Flavonoide im Rooibos (Aspalathus linearis) - Bestimmung, Nutrikinetik, Veränderung bei Extraktion und Lagerung (English shop)

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Rooibos (Aspalathus linearis) is a shrub with rod-like branches and needle-like leaves native to the mountain slopes of the Cederberg Mountains in the southwest of the Republic of South Africa, which is used in particular for preparing tea infusions. Rooibos tea is regarded as the national beverage of South Africa and is also enjoying growing popularity on the German market.

Herbal and fruit teas generally have a positive image as health-promoting beverages. These effects are mostly attributed to the class of compounds known as flavonoids, which are among the qualitatively and quantitatively dominant constituents of these products.

A main objective of this work is therefore to improve the hitherto incomplete data situation regarding these constituents in both fermented and unfermented rooibos.

In order to assess possible health effects of rooibos in vivo, the bioavailability and metabolism of the principal flavonoids of the unfermented plant material are determined on the basis of these results within the framework of a human study with a cross-over design. For this purpose, the complex tea infusion and an active fraction identified by means of an in vitro bioactivity screening are compared with a placebo (water). The active fraction is isolated from the unfermented rooibos using, among other methods, countercurrent chromatographic separation techniques (e.g. High-Speed Countercurrent Chromatography – HSCCC).

The urine and plasma samples of the study participants are analysed qualitatively and quantitatively by mass spectrometry (via HPLC-ESI-MS/MS) for intact flavonoids and their corresponding metabolites. As a further parameter, the antioxidant potential of the plasma samples is determined by means of the ORAC assay (Oxygen Radical Absorbance Capacity). The main metabolites detected in vivo are synthesised, isolated and examined for their antioxidant potential in order to determine their contribution to the overall potential.

A further aspect of this work is the consideration of the storage stability of rooibos flavonoids in ready-to-drink beverages, since, owing to the positive assessment of herbal and fruit teas by consumers, tea extracts are increasingly being used for the manufacture of such products. A second human study is carried out with a freshly produced and a stored ready-to-drink beverage of the same formulation. Both products are compared in a cross-over design with a ready-to-drink beverage without added rooibos extract.

The results of the human studies are of particular interest for the development of innovative products and the substantiation of health-related claims in accordance with the Health Claims Regulation (Regulation (EC) No 1924/2006). In addition, statements can be made about the dosages of the value-determining rooibos constituents required for a potential effect.

Christian Laue