Reducing power of Eucalyptus oleosa leaf extracts and green synthesis of gold nanoparticles using the extract

Assay of the antioxidant content and reducing power of the plant extracts is a crucial point in phytochemistry, the food industry, and nutrition. On the other hand, green synthesis of noble metal nanoparticles, such as gold by the aid of plant extract is dependent on the reducing power and antioxidant content of the extract. In this work, cyclic voltammetry was utilized as a facile technique for screening antioxidant properties and estimating the reducing power of the medicinal plant extracts. The effect of different extraction conditions on the reducing power of the aqueous extract was also determined through the cyclic voltammetry technique. The extract of Eucalyptus oleosa leaves obtained at optimum conditions of this study (with maximum reducing power based on cyclic voltammetry assay) was utilized for the green synthesis of gold nanoparticles. Furthermore, the kinetic of the synthesis reaction was investigated by the aid of ultraviolet-visible spectrophotometry based on surface Plasmon resonance for gold nanoparticles at 552 nm. Meanwhile, the synthesized gold nanoparticles were characterized by the transmission electron microscopy technique.     

Biological screening of 100 plant extracts for cosmetic use (I): inhibitory activities of tyrosinase and DOPA auto-oxidation

The aim of this study was to evaluate several plant extracts with a view to developing melanogenesis inhibitors. In this study, 100 plant extracts were screened to elucidate their whitening effects using in vitro inhibition of tyrosinase and DOPA auto-oxidation activity. Several plant extracts such as Chaenomeles speciosa, Dryopteris crassirhizoma, Gastrodia ellata, Glycyrrhiza glabra, Morus alba, Myristica fragrans, Rheum palmatum and Sophora japonica showed inhibition of mushroom tyrosinase activity. Plant extracts including Bupleurum falcatum, Caragana sinica, Morus alba and Tussilago farfara showed inhibition of DOPA auto-oxidation activity.     

三叶青茎部不同溶剂提取物的功能成分、抗氧化及酪氨酸酶抑制活性研究

目的 以三叶青茎部为原料,探究三叶青不同溶剂提取物的功能成分、抗氧化及酪氨酸酶抑制活性。方法 采用乙醇超声法提取三叶青,获得醇提液及残渣。醇提液依次用石油醚、乙酸乙酯、正丁醇对其进行分步萃取,残渣则采用蒸馏水多次提取,最终得到4种提取物。分别测定4种提取物总酚、总黄酮、总皂苷、总多糖、抗氧化及酪氨酸酶抑制活性,并进行相关性分析。结果 4种提取物中乙酸乙酯萃取物总酚、总黄酮、总皂苷含量最高,分别为40.22%±1.01%、38.56%±0.64%、6.15%±0.21%,正丁醇萃取物总多糖含量最高,为9.29%±0.25%。各萃取物均具有抗氧化和酪氨酸酶抑制活性,其中乙酸乙酯萃取物清除1,1-二苯基-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基、超氧阴离子、2-苯基-4,4,5,5-四甲基咪唑啉-3-氧代-1-氧(2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl,PTIO)自由基、羟自由基能力和铁离子还原能力(ferric reducing antioxidant power, FRA...     

Antioxidant and tyrosinase inhibitory activities of a novel chitosan–phloroglucinol conjugate

A novel chitosan–phloroglucinol conjugate was developed by conjugating phloroglucinol onto a chitosan backbone. The chitosan–phloroglucinol conjugate was characterised by ¹H nuclear magnetic resonance (NMR), and the NMR spectra confirmed the conjugation. Antioxidant and tyrosinase inhibitory activities of the chitosan–phloroglucinol conjugate were investigated. The chitosan–phloroglucinol conjugate showed strong 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH), hydrogen peroxide and ABTS⁺ radical scavenging activities as well as reducing power compared with those of the unmodified chitosan (P < 0.05). The formation of malondiadehyde (MDA) as an indicator of lipid peroxidation in a linoleic acid emulsion was 30.56 μM in the absence of the chitosan–phloroglucinol conjugate after 4 days incubation, whereas MDA was 4.14 μM in the presence of the chitosan–phloroglucinol conjugate (P < 0.05). The activity was higher than that of ascorbic acid, which is currently used as a food preservative. Moreover, the chitosan–phloroglucinol conjugate inhibited 56.30% tyrosinase activity, which is responsible for browning of foods, and acted as non‐competitive inhibitor. Taken together, the chitosan–phloroglucinol conjugate may have potential for application in functional foods and/or as a food preservative.     

对香豆酸、阿魏酸和低聚糖阿魏酸酯对酪氨酸酶的抑制效果

通过测定酶的稳态活力、迟滞时间和动力学参数,研究对香豆酸、阿魏酸及低聚糖阿魏酸酯对酪氨酸酶的抑制效果。结果表明,3种物质对酪氨酸酶单酚酶活性均有抑制作用,其中对香豆酸的抑制作用最强,其次为低聚糖阿魏酸酯和阿魏酸。对香豆酸、低聚糖阿魏酸酯和阿魏酸对单酚酶的IC_(50)值分别为0.75,3.20,9.30 mmol/L。对香豆酸和阿魏酸抑制二酚酶活性,IC_(50)值分别为4.3,12.7mmol/L;但低聚糖阿魏酸酯对二酚酶活力没有影响。对香豆酸能明显延长单酚酶反应的迟滞时间,阿魏酸影响很小,而低聚糖阿魏酸酯则缩短迟滞时间。动力学研究结果显示,阿魏酸和低聚糖阿魏酸酯对单酚酶的抑制作用表现为混合性抑制,而对香豆酸为竞争性抑制。     

远东拟沙丁鱼蛋白多肽(Sardinops sagaxp olypeptide)的制备及其对酪氨酸酶的抑制作用

以远东拟沙丁鱼为原料,采用动物蛋白水解酶和风味酶联合水解,通过膜分离等工序制备远东拟沙丁鱼蛋白多肽(Sardinops sagax Polypeptide/SSP),测定其分子量的分布,以生化水平上对酪氨酸酶的抑制率、细胞水平上对小鼠B16细胞中酪氨酸酶活性及黑色素含量的抑制率为检测指标,研究SSP对酪氨酸酶活性及黑色素合成的影响。结果显示:SSP的重均分子量为1664 u,其分子量区间主要为500~3000 u;无论是在生化水平还是细胞水平上,SSP对酪氨酸酶都具有一定的抑制作用,且SSP还能在一定程度上抑制细胞中黑色素的合成,这一结果表明了SSP具有一定的美白功能,有望作为无毒副作用的天然酪氨酸酶抑制剂,在医药、食品、化妆品等行业具有广泛的应用前景。      

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。     

花生红衣总多酚抑制酪氨酸酶活性和抗氧化作用研究

通过单因素实验和正交实验,确定了闪式提取花生红衣总多酚的最佳工艺条件;并研究了花生红衣总多酚对酪氨酸酶的抑制作用及清除DPPH自由基的能力。闪式提取最佳工艺条件为:乙醇浓度80%,料液比1∶25(g/mL),提取电压90V,提取3次,每次2min,该条件下,花生红衣总多酚的平均提取率为96.94%;花生红衣总多酚对酪氨酸酶的抑制率达到50%(IC50)时所需的花生红衣总多酚的质量浓度为0.451mg/mL,最高抑制率可达89.65%;并且花生红衣总多酚清除DPPH自由基的能力大于VC,稍弱于没食子酸。      

基于金纳米簇与纳米金的荧光内滤效应检测脂肪酶活性

目的 建立一种基于吐温80自氧化作用催化纳米金形成与荧光内滤机制,相对简单、快速、适用于蛋白浓度较高的游离酶的脂肪酶活性检测方法。方法 使用金纳米簇作为荧光基团,纳米金作为吸收剂,基于荧光内滤机制测定游离脂肪酶活力。设置对照试验对吐温80浓度、氯金酸浓度、温度、pH等反应条件进行优化,探索最适条件下脂肪酶水解反应时间及吐温80还原纳米金的时间并对反应体系进行抗干扰检测,验证该方法的可行性。结果 当脂肪酶酶活力在13.5～15092.0 U/L时,荧光强度的差值随脂肪酶活力的升高而增加,相关系数为0.9977,脂肪酶活力的检出限为2.34 U/L (信噪比为3)。结论 该方法操作相对简单、快速、检测范围较大、灵敏度高,具有实用性,可适用于蛋白浓度较高的游离酶的脂肪酶活力测定。     

3‐Hydroxypyridinone‐l‐phenylalanine conjugates with antimicrobial and tyrosinase inhibitory activities as potential shrimp preservatives

To explore the potential of novel tyrosinase inhibitors, 3‐hydroxypyridinone‐l ‐phenylalanine conjugates, as shrimp preservatives, compounds 1 and 2 were evaluated for the antimicrobial activity, and compound 2 was investigated for the shrimp preservative efficacy. It was found that they both possess a stronger antibacterial effect than kojic acid against two Gram‐positive bacteria and three Gram‐negative bacteria. The minimum inhibitory concentrations (MICs) of compound 2 against Escherichia coli, Staphylococcous aureus, Salmonella gallinarum, Vibrio parahaemolyticus and Bacillus subtilis were determined as 18.5, 37, 148, 37 and 295 μg mL^?1, respectively, whereas MICs of kojic acid against the same 5 bacterial strains were determined to be 355, 178, 1420, 1420 and 355 μg mL^?1, respectively. It has also been demonstrated that treatment with compound 2 improves the sensory properties, retards the growth of spoilage bacteria, decreases the total volatile basic nitrogen (TVB‐N) and increases the pH of Penaeus vannamei Boone, thereby extending the shelf life to 10 days. In contrast, the shelf life of shrimp treated with kojic acid and the control group was 7 and 6 days, respectively. Clearly, 3‐hydroxypyridinone‐l ‐phenylalanine conjugates could find application as shrimp preservatives by inhibiting melanosis and by preventing the growth of bacteria during the storage.     

花椒生物碱提取工艺及抗氧化、抑制酪氨酸酶活性研究

以花椒为实验材料,选用超声波辅助提取法提取花椒中的生物碱,应用单因素和响应面实验优化花椒生物碱的提取工艺,用DPPH法研究其抗氧化活性,并对其抑制酪氨酸酶的活性进行了研究。结果表明,花椒生物碱的最佳提取工艺条件为:超声功率233W,超声时间11min,料液比1∶16g/mL,乙醇浓度79%,花椒生物碱提取率达到1.19%。花椒生物碱对DPPH自由基清除的IC50值为0.0599mg/mL,抑制酪氨酸酶活性的IC50为1.212mg/mL,说明花椒生物碱有一定的抗氧化和抑制酪氨酸酶活性的能力,但此两种活性均弱于VC。      

Antibrowning and antimicrobial activities of the water-soluble extract from pine needles of Cedrus deodara

The antibrowning and antimicrobial activities of the water-soluble extract from pine needles of Cedrus deodara (CDE), a traditional Chinese medicine and raw materials of pine needle tea, was investigated. Total phenols of CDE were 31.4 ± 0.53 mg gallic acid equivalent/g, and total flavonoids were 23.1 ± 0.79 mg rutin equivalent/g. CDE showed a strong antioxidant activity against ABTS free radicals with IC(50) (the half-inhibitory concentration) of 25.5 ± 0.64 μg/mL. In mushroom tyrosinase inhibitory assay, IC(50) values were 2.1 ± 0.98 and 2.27 ± 0.93 mg/mL for monophenolase and diphenolase, respectively. Evaluated by detecting changes of L* (indicated the darkness of sample), a* (indicated the redness of sample), and b* (indicated the yellowness of sample) values in fresh-cut apple slices model, CDE showed a significant antibrowning effect when compared with ascorbic acid. In addition, it was discovered that CDE in combination with 0.5% ascorbic acid exhibited a synergistic antibrowning effect. Meanwhile, CDE was observed to show a potent antimicrobial effect on all of the tested Gram-positive and Gram-negative bacteria. In conclusion, the results of the present research suggested that pine needles of C. deodara could be used as a natural resource of antibrowning and antimicrobial agents in food preservation. PRACTICAL APPLICATION: The present study provides a theoretical basis for the potential application of pine needles of C. deodara to be used as a natural resource of antibrowning and antimicrobial agents in food industry.     

荔枝果实不同部位提取物的总黄酮含量及其稳定性、抗氧化、美白活性分析

目的 探究荔枝果实不同部位多酚提取物（果肉、鲜干果核、鲜干果壳）中总黄酮含量及其稳定性、抗氧化及美白活性。方法 通过亚硝酸钠显色法测定荔枝果实不同部位多酚提取物中的黄酮类物质含量,并以紫外分光光度法测定其对1,1-二苯基-2-苦基肼(1,1-diphenyl-2-picrylhydrazyl, DPPH)自由基的清除能力、稳定性（温度、pH及光照）及对酪氨酸酶的抑制活性。 结果 荔枝果实不同部位多酚提取物中均有较高的总黄酮含量,其中荔枝果肉多酚中黄酮占比最高为93.24%;其DPPH抗氧化活性顺序是荔枝果肉＞鲜荔枝核＞干荔枝核＞鲜荔枝壳＞干荔枝壳;对酪氨酸酶抑制能力分别是：荔枝果肉＞干荔枝核＞鲜荔枝核＞鲜荔枝壳＞干荔枝壳,其中荔枝果肉与干荔枝核的半抑制浓度(half maximal inhibitory concentration, IC50) 分别为0.197与0.241,均优于熊果苷(IC50为0.343)。在同等温度、pH、自然光条件下,荔枝果实总黄酮稳定性顺序分别是干荔枝壳＞干荔枝核＞鲜荔枝壳＞鲜荔枝核＞荔枝果肉;结论 荔枝果实不同部位多酚提取物均具有一定DPPH抗氧化活性、稳定性与酪氨酸酶抑制活性,且其DPPH抗氧化活性和酪氨酸酶抑制活性均与其总黄酮含量和成分相关。荔枝果肉和荔枝壳、荔枝核等废弃物均可成为天然抗氧化剂与美白成分的原料来源,为拓展荔枝果实在食品及日化行业的应用提供参考。