). The most active compound, p-coumaric acid (10) (IC50, 2.3 microM), was 22 times more active in tyrosinase inhibitory activity than kojic acid.     

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.     

Inhibitory effect of ammonium tetrathiotungstate on tyrosinase and its kinetic mechanism

Tyrosinase requires two copper ions at the active site, in order to oxidize phenols to catechols. In this study, the inhibitory effect of the copper-chelating compound, ammonium tetrathiotungstate (ATTT), on the tyrosinase activity was investigated. ATTT was determined to inactivate the activity of mushroom tyrosinase, in a dose-dependent manner. The kinetic substrate reaction revealed that ATTT functions as a kinetically competitive inhibitor in vitro, and that the enzyme-ATTT complex subsequently undergoes a reversible conformational change, resulting in the inactivation of tyrosinase. In human melanin-producing cells, ATTT evidenced a more profound tyrosinase-inhibitory effect than has been seen in the previously identified tyrosinase inhibitors, including kojic acid and hydroquinone. Our results may provide useful information for the development of whitening agent.     

胀果甘草提取物对蘑菇酪氨酸酶的抑制作用

筛选胀果甘草是对蘑菇酪氨酸酶抑制活性最强的提取物,并研究其对蘑菇酪氨酸酶的抑制类型,探究其抑制作用机理。 考察了胀果甘草7种不同溶剂包括甘草酸、提酸废液、石油醚、氯仿、乙酸乙酯、正丁醇及水提取物对蘑菇酪氨酸酶的抑制作用和对2,2-联氮-双(3-乙基苯并噻唑啉-6-磺酸)二胺盐(ABTS)自由基阳离子(ABTS·﹢)、羟基自由基(HO·)的清除作用,根据双倒数曲线图形判断对蘑菇酪氨酸酶的抑制作用类型,结合抗氧化能力探究对蘑菇酪氨酸酶的抑制作用机理。 在胀果甘草7种溶剂提取物中,以乙酸乙酯提取物对蘑菇酪氨酸酶具有最强的抑制作用,IC50为3.4775 g/L,双倒数曲线做图得到了一组纵轴截距不变的曲线,抑制常数K1为0.6667 g/L,胀果甘草乙酸乙酯提取物也具有最强的清除ABTS·﹢、HO·的能力,半清除浓度和速率常数分别为0.0442 g/L和4.634×108 L/(g·s)。 胀果甘草乙酸乙酯提取物对蘑菇酪氨酸酶的抑制作用是可逆竞争性抑制,推测其对酪氨酸酶的抑制是通过清除了氧自由基和作为竞争性底物而实现的。     

Biochemical Properties of Tyrosinase from Aspergillus terreus and Penicillium copticola; Undecanoic Acid from Aspergillus flavus,an Endophyte of Moringa oleifera,Is a Novel Potent Tyrosinase Inhibitor

Tyrosinase is a copper-containing monooxygenase catalyzing the O-hydroxylation of tyrosine to 3,4-dihydroxyphenylalanine then to dopaquinone that is profoundly involved in melanin synthesis in eukaryotes. Overactivation of tyrosinase is correlated with hyperpigmentation that is metabolically correlated with severe pathological disorders, so, inhibition of this enzyme is the most effective approach in controlling the overproduction of melanin and its hazardous effects. Thus, searching for a powerful, selective inhibitor of human tyrosinase to limit the hyper-synthesis of melanin is a challenge. Unlike the difficulty of overexpression of human tyrosinase, using fungal tyrosinase as a model enzyme to the human one to evaluate the mechanistics of enzyme inhibition in response to various compounds is the most feasible strategy. Thus, the purification of highly catalytic-efficient fungal tyrosinase, exploring a novel inhibitor, and evaluating the mechanistics of enzyme inhibition are the main objectives of this work. Aspergillus terreus and Penicillium copticola were reported as the most potential tyrosinase producers. The biochemical properties suggest that this enzyme displays a higher structural and catalytic proximity to human tyrosinase. Upon nutritional bioprocessing by Plackett–Burman design, the yield of tyrosinase was increased by about 7.5-folds, compared to the control. The purified tyrosinase was strongly inhibited by kojic acid and A. flavus DCM extracts with IC₅₀ values of 15.1 and 12.6 µg/mL, respectively. From the spectroscopic analysis, the main anti-tyrosinase compounds of A. flavus extract was resolved, and verified as undecanoic acid. Further studies are ongoing to unravel the in vivo effect and cytotoxicity of this compound in fungi and human, that could be a novel drug to various diseases associated with hyperpigmentation by melanin.     

曲酸对马铃薯酪氨酸酶的抑制作用研究

曲酸等几种化合物对马铃薯酪氨酸酶的抑制作用表明：巯基类化合物、抗坏血酸和曲酸具有较强的抑制作用。预水浴温度和时间对曲酸的抑制作用并没有显著影响,曲酸通过延长L-tyrosine加氧羟化的迟滞时间,从而抑制单酚酶活性,以L—DOPA为底物测得曲酸为竞争性抑制,抑制常数艏为0．17mM。紫外光谱表明曲酸能将二酚酶催化的产物o-醌还原成二酚,从而抑制黑色素的生成。     

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.     

Tyrosinase inhibitors from Rhododendron collettianum and their structure-activity relationship (SAR) studies

A new coumarinolignoid 8'-epi-cleomiscosin A (1) together with the new glycoside 8-O-beta-D-glucopyranosyl-6-hydroxy-2-methyl-4H-1-benzopyrane-4-one (2) have been isolated from the aerial parts of Rhododendron collettianum and their structures determined on the basis of spectroscopic evidences. Tyrosinase inhibition study of these compounds and their structure-activity relationship (SAR) were also investigated. The compounds exhibited potent to mild inhibition activity against the enzyme. Especially, the compound 1 showed strong inhibition (IC50=1.33 microM) against the enzyme tyrosinase, as compared to the standard tyrosinase inhibitors kojic acid (IC50=16.67 microM) and L-mimosine (IC50=3.68 microM), indicating its potential used for the treatment of hyperpigmentation associated with the high production of melanocytes.     

Tyrosinase inhibition studies of diterpenoid alkaloids and their derivatives: structure-activity relationships

In the present article, tyrosinase inhibition studies on fifteen diterpenoid alkaloids, with lycoctonine skeleton, and their semisynthetic derivatives 1-15 and six napelline-type compounds 16-21 are discussed. Their structure-activity relationship for tyrosinase inhibition is also discussed. These activities were compared with two referenced tyrosinase inhibitors, kojic acid and L-mimosine. The study showed that lappaconitine HBr (1) is the most potent member of the series (IC50 = 13.30 microM).