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1.
Tyrosinase is known to be a key enzyme in melanin biosynthesis, involved in determining the color of mammalian skin and hair. Various dermatological disorders, such as melasama, age spots, and sites of actinic damage, arise from the accumulation of an excessive level of epidermal pigmentation. The inadequacy of current therapies to treat these conditions as well as high cytotoxicity and mutagenicity, poor skin penetration, and low stability of formulations led us to seek new whitening agents to meet the medical requirements for depigmenting agents. The inhibitory effect of licorice extract on tyrosinase activity was higher than that expected from the level of glabridin in the extract. This led us to test for other components that may contribute to this strong inhibitory activity. Results indicated that glabrene and isoliquiritigenin (2',4',4-trihydroxychalcone) in the licorice extract can inhibit both mono- and diphenolase tyrosinase activities. The IC(50) values for glabrene and isoliquiritigenin were 3.5 and 8.1 microM, respectively, when tyrosine was used as substrate. The effects of glabrene and isoliquiritigenin on tyrosinase activity were dose-dependent and correlated to their ability to inhibit melanin formation in melanocytes. This is the first study indicating that glabrene and isoliquiritigenin exert varying degrees of inhibition on tyrosinase-dependent melanin biosynthesis, suggesting that isoflavenes and chalcones may serve as candidates for skin-lightening agents.  相似文献   

2.
The antibrowning activity of sodium hydrogen sulfite (NaHSO(3)) was compared to that of other sulfur-containing compounds. Inhibition of enzymatic browning was investigated using a model browning system consisting of mushroom tyrosinase and chlorogenic acid (5-CQA). Development of brown color (spectral analysis), oxygen consumption, and reaction product formation (RP-UHPLC-PDA-MS) were monitored in time. It was found that the compounds showing antibrowning activity either prevented browning by forming colorless addition products with o-quinones of 5-CQA (NaHSO(3), cysteine, and glutathione) or inhibiting the enzymatic activity of tyrosinase (NaHSO(3) and dithiothreitol). NaHSO(3) was different from the other sulfur-containing compounds investigated, because it showed a dual inhibitory effect on browning. Initial browning was prevented by trapping the o-quinones formed in colorless addition products (sulfochlorogenic acid), while at the same time, tyrosinase activity was inhibited in a time-dependent way, as shown by pre-incubation experiments of tyrosinase with NaHSO(3). Furthermore, it was demonstrated that sulfochlorogenic and cysteinylchlorogenic acids were not inhibitors of mushroom tyrosinase.  相似文献   

3.
Flavonoids, a group of naturally occurring antioxidants and metal chelators, can be used as tyrosinase inhibitors due to their formation of copper-flavonoid complexes. Thus, to investigate the underlying inhibition mechanism, a large group of flavonoids from several major flavones and flavonols were tested using fluorescence quenching spectroscopy. In addition, large differences in the tyrosinase inhibitory activities and chelating capacities according to the location of the hydroxyl group(s) in combination with the A and B rings in the flavonoids were confirmed. Accordingly, the major conclusions from this work are as follows: (i) The tyrosinase inhibitory activity is not only dependent on the number of hydroxyl groups in the flavonoids, (ii) the enzyme is primarily quenched by the hydroxyl group(s) of A and B rings on the ether side of the flavonoids, and (iii) the tyrosinase inhibitory activity of 7,8,3',4'-tetrahydroxyflavone is supported by a virtual model of docking with the mushroom tyrosinase, which depicts the quenching of the enzyme. The results also demonstrated that the dihydroxy substitutions in the A and B rings are crucial for Cu2+-chelate formation, thereby influencing the tyrosinase inhibitory activity.  相似文献   

4.
p-Hydroxybenzaldehyde thiosemicarbazone (HBT) and p-methoxybenzaldehyde thiosemicarbazone (MBT) were synthesized and established by (1)H NMR and mass spectra. Both compounds were evaluated for their inhibition activities on mushroom tyrosinase and free-cell tyrosinase and melanoma production from B(16) mouse melanoma cells. Results showed that both compounds exhibited significant inhibitory effects on the enzyme activities. HBT and MBT decreased the steady state of the monophenolase activity sharply, and the IC(50) values were estimated as 0.76 and 7.0 μM, respectively. MBT lengthened the lag time, but HBT could not. HBT and MBT inhibited diphenolase activity dose-dependently, and their IC(50) values were estimated as 3.80 and 2.62 μM, respectively. Kinetic analyses showed that inhibition type by both compounds was reversible and their mechanisms were mixed-type. Their inhibition constants were also determined and compared. The research may supply the basis for the development of new food preservatives and cosmetic additives.  相似文献   

5.
Kinetic study of oxalic acid inhibition on enzymatic browning   总被引：6，自引：0，他引：6  
Oxalic acid has a strong antibrowning activity. The inhibitory pattern on catechol-PPO model system appeared to be competitive, with a K(i) value of 2.0 mM. When the PPO was incubated with oxalic acid, the activity was not recovered via dialysis, but the inactivated enzyme partially recovered its activity when cupric ion was added. Comparing the relative antibrowning effectiveness of oxalic acid with other common antibrowning agents, oxalic acid with I(50) value of 1.1 mM is as effective as kojic acid and more potent than cysteine and glutathione.  相似文献   

6.
The effects of apple polyphenols on melanogenesis in B16 mouse melanoma cells were investigated. The inhibitory effect of apple polyphenols was stronger than that of arbutin or kojic acid. Three polyphenol fractions (phenolic acid derivatives, procyanidins and other flavonoids) were isolated, and the procyanidins were fractionated according to the degree of polymerization using normal-phase chromatography. The procyanidin trimer-to-pentamer fractions were found to have the most pronounced effect on melanogenesis. Furthermore, each procyanidin fraction inhibited mushroom tyrosinase. No correlation between the degree of procyanidin polymerization and tyrosinase inhibitory activity was observed. Nevertheless, these observations suggest that procyanidins are effective inhibitors of tyrosinase.  相似文献   

7.
Tyrosinase is a copper enzyme with broad substrate specifity toward a lot of phenols with different biotechnological applications. The availability of quick and reliable measurement methods of the enzymatic activity of tyrosinase is of outstanding interest. A series of spectrophotometric methods for determining the monophenolase and diphenolase activities of tyrosinase are discussed. The product of both reactions is the o-quinone of the corresponding monophenol/diphenol. According to the stability and properties of the o-quinone, the substrate is classified as four substrate types. For each of these substrate types, we indicate the best method for measuring diphenolase activity (among eight methods) and, when applicable, for measuring monophenolase activity (among four methods). The analytical and numerical solutions to the system of differential equations corresponding to the reaction mechanism of each case confirm the underlying validity of the different spectrophotometric methods proposed for the kinetic characterization of tyrosinase in its action on different substrates.  相似文献   

8.
为筛选出欧李叶片类黄酮和9种类黄酮物质中单一物质含量较高的品种,并分析确定具有抗氧化和抑制酪氨酸酶活性的物质,本研究以38份欧李种质基生枝成熟期叶片为试材,利用超高效液相色谱法(UHPLC)测定儿茶素、表儿茶素、甘草素、芦丁、槲皮素、槲皮素-7-O-葡萄糖苷、杨梅素、光甘草定、根皮素活性物质含量,对其抗氧化及抑制酪氨酸酶能力进行分析。结果表明,38份欧李种质叶片中,Y09-14品种类黄酮含量最高,为64.84 mg·g-1,且类黄酮及其9种组分的变异系数均超过20%,表明其遗传多样性丰富。根据叶片类黄酮含量进行聚类分析,发现70%以上的种质为中类黄酮类型。通过对不同种质欧李叶片类黄酮及不同组分物质含量的测定发现,儿茶素、表儿茶素、芦丁、槲皮素-7-O-葡萄糖苷在38份种质中均能被检测到,且儿茶素含量为6.271~935.295 mg·100 g-1,极显著高于另外8种物质。4种不同活性物质(儿茶素、表儿茶素、芦丁、槲皮素-7-O-葡萄糖苷)与DPPH清除率呈极显著正相关(P<0.01),表明这种活性物质的抗氧化能力较强;芦丁、槲皮素-7-O-葡萄糖苷、光甘草定与酪氨酸酶抑制率呈正相关。本研究为欧李后期相关物质的检测及提取提供了依据。  相似文献   

9.
The inhibitory characteristics of two isoflavone metabolites, 7,8,4'-trihydroxyisoflavone and 5,7,8,4'-tetrahydroxyisoflavone, on mushroom tyrosinase were investigated. The two isoflavones were isolated from soygerm koji and inhibited both monophenolase and diphenolase activities of tyrosinase. Their inhibition type was demonstrated to be irreversible inhibition by preincubation and recovery experiments. By using HPLC analysis, it was found that mushroom tyrosinase could catalyze the two isoflavones. These results revealed that the two isoflavones belonged to suicide substrates of mushroom tyrosinase. The partition ratios between molecules of suicide substrate in the formation of product and in the inactivation of enzyme were determined to be 81.7 +/- 5.9 and 35.5 +/- 3.8 for 7,8,4'-trihydroxyisoflavone and 5,7,8,4'-tetrahydroxyisoflavone, respectively. From kinetic studies, maximal inactivation rate constants and Michaelis constants were 0.79 +/- 0.08 and 1.01 +/- 0.04 min(-1) and 18.7 +/- 2.31 and 7.81 +/- 0.05 microM for 7,8,4'-trihydroxyisoflavone and 5,7,8,4'-tetrahydroxyisoflavone, respectively, when L-DOPA was used as the enzyme substrate. Structure analysis comparing the inactivating activity between the two isoflavones and their structure analogues showed that not only the 7,8-dihydroxyl groups but also the isoflavone skeleton of the two isoflavones played an important role in inactivating tyrosinase activity. The present study demonstrated that 7,8,4'-trihydroxyisoflavone and 5,7,8,4'-tetrahydroxyisoflavone are potent suicide substrates of mushroom tyrosinase.  相似文献   

10.
The main polyphenols were isolated from the leaves of six selected persimmon cultivars. Seven compounds were obtained by reverse-phase HPLC, and their structures were elucidated by multiple NMR measurements. These compounds are hyperoside, isoquercitrin, trifolin, astragalin, chrysontemin, quercetin-3-O-(2'-O-galloyl-β-D-glucopyranoside) (QOG), and kaempferol-3-O-(2'-O-galloyl-β-D-glucopyranoside) (KOG). Their inhibitory activity was tested against tyrosinase for the oxidation of L-DOPA, and only chrysontemin showed inhibitory activity. To investigate the differences of their inhibitory effects, the tyrosinase inhibitory activities of their aglycons, cyanidin, quercetin, and kaempferol, were also tested. As a result, it was confirmed that the most influential moiety for tyrosinase inhibition was the 3',4'-dihydroxy groups of the catechol moiety. Moreover, the tyrosinase inhibitory activity of chrysontemin, which was identified in persimmon leaves for the first time, is supported by a simulated model of chrysontemin docking into mushroom tyrosinase.  相似文献   

11.
Tyrosinase inhibitory and antioxidant activity of gallic acid and its series of alkyl chain esters were investigated. All inhibited the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) catalyzed by mushroom tyrosinase. However, gallic acid and its short alkyl chain esters were oxidized as substrates yielding the colored oxidation products. In contrast, the long alkyl chain esters inhibited the enzyme activity without being oxidized. This indicates that the carbon chain length is associated with their tyrosinase inhibitory activity, presumably by interacting with the hydrophobic protein pocket in the enzyme. On the other hand, the esters, regardless their carbon chain length, showed potent scavenging activity on the autoxidation of linoleic acid and 1,1-diphenyl-2-p-picryhydrazyl (DPPH) radical, suggesting that the alkyl chain length is not related to the activity. The effects of side-chain length of gallates in relation to their antibrowning activity are studied.  相似文献   

12.
Tyrosinase inhibitors of Pulsatilla cernua root-derived materials   总被引：3，自引：0，他引：3  
The inhibition of mushroom tyrosinase by Pulsatilla cernua root-derived materials was evaluated. The bioactive components of Pulsatilla cernua root were characterized by spectroscopic analyses as 3,4-dihydroxycinnamic acid and 4-hydroxy-3-methoxycinnamic acid, which exhibited potent antityrosinase activity. The ID50 values of 3,4-dihydroxycinnamic acid and 4-hydroxy-3-methoxycinnamic acid were 0.97 and 0.33 mM, respectively. The compounds isolated from Pulsatilla cernua roots exhibited noncompetitive inhibition against oxidation of L-DOPA by mushroom tyrosinase. This activity was compared with that of three cinnamic acid derivatives and four well-known tyrosinase inhibitors. The ID50 of 4-hydroxy-3-methoxycinnamic acid exhibited superior activity relative to anisaldehyde, anisic acid, benzoic acid, benzaldehyde, cinnamic acid, and cinnamaldehyde; but antityrosinase inhibitors and cinnamic acid derivatives, except for cinnamyl alcohol, were slightly more effective than 3,4-dihydroxycinnamic acid. In the case of benzaldehyde and cinnamaldehyde, the aldehyde group is, apparently, a key group in eliciting potent inhibitory activity, whereas anisaldehyde is more effective than anisic acid. Methoxy substitutions, such as 2-methoxycinnamic acid, 3-methoxycinnamic acid, and 4-methoxycinnamic acid, enhanced inhibition of tyrosinase activity. As a naturally occurring tyrosinase inhibitor, 3,4-dihydroxycinnamic acid and 4-hydroxy-3-methoxycinnamic acid may be useful as new agents to inhibit the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) by mushroom tyrosinase.  相似文献   

13.
A cDNA encoding mature human tyrosinase was cloned into pET-23a(+) and transformed into E. coli BL21(DE3). Three major recombinant proteins, mature human tyrosinase (RHT??????), N-terminal truncated human tyrosinase (RHT???????), and β-lactamase, were overexpressed as inclusion bodies in E. coli after 12 h of induction with 1.0 mM isopropyl-β-D-thiogalactopyranoside at 37 °C. After sonication and centrifugation, the inclusion body was harvested, solubilized, dialyzed, and refolded into the active form with monophenolase and diphenolase activities. It was purified to homogeneity by DEAE-Sepharose FF and Sephadex G-75. The molecular mass and N-terminal sequence were 57.0 kDa and GHFPRAC, respectively, and corresponded to those of mature human tyrosinase. The RHT was active in a broad range of temperature and pH, and with optimum activity at 70 °C and pH 8.5.  相似文献   

14.
The inhibition of (R)-, (S)-, and (+/-)-6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acids (HTCCA) on mushroom tyrosinase was evaluated. All HTCCAs inhibited the tyrosinase activity. The ID(50) values were 1.88, 1.84, and 1.88 for the (R)-, (S)-, and (+/-)-HTCCAs, respectively. The inhibition kinetics analyzed by Hanes-Woolf plots indicated that both (R)- and (S)-HTCCAs are competitive inhibitors of the tyrosinase, with K(i) values of 0.83 and 0.61 mM, respectively. Dimethyl sulfoxide (DMSO) was also tested for its direct inhibitory activity against the tyrosinase and its potential influence on the tyrosinase inhibitory effects of (R)- and (S)-HTCCAs. DMSO, a widely used solvent for tyrosinase inhibitors, was found to dose-dependently inhibit the tyrosinase activity. Addition of DMSO in a tyrosinase digest containing either (R)- or (S)-HTCCA further dose-dependently reduced the tyrosinase activity. These data indicated a potential to use a HTCCA as a tyrosinase inhibitor in food, cosmetic, and medicinal products and a need to improve the solvent system for the studies of tyrosinase inhibitions.  相似文献   

15.
Competitive inhibition of mushroom tyrosinase by 4-substituted benzaldehydes   总被引：24，自引：0，他引：24  
A kinetic study of the inhibition of mushroom tyrosinase by 4-substituted benzaldehydes showed that these compounds behave as classical competitive inhibitors, inhibiting the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) by mushroom tyrosinase (o-diphenolase activity). The kinetic parameter (K(I)) characterizing this inhibition was evaluated for all of the seven compounds assayed. Cuminaldehyde showed the most potent inhibitory activity (K(I) = 9 microM). It also inhibited the oxidation of L-tyrosine by mushroom tyrosinase (o-monophenolase activity) in a competitive manner. The corresponding kinetic parameter for this inhibition was evaluated (K(I) = 0.12 mM).  相似文献   

16.
In insects, tyrosinase plays important roles in normal developmental processes, such as cuticular tanning, scleration, wound healing, production of opsonins, encapsulation and nodule formation for defense against foreign pathogens. Thus, tyrosinase may be regarded as a potential candidate for novel bioinsecticide development. A family of alkyl 3,4-dihydroxybenzoates (C?-C?), new tyrosinsase inhibitors, were synthesized. Their inhibitory effects on the activity of tyrosinase have been investigated. The results showed all of them could inhibit the activity of tyrosianse effectively. The order of potency was nonyl 3,4-dihydroxybenzoate (C?DB) > octyl 3,4-dihydroxybenzoate(C?DB) > heptyl 3,4-dihydroxybenzoate(C?DB) > hexyl 3,4-dihydroxybenzoate (C?DB). The kinetic analysis of these four compounds on tyrosinase was taken to expound their inhibitory mechanism. The research of the control of insects in agriculture was taken as C?DB for example. C?DB could inhibit the development and molting of Plutella xylostella effectively. To clarify its insecticidal mechanism, we researched the expression of tyrosinase in the P. xylostella treated with C?DB by real-time quantitative PCR. The results showed C?DB could inhibit the expression of tyrosinase in the P. xylostella as expected.  相似文献   

17.
Mushroom tyrosinase was immobilized from an extract onto glass beads covered with the cross-linked totally cinnamoylated derivates of d-sorbitol (sorbitol cinnamate) and glycerine (glycerine cinnamate). The enzyme was immobilized onto the support by direct adsorption, and the quantity of immobilized tyrosinase was higher for sorbitol cinnamate, the support with the higher number of esterified hydroxyls per unit of monosacharide, than for glycerine cinnamate. The results obtained from the stereospecificity study of the monophenolase and diphenolase activity of immobilized mushroom tyrosinase are reported. The enantiomers L-tyrosine, DL-tyrosine, D-tyrosine, L-dopa, DL-dopa, D-dopa, L-alpha-methyldopa, DL-alpha-methyldopa, L-isoprenaline, DL-isoprenaline, L-adrenaline, DL-adrenaline, L-noradrenaline, and D-noradrenaline were assayed with tyrosinase immobilized on a chiral support (sorbitol cinnamate), whereas L-tyrosine, DL-tyrosine, D-tyrosine, L-dopa, DL-dopa, D-dopa, L-alpha-methyldopa, and DL-alpha-methyldopa were assayed with tyrosinase immobilized on a nonchiral support (glycerine cinnamate). The same Vmax(app) values for each series of enantiomers were obtained. However, the Km(app) values were different, the l isomers showing lower values than the dl isomers, whereas the highest Km(app) value was obtained with d isomers. No difference was observed in the stereospecificity of tyrosinase immobilized on a chiral (sorbitol cinnamate) or nonchiral (glycerine cinnamate) support.  相似文献   

18.
Antibrowning activities of Morus alba L. twig extracts, oxyresveratrol, and mulberroside A isolated from mulberry twig on cloudy apple juices and fresh-cut apple slices were evaluated by monitoring the change of a* value, total color difference (DeltaE), and visual observation. It was found, similar to 4-hexylresorcinol, that oxyresveratrol could effectively inhibit browning in cloudy apple juices at a concentration as low as 0.01% and that mulberry twig extract also showed remarkable antibrowning effects on cloudy apple juices. However, for fresh-cut apple slices, mulberry twig extract and oxyresveratrol needed to be used in combination at least with ascorbic acid to exhibit their antibrowning effects. Apple slice samples treated by dipping in a solution containing 0.001 M oxyresveratrol, 0.5 M isoascorbic acid, 0.05 M calcium chloride, and 0.025 M acetylcysteine did not undergo any substantial browning reaction for 28 days at 4 degrees C. However mulberroside A did not show antibrowning effects on cloudy apple juices although it is also a good mushroom tyrosinase inhibitor.  相似文献   

19.
Cardol triene was first purified from cashew (Anacardium occidentale L.) nut shell liquid and identified by gas chromatography coupled to mass spectroscopy and nuclear magnetic resonance. The effects of this compound on the activity of mushroom tyrosinase were studied. The results of the kinetic study showed that cardol triene was a potent irreversible competitive inhibitor and the inactivation was of the complexing type. Two molecules of cardol triene could bind to one molecule of tyrosinase and lead to the complete loss of its catalytic activity. The microscopic rate constants were determined for the reaction of cardol triene with the enzyme. The anti-tyrosinase kinetic research of this study provides a comprehensive understanding of inhibitory mechanisms of resorcinolic lipids and is beneficial for the future design of novel tyrosinase inhibitors.  相似文献   

20.
Treatments to inhibit browning and decay and prolong shelf life of fresh-cut mangoes were investigated. Combinations of antibrowning agents and modified atmosphere packaging (MAP) resulted in a reduction of browning and deterioration of fresh-cut mangoes stored at 10 degrees C. Combinations of several browning inhibitors were more effective than those applied individually. Among these treatments, solutions containing 4-hexylresorcinol (0.001 M) (HR) plus potassium sorbate (0.05 M) (KS) and HR plus KS plus D-isoascorbic acid (0.5 M) (ER) reduced changes in color (L, a, and b) and microbial growth and did not affect sensory characteristics of fresh-cut mangoes. In general, these treatments did not affect significantly the changes in organic acids and sugar content of slices during the 14 days of storage at 10 degrees C. High humidity created in the in-package atmosphere alleviated tissue dryness and was an important factor in the ability of the antibrowning solutions to prevent browning and decay. It appears that the maintenance of quality of fresh-cut mangoes is more related to particular combinations of the antibrowning agents used rather than the modified atmosphere created inside the package. HR + ER + KS treatment in combination with MAP could be used to inhibit browning, decay, and deterioration of fresh-cut mangoes.  相似文献   

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