Whether it be black or green tea, physicians and nutrition researchers have long been convinced of the health benefits of certain components of tea. Tea (Camellia sinensis) is an evergreen, originally tree-sized plant from the family Camellia and the most complex scientifically analysed food source. For over 50 years, scientists have been dealing with the structural analysis of its contents. The previous analysis methods were not detailed enough to differentiate the many molecularly very similar compounds.
Tea – the mysterious being
Two years ago, Bremen scientists led by chemistry professor Dr. Nikolai Kuhnert and scientists at the University of Surrey succeeded by using a custom-built, high-resolution mass and chiroptical spectroscopy method – so-called Fourier transformative ion cyclotron resonance mass spectrometry – in revealing about 10,000 of the aromatic compounds in thearubigen, which makes up 60-70% of the dissolved ingredients in black tea. Thearubigens are aromatic, orange to red-brown compounds of the polyphenols group with a molecular weight of 300-2100 Dalton. During fermentation in the production of black tea and oolong tea, a portion of the polyphenols is oxidised to thearubigen and theaflavin. Thanks to a computer-based interpretation process, a total of 1,517 individual structural formulas of uniquely individual measurement signals were assigned, 500 of which were verified experimentally.
So far, aside from the well-known ingredient caffeine, only about a third of the tea components, summarised under the term “tannin”, have been chemically characterised. Among those labelled as tannins were polyphenolic compounds, which represent approximately 30 percent of the ingredients of unprocessed tea leaves. Besides caffeine and polyphenols, tea contains many other ingredients such as amino acids, vitamin A, B1, B2, C, D as well as enzymes, pigment substances (chlorophyll), minerals (e.g. magnesium, calcium, magnesium, fluorine) and organic fats. The caffeine content of black tea as it happens is estimated at 25-120 mg, for green tea it is approximately 8.3 mg (caffeine per 100 ml). In contrast, the caffeine in tea acts more slowly and for longer than in coffee, as the tannins in tea buffer the effect of caffeine. The processing of tea leaves decides whether green or black tea is produced. With black tea the green leaves are fermented, with green tea they are not fermented.
Antioxidants kill free radicals
Polyphenols occur in plants as flower pigments (e.g. flavonoids), flavours or tannins. They protect the plant from leaf-eating “predators” or UV radiation. Tea polyphenols in green and black tea exert a positive impact on our health. This has been known to medical and food scientists for a long time. Until now it had been assumed that these health benefits were due mainly to the antioxidative effect of the polyphenols. These natural substances represent up to 70 percent of the dry weight of a cup of tea and in a cup of black tea up to to 30,000 different compounds turn up.
Antioxidants help prevent tissue damage by binding to so-called free radicals – aggressive chemical culprits – which originate from negative environmental factors, and neutralise them. Recent studies from the past five years, however, have been able to convincingly demonstrate that the health benefits of tea polyphenols are not primarily brought by their antioxidative effects. Therefore, the precise mechanism for the beneficial health effects of these tea-type plant substances has until now still been unclear.
The Bremen-based research team led by Nikolai Kuhnert was able to show for the first time that the positive effect of tea polyphenols is probably based on biological interaction at the molecular level with the genetic tissue stored in cells. Based on findings that the polyphenols in tea plants accumulate especially in the nuclei, the researchers studied using various spectroscopic methods (mass and chiroptical spectroscopy) whether and how individual polyphenol molecules interact with the nuclear DNA. They found that two of the frequent tea polyphenols, epigallocatechin gallate from green tea and theaflavin digallate from black tea, very often bond with pieces of DNA and proteins which sit at the end of chromosomes. These sections of DNA also known as “telomeres” are largely responsible for the stability of chromosomes and protect them from decay.
Fountain of Youth telomerase extends length of life
In healthy cells, with each division a piece of genetic material gets lost. The ends of the genetic strand, the telomeres (Greek “telos” for end, and “meros” for part) keep getting shorter, until the cell ages and eventually dies. Not without reason, therefore, the length of telomeres is seen as runnng in conjunction with the ageing process because cell division cannot occur with indefinite frequency and is restricted by the telomere length. The shorter the telomeres, the less frquently the cells can divide and renew. This danger is averted by the “fountain of youth” enzyme telomerase, which keeps re-depositing genetic tissue at the end, so that the cells are able to keep on dividing. The gene for telomerase in humans is mainly in germ cells, but is also active in tumour cells. The telomerase causes the cells to be capable of dividing indefinitely. In both cases, the cells do not age, so to speak. It is here that tea comes into play. The polyphenolic compounds from the tea stimulate telomerase in the body cells, thus slowing down the process of shortening telomeres and prolonging the cell life. “We understand from this that the positive stabilising effect improves the genetic information in the long run and the health and life expectancy of the entire organism. This is confirmed by experiments with the fruit fly Drosophila, whereby their lives were extended by 20 percent via the consumption of tea. In principle, any chemical compound which in this way docks onto the telomeres can have this effect; interestingly, we know to date however no other natural substance which stabilises telomeres as effectively as tea polyphenols”, says Kuhnert.
How do polyphenols behave in humans?
The results derived by Nikolai Kuhnert have been based until now on in-vitro studies with human telomere DNA. Together with his team, Kuhnert now wants to find out as quickly as possible how the tea polyphenols behave in the human body under everyday conditions. “If it turns out that by regular tea consumption tea polyphenols accumulate in the nucleus in human tissue, we would have in fact for the first time demonstrated that a food may extend human life. This would be a highly interesting starting point for medical and clinical studies to explore the therapeutic potential of tea polyphenols”, says Kuhnert in closing.
Digression: The economic importance of tea
Black tea is the most consumed beverage in the world after water, with an average per capita consumption of half a litre a day. According to the German Tea Association, the world’s tea production in 2010 was 4.1 million tonnes. Not included were the production of fruit tea infusions such as rooibos or herbal tea. In Germany in 2010 about 18,300 tons of tea were consumed, which corresponds to a tea consumption of about 25.5 litres per person. Of this, black tea accounted for 77% and green tea 23%. Depending on the world market price, an annual harvest has a combined value of more than 10 billion U.S. dollars.