Analysing the anti-ageing activity of tea

Tea was first introduced into European countries from China by Portuguese and Dutch explorers.1 A wide spectrum of biologically active substances present in this plant has resulted in wide application in cosmetology. At the present time, one of the most important trends in modern cosmetology is the application of active substances of natural origin. Raw materials of plant origin possess a wide spectrum of multidimensional activity and can impart many beneficial properties to the cosmetic product. The field of cosmetology is also interested in plants that have been used for many years in traditional medicine as well as hunting for completely new raw materials. Various kinds of teas are produced mainly from the same plant species, Camellia sinensis. However, the word ‘tea’ is very often applied also to other plants that can be used in preparation of hot beverages from leaves or flowers. Thus, the name ‘tea’ is used also very often used for rooibos tea (the beverage obtained from the South African plant Aspalathus linearis) or honey-bush tea (Cyclopia intermedia). Tea has been made from plants used by Man for many years for different purposes, including cosmetics. The leaves of Camellia sinensis are a very rich source of anti-radical substances which has resulted in a wide application of this plant in anti-ageing formulations.

Fermentation process

According to the manufacturing process four different kinds of tea are distinguished – black, oolong, green and white. The classification of the tea depends on the degree of fermentation: fully fermented black tea, partially fermented ollong tea, unfermented green tea and unfermented white tea manufactured from buds. To produce the green tea, the leaves of Camellia sinensis are harvested and subjected to withering. After this process leaves are steamed or panfried and then rolled, shaped and dried. Steaming at 95°C to 100°C for 30-45 seconds inhibits enzymes which are responsible for fermentation, hence the green tea belongs to unfermented teas. This method is used mainly in Japan, while the Chinese method is based mainly on roasting. The fermentation process does not require microbiological activities. The main difference between manufacturing of green and black tea is the additional step in the case of black tea: the leaves are bruised and crushed which induces the process of fermentation.2 The substances responsible for this process are oxidising enzymes contained in tea leaves –mainly polyphenol oxidase. In the presence of polyphenol oxidase, catechins present in high levels in green tea are converted into theaflavins, thearubigins and other complex polyphenols which are characteristic of fermented teas.3 The degree of fermentation is responsible for biological properties such as taste and the aroma of the tea. Carotenoids and unsaturated acids are recognised as the influential precursors for aroma. It is documented that enzymatic oxidation of linolenic and linoleic acids can result in the production of the unsaturated aliphatic compounds that are responsible for the tea aroma. A simple indicator of the fermentation degree can be changes in the colour of the tea leaves.