SENSORS AND ACTUATORS B-CHEMICAL
·
2018
·
IF 5.667
Xiangui Ma,Wenyue Gao,Mohamed Ibrahim Halawa,Yixiang Lan,Jianping Li,Guobao Xu
Tyrosinase is a key enzyme in melanin biosynthesis and its serum level is an important biomarker for some dermatoses such as vitiligo and melanoma. Thus, a sensitive and facile assay for tyrosinase activity is in urgent demands. Lucigenin is a well-known chemiluminescent luminophore, but has been rarely been employed for fluorescence detection. In this work, a facile method to detect tyrosinase activity based on lucigenin fluorescence has been reported for the first time. When tyrosinase was mixed with tyrosine, tyrosine was oxidized to generate melanin-like polymers which can effectively quench the fluorescence of lucigenin. A linear range of tyrosinase from 0.25 to 25 μg/mL was obtained with detection limit of 0.2 μg/mL. In addition, a useful platform for screening potential tyrosinase inhibitors was constructed based on the proposed system. The linear range is from 2.5 to 62.5 μg/mL and the detection limit is as low as 1.0 μg/mL for kojic acid , a typical tyrosinase inhibitor.
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高影响因子
ANALYTICAL CHEMISTRY
·
2015
·
IF 5.636
Ye Teng,Xiaofang Jia,Jing Li,Erkang Wang
In this work, a sensitive and selective ratiometric fluorescence sensing platform was built for the detection of tyrosinase (TYR) activity and dopamine (DA) using glutathione (GSH) protected gold nanoclusters (Au NCs) as probes. Upon excitation at 350 nm, Au NCs displayed an intense red emission, which could be effectively quenched by quinones. TYR, a typical polyphenol oxidase, can catalyze the oxidization of DA to o-quinone and therefore quenched the fluorescence of Au NCs. Moreover, the reaction of TYR and DA gave rise to an emission band at 400 nm, which increased in a TYR/DA-concentration-dependent manner. The ratiometric signal variations were utilized for facile, sensitive, and selective detection of TYR activity and DA. A linear range was obtained from 0.006–3.6 unit mL–1 of TYR activity, while the linear range for detection of DA was 1.0 nM to 1.0 mM. Additionally, it constructed a useful platform for TYR inhibitor screening in biomedical research.
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PubMed
高影响因子
Food Analytical Methods
·
2013
·Vol. 7
·期 7
·1458-1464
·
IF 1.969
Ma Xinying,Chao Mingyong
A poly(glutamic acid)-modified glassy carbon electrode (PGA/GCE) for the electrochemical determination of kojic acid was developed. The polymerization mechanism of glutamic acid at the glassy carbon electrode, the electrocatalytic mechanism of the poly(glutamic acid) film toward kojic acid, and the electrochemical behavior of kojic acid at the PGA/GCE were investigated. The studies revealed that the oxidation of kojic acid at the PGA/GCE is greatly facilitated, which is attributed to the weakening of the bond energy between oxygen and hydrogen due to the formation of hydrogen bond between hydroxyl group in kojic acid and the nitrogen atom in poly(glutamic acid). The oxidation of kojic acid at the PGA/GCE is a one proton–one electron process. The catalytic effect was further used to determine kojic acid by cyclic voltammetry. The oxidation peak current shows a linear relationship with the concentrations of kojic acid in the range of 8.00 × 10 −6 to 6.60 × 10 −4 mol L −1 with the detection limit of 8.00 × 10 −7 mol L −1 . The modified electrode shows excellent sensitivity, selectivity, and stability and has been applied to detect kojic acid in a variety of food products with satisfactory results.
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TALANTA
·
2013
·
IF 3.498
Bing-bing Sun,Li Qi,Xiao-yu Mu,Juan Qiao,Ming-lin Wang
A facile chiral ligand exchange capillary electrophoresis (CLE-CE) system with Zn(II)- l -alanine as the chiral selector in the presence of β-cyclodextrin has been developed for enantioseparation of dansyl amino acids . The influence of the key factors, such as buffer pH, the ratio of Zn (II) to ligand, the concentration of β-cyclodextrin and the concentration of the complex, were investigated in detail when d , l -Tyr and d , l -Thr were selected as the model analytes. The proposed method showed favorable quantitative analysis property of dansyl d , l -tyrosine with good linearity ( r 2 ≥0.999) and reproducibility (RSD≤3.8%), then, it was applied in studying the activity of tyrosinase through the determination of l -tyrosine concentration variation after being incubated with the enzyme. Further, the inhibitory efficiency of kojic acid and soy sauce on the tyrosinase was investigated. The IC 50 of kojic acid obtained from the sigmoidal inhibitory curve was 21.35 μM. The results imply that the proposed CLE-CE system has the potential in exploring the activity of enzyme and screening the inhibitors of enzyme.
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PubMed
高影响因子
JOURNAL OF PHARMACEUTICAL AND BIOMEDICAL ANALYSIS
·
2013
·
IF 2.947
Ting-Fu Jiang,Ting-Ting Liang,Yuan-Hong Wang,Wen-Hui Zhang,Zhi-Hua Lv
A method for creating an immobilized capillary tyrosinase (TRS) reactor based on a layer-by-layer (LBL) assembly for inhibitor screening is described. Tyrosinase was immobilized on the surface of fused-silica capillary via ionic binding technique with cationic polyelectrolyte hexadimethrine bromide (HDB). Then, HDB solution with the same plug length as the TRS was injected again into the capillary to cover the immobilized enzyme by forming HDB–TRS–HDB sandwich-like structure. Then, the substrate of l -tyrosine was introduced into the capillary and on-line enzyme inhibition study was performed by capillary electrophoresis (CE). The enzyme activity was determined by the quantification of peak area of the product of l -DOPA. Enzyme inhibition can be read out directly from the reduced peak area of the product in comparison with a reference electropherogram obtained in the absence of any inhibitor. The immobilized enzyme could withstand 25 consecutive assays by only losing 12% activity. A known TRS inhibitor, kojic acid was employed as a model compound for the validation of the inhibitor screening method. Finally, screening 19 natural extracts of traditional Chinese drugs was demonstrated. The results indicated that inhibition activity could be straightforwardly identified with the system.
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高影响因子
JOURNAL OF FOOD BIOCHEMISTRY
·
2017
·Vol. 41
·期 4
·e12377
·
IF 1
Zeynep Tohtahon,Lu Zhang,Jianxin Han,Xing Xie,Zongcai Tu,Tao Yuan
This research aimed to optimize the extraction condition, and to identify and investigate the bioactivities of triterpenoids from Crataegus cuneata . The optimum extraction conditions for recovering triterpenoids from hawthorn were ultrasound-assisted extraction with 80% methanol at 30°C, 400 W for 20 min, which resulted in the recovery of total triterpenoids of 28.47 mg/g dry material. Further isolation work led to the isolation and identification of six triterpenoids: ursolic acid ( 1 ), maslic acid ( 2 ), corsolic acid ( 3 ), pomolic acid ( 4 ), euscaphic acid ( 5 ), and 2 α , 19 α -dihydroxy-3-oxo-urs-12-en-28-oic acid ( 6 ) from the triterpenoid-enriched C. cuneata fruits extracts (TCFE). Among which pomolic acid and euscaphic acid were firstly found in genus Crataegus . Biological evaluation revealed that all of the isolated triterpenoids and TCFE showed considerable xanthine oxidase and tyrosinase inhibitory activities, while some of isolates exhibited considerable acetylcholinesterase inhibitory activities. Practical applications Triterpenoids are one class of the major compounds with broad biological activities in hawthorn species . Crataegus cuneata is one of the two major hawthorn species found in China. But, there is few data on the constituents and bioactivity of triterpenoids present in C. cuneata . This research indicated that ultrasound-assisted extraction is the suitable method for extracting triterpenoids from C. cuneata , and TCFE could be potentially used for against xanthine oxidase and tyrosinase-induced diseases, which could provide useful information for the further development of C. cuneata fruits.
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FOOD CHEMISTRY
·
2017
·
IF 4.529
Le-Le Shao,Xiao-Ling Wang,Kai Chen,Xiao-Wu Dong,Li-Min Kong,De-Yin Zhao,Robert C. Hider,Tao Zhou
A range of hydroxypyridinone derivatives were synthesized starting from kojic acid. Among them, 10 and 11 were found to possess the strongest inhibitory effect on monophenolase activity of mushroom tyrosinase, having IC 50 values of 2.04 and 1.60 μM, respectively. The IC 50 values of 10 and 11 for the inhibition of diphenolase activity of mushroom tyrosinase were determined as 13.89 and 7.99 μM, respectively. Investigation of the inhibitory mechanism of these two compounds indicated that the inhibition was reversible and of a competitive-uncompetitive mixed type. The K I and K IS values of 10 were determined to be 24.84 and 32.54 μM, respectively, and the corresponding values for 11 being 18.07 and 21.34 μM, respectively. The effect of 11 on the browning process of fresh-cut apples was evaluated by measuring the color change and browning index. The results indicated that 11 had a significant effect on controlling the browning of fresh-cut apple slices.
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SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
·
2016
·
IF 2.653
Jianmin Chen,Xiaojing Yu,Yufeng Huang
Tyrosinase is an oxidase that is the rate-limiting enzyme for controlling the production of melanin in the human body. Overproduction of melanin could lead to a variety of skin disorders. Glabridin , an isoflavan , isolated from the root of Glycyrrhiza glabra Linn, has exhibited several pharmacological activities, including excellent inhibitory effects on tyrosinase. In this paper, the inhibitory kinetics of glabridin on tyrosinase and their binding mechanisms were determined using spectroscopic, zebrafish model and molecular docking techniques. The results indicate that glabridin reversibly inhibits tyrosinase in a noncompetitive manner through a multiphase kinetic process with the IC 50 of 0.43 μmol/L. It has been shown that glabridin had a strong ability to quench the intrinsic fluorescence of tyrosinase mainly through a static quenching procedure, suggesting a stable glabridin-tyrosinase complex may be generated. The results of molecular docking suggest that glabridin did not directly bind to the active site of tyrosinase. Moreover, according to the results of zebrafish model system, glabridin shows no effects on melanin synthesis in zebrafish but presents toxicity to zebrafish embryo. The possible inhibitory mechanisms, which will help to design and search for tyrosinase inhibitors especially for glabridin analogues, were proposed.
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ANALYTICAL BIOCHEMISTRY
·
2017
·
IF 2.334
Dong-Mei Liu,Jun-Li Yang,Wei Ha,Juan Chen,Yan-Ping Shi
In the present study, pressure mediated microanalysis (PMMA), a fast, convenient and efficient capillary electrophoresis (CE) method was developed for studying enzyme kinetics of tyrosinase and inhibition kinetics of kojic acid , a model inhibitor of tyrosinase. The enzymatic reaction conditions and CE conditions were optimized in order to obtain high enzyme activity and short analysis time. By PMMA, only the product could be detected at 475 nm, and no voltage was applied to separate the product from the reaction mixture thus greatly simplifying the optimization procedure. The spectrophotometric assay and electrophoretically mediated microanalysis (EMMA) were also performed to validate the developed method. With the present method, the Michaelis-Menten constant ( K m ) was calculated to be 1.347 mM for tyrosinase. The inhibition constant of kojic acid to free tyrosinase ( K I ) and kojic acid to tyrosinase/L-DOPA complex ( K IS ) were calculated to be 36.64 and 74.35 μM, respectively, and the half-maximal inhibitory concentration (IC 50 ) was determined to be 46.64 μM for kojic acid. The developed method is fast and convenient for studying enzyme kinetics, inhibition kinetics and further screening enzyme inhibitors .
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RSC Advances
·
2016
·Vol. 6
·期 76
·72670-72675
·
IF 3.289
X. E. Zhao,C. H. Lei,Y. H. Wang,F. Qu,S. Y. Zhu,H. Wang,J. M. You
In this work, a sensitive and selective fluorescence sensing platform was developed for the detection of tyrosinase (TYR) activity and its inhibitor screening using graphene quantum dots (GQDs) as probes. Upon excitation at 383 nm, GQDs displayed an intense emission at 445 nm. TYR, a typical polyphenol oxidase, can catalyze the oxidation of dopamine (DA) to dopaquinone and then a fluorescence resonance energy transfer (FRET) process between GQDs and dopaquinone took place. Therefore, the fluorescence of GQDs could be quenched. Thus, quantitative evaluation of TYR activity was established in terms of the relationship between fluorescence quenching efficiency and TYR activity. A linear range was obtained from 0.005 to 0.5 U mL−1 and from 0.5 to 5.0 U mL−1, respectively. A detection limit of 0.0015 U mL−1 was obtained, which was lower than those of reported papers. In addition, it constructed a useful platform for TYR inhibitor screening.
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TALANTA
·
2017
·
IF 4.162
Cuihua Lei,Xian-En Zhao,Jing Sun,Xiaolu Yan,Yue Gao,Han Gao,Shuyun Zhu,Hua Wang
A novel colorimetric method for the detection of tyrosinase (TYR) and its inhibitor by taking utilization of Ag + −3,3′,5,5′-tetramethylbenzidine (TMB) detection system has been proposed. Ag + could oxidize TMB to oxidized TMB (oxTMB) and induce a blue color solution corresponding to an absorption peak centered at 652 nm. The addition of dopamine (DA) could cause the reduction of oxTMB which resulted in the fading of the blue color and a decrease of the absorbance at 652 nm. However, in the presence of TYR, DA could be oxidized to dopaquinone, which inhibited the reduction of oxTMB by DA, resulting in a blue color recovery and an increase of the absorbance at 652 nm. Based on this finding, we propose a method to quantitatively detect TYR activity with the help of UV–vis spectroscopy. The developed assay is highly sensitive with a low detection limit of 0.010 U/mL. More importantly, this method is fairly simple and inexpensive without the use of complicated nanomaterials . In addition, it constructs a useful platform for TYR inhibitor screening.
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Chemistry Africa-A Journal of the Tunisian Chemical Society
·
2024
·
IF 2.3
Wang Wenchao,An Lianhao,Lei Junrong,Li Dan,Shen Zheluan,Wang Hong,Li Qingyong
Pearl powder has been used in medicine and beauty treatment since ancient times in China. However, it is still unclear whether the biological activities of pearl powder are affected by different extraction methods or not. In this study, we determine the total protein yield, protein molecular weight and biological activities including antioxidant, tyrosinase inhibition and melanogenesis inhibition activities and cytotoxicity of different pearl powder extracts prepared by five different preparation methods. The ultrasonic-assisted extraction (UAE) and microwave-assisted extraction (MAE) of pearl powder were optimized by the response surface method based on total protein yield. Compared with solid-liquid extraction (SLE), the optimized UAE and MAE increased the total protein yield without changing protein molecular weight. In addition, the extract by MAE enhanced the tyrosinase inhibition activity and anti-melanogenesis activity slightly. Acidolysis hydrolyzes macromolecular protein into small molecules with obvious cytotoxicity and low activities. Enzymolysis can hydrolyze macromolecular protein into small molecules with high protein yield and improvement of bioactivities. In the determination of the antioxidant assay, the extract prepared by the enzymolysis showed significant activity. These results suggest that protein molecules of the pearl powder extract are degraded appropriately by enzymolysis to smaller molecules to obtain the enhanced biological activities that can be applied in the cosmetic industry.
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危险品化学品经营许可证（带存储）