Study On The Novel Alkaloids And Hydroxycinnamoylated Catechins In Tea

Tea is rich in chemical components,mainly including tea polyphenols,aromatic compounds,alkaloids,amino acids,pigments and sugars.Among them,tea polyphenols and alkaloids have been become the research hotspots of tea chemical components,especially for their main components in catechins and purine alkaloids.Researches have reported that catechins and alkaloids gave the tea soup a unique bitterness and astringency.They were also been found having a variety of health effects,such as anti-cancer,lipid-lowering and hypoglycemic etc.In this paper,these two kinds of chemical components in tea were studied.The main results are as follows:1.Seventeen alkaloids were isolated from Keemun Black tea by traditional separation technology for natural products.Sixteen alkaloids were identified by NMR,LC-MS and X-ray diffraction,including nine new alkaloids.Among them,three of them were dimeric imidazole alkaloids,one was mesomeric dimer alkaloid,two were racemic alkaloids（one of which was dimer）.The results of quantification for compound4 showed that there were obvious differences among different teas.Meanwhile,the results of activity experiments showed that some new alkaloids had significant protective effects against hydrogen peroxide induced neuronal damage in human neuroblastoma SH-SY5Y cells and high glucose induced cellular senescence in human umbilical vein endothelial cells（HUVECs）.A new pathway of caffeine metabolism in tea has been found through varieties of isotopic tracing experiments,that is three methyl groups can be retained in the process of caffeine metabolism,which can be metabolized into 1,3,8-trimethylallantoin through multi-step reaction.1,3-¹⁵N₂-Caffeine tracing experiment not only confirmed that caffeine can be metabolized to form 1,3,8-trimethylallantoin,but also confirmed that the five-membered ring of 1,3,8-trimethylallantoin was from the pyrimidine ring（six-membered ring）instead of the imidazole ring（five-membered ring）.These results indicated that the metabolism of caffeine in tea can be through the opening of the ring and recombination to form 1,3,8-trimethylallantoin,while the three methyl groups were retained.2.Four hydroxycinnamoylated catechins（HCCs）were synthesized by chemical synthesis in this paper.They were identified in forty kinds of teas by UPLC-Q-TOF-MS.A method for quantification of these four catechins was established by UPLC-QQQ-MS using the multiple reaction monitoring mode.The four catechins were quantified in selected 20 cultivars,including 10 broad（Camellia sinensis var assamica,CSA）and 10 small（Camellia sinensis var.sinensis,CSS）leaf tea.And their content in different teas at different months were also quantified.The results showed that the total content of the four HCCs in CSS was higher than that in CSA（729–1398 vs 466–1056μg/g,P=0.0076）;the content of EC-C in Camellia sinensis var.assamica was higher than that in Camellia sinensis var.sinensis（65–176 vs 21–46μg/g,P=0.000024）while EGC-p C presented higher content in Camellia sinensis var.sinensis than Camellia sinensis var.assamica（483–1052 vs 135–479μg/g,P=0.00054）.Among all the four HCCs,EC-C contributed about 14–33%in in CSA while only 2–6%in CSS;EGC-p C contributed about 63–77%to the total content of the four HCCs in CSS while only 23–49%in CSA.The total content of the four catechins,the contents of EC-C and EGC-p C,and the proportion of EC-C or EGC-p C against the level of the total four HCCs（EC-C or EGC-p C/total four HCCs）showed significant differences between CSS form Anhui Province and CSA cultivars from Yunnan Province,suggesting that EC-C and EGC-p C could be the potential chemical markers to differentiate these two primary tea cultivars.