UC Davis

Tea has been enjoyed by many cultures world-wide for thousands of years. Recently, an expanded interest in tea drinking has occurred, which is attributed to the health benefits associated with tea consumption. This increase in demand is growing particularly quickly within the United States, where very few commercial tea fields and production outfits exist. Therefore, most tea that is consumed in the U.S. must travel internationally travel consumption. Unfortunately, tea consumed within the U.S. may undergo up to four rounds of international transportation: harvest to processing, processing to blending, blending to packaging, and packaging to retail. Given the reasonable international push towards sustainability, it then makes sense for tea fields and production facilities to be established within the U.S. to meet the growing demand. California boasts a rich agricultural history and UC Davis has continually provided cutting edge agricultural research. However, tea is historically grown in regions with higher levels of humidity, such as Taiwan, China, and Japan, and has only been established commercially in the Southern part of the United States previously. Therefore, the first task was to establish a test plot of Camellia sinensis in California. Such a field was established in conjunction with the University of California’s Agriculture and Natural Resources division at Kearney Agricultural Research and Extension Center in Parlier, CA. Two varieties (UC-K) were planted in December 2018 and sixteen varieties (UC-N) were planted in November 2019. A major reason for the increase in demand for tea in the U.S. stems from the reported health benefits. These health effects are generally credited to polyphenols, specifically the catechin (flavan-3-ol) subclass of flavonoids. However, only a few scientific endeavors have been attempted to determine the natural chemical profile of the flavan-3-ol compounds in tea plants. To overcome the lack of a more comprehensive survey, multiple methods were developed while waiting for the California test plot to mature enough for processing. Such methods include harvest, transportation, extraction, quantitative analysis, and qualitative analysis. In particular, the methods developed in this study limited the time between harvest and cryogenically freezing tea leaves to minimize the effects of oxidation on the flavan-3-ol profile. Tea samples were extracted with water to closely mimic the chemical profile ingested by a consumer, and compounds were identified and measured with a high-performance liquid chromatography (HPLC) instrument coupled with an ultraviolet-visible (UV-Vis) detector and a single quadrupole mass spectrometer (SQMS). The developed HPLC-UV-Vis-SQMS method was capable of independently analyzing nine phenol compounds and three alkaloid compounds. Once the California test field had matured, the natural flavan-3-ol profiles of six varieties was studied. The change in flavan-3-ol profile among black tea processing steps was also studied for a single variety. Both analyses were compared to previously reported values of flavan-3-ols, alkaloids, and select amino acids. Additionally, peaks not related to the twelve standards used were investigated and identified via standard and/or library comparison. Finally, one initially unknown metabolite was identified as theogallin and analyzed with the developed HPLC-UV-Vis-SQMS method. Theogallin is a conjugate of the well-studied quinic and gallic acids but is often not included in reported phenol profiles of tea. Present research into the potential health benefits of theogallin is therefore lacking. Furthermore, commercially available theogallin is extracted from tea leaves making the standard expensive to obtain and difficult to test for potential therapeutic effects. Such a deficiency makes the efficient synthesis of theogallin valuable for further studies. Given the potential benefits of theogallin, a four-step synthetic route utilizing previously developed regioselective silyl exchange technology (ReSET) was investigated. The current work presents the optimization, purification, and characterization of the first two steps, including a previously unreported crystal structure. The third step was attempted but not purified. With the first half of the synthesis available, further development of an efficient theogallin synthesis using ReSET is primed to continue.