番石榴不同部位乙醇提取物的抗氧化、降血糖及酪氨酸酶抑制活性

目的:比较研究番石榴不同部位（根、茎、叶、果实）乙醇提取物抗氧化、降血糖和抑制酪氨酸酶活性。方法:分别采用ABTS法和DPPH法、pNPG法和DNS法、L-DOPA法评价番石榴不同部位抗氧化活性、降血糖活性和酪氨酸酶抑制活性。结果:番石榴不同部位乙醇提取物均具有一定的体外抗氧化、降血糖和酪氨酸酶抑制活性,并呈现一定的量效关系。番石榴各部位中,番石榴根乙醇提取物的抗氧化、降血糖和抑制酪氨酸酶活性均强于其他部位。番石榴根对DPPH、ABTS+自由基清除能力与维生素C接近,清除能力IC₅₀值分别为:(8.45±0.12)、(0.09±0.002) mg/mL,且其对α-淀粉酶和酵母菌来源α-葡萄糖苷酶的抑制活性强于阿卡波糖,抑制活性的IC₅₀值分别为:(0.10±0.02)、(8.74±0.25) μg/mL;而对小鼠小肠来源α-葡萄糖苷酶的抑制活性弱于阿卡波糖;对酪氨酸酶抑制活性弱于维生素C。结论:番石榴根乙醇提取物的抗氧化、降血糖和酪氨酸酶抑制活性最强,表明番石榴根是潜在抗氧化剂和α-葡萄糖苷酶、α-淀粉酶和酪氨酸酶抑制剂的来源。     

辣木叶多酚抗酶促褐变效果及其评价

研究辣木叶多酚对酪氨酸酶二酚酶活力的抑制作用及对苹果切片的抗酶促褐变效果。在多巴测活体系中,通过改变底物浓度和酶量,研究辣木叶多酚对酪氨酸酶的抑制效果、机制及类型。结果表明,辣木叶多酚对酪氨酸酶抑制作用明显,半抑制率IC_(50)为6.67μg/mL,其对酪氨酸酶二酚酶的抑制作用为可逆的混合竞争型抑制,其抑制常数K_I、K_(IS)分别为1.51 mg/mL和7.82 mg/mL。通过对多项指标的检测和方差分析,发现辣木多酚对苹果的保鲜有差异显著(p0.05)。在苹果低温储藏期间,辣木多酚能调控POD活性,降低苹果切片的褐变程度,同时能有效提高蔗糖含量和抗坏血酸含量,而对蛋白含量和GSH含量影响不大。研究有望为开发新式辣木叶多酚高效酪氨酸酶抑制剂提供一定的理论依据。     

籽瓜瓤提取物对酪氨酸酶抑制作用及其成分分析

探讨籽瓜瓤提取物对酪氨酸酶活性的抑制作用,以期为天然酪氨酸酶抑制剂提供新的原料选择。以水和30%、60%、95%乙醇为提取剂采用热回流提取法对籽瓜瓤冻干粉、烘干粉、鲜瓤进行提取,以酶活性测定方法检测提取物对酪氨酸酶活性的抑制作用,以化学显色法和色谱法检测分析籽瓜瓤的有效成分。结果表明烘干粉水提物的酪氨酸酶抑制活性最强,50 mg/mL时抑制率高达60.15%,其活性成分至少含有6种,对主要成分糖类和有机酸检测酶活发现,抑酶效果有机酸好于多糖,烘干粉中还可能有其它抑酶成分。籽瓜瓤拥有多种生物活性成分,其中有机酸和多糖具有一定的抑酶效果,烘干籽瓜粉水提物具有较强酪氨酸酶抑制作用,可作为潜在天然酪氨酸酶抑制剂以提高籽瓜的综合利用率。     

固态发酵番石榴叶精油释放及其活性变化

本研究采用红曲霉和巨大芽孢杆菌对番石榴叶基质进行混菌固态发酵,探讨发酵过程中番石榴叶精油成分的释放。结果表明,发酵后番石榴叶精油中的20种主要成分种类不变,但精油提取率显著提高,发酵10 d提取率达到未发酵组的6.53倍。组织结构分析结合酶学分析推断,糖苷酶破坏了番石榴叶的细胞壁、腺毛和液泡等结构,并进一步切断糖间链接和糖苷键,促进番石榴叶中芳香化合物的释放。发酵后番石榴叶精油的2,2-二苯基-1-苦基肼DPPH自由基清除能力下降26.15%,但是2,2′-联氮双-3-乙基苯并噻唑啉-6-磺酸阳离子ABTS+自由基清除能力,5-脂氧合酶和酪氨酸酶的抑制能力分别提高 32.66%、18.73%和7.87%,发酵10 d后相应IC50分别达到20.47±2.49 mg/mL、23.21±1.92 μg/mL和107.41±3.48 μg/mL,综合来看发酵能改善该精油的抗氧化和生物活性。本成果可为果树叶精油高效提取提供新方法,为开发新型活性天然保健产品提供途径。     

番石榴叶黄酮的微波提取及其抗氧化作用研究

以番石榴叶为原料,采用微波技术优化番石榴叶中黄酮类物质的提取工艺,并研究番石榴叶黄酮对油脂的抗氧化作用。试验结果表明,番石榴叶中黄酮类物质的最佳微波萃取工艺参数是:微波提取时间10 min,微波功率400 W,料液比1∶30,乙醇体积分数50%。在此提取条件下,番石榴叶中总黄酮的提取率为134.46 mg/g。番石榴叶黄酮提取物对植物油脂具有一定的抗氧化作用,可作为植物油脂的天然抗氧化剂。     

茶多酚对酪氨酸酶的抑制作用及分子机制研究

目的 研究茶多酚对酪氨酸酶的抑制作用及分子机理。方法 通过生化分析法,测定茶多酚对酪氨酸酶的抑制作用并分析其抑制动力学;采用荧光光谱、圆二色谱和分子模拟技术,剖析茶多酚对酪氨酸酶抑制作用的分子机理。结果 茶多酚对酪氨酸酶有良好的抑制作用,对其单酚和多酚活性的半数抑制浓度分别为0.662 mg/mL和1.76 mg/mL,为竞争性抑制;茶多酚可使酪氨酸酶出现明显的荧光淬灭和最大发射波长红移,并使酪氨酸酶二级结构中的α-螺旋结构显著增加,β-折叠、β-转角和无规则卷曲结构减少,显著改变酪氨酸酶的三级和二级结构。结论 茶多酚主要通过氢键和静电相互作用与酪氨酸酶进行结合,从而改变酪氨酸酶的空间结构并阻碍其与底物进行结合,进而抑制酪氨酸酶的活性。     

酸枣叶缩合单宁的分离鉴定及其对黑色素生成的抑制机制

目的:研究酸枣叶缩合单宁的结构特征及其对酪氨酸酶的效应和黑色素生成的抑制机制。方法:利用Sephadex LH-20凝胶柱色谱技术分离制备酸枣叶缩合单宁纯化物,采用硫醇降解结合高效液相色谱-电喷雾电离质谱（Thiolysis-HPLC-ESI-MS）解析酸枣叶缩合单宁的结构单元组成,运用酶动力学、紫外光谱、荧光猝灭等方法系统研究酸枣叶缩合单宁对酪氨酸酶的抑制作用机理,应用CCK-8法、多巴氧化法、NaOH裂解法和实时荧光定量PCR检测酸枣叶缩合单宁对小鼠黑色素瘤细胞（B16F10）的增殖、酪氨酸酶活性、黑色素合成及其相关基因表达水平的影响。结果:构成酸枣叶缩合单宁的主要结构单元是（表）儿茶素和（表）棓儿茶素;酸枣叶缩合单宁具有较强的酪氨酸酶单酚酶和二酚酶抑制活性,是二酚酶可逆的混合型抑制剂;酸枣叶缩合单宁可有效抑制B16F10细胞的增殖、酪氨酸酶活性、黑色素生成量以及酪氨酸酶（TYR）、酪氨酸酶相关蛋白-1（TRP-1）、小眼畸形相关转录因子（MITF）等基因的表达。结论:通过在酶水平和细胞水平的综合分析,阐明酸枣叶缩合单宁对B16F10细胞黑色素合成的分子抑制机制,为后期酸枣叶缩合单宁开发为新的美白化妆品添加剂和果蔬保鲜剂提供理论依据。     

沙棘黄酮对酪氨酸酶活力抑制作用的研究

研究沙棘黄酮对酪氨酸酶活性的抑制作用。实验测定了沙棘黄酮分别在温度、pH、时间、底物浓度、酶液加入量等因素条件下对酪氨酸酶活力的影响。结果显示,沙棘黄酮对酪氨酸酶活性的抑制率随着时间的延长,底物浓度的增加,酶量的增加而增强,而且在35℃及pH7.1时沙棘黄酮对酪氨酸酶活力的抑制作用最强可达到47.45%。说明沙棘黄酮对酪氨酸酶的活性具有较强的抑制作用。     

4种茶叶醇提物对酪氨酸酶的抑制作用

采用提取分离法提取土豆中的酪氨酸酶,并以多巴为底物,运用酶活性测定法研究4种茶叶醇提物对土豆酪氨酸酶活性的抑制作用.结果表明,在4种茶叶的50%乙醇(V/V)提取液中,生药质量浓度达到4.0 mg/mL时,茶叶醇提物对土豆酪氨酸酶的活性有不同程度的抑制作用,其中青茶对酪氨酸酶的抑制作用最大,抑制率为62.28%.     

酱油对酪氨酸酶抑制作用的研究

酪氨酸酶是合成黑色素过程的关键酶,通过测定酱油对酪氨酸酶活性的影响来确定其对酪氨酸酶的抑制作用及抑制机理。结果表明:酱油对酪氨酸酶具有较强的抑制作用,酶抑制率达到50%时(IC50)酱油固形物含量浓度为19.8g/L。酱油对酪氨酸酶的抑制作用动力学行为表现为可逆混合性抑制类型。     

Antioxidant and tyrosinase inhibitory activities of different parts of guava (<Emphasis Type="Italic">Psidium guajava</Emphasis> L.)

The antioxidant and the tyrosinase inhibitory activities of 4 different solvents (acetone, ethanol, methanol, and water) for preparation of extracts from guava (branch, fruit, leaf, and seed) were evaluated by measuring total phenolic contents (TPC), DPPH radical scavenging activity, ABTS radical scavenging activity, reducing power (RP), and tyrosinase inhibitory activity. The extracts of branch and leaf showed relatively higher antioxidant properties than those of fruit and seed. The highest TPC (141.28 mg/g gallic acid equivalents), DPPH radical scavenging activity (IC₅₀=34.01 μg/mL), ABTS radical scavenging activity (IC₅₀=3.23 μg/mL), and RP (IC₅₀= 75.63 μg/mL) were found in acetone extract of leaf, while water extract of seed had the lowest antioxidant activity. The tyrosinase inhibitory activity of ethanol extract from guava leaf was 69.56%, which was the highest activity among the extracts. These results indicate that useful bioactive substances exist in the guava branch as well as leaf extracts.     

白附子酪氨酸酶活性抑制成分的提取与分离

研究了不同溶剂及提取方式对白附子中酪氨酸酶抑制成分的影响,并应用活性追踪法对白附子中酪氨酸酶活性抑制成分进行考察。结果表明,以20%乙醇水溶液为溶剂从白附子中提取的粗提物对酪氨酸酶活性的抑制作用最强,抑制率可达到96.35%,与恒温水浴振荡提取法相比,超声波辅助提取法对活性成分的提取效果更好。在此提取条件下所得白附子粗提物对酪氨酸酶的半抑制浓度IC50为24.69mg/mL。该粗提物依次经乙醚和正丁醇萃取,所得正丁醇萃取组分对酪氨酸酶的抑制率达71.94%。对高活性的正丁醇萃取组分进行分离,获得了一种酪氨酸酶抑制率高达98.82%的组分,是一种潜在的酪氨酸酶抑制剂。研究结果对白附子及其活性组分在医药和食品领域的应用有指导意义。     

Effect of Guava (Psidium guajava L.) Leaf Extract on Glucose Uptake in Rat Hepatocytes

ABSTRACT:  People in oriental countries, including Japan and Taiwan, boil guava leaves ( Psidium guajava L.) in water and drink the extract as a folk medicine for diabetes. The present study investigated the enhancement of aqueous guava leaf extract on glucose uptake in rat clone 9 hepatocytes and searched for the active compound. The extract was eluted with MeOH-H₂O solutions through Diaion, Sephadex, and MCI-gel columns to separate into fractions with different polarities. The uptake test of 2-[1-¹⁴C] deoxy-D-glucose in rat clone 9 hepatocytes was performed to evaluate the hypoglycemic effect of these fractions. The active compound was identified by nuclear magnetic resonance analysis and high-performance liquid chromatography (HPLC). The results revealed that phenolics are the principal component of the extract, that high polarity fractions of the guava leaf extract are enhancers to glucose uptake in rat clone 9 hepatocytes, and that quercetin is the major active compound. We suggest that quercetin in the aqueous extract of guava leaves promotes glucose uptake in liver cells, and contributes to the alleviation of hypoglycemia in diabetes as a consequence.     

番石榴叶中广寄生苷和番石榴苷的降糖作用

目的：研究番石榴叶、广寄生苷和番石榴苷的降糖活性和相关性。方法：采用反相高效液相色谱法测定不同月份番石榴叶中番石榴苷和广寄生苷的含量;建立降糖脂肪细胞模型,测定不同季节番石榴叶提取物的降糖活性;给药干预后,测定细胞培养液中游离脂肪酸的含量,采用Western blotting法测定脂肪细胞膜葡萄糖转运蛋白4（glucose transporter 4,GLUT4）表达。结果：6-9月份番石榴叶中番石榴苷和广寄生苷的含量较高,同时6-9月份番石榴叶的降糖活性也最好,降糖活性与化合物含量存在正相关性。番石榴叶提取物、番石榴苷和广寄生苷均能显著促进脂肪细胞膜上GLUT4蛋白的表达;番石榴叶提取物、番石榴苷和广寄生苷均能显著抑制游离脂肪酸的释放,降糖活性和抑制脂肪分解也存在正相关性。结论：番石榴苷和广寄生苷两种黄酮苷类化合物是番石榴叶降糖、抑制游离脂肪酸释放的主要活性物质基础。     

Antioxidant and tyrosinase inhibitory activities of different parts of oriental cherry (Prunus serrulata var. spontanea)

Six different parts (branch, flesh, flower, fruit, leaf, and seed) of oriental cherry (Prunus serrulata var. spontanea) were extracted with ethanol or water, then total phenol content (TPC), antioxidant activity, and tyrosinase inhibitory activity of the extracts were evaluated. The ethanol extracts showed higher TPC and antioxidant activity than the water extracts regardless of parts. The ethanol extracts of leaf as well as branch possessed superior TPC and antioxidant activity. The highest tyrosinase inhibitory activity was found in ethanol extract of leaf. There was no dramatic difference of tyrosinase inhibitory activities according to parts of cherry. The results suggest that leaf and branch of oriental cherry could be a candidate for antioxidant and anti-whitening materials in food or cosmetic industries.     

Factors influencing antioxidant activities and total phenolic content of guava leaf extract

The aim of this study is to investigate the influence of certain factors on the yield, antioxidant activity (AA) and total phenolic content (TPC) of guava leaf extract. The effects of pretreatment of leaf sample prior to extract, extraction method, and the leaf age were investigated. Folin-Ciocalteau was used to determine the TPC. Trolox equivalent antioxidant capacity (TEAC) and equilibrium concentration (EC) were used for evaluation of AA. Results indicated that ultrasonication is the most suitable method for guava leaf extraction as it yielded the extract with the significantly highest TPC and AA. Blanching followed by ice water cooling (BCD) was suggested for the pretreatment process of guava leaves. The study of leaf maturity demonstrated that the highest activity was from the young leaves. Hot water was the best solvent to extract the active principles. The extract of BCD pretreated young leaves, extracted by hot water exhibited the highest TPC and AA with the TEAC and EC values of 24.30 ± 0.50 and 20.41 ± 0.67 mM/mg, respectively. These values are 1.88 and 8.72 times higher than the synthetic antioxidant butylated hydroxy toluene (BHT) and 1.75 and 1.21 times higher than vitamin E, respectively. It was concluded that pretreatment and drying process, method of extraction and leaf maturity played important roles on the bioactive compounds and their antioxidant power of guava leaf extract.     

Effects of Gamma Irradiation on the Biological Activity of Green Tea Byproduct Extracts and a Comparison with Green Tea Leaf Extracts

ABSTRACT:  Green tea byproduct extract powder, a major byproduct of the green tea industry, was prepared and investigated for its biological activities after a gamma-irradiation treatment for the purpose of a brightened color. The color, total phenolic contents, antioxidative activity, tyrosinase inhibition activity, cancer cell proliferation inhibition effect, and antimutagenicity were measured and compared with those of a green tea leaf extract powder. Hunter L* values of the irradiated green leaf and byproduct extracts were increased in a comparison with the nonirradiated extracts. The contents of total phenolic compounds of the green tea leaf and byproduct extracts were 424.2 ± 11.45 and 335.5 ± 18.65 mg/g of sample, respectively. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of the 20 ppm green tea leaf and byproduct extracts were 68.2% and 57.6%, respectively. Ferric-reducing ability of the samples showed similar results to the DPPH radical scavenging capacity. The samples showed an inhibition of tyrosinase and also a cancer cell proliferation inhibition effect. Especially, the antimutagenicities of the byproduct extracts showed a strong inhibition effect (96.20% and 57.77%) on 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp) and 2-nitrofluorene (NF), respectively. Results indicated that, although the biological activity of green tea byproduct extracts is less than that of green tea leaf extract, it may be a potential source of a functional ingredient. In addition, irradiation can be applied to improve the color and biological activity of the material.     

Anti-inflammatory effects of 4 medicinal plant extracts in lipopolysaccharide-induced RAW 264.7 cells

The anti-inflammatory activity of 4 plant extracts [guava (Psidium guajava) leaf, capillary wormwood (Artemisia capillaris Thunb.), Chinese goldthread (Coptis chinensis), and dandelion (Taraxacum platycarpum)] was investigated in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Six phenolic compounds (gallic acid, caffeic acid, chlorogenic acid, catechin, quercetin, and baicalin) were analyzed using LC-MS/MS. Guava leaf extracts showed the highest inhibitory effects on LPS-induced nitric oxide (NO, 52.58%) and prostaglandin E₂ (PGE₂, 43.45%) production. The total phenolic contents (TPC) in guava leaf, capillary wormwood, Chinese goldthread, and dandelion were 426.84, 154.42, 41.73, and 122.04 mg of gallic acid equivalent (GAE)/g of extract, respectively. TPC was positively correlated with the NO-inhibitory effect (r= 0.963, p<0.05) and the PGE₂-inhibitory effect (r=0.971, p<0.05) at 30 μg/mL of treatment. The guava leaf extracts contained the highest levels of gallic acid and catechin, while the capillary wormwood extracts contained the highest levels of chlorogenic acid and quercetin.

     

番石榴叶对食品中几种常见细菌的抑菌作用

应用药敏纸片法和试管二倍稀释法,对比研究番石榴叶水提取物和乙醇提取物对食品中4种常见细菌(金黄色葡萄球菌、沙门氏菌、大肠杆菌和枯草芽孢杆菌)的抑菌效果,分析抑菌作用与其总黄酮含量的关系.结果表明:番石榴叶水提取物、乙醇提取物对金黄色葡萄球菌、沙门氏菌、大肠杆菌、枯草芽孢杆菌均有一定的抑菌活性,总体上,水提取物抑菌活性优于乙醇提取物,水提取物的抑菌效果为金黄色葡萄球菌＞沙门氏菌＞大肠杆菌＞枯草芽孢杆菌;黄酮类化合物是番石榴叶中重要的抑菌物质之一.     

Inhibitory effects of guava (Psidium guajava L.) leaf extracts and its active compounds on the glycation process of protein

Hyperglycaemia causes increased protein glycation and the formation of early glycation products and advanced glycation end products (AGEs) which are major factors responsible for the complications of diabetes. This study investigated the ability of guava leaf and compounds to inhibit glycation process in an albumin/glucose model system and compared the potency of these extracts with Polyphenon 60 which is a commercial polyphenol product extracted from green tea and with the standard antiglycation agent, aminoguanidine. The results showed that the inhibitory effects of guava leaf extracts on the formation of α-dicarbonyl compounds were over 95% at 50 μg/ml. Phenolic compounds present, namely gallic acid, catechin and quercetin exhibited over 80% inhibitory effects, but ferulic acid showed no activity. The guava leaf extracts also showed strong inhibitory effects on the production of Amadori products and AGEs from albumin in the presence of glucose. The phenolic compounds also showed strong inhibitory effects on the glycation of albumin, especially quercetin exhibited over 95% inhibitory effects at 100 μg/ml. According to the results obtained, guava leaf extracts are potent antiglycation agents, which can be of great value in the preventive glycation-associated complications in diabetes.