茶黄素抗菌活性研究进展

茶黄素是红茶发酵过程中儿茶素类组分氧化聚合的产物,是红茶品质优劣的标志性成分之一。茶黄素具有独特的苯骈卓酚酮结构和更多的酚羟基团,具有多种功能活性,在抑菌性能方面有时优于儿茶素和其他多酚类成分。本文梳理了近年来国内外在茶黄素抑菌活性领域的研究进展,从抑菌谱系(细菌、真菌、病毒)、作用机制、应用范畴等方面进行了系统综述和分析总结,发现茶黄素作为天然来源的广谱抑菌剂,在与人类相关的多种致病菌干预方面具有潜在的应用价值。从天然抑菌剂终端价值开发角度对其可能应用途径进行了展望,以期为茶叶次生代谢产物应用技术研究深入开展提供技术依据。     

Effects of catechins on the polymerisation behaviour,conformation and viscoelasticity of wheat gluten

The effects of catechins on the structural properties of wheat gluten were investigated in terms of their polymerisation behaviour, conformation and viscoelasticity. Depolymerisation of glutenin macropolymers was analysed by size-exclusion high-performance liquid chromatography (SE-HPLC) of gluten with catechins, revealing major variation in sulfhydryl (SH) content. Compared with controls, the SH content of catechin-enhanced gluten was significantly increased due to breakage of disulphide (SS) bonds. Reversed-phase HPLC revealed that catechins had minimal effect on subunit distribution of gliadin and glutenin. Fourier transform infrared (FTIR) spectroscopy showed that catechins induced the transformation of α-helices to β-sheets, β-turns and antiparallel β-sheets. Rearrangement of secondary structure when supplemented with catechins might be a consequence of altered non-covalent interactions. Catechins increased tan δ, indicating enhanced gluten fluid properties. These results imply that catechins might weaken the network structure of gluten and change the rheological properties by inhibiting SS cross-linkage formation and influencing non-covalent bonds.     

Comparison of the main compounds in Fuding white tea infusions from various tea types

The purpose of this study was to compare the main components, and particularly catechins, caffeine, theanine, free amino acids, and water extracts, in Bai Hao Yin Zhen, Bai Mu Dan, and Shou Mei Fuding white tea infusions brewed at different temperatures, and their contributions to taste were estimated by dose-over-threshold value. Infusion temperature had a distinct effect on the main components extracted, and 100 °C was found to be optimal for extracting catechins and caffeine. However, the effect of temperature on theanine, free amino acids, and water extracts varied with tea type. Bai Mu Dan and Shou Mei yielded a higher content of the major compounds than did Bai Hao Yin Zhen. Thus, infusion temperature had a large effect on extracting the main compounds, and the differences in content between the three white teas presumably reflected differences in the harvest time, processing method or leaf shape.     

基于斑马鱼模型评价白茶的降糖作用

研究以白茶为对象,采用新型斑马鱼实验技术开展了白茶降糖比较研究。基于非胰岛素依赖型糖尿病（NIDDM）斑马鱼研究发现,50和100 μg/mL老白牡丹茶（AWP）孵育24 h葡萄糖（GLU）值水平分别降低了29.68%和20.51%,孵育48 h GLU值分别降低了42.16%和51.54%,差异均显著（P<0.05）;25、50和75 μg/mL白牡丹茶（WP）孵育24 h GLU值分别降低了40.18%、52.57%和62.11%,差异均显著（P<0.05）。另外,基于胰岛素依赖型糖尿病（IDDM）斑马鱼研究,20和30 μg/mL AWP孵育24 h GLU值分别降低了24.92%和23.66%,孵育48 h分别降低了54.35%和38.38%,差异均显著（P<0.05）;40 μg/mL WP孵育24 h GLU值降低了22.58%（P<0.05）,20 μg/mL WP孵育48 h降低了26.51%（P<0.05）;30 μg/mL茶多酚（TP）孵育48 h GLU值降低了24.53%（P<0.05）。重要的是,在同等生药量下,20 μg/mL WP和AWP对NIDDM斑马鱼的降糖效果显著优于TP;30 μg/mL AWP对IDDM斑马鱼的降糖效果略优于TP,再明显优于WP。结果表明白茶具有明显的降糖功效,TP也具有明确的降糖作用,但白茶的降糖效应并不仅限于依赖TP,具体何成分起关键作用尚值得关注和研究。     

茶酒挥发性物质及其不同检测条件对比研究

基于茶酒挥发性物质的检测分析,采用顶空固相微萃取-气相色谱-质谱联用（HS-SPME-GC-MS）,对比分析4种不同GC-MS条件对茶酒挥发性物质定性定量结果,并研究了茶酒中挥发性物质组成。结果表明：基于HS-SPME-GC-MS方法,4种条件共检出94种挥发性物质,不同分析条件的检测结果存在一定差异;茶酒挥发性物质主要由酯类、酸类、醇类、醛类、酮类、烯类物质组成,酯类物质占83.82%～93.80%,其中己酸乙酯含量最高,可达67.26%;醇类物质中1-己醇和异戊醇含量相对较高,酸类物质以己酸含量最高;茶酒中检出了芳樟醇、苯乙醇、水杨酸甲酯、苯甲醛、月桂酸乙酯等茶叶中常见的挥发性物质。