天然富含可可碱茶树的研究进展

天然富含可可碱茶树是一类以可可碱为代表性生物碱的稀有茶树种质资源,具有独特的保健功效与挖掘利用价值。从生化成分组成特征、生物代谢途径和可可碱在茶树体内富含的分子机理,对可可茶、红芽茶、秃房茶和厚轴茶4份新近发现的天然富含可可碱茶树进行比较研究与综述。结果发现,可可碱占茶叶干重的质量分数高达2%～6%,咖啡碱则低于0.5%;优势儿茶素单体为没食子酸儿茶素没食子酸酯,而表没食子酸儿茶素没食子酸酯含量较低;咖啡碱合成酶活性位点精氨酸突变为组氨酸使N-甲基转移酶的底物特异性发生变化,从而导致咖啡碱合成酶终止合成咖啡碱并使得可可碱在茶树体内富集。天然富含可可碱茶树资源丰富了茶种的多样性,但开发利用度尚有限,结合当前茶树育种技术的发展状态,对天然富含可可碱茶树种质的繁育与资源挖掘利用进行了展望。

Research Progress in Natural TheobromineEnriched Tea Plants

Theobromine-enriched tea is a kind of rare tea germplasm resource with theobromine as the representative alkaloid, which has unique health care effect and utilization value. In this paper, four newly discovered natural theobromineenriched tea plants, including cocoa tea, Hongya tea, Camellia gymnogyna Chang and Camellia crassicoluma Chang were compared and reviewed from the aspects of the biochemical component characteristics, biological metabolism pathways and molecular mechanism of theobromine in tea plants. Theobromine accounts as high as 2%-6% of the dry weight of these tea leaves while caffeine is less than 0.5%. The dominant catechin monomer is gallocatechin gallate, while the content of epicatechin gallate is low. The mutation of arginine to histidine at the active site of caffeine synthetase changes the substrate specificity of N-methyltransferase, which leads to the termination of caffeine synthesis by caffeine synthetase and the enrichment of theobromine in tea plants. The natural theobromine-enriched tea resources enrich the diversity of tea species, but the level of excavation and utilization is still limited. Combining with the current development of tea breeding technology, the breeding and resource exploitation of natural theobromine-enriched tea germplasm are prospected.