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Bioactive Compounds in Tea
Tea is an extremely complex product and, of course, I am referring here to Camellia sinensis, which is cultivated and produced in over sixty countries around the world. To date, over one hundred constituents have been found in its leaves; however, not all of these constituents have been studied in depth, so it is hard to understand and appreciate the complexity of tea to its fullest extent. Some of this complexity is a result of the bioactive compounds that are present in tea, which are constituents that have a biological effect on the body, and they are at the core of how tea appeals to a multitude of interests. The constituents in tea, including the bioactives, are the reason why it has broad appeal to those with interests in its health benefits, those with epicurean tendencies, those in the culinary arts, those who want to explore the diverse aspects of terroir where the teas are grown, and those who just may simply want to enjoy the tea, hot or iced, without delving deeper into its many complexities. But did you ever stop to wonder why you may like one tea, but not another? Or why one tea may be stronger than other? Or why one tea may be more aromatic than other? Or a myriad of other questions about these differences among teas even though they are all from the same plant. It is the bioactive compounds that are responsible for the flavors, aromas, textures, and health-promoting aspects of tea.
There are several categories of bioactive compounds in the Camellia sinensis plant and the processed leaves. These compounds may fluctuate in their levels based on several variables, some of which include: the part of the plant that is harvested, the time of year of harvest, and how the leaves are processed (i.e. tea type). While papers and books have been written about these compounds, I am providing a very high-level outline of them. In addition, the many sources will identify different categories, some of which are actually subcategories of another listed category. Please keep this in mind if you happen to read other articles about this topic. I am presenting the following bioactive categories: alkaloids, polysaccharides, amino acids, minerals, vitamins, and the largest categories - terpenoids and polyphenolic compounds. Here are the categories that are covered in this newsletter:
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Alkaloids - caffeine is the most well-known; however, two others are theobromine and theophylline. All are categorized as methylxanthines, which is a subcategory within alkaloids. They are known for their stimulating effects on the central nervous system, but they may also have cardiac stimulant, vasodilation and diuretic effects, as well as relaxing the smooth muscles. Theophylline's smooth muscle relaxant properties make it a potentially useful compound for asthma, bronchial spasms, and other respiratory issues. Each of these compounds imparts a bitter taste. Since I dedicated an entire newsletter to caffeine in March 2022, I won't provide more details here. Feel free to check that newsletter out when the website is back up and running.
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Polysaccharides - type of carbohydrate in tea leaves that may have a blood glucose-lowering effect. These polysaccharides are composed of smaller monosaccharides (sugar molecules) that impart a sweet taste.
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Amino acids - twenty seven amino acids have been identified in tea leaves, with L-theanine being the dominant one. Also known as theanine, this compound has relaxing properties that may reduce stress, reduce blood pressure, and increase neurotransmitter action in the brain. Theanine is also responsible for the savory taste and aromas in tea, which is referred to as umami.
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Minerals and trace elements - calcium, sodium, potassium, magnesium, manganese, copper, iron, and zinc are present in tea leaves and may assist in meeting daily requirements.
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Vitamins - vitamins C, E, B1, B2, B3, B5 and K are all present in tea leaves. Many sources claim that there is a significant amount of these vitamins, enough to contribute to daily intake. When looking closer, however, the amounts are based on 100g of tea, which is way too much tea to consume in a day. As a reference, a standard 12-16-ounce mug would only use 5-6g of tea leaves. So while tea may not be a primary source of these vitamins, it will help to contribute to the daily total. Another thing to consider regarding Vitamin K, which is a fat-soluble vitamin, is that only a small percentage of the overall amount in the leaves can be extracted into the water. The other vitamins are water soluble and, therefore, a greater percentage can be extracted into the infused beverage.
I hope this helps to shed some light on just some of the bioactive compounds in your daily cup of tea. Next month I'll be covering the polyphenolic compounds and terpenoids. See you then!
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