茶氨酸的研究现状及发展前景

茶氨酸是一种新型天然的食品添加剂，是茶叶中的特有氨基酸。本较全面地综述了目前国内外茶氨酸研究的最新现状，包括茶氨酸的分布、理化特性、在体内的吸收和代谢、检测方法、合成方法、生理功能、安全性以及在食品中的应用和开发前景。     

Production of theanine by Xerocomus badius (mushroom) using submerged fermentation

Theanine is a rare amino acid mainly produced by the genus Camellia, which is also found in the Basidiomycete fungus (mushroom) Xerocomus badius. Besides its favorable taste, broad potential physiological effects have been reported in the recent years, leading to the very fast growing demand for theanine worldwide. Thus a series of methods to produce theanine have been developed, including tea callus cultivation, chemical synthesis, extraction from the fresh leaves of the tea plant, and enzymatic synthesis. Different from the previous procedures, we reported here a novel protocol to produce theanine from the mushroom X. badius by means of submerged fermentation. Moreover, response surface methodology (RSM) was employed to optimize various parameters during fermentation. The statistic results indicated that the maximum theanine yield of X. badius (17.2420 mg/L) could be achieved at the optimal conditions, with glucose of 29.17 g/L, yeast extract of 6.38 g/L in a broth volume of 61.43 mL (within a flask of 250 mL) at an initial pH at 5.63. These predicted values were also validated by experiments. Taken together, these findings provided us a promising strategy for the production of theanine from X. badius in addition to the traditional preparation processes.     

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.     

茶氨酸的保健功能及合成

茶氨酸是茶叶中的一种特殊的氨基酸 ,对于茶叶品质的形成有重要的意义。本文就茶氨酸的理化性质、结构与功能、合成方法及未来的发展方向等几方面进行了综述。     

茶氨酸复合剂对酒精性肝损伤大鼠肝脏保护作用研究

研究茶氨酸复合剂对酒精性肝损伤大鼠肝脏的保护作用。采用小剂量50%乙醇每日1次灌胃1个月建立大鼠慢性酒精肝损伤(AIL)模型;正常大鼠作为空白组;除正常组外,其余各组以等体积50%乙醇每日1次灌胃1个月;对照组以市售海王星辰(HWXC)1.5g/kg,茶氨酸复合剂低、中、高剂量组分别为0.1、0.2、0.4g/kg的剂量灌胃,1次/d,连续1个月;以大鼠血液ALT、AST、TG和肝脏病理检查为主要衡量指标,观察其对肝脏的保护作用。结果显示茶氨酸复合剂各组与模型组相比大鼠血液ALT、AST、TG含量显著降低,病理检查HE染色显示肝内脂变显著减轻,表明茶氨酸复合剂对酒精性肝损伤大鼠的肝脏具有保护作用。     

茶叶组分抗菌、抗病毒和免疫增强作用的研究进展

饮茶对人身体健康有许多益处,如抗氧化、抗衰老、抗肿瘤、降低某些疾病的发病率等。近年来,越来越多的文献报道了茶叶组分具有抗菌、抗病毒和增强人体免疫力的作用。本文对茶叶中的主要组分茶多酚、茶色素、茶多糖和茶氨酸的抗菌、抗病毒和免疫增强作用的研究进展作一综述。     

茶氨酸的国内外研究现状

茶氨酸是绿茶中特有的一种氨基酸。50年代首次从茶叶中提取、精制出茶氨酸，并确定了它的化学结构，此后许多学者对其进行了大量的研究工作。包括在体内的吸收与代谢，检测方法，生理功能及在食品中的应用研究。茶氨酸主要作为食品添加剂，用于几乎所有食品中，除了改善食品风味外，还有多种保健功能，如降血压、抗疲劳，并对临床癌症患者的化疗有益。本文对茶氨酸的国内外最新研究进展进行了综述。     

Comparison of Azorean tea theanine to teas from other origins by HPLC/DAD/FD. Effect of fermentation,drying temperature,drying time and shoot maturity

The objectives of the present study were the determination of theanine (a specific amino acid of tea leaves with repercussion in human neuronal activity) by HPLC with o-phthaldialdehyde derivatisation prior analysis and comparison of its level in samples from different origins or from the same origin (Azores Islands) but with different processing conditions (fermentation, drying temperature and drying time) and shoot maturity. The results revealed a higher level of theanine in the Azorean green tea (3.10%), the only one produced in Europe, as compared with the Chinese, Japanese, Korean and Taiwan green teas that have an average theanine content of 1.52%, 1.34%, 0.89% and 2.76% of the dry weight (dw) of tea leaves, respectively. The fermentation for a longer period of time results in less theanine remaining (2.28% and 3.10% of dw for fermented and non-fermented tea, respectively). The drying temperature and time of the drying process have an inversely strong effect (4.45% and 5.65% of dw for dried at 55 °C during 8.50 h and at 40 °C during 7.10 h, respectively). The younger tea shoots have a higher theanine content than mature leaves (7.02% and 6.10% of dw, respectively). Our data suggested that a new type of Azorean theanine-rich tea may be produced by modifying the manufacturing processes of the younger tea shoots.     

Tumorigenicity study of l-theanine administrated orally to mice

l-Theanine was orally administered at a concentration of 0–5% (maximum tolerated dose) of the diet to B6C3F₁ mice for 13 weeks in a subacute test and 78 consecutive weeks, in a chronic toxicity test. There were no significant differences in intake of diet, weight gains or survival rates between treated and control groups. Unignorable differences in tumor incidence were observed at the end of 78 weeks; however, total number of tumors decreased significantly in the l-theanine administered groups. Thus, the long-term oral administration of l-theanine to mice did not show any chronic toxicological evidence or tumorigenic aberration.     

Sequential determination of tannin and total amino acid contents in tea for taste assessment by a fluorescent flow-injection analytical system

A novel fluorometric flow-injection analytical system is utilised to determine tannin and total amino acid levels in tea for taste assessment of astringency and umami, respectively. The quenching effect on fluorescence of 3-aminophthalate was employed to determine tannin levels, and the fluorogenic reaction of o-phthalaldehyde (OPA) was applied to quantify amino acid content. Both reactions were measured by a single fluorescence sensing system with same excitation and emission wavelengths (340/425 nm). A three-way valve was introduced to switch reagents for sequential determination of tannin and amino acids levels. Parameters of operational conditions were optimised, and the effect of tannic acid on OPA-based amino acid determination was also investigated. The linear dynamic ranges for tannic acid and theanine are 50–250 and 0.1–1.0 μg mL⁻¹ (CV < 5%, n = 3), respectively. Each sample throughout was 20 samples h⁻¹. This system was also applied to quantitatively assess the quality of partially fermented teas.