Determination of catechins in green tea infusions by reduced flow micellar electrokinetic chromatography

A sulfated-β-cyclodextrin (s-β-CD) modified reduced flow micellar electrokinetic chromatography (RF-MEKC) method was developed and validated for the determination of catechins in green tea. The optimal electrolyte consisted of 0.2% triethylamine, 50 mmol/L SDS and 0.8% s-β-CD (pH = 2.9), allowing baseline separation of five catechins in 4 min. The samples and standards were injected at 0.6 psi for 5 s under constant voltage of −30 kV. Sample preparation simply involved extraction of 2 g of tea with 200 mL water at 95 °C under constant stirring for 5 min. The method demonstrated excellent performance, with limits of detection (LOD) and quantification (LOQ) of 0.02–0.1 and 0.1–0.5 μg/mL, respectively, and recovery percentages of 94–101%. The method was applied to six samples of Brazilian green tea infusions. Epigallocatechin gallate (23.4–112.4 μg/mL) was the major component, followed by epigallocatechin (18.4–78.9 μg/mL), epicatechin gallate (5.6–29.6 μg/mL), epicatechin (4.6–14.5 μg/mL) and catechin (3.2–8.2 μg/mL).     

Correlation between leaf age,shade levels,and characteristic beneficial natural constituents of tea (Camellia sinensis) grown in Hawaii

This study showed the relationship between tea leaf age, bud and first two leaves, and shade levels, on the relative concentrations of six major compounds of tea leaf, namely l-theanine, caffeine, and the major tea catechins; (−)-epigallocatechin gallate (EGCG), (−)-epigallocatechin (EGC), (−)-epicatechin (EC), and (−)-epicatechin gallate (ECG), all of which are reported to have positive effects on human health, as well as at the ferric reducing antioxidant power of bud and leaf extracts. The concentration of l-theanine and caffeine decreased as leaf age increased moving from bud to first and then second leaf, while the concentration of the four catechins increased from the bud to first and second leaves. In most cases this increase was generally relatively small but in the case of EGC it was 7 to 10-fold. Certain chemical components of freshly picked, minimally processed and essentially unoxidised tea may potentially be used as markers for age, quality, authenticity and area of growth.     

茶籽饼中茶皂素提取工艺的优化

采用榨油后茶籽饼为原料,以茶皂素提取率为指标,利用超声辅助提取法优化了茶皂素的提取工艺。试验得到的最佳提取条件：常温下提取,95%甲醇：丙酮为6∶1、料液比为1∶5、超声时间为15min和超声功率为250W。此时,茶皂素的提取率为16.5%,纯度为93%。     

Variations in the leaf standard,chemical composition and quality of black tea (Camellia sinensis) due to plucking intervals

Green leaf standard, chemical composition and quality of black tea (Camellia sinensis (L) O Kuntze) change with plucking intervals. Long plucking intervals lead to poor leaf standard with a lot of mature leaves and lower theaflavins, the sum of volatile flavour compounds imparting a sweet flowery aroma (group II volatile flavour compounds), caffeine contents and tasters' evaluations of black tea. The sum of volatile flavour compounds imparting inferior, grassy, green flavour (group I volatile flavour compounds) to tea, however, increases with long plucking intervals.     

乳酸菌发酵对茶花粉营养成分及生物活性的影响

为研究茶花粉乳酸菌发酵前后基本营养成分以及生物活性的影响。以茶花粉为原料在嗜热链球菌和植物乳杆菌的共同作用下进行发酵处理后分析测定发酵前后基本营养成分,α-葡萄糖苷酶抑制活性以及清除羟自由基能力的变化。结果表明,乳酸菌发酵茶花粉发酵终点为72 h,发酵茶花粉与未发酵茶花粉相比,还原糖、脂肪含量有所降低,灰分、蛋白质、多酚、黄酮含量分别有不同程度的提高,对α-葡萄糖苷酶的半抑制浓度(IC₅₀)由49.09 mg/mL降低到38.79 mg/mL,并且清除羟自由基能力的半抑制浓度(EC₅₀)由4.49 mg/mL提高到5.78 mg/mL。该研究为茶花粉乳酸菌发酵产物的开发利用提供了实验参考。     

利用异或运算和编码约束的降维LDP人脸识别方法

为了有效表示面部特征,在局部方向模式(LDP)的基础上,提出降维局部方向模式(RDLDP);首先,修改LDP编码模式约束以完成模式的重构,通过对LDP码进行异或运算来计算每个块的单一码;然后,将所得编码图像划分为生成直方图,连接所有区域的直方图块以形成最终描述符;最后,计算特征向量间的卡方相异性度量值,并使用最近邻分类器完成最终的人脸识别;实验采用了3个公开的标准数据库FERET、扩展YALE-B和ORL,提出的改进方法在3个数据集上的最高识别率分别可高达96.97%、96.10%、97.61%,该结果验证了提出方法的有效性。与其他基于局部描述符的先进方法相比,提出方法在准确度和错误识别率等方面更优。     

碱处理对油茶籽蛋白降解及其胶黏剂性能的影响

为了促进油茶产业的发展以及开发新的蛋白胶黏剂,以油茶籽蛋白为原料（蛋白质含量36%,纤维含量15%）,采用碱（NaOH）对其进行降解处理,并与交联剂混合作为胶黏剂应用于胶合板的热压中。考察了NaOH加量对油茶籽蛋白水解度和降解液甲醛反应能力、黏度和胶黏剂胶合性能的影响,并对降解前后油茶籽蛋白进行了红外表征。结果表明：NaOH可使油茶籽蛋白有效降解,并产生活性基团和活性点;随着NaOH加量的增加,油茶籽蛋白水解度和降解液甲醛反应能力呈先急剧增加后缓慢增加的趋势,降解液黏度呈先增加后急剧减小再缓慢减小的趋势;所制备的胶合板的湿状胶合强度总体呈先增加后减小的变化趋势。NaOH加量为7%时,油茶籽蛋白降解液具有较高的反应活性、较大的内聚强度、较好的施胶性能和优良的胶合性能。     

茶蜂花粉提取物BPE对LPS诱导的Raw 264.7细胞的体外抗炎症作用

以茶蜂花粉提取物(BPE)为实验材料,研究了其可能的抗炎活性。通过福林酚法和三氯化铝比色法测定BPE中的总酚酸和总黄酮质量分数,ABTS自由基清除实验评价BPE体外自由基清除能力,并采用LPS诱导的小鼠Raw 264.7细胞体外炎症模型,探究BPE对炎症因子和相关基因表达的调控作用。结果显示,BPE的总酚酸及总黄酮质量分数分别为(255.23±21.43)mg/g(绿原酸当量)和(132.85±14.77)mg/g(芦丁当量);BPE的ABTS自由基清除力的IC_(50)值为(53.9±5.38)μg/m L;在体外抗炎实验中,BPE能显著抑制Raw 264.7细胞NO的释放,显著抑制i NOS、IL-1β和IL-10,增强HO-1基因mRNA水平的表达,并呈一定的剂量相关性。表明,BPE富含黄酮和酚酸类物质并具有很强的自由基清除能力,在体外细胞实验中表现出了良好的抗炎症效果。     

茶饼病侵染对茶树游离氨基酸组分及含量的影响

为揭示茶饼病菌对茶树叶片中游离氨基酸组分及其含量的影响,以3个不同抗性品种茶树的病、健叶为试验材料,利用高效液相色谱法(HPLC)检测不同抗性品种茶树未感病和感病后鲜叶中氨基酸的组分和含量。结果表明:不同抗性品种未感病叶片中游离氨基酸的的种类和含量有差异,茶氨酸含量最高,其次是γ-氨基丁酸、蛋氨酸、胱氨酸;感病后氨基酸总量上升,高抗品种紫娟叶片中游离氨基酸的种类减少,含量下降,仅γ-氨基丁酸含量增加;中抗品种云抗10号叶片中游离氨基酸的种类增加,含量均增加;感病品种佛香1号叶片中游离氨基酸的种类不变,γ-氨基丁酸、茶氨酸、赖氨酸、色氨酸、精氨酸5种游离氨基酸的含量增加,其余氨基酸的含量下降,因而可以以此分析氨基酸与茶树抗病性的关系。本研究结果可为从生理生化角度探讨茶饼病致病机理提供基础数据。     

油茶肉质果、肉质叶提取液的保健功效

研究油茶肉质果、肉质叶提取液（EFF,EFY）的抗自由基、降血糖和抗癌作用。采用TBA比色法和小鼠红细胞氧化溶血抑制试验测定抗自由基作用;采用四氧嘧啶诱导糖尿病小鼠模型,分别用EFF和EFY灌胃7d测定降血糖作用;利用H22移植性实体瘤的方法研究抗癌作用。EFF具有显著消除体内自由基及抗脂质过氧化作用,与维生素E抗自由基及脂质过氧化效果相同;对实验性糖尿病小鼠血糖有明显的降低作用,接近中药消渴丸的效果;能明显抑制小鼠H22移植性实体瘤的生长,油茶肉质果组的抑瘤率为54．9％,油茶肉质叶组的抑瘤率为30．2％,对动物白细胞、脾指数、胸腺指数无明显影响。EFF和EFY能有效控制糖尿病小鼠的血糖水平,维持正常代谢,对正常血糖小鼠无影响;具有提高SOD活性,清除自由基的作用;对癌症小鼠有显著的抑癌效果,与已报道的20种具有显著抗癌作用的蔬菜相比,油茶肉质果排在第9位,油茶肉质叶排在第15位。