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1.
《Food chemistry》2005,89(4):583-587
This study was aimed to evaluate the kinetic properties and capacities of 95% ethanolic (GE95), 50% ethanolic (GE50) and water (GWE) extracts from Graptopetalum paraguayense for their potential to inhibit mushroom tyrosinase activity. The results showed that GE95, GE50 and GWE showed potent inhibitory effects on l-3,4-dihydroxyphenylalanine (l-Dopa) oxidation catalyzed by tyrosinase. It was found that the tyrosinase inhibitory activities of all the extracts increased with the increase of their concentrations. The inhibition kinetics, analyzed by Lineweaver–Burk plots, revealed that G. paraguayense extracts showed a mixed-type inhibition for mushroom tyrosinase when l-Dopa was used as substrate. A comparison of the IC50 and Ki values showed that GE95 exhibited the most effective inhibition of tyrosinase among the extracts.  相似文献   

2.
This study aimed to evaluate the inhibition properties of six lavender species, including Lavendula angustifolia, Lavandula angustifolia “Vera”, Lavendula X allardii, Lavendula stoechas, Lavendula viridis and Lavendula X heterophylla, toward the activity of mushroom tyrosinase. When using l-3,4-dihydroxyphenylalanine (l-Dopa) as the substrate for mushroom tyrosinase, the water extracts of leaves and stems from L. stoechas and L. angustifolia “Vera” showed strong inhibitory effects against the activity of mushroom tyrosinase (70% and 66.4% inhibition, respectively). Oven-drying the leaves and stems or free-drying the water extracts significantly decreased the inhibitory abilities of the water extracts from all lavender species. The water extract from L. stoechas decreased the Vmax values when using l-Dopa, catechol and 3,4-dihydroxyphenylacetic acid (DHPAA) as the substrates. It increased the value of Km when l-Dopa and catechol were the substrates but it decreased the Km when DHPAA was used. It behaved as a mixed-type inhibitor toward mushroom tyrosinase.  相似文献   

3.
The inhibitory effects of hydroxyphenolic acid–aromatic amino acid conjugates on the activity of mushroom tyrosinase were investigated. Amongst the hydroxyphenolic acid–amino acid derivatives, protocatechuic acid–amino acid amide (PA-AA-NH2) showed highly increased tyrosinase inhibitory activity. The results show that it could strongly inhibit both the monophenolase and diphenolase activities of tyrosinase. The IC50 values, inhibition type, and KI values of these hydroxyphenolic acid derivatives (PA-F-NH2, PA-W-NH2, PA-Y-NH2) were evaluated and compared. Kinetic analyses of PA-AA-NH2 as a tyrosinase inhibitor revealed that it acted as a reversible mixed-? type inhibitor, possibly by chelating copper at the active site of tyrosinase. These results suggest that aromatic amino acid conjugation assisted PA in binding to the active site of mushroom tyrosinase where it interrupted access to the substrate.  相似文献   

4.
《Food chemistry》2005,92(4):707-712
The effects of cinnamic acid and its derivatives (2-hydroxycinnamic acid, 4-hydroxycinnamic acid and 4-methoxycinnamic acid) on the activity of mushroom tyrosinase have been studied. Results showed that cinnamic acid, 4-hydroxycinnamic acid and 4-methoxycinnamic acid strongly inhibited the diphenolase activity of mushroom tyrosinase and the inhibition was reversible. The IC50 values were estimated to be 2.10, 0.50 and 0.42 mM, respectively. 2-Hydroxycinnamic acid had no inhibitory effect on the diphenolase activity of the enzyme. Kinetic analyses showed that the inhibition type of cinnamic acid and 4-methoxycinnamic acid was noncompetitive with the constants (KI) determined to be 1.994 and 0.458 mM, respectively. The inhibition type of 4-hydroxycinnamic acid was competitive, with the inhibition constant (KI) was 0.244 mM.  相似文献   

5.
The effects of α-cyano-4-hydroxycinnamic acid (HCCA) on the activity of mushroom tyrosinase have been studied. Results showed that HCCA could inhibit both the monophenolase activity and diphenolase activity of mushroom tyrosinase. For the monophenolase activity, the lag phase was obviously lengthened, and the steady-state activity of the enzyme decreased sharply. When the concentration of HCCA reached to 80 μM, the lag time was lengthened from 20 s to 150 s and the steady-state activity was lost by about 75%. The IC50 value was estimated to be 48 μM. For the diphenolase activity, the inhibitory effect of HCCA was also dose-dependent and the IC50 value was estimated to be 2.17 mM. The kinetic analyses showed that the inhibition of HCCA on the diphenolase activity was reversible and competitive with the inhibition constants (KI) determined to be 1.24 mM.  相似文献   

6.
4-Hexylresorcinol, a Potent Inhibitor of Mushroom Tyrosinase   总被引:4,自引:0,他引:4  
4-hexylresorcinol (4HR) was a potent inhibitor of mushroom tyrosinase in crude extracts, causing 90% loss of activity at 100 μM. The concentration of 4HR needed to cause 50% inhibition (I50) was = 5 μM. Partially purified tyrosinase was inhibited by lower concentrations of 4HR and was characterized with an I50 of = 1 μM. Electro-phoretic analysis, coupled with isoenzyme staining in the presence and absence of 4HR, showed inhibition of tyrosinase isoforms but not of laccase isoforms.  相似文献   

7.
In our study, we investigated the inhibition of mushroom tyrosinase in Smilax china. A methanol (MeOH) extract of S. china was partitioned into hexane, ethyl acetate (EtOAc) and water. Of the three fractions, EtOAc extract showed the strongest inhibition of tyrosinase activity with l-tyrosine or l-DOPA as a substrate. Two compounds were isolated from a final active fraction by activity-guided column chromatography. These compounds were identified as dioscin and oxyresveratrol by comparing their mass, 1H- and 13C-NMR spectral data with those reported in the literature. Dioscin showed little inhibition activity of tyrosinase, whereas oxyresveratrol, a known tyrosinase inhibitor, showed a strong tyrosinase inhibitory activity. We discovered that a mixture of oxyresveratrol and dioscin (IC50 = 5.1 and 5.7 μg/ml) highly increased the inhibition of tyrosinase activity with l-tyrosine or l-DOPA as the substrate as compared to either oxyresveratrol (IC50 = 7.8 and 10.9 μg/ml) or dioscin (IC50 > 100 and 100 μg/ml) alone.  相似文献   

8.
In order to search for a new method for the anti-browning of food products, a novel hydroxypyridinone (HPO) derivative with a formyl group was evaluated for its anti-tyrosinase property. This compound was found to exhibit potent tyrosinase inhibition on the monophenolase activity of mushroom tyrosinase with an IC50 value of 1.33 μM, indicating that this HPO derivative was 12-fold stronger than kojic acid (IC50 15.89 μM). This molecule can inhibit tyrosinase via two action modes, namely copper reduction and chelation, and the formation of a Schiff’s base with the amino group at the active site of the enzyme. A synergistic effect of these two action modes to enhance the inhibitory activity was observed. This compound was also investigated for the inhibitory effect on diphenolase activity of mushroom; the inhibitory mechanism was found to be reversible and of competitive-uncompetitive mixed-type inhibition. This hydroxypyridinone was demonstrated to effectively control the browning of vegetable products.  相似文献   

9.
以抑菌圈大小及对酪氨酸酶活性的抑制率为指标,筛选出藜麦麸皮中具有抑菌活性以及抑制酪氨酸酶活性的极性部位。采用75%的乙醇对藜麦麸皮进行超声提取,三种不同极性溶剂石油醚、乙酸乙酯、正丁醇进行萃取,获取四个极性部位。纸片法观察不同的极性部位对于四种致病菌的体外抑制效果,同时探究对酪氨酸酶活性的抑制效果,利用液质推断其有效成分并用高效液相对高活性成分进行定量分析。结果表明:正丁醇萃取层的活性最高,且对革兰阳性菌较为敏感但对革兰阴性菌无明显效果。对金黄色葡萄球菌的最低抑菌浓度和最低杀菌浓度分别为1.04、2.08 mg/mL,对表皮葡萄球菌的最低抑菌浓度和最低杀菌浓度分别为0.52、1.04 mg/mL。比较可知藜麦麸皮极性部位的抑菌效果要优于某些常见的中药;在浓度为1 mg/mL时对酪氨酸酶活性的抑制率为55.86%,是同浓度VC抑制效果的58.96%;液质推断出正丁醇层主要物质为藜麦皂苷,定量分析藜麦皂苷的纯度为62.6%。综上,藜麦麸皮不同极性部位中,正丁醇萃取层的抑菌活性以及对于酪氨酸酶活性的抑制效果较好,且主要活性物质为藜麦皂苷。  相似文献   

10.
The inhibition of mushroom tyrosinase in soygerm koji, fermented with Aspergillus oryzae BCRC 32288, was investigated. A methanol extract of the soygerm koji was partitioned into hexane, ethyl acetate and water. The ethyl acetate extract showed potent anti-tyrosinase activity with an IC50 value of 0.19 mg/ml. The active compounds were isolated by activity-guided silica gel column chromatography and high-performance liquid chromatography (HPLC) methods. Seven tyrosinase inhibitors were purified and identified as 6,7,4′-trihydroxyisoflavone, 7,8,4′-trihydroxyisoflavone, 5,7,8,4′-tetrahydroxyisoflavone, 7,4′-dihydroxyisoflavone (daidzein), 6-methoxy-7,4′-dihydroxyisoflavone (glycitein), 4′-hydroxyisoflavone-7-O-glucoside (daidzin), and 5,4′-dihydroxyisoflavone-7-O-glucoside (genistin) by comparing their mass, 1H NMR, and 13C NMR spectral data with those in the literature. The purified seven isoflavones from fermented soygerm koji were divided into two groups, based on their inhibitory effects on mushroom tyrosinase. Five isolated isoflavones showed inhibitory activity against monophenolase activity of mushroom tyrosinase only, with IC50 values of 0.009 ± 0.001 (6,7,4′-trihydroxyisoflavone), 0.203 ± 0.018 (daidzein), 0.218 ± 0.007 (glycitein), 0.267 ± 0.008 (daidzin), and 0.343 ± 0.013 (genistin) mM. The kinetic study indicated that the five inhibitors significantly lengthened the lag time of the monophenolase activity of tyrosinase and acted competitively for the l-tyrosine binding site of the enzyme. So, the five isoflavones were competitive inhibitors for the monophenolase activity of tyrosinase. The other two isoflavones, 7,8,4′-trihydroxyisoflavone and 5,7,8,4′-tetrahydroxyisoflavone, inhibited both monophenolase and diphenolase activities of tyrosinase. Moreover, pre-incubation of each of the two isoflavones with tyrosinase resulted in total irreversible inhibition of the enzyme activity, even at concentrations as low as of 10 μM. Hence, 7,8,4′-trihydroxyisoflavone and 5,7,8,4′-tetrahydroxyisoflavone were irreversible inhibitors of mushroom tyrosinase.  相似文献   

11.
This paper reports for the first time the inhibition of the catecholase activities of mushroom, artichoke (Cynara scolymus L) and Ocimum basilicum L polyphenol oxidase by 2,3‐diaminopropionic acid. Polyphenol oxidases from artichoke and O basilicum L were purified by ammonium sulfate precipitation, dialysis and a Sepharose 4B‐L ‐tyrosine‐p‐aminobenzoic acid‐affinity column. In inhibition studies, 2,3‐diaminopropionic acid showed uncompetitive inhibition for mushroom PPO using catechol and pyrogallol as substrates, competitive inhibition for O basilicum L PPO using catechol as a substrate, and uncompetitive inhibition for artichoke PPO using catechol as a substrate. Furthermore, sodium azide, which is an inhibitor of PPO, was used as an inhibitor for comparison with the inhibition potency of 2,3‐diaminopropionic acid. The highest 2,3‐diaminopropionic acid inhibition observed with O basilicum L (Ki = 0.89 mM ), followed by artichoke (Ki = 1.42 mM ) and mushroom (Ki = 2.47 mM ), respectively. Copyright © 2005 Society of Chemical Industry  相似文献   

12.
Tyrosinase is a copper-containing enzyme that controls mammalian melanogenesis. Tyrosinase inhibitors are important for their potential application in cosmetic products. Chicken feather meal is a rich source of amino acids, which have been linked with tyrosinase inhibition activity. This study investigated the tyrosinase inhibitory properties of protein hydrolysates prepared from chicken feather meal. Protein hydrolysates prepared by pepsin-pancreatin with MW <3 kDa exhibited strong tyrosinase inhibition activity for both monophenolase (IC50 5.780 ± 0.188 µg/mL) and diphenolase activities (IC50 0.040 ± 0.024 µg/mL) in a cell-free mushroom tyrosinase system. These samples were uncompetitive inhibitors with Ki values of 18.149 and 27.189 µg/mL in monophenolase and diphenolase activities, respectively. A cell culture model showed that this hydrolysate had the strongest inhibition on the viability of B16F10 cells (IC50 1.124 ± 0.288 µg/mL) and 0.210 µg/mL of the sample exhibited inhibition of tyrosinase activity by 50.493% and melanin synthesis by 14.680% compared to the control.  相似文献   

13.
Tyrosinase can catalyze the oxidation of o-diphenols to o-quinones. In this paper, some o-diphenols were used as mushroom tyrosinase substrates to study the catalyzed specificity of the enzyme. The enzyme kinetic analysis of substrate specificities and the substrate analogues towards mushroom tyrosinase has been investigated. Taking l-3,4-dihydroxyphenylalanine (I), 3,4-dihydroxyhydrocinnamic acid (II), 3,4-dihydroxycinnamic acid (III) and 1,2,4-benzenetriol (IV) as substrates, the results of specificity studies showed that the oxidation reaction of tested o-diphenols by mushroom tyrosinase followed Michaelis–Menten kinetics. The Michaelis–Menten constants for these four substrates were determined to be 0.615, 1.238, 0.331 and 1.886 mM, respectively. The values of Vm/Km, which denotes the affinity of the enzyme to the substrate, were determined and compared, and the results showed that the affinity of the enzyme to these substrates followed the order: compound IV > III > I > II. Furthermore, mushroom tyrosinase cannot catalyze the oxidation of 3,4-dihydroxybenzonitrile (a), 3,4-dihydroxybenzaldehyde (b), 3,4-dihydroxybenzoic acid (c) and 2,3-dihydroxybenzoic acid (d). On the contrary, compounds a, b and c can inhibit the activity of tyrosinase for the oxidation of DOPA, while compound d had no effects on enzyme activity. The results show that compounds a and b are reversible non-competitive inhibitors.  相似文献   

14.
The inhibitory effects of 4-chlorosalicylic acid on the activity of mushroom tyrosinase have been investigated. The results showed that 4-chlorosalicylic acid could strongly inhibit both monophenolase activity and diphenolase activity. The IC50 values were estimated as 1.89 mM and 1.10 mM for monophenolase and diphenolase activities, respectively. For the monophenolase activity, 4-chlorosalicylic acid could not only lengthen the lag time, but also decrease the steady-state rate. For the diphenolase activity, kinetic analyses showed that the inhibition by 4-chlorosalicylic acid was reversible and its mechanism was mixed-II type, which is different from salicylic acid. The inhibition constants (KI and KIS) were determined to be 1.51 mM and 0.82 mM, respectively. Furthermore, the antibacterial activity against Escherichia coli, Bacillus subtilis and Staphyloccocus aureus and antifungal activity against Aspergillus niger and Candida boidinii were investigated. The results showed that 4-chlorosalicylic acid was the most effective against E. coli with the MIC of 250 μg/ml and with the MBC of 500 μg/ml.  相似文献   

15.
2, 4, 5-THBP (2, 4, 5-trihydroxybutyrophenone) is a substrate for mushroom tyrosinase with a Km value of 1.00 mM. The final product(s) formed is red (λ.max 480–490 nm) and it is rather stable with time. An intermediate red product(s), having a maximum at λ 505–515 nm, was detected and the time course of its conversion to the final red product(s) was studied. The data suggest that the intermediate red product(s) is 2, 4, 5-THBP-quinone which is converted to colorless polymerized 2, 4, 5-THBP-OH, which is then oxidized to a red polymerized 2, 4, 5-THBP-quinone(s), which is the final red product(s).  相似文献   

16.
Ca-independency with potential activity and stability at low pH are among the most interesting characteristics of α-amylase in starch industry. In this attempt the synergetic effect of low pH on activity of crude Ca-independent α-amylase isolated from a native Bacillus sp. KR-8104 in solid-state fermentation (SSF) was studied using wheat bran (WB) as a substrate. The effects of different parameters including moisturizing agents, solid substrate to moisture ratio, particle size, incubation temperature and period, inoculum (v/w) and supplementation with 1% (w/w) different carbon and nitrogen sources on enzyme production were investigated. Maximum enzyme production of 140 U/g dry fermented substrate was obtained from wheat bran moistened with tap water at a ratio of 1:1.5 and supplemented with 1% (w/w) NH4NO3 and 1% (w/w) lactose after 48 h incubation at 37 °C. Even though the production of α-amylase was lower at 40 and 45 °C, the viable cell count was higher. In addition response surface methodology (RSM) was applied to find optimum conditions of temperature and pH on crude amylase activity. Using central composite design (CCD) a quadratic mathematical model equation was derived for the prediction of enzyme activity. The results showed that the model was in good agreement with experimental results, with R2 = 0.90 (p < 0.0001) and the low pH has a synergetic effect on enzyme activity at higher temperature.  相似文献   

17.
麦麸是小麦加工的主要副产物,营养丰富且产量大,采用乳酸菌处理麦麸可提高其附加值。为明确乳酸菌发酵对麦麸各组分的影响,作者采用植物乳杆菌、鼠李糖乳杆菌、戊糖片球菌和布氏乳杆菌分别对麦麸进行固态发酵,在48 h内每隔8 h取样,分析可溶性膳食纤维、粗蛋白质、淀粉、总酚、植酸等成分的质量分数及DPPH自由基清除能力的动态变化。结果表明,在麦麸基质中,4株乳酸菌在24 h内生长较为迅速;麦麸经乳酸菌发酵后可溶性膳食纤维质量分数显著提高,其中布氏乳杆菌发酵48 h后可溶性膳食纤维质量分数由4.72%增加至6.58%;随着发酵时间的增加,麦麸中淀粉质量分数逐渐降低,粗蛋白质量分数先增加后降低最后趋于稳定;植物乳杆菌在提高麦麸多酚质量分数方面有更好的效果,多酚质量分数由1.34 mg/g增加至3.86 mg/g,麦麸抗氧化活性显著增加;此外,乳酸菌发酵麦麸可显著降低其植酸质量分数。综合而言,植物乳杆菌和布氏乳杆菌在提高麦麸的营养特性方面具有较好的效果,可有效改善麦麸的综合利用价值。  相似文献   

18.
South-East Asian population is daily exposed to strong sunlight. As a result, the majority of population will have darker, ethnic skin. Moreover, many people suffer from dark spots, hyperpigmentation, which is considered to be a skin disorder and causes psychological disturbance. To treat dark spots, most of the population will still rely on traditionally used crude drugs, knowledge about which is transferred from generation to generation. Fifty-two crude drugs were selected based on the survey performed among local healers and beauticians of different ethnic origin. These crude drugs were screened for mushroom tyrosinase inhibitory activity, as tyrosinase inhibitors are becoming increasingly important as cosmetic and medicinal products, primarily to control hyperpigmentation. Among the tested crude drugs, methanolic extracts of Glycyrrhiza glabra, Morus alba, Syzygium aromaticum, Citrus aurantifolia, Cypreae moneta, Punica granatum and Citrus aurantium, at the final concentration of 50 microg mL(-1), showed mushroom tyrosinase inhibitory activity of 78.9%, 71.0%, 69.4%, 59.0%, 56.0%, 53.4 and 51.9%, respectively, with 91.4% inhibitory activity of kojic acid taken as positive control. To our knowledge, this is the first report that extracts of Cypreae moneta shell and Syzygium aromaticum flowering bud have tyrosinase inhibitory activity. These potent extracts were further evaluated at different concentration. The final concentration of the extracts in reaction mixtures was 50, 25 and 5 microg mL(-1) for the initial concentration of 1000, 500 and 100 microg mL(-1), respectively. They showed concentration-dependent inhibition of mushroom tyrosinase. Those extracts expressing relatively weak tyrosinase inhibitory activity may act through different inhibition pathway which is not based on tyrosinase activity. Further evaluation of the most potent tyrosinase inhibitors in in vivo conditions would be recommended.  相似文献   

19.
This study aimed to evaluate the free radical scavenging and inhibition properties of five medicinal plants, including Quercus infectoria Olive., Terminalia chebula Retz. , Lavendula stoechas L., Mentha longifolia L., Rheum palmatum L., toward the activity of mushroom tyrosinase using l -tyrosine and l -3,4-dihydroxyphenylalanine ( l -DOPA) as the substrate. The methanol extracts of Q. infectoria and T. chebula showed strong radical scavenging effect in 2,2'-dipheny l -1-picrylhydrazyl (DPPH) assay (IC50 = 15.3 and 82.2 μg mL−1 respectively). These plants also showed inhibitory effects against the activity of mushroom tyrosinase in hydroxylation of l -tyrosine (85.9% and 82.2% inhibition, respectively). These two plants also inhibited the oxidation of l -DOPA similar to kojic acid as positive control (IC50 = 102.8 and 192.6 μg mL−1 respectively). In general Q. infectoria and T. chebula significantly inhibited tyrosinase activity and DPPH radical. Both activities were concentration-dependant but not in linear manner. It is needed to study the cytotoxicity of these plant extracts in pigment cell culture before further evaluation and moving to in vivo conditions.  相似文献   

20.
The inhibition of rice bran lipase (RBL) by diethyl-p-nitrophenyl phosphate was studied with reference to kinetics, nature of inhibition and also elucidate the effect of the inhibitor on the structure—function of the enzyme. Enzyme activity measurements shows that the inhibitor is more effective at 0.050 mM concentration of diethyl-p-nitrophenyl phosphate and the activity is 50% at this level of inhibitor concentration. The affinity of substrate for the enzyme was observed by the increase in the velocity of the reaction with increase in the substrate concentrations and double reciprocal plot indicates that the inhibition followed a competitive in nature and inhibition constant K i is found to be 0.016 mM at pH 7.0. The decrease in apparent thermal denaturation temperature to 4 °C compared to control indicates the destabilization of enzyme in the presence of inhibitor. Fluorescence spectral measurements suggests that pronounced quenching of fluorescence intensity of RBL occurs at higher concentrations of diethyl-p-nitrophenyl phosphate and ‘K a’ value was found to be 2.4 × 104 M−1 with free energy change ΔGo—26 kJ/mol at 30 °C suggesting strong binding between the enzyme and the inhibitor with microenvironmental changes occur at the active site or in the neighbourhood of active site. The far UV-CD data suggest that there is no significant changes in the conformation of the enzyme as a result of binding of diethyl-p-nitrophenyl phosphate. These results indicate that diethyl-p-nitrophenyl phosphate is a inhibitor of RBL and binds to the enzyme in brining about inhibition without any structural alterations.  相似文献   

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