葛根有效成分抑制酪氨酸酶活性的研究

为了探讨葛根对酪氨酸酶的抑制作用,将葛根用75%(v/v)的乙醇水溶液回流提取,用不同极性的溶剂萃取,经硅胶柱层析和重结晶后,分别检测对酪氨酸酶的抑制率.结果表明,在萃取物中,葛根的乙酸乙酯萃取物对酪氨酸酶的抑制率最高,为61.2%;硅胶柱层析分离得到的一部分层析物对酪氨酸酶的抑制率为89.2%,它对酪氨酸酶的抑制作用明显强于其它柱层析组分,该层析物纯化后得到的葛根素对酪氨酸酶的抑制率与浓度呈非线性变化,以熊果苷为阳性对照物.上述研究为进一步开发葛根中的美白成分提供了依据.     

艾纳香地上部分化学成分及其抗氧化与酪氨酸酶抑制活性研究

本文对艾纳香(Blumea balsamifera DC.)中的化学成分及其抗氧化与酪氨酸酶抑制活性进行了研究.利用各种色谱手段和波谱学方法,从艾纳香地上部分分离得到18个化合物,分别鉴定为:7,3',4'-三甲基槲皮素(1)、4',5-二羟基-3',7-二甲氧基黄酮(2)、木犀草素-7-甲醚(3)、鼠李素(4)、(2...     

化橘红黄酮类化合物抑制亚硝化反应活性研究

根据超声波最佳提取工艺条件提取得到化橘红总黄酮,经乙酸乙酯萃取分为酯溶性和水溶性两部分,比较它们对亚硝化反应的抑制作用,并分别采用硅胶柱层析对酯溶性成分分离纯化,采用大孔吸附树脂法对水溶性成分进行分离纯化,得到4个主要的黄酮类化合物,研究它们对亚硝化反应的抑制作用,以期得到抑制亚硝化活性较强的化合物。结果表明化橘红总黄酮提取率可达26.42%,酯溶性和水溶性部分均能阻断亚硝胺的合成及清除亚硝酸盐,其中水溶性黄酮提取物作用较强,分离得到的4个黄酮类化合物中柚皮苷的抑制作用较强,对亚硝胺的合成的最大阻断率可达94.7%,对亚硝酸盐的最大清除率可达92.3%。     

降香中的酚性化合物

从降香(Dalbergia odorifera)中分离得到10个酚性化合物,运用波谱学方法分别鉴定为dalbergin(1),7-O-methylvestitol(2),syringaresinol(3),3,7-dihydroxy-2',4'-dimethoxyisoflavanone(4),3'-hydroxy-8-methoxyvestitol(5),2',6-dihydroxy-4'-methoxy-2-arylbenzofuran(6),3'-O-methylviolanone(7),pinocembrin(8),prunetin(9),mucronulatol(10)。其中化合物1具有乙酰胆碱酯酶抑制活性,化合物2~5为首次从降香中分离得到。     

薰衣草精油对酪氨酸酶活性影响的研究

以L-酪氨酸为底物,从马铃薯中制备酪氨酸酶粗酶液,以熊果苷为阳性对照,研究了薰衣草精油对酪氨酸酶活性影响,结果表明薰衣草精油对酪氨酸酶活性的抑制表现出良好的剂量-效应关系,其抑制率均随剂量的增大而升高,1 mg/mL、2 mg/mL、4 mg/mL、8 mg/mL抑制率分别为22.59%、31.46%、50.91%、81.96%。     

氨基葡萄糖对酪氨酸酶的抑制作用

通过对酪氨酸酶催化底物L-DOPA反应速率的观察测定,研究了氨基葡萄糖（G-NH2）对酪氨酸酶的抑制作用。在反应液中加入50μL浓度为2.2 mg/mL G-NH2时（体系中G-NH2终浓度为36μg/mL）,酶抑制率为50%。GNH2对酪氨酸酶的抑制作用是个复杂的过程,酶反应呈先促进后抑制。分析酶抑制曲线Lineweaver-Burk双倒数图,得出G-NH2为混合抑制剂,进一步研究发现多巴醌生产量会减少,抑制类型是不可逆抑制。     

刺果甘草中黄酮类化合物的提取与分析

With three different methods, the total flavonoids from the roots of cultivated Gtycyrrhiza pallidiflora Maxim. were determined and compared by ultraviolet-visible spectrophotometry. The results showed that the extract yield of total flavonoids in crude extracts was 4.54% by direct determination method, 4.27% by AI（ NO3）3 colorimetry method and 2.09% by AlCl3 colorimetry method. The content of total flavonoids in roots of cultivated G. pallidiflora was only 0.05%. The cultivated G. pallidiflora in Lanzhou is not unfit for the medicine source of flavonoids.     

甘草有效成分的药理作用研究进展

综述了近年来甘草中有效成分甘草酸、甘草次酸、甘草黄酮类物质、甘草多糖的药理活性。     

山嵛菜抗氧化与抑制酪氨酸酶的实验研究

为了探讨山嵛菜植物各部分的抗氧化与抑制酪氨酸酶能力,将新鲜山嵛菜的叶、叶柄、块茎、根须等,用20%乙醇水溶液提取后,分别检测各部分的总抗氧化能力、灭活超氧阴离子能力和抑制酪氨酸酶能力。结果表明,总抗氧化能力以山嵛菜叶最强(68.4单位,0.1 g/mL);灭活超氧阴离子能力也是山嵛菜叶最强(IC50值0.7mg/mL);抑制酪氨酸酶能力以山嵛菜块茎、根须最强(IC50值0.3或0.4 mg/mL)。上述资料为进一步开发利用山嵛菜提供了依据。     

滨海白首乌提取物对酪氨酸酶活力的影响

以l-dopa为底物,研究了白首乌提取物的酪氨酸酶活性影响作用。结果表明白首乌提取物对酪氨酸酶抑制作用显著,可使酶促反应进程出现较长迟滞期,稳态酶活力缓慢下降。白首乌提取物终浓度80.0μg/mL时,迟滞时间为626 s,稳态酶活力相对维生素C抑制率为56.25%。白首乌提取物对酪氨酸酶的抑制机理为可逆的竞争性抑制。     

Inhibitory Effects of 4-Halobenzoic Acids on the Diphenolase and Monophenolase Activity of Mushroom Tyrosinase

The effects of 4-halobenzoic acids (4-fluorobenzoic acid, 4-chlorobenzoic acid, and 4-bromobenzoic acid) on the activity of mushroom tyrosinase have been studied. The results show that 4-halobenzoic acids can strongly inhibit both monophenolase activity and diphenolase activity of the enzyme, and the inhibition displays a reversible course. The IC50 values were estimated as 0.26, 0.20, and 0.18 mM for diphenolase activity and as 1.03, 0.75, and 0.60 mM for monophenolase activity, respectively. Kinetic analyses show that the inhibition mechanism of all three 4-halobenzoic acids is noncompetitive inhibition to the diphenolase activity, and the inhibition constants (K1) were determined to be 0.25, 0.20, and 0.17 mM, respectively. The lag time of the monophenolase was obviously lengthened by these three 4-halobenzoic acids. When the concentration of inhibitors reached 1.4 mM, the lag time was lengthened from 30 s to 120, 125, and 150 s, respectively.     

Inhibitory Effects of Hexylresorcinol and Dodecylresorcinol on Mushroom (Agaricus bisporus) Tyrosinase

The effects of hexylresorcinol and dodecylresorcinol on the monophenolase and diphenolase activity of mushroom tyrosinase have been studied. The results show that hexylresorcinol and dodecylresorcinol can inhibit both monophenolase and diphenolase activity of the enzyme. The lag period of the enzyme was obviously lengthened, and the steady-state activity of the enzyme decreased sharply. Two microM of hexylresorcinol and dodecylresorcinol can lengthen the lag period from 98 s to 260 and 275 s, respectively. Both hexylresorcinol and dodecylresorcinol can lead to reversible inhibition of the enzyme. The IC50 values of hexylresorcinol and dodecylresorcinol were estimated as 1.24 and 1.15 microM for monophenolase and as 0.85 and 0.80 microM for diphenolase, respectively. A kinetic analysis shows that hexylresorcinol and dodecylresorcinol are competitive inhibitors. The apparent inhibition constant for hexylresorcinol and dodecylresorcinol binding with free enzyme has been determined to be 0.443 and 0.405 microM for diphenolase, respectively.     

黄酮类化合物对大豆脂肪氧合酶的抑制作用研究

研究了几种不同黄酮化合物(黄酮醇类化合物、异黄酮类化合物、查尔酮类化合物、二氢黄酮类化合物)对大豆脂肪氧合酶(LOX)的抑制作用,并根据实验结果初步探讨了不同结构黄酮类化合物对大豆脂肪氧合酶抑制作用的结构-活性抑制作用关系.结果表明:黄酮化合物均可对LOX有不同程度的抑制作用,除橙皮苷外,它们的抑制效果均与加入量成正比,黄酮醇类化合物的抑制效果最为明显,它们对LOX的半数抑制浓度(IC50)依次为芦丁>槲皮素>根皮素>大豆黄素>异甘草素>芒柄花素>甘草素,而橙皮苷的最大抑制率为0.47 μg/mL时的45.1%.     

十种蜂花粉醇提物对酪氨酸酶的二酚氧化活性抑制作用研究

本实验主要研究了五味子、桃花、蒲公英、山楂、野藿香、山花、黄柏、野玫瑰、黄玫瑰、野菊花十种蜂花粉醇提物对酪氨酸酶二酚氧化活性的抑制作用。结果表明：这十种蜂花粉醇提物对酪氨酸酶均有明显抑制作用,抑制率随着蜂花粉醇提物浓度的提高而提高。其中野玫瑰、黄柏、蒲公英花粉醇提物对两步催化氧化作用都有较好的抑制作用;五味子和野藿香花粉醇提物对酪氨酸酶二酚氧化活性有较好的抑制作用。     

香水莲花提取物抑制酪氨酸酶活性的研究

本实验以L-酪氨酸为底物,从马铃薯中提取酪氨酸酶,以熊果苷为阳性对照,采用比色法测定了香水莲花醇提物、水提物及总黄酮提取物对酪氨酸酶的抑制率,以探讨香水莲花醇提物、水提物及总黄酮提取物对酪氨酸酶的活性的抑制作用。结果表明,三种提取物对酪氨酸酶活性的抑制效果从高到低依次为总黄酮提取物、醇提物、水提物,说明其有效成分为醇溶性物质;总黄酮提取物对酪氨酸酶活性的抑制效果明显高于醇提物和水提物对酪氨酸酶活性的抑制效果,可以考虑将其作为一种新型的植物源美白剂,应用于化妆品行业。     

Taxiphyllin:苦竹笋中具有酪氨酸酶抑制活性的氰苷

从苦竹笋Pleioblastus amarus（Keng）Keng f．中首次分得一个氰苷化合物,通过光谱分析及其物理化学性质鉴定为taxiphyllin（1）。该化合物在体外能显著抑制酪氨酸酶活性,是一个强有效的酪氨酸酶抑制剂。     

Inhibitory Effect of an Ellagic Acid-Rich Pomegranate Extract on Tyrosinase Activity and Ultraviolet-Induced Pigmentation

A pomegranate extract (PE) from the rind containing 90% ellagic acid was tested for its skin-whitening effect. PE showed inhibitory activity against mushroom tyrosinase in vitro, and the inhibition by the extract was comparable to that of arbutin, which is a known whitening agent. PE, when administered orally, also inhibited UV-induced skin pigmentation on the back of brownish guinea pigs. The intensity of the skin-whitening effect was similar between guinea pigs fed with PE and those fed with L-ascorbic acid. PE reduced the number of DOPA-positive melanocytes in the epidermis of UV-irradiated guinea pigs, but L-ascorbic acid did not. These results suggest that the skin-whitening effect of PE was probably due to inhibition of the proliferation of melanocytes and melanin synthesis by tyrosinase in melanocytes. PE, when taken orally, may be used as an effective whitening agent for the skin.     

Inhibitory effects of some flavonoids on the activity of mushroom tyrosinase

Mushroom tyrosinase (EC 1.14.18.1) is a copper containing oxidase that catalyzes both the hydroxylation of tyrosine into o-diphenols and the oxidation of o-diphenols into o-quinones, and then forms brown or black pigments. In the present study, the effects of some flavonoids on the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) have been studied. The results show that flavonoids can lead to reversible inhibition of the enzyme. A kinetic analysis showed that the flavonols are competitive inhibitors, whereas luteolin is an uncompetitive inhibitor. The rank order of inhibition was: quercetin > galangin > morin; fisetin > 3,7,4"-trihydroxyflavone; luteolin > apigenin > chrysin.