Antioxidative Activity and Flavonoid Composition of the Acid Precipitates from a Rooibos Tea Extract

Abstract

Rooibos (Aspalathus linearis) tea has been widely drunk in Africa, Europe and East Asia as a health beverage. Rooibos is a leguminous shrub grown in the mountainous areas of the northwestern Cape Province in South Africa. This tea is made from leaves and stems through a fermentation process. Fermented rooibos tea has been reported to have many biological and physiological benefits, including the alleviation of constipation and various other digestive disorders, as well as the reduction of nervous tension, the alleviation of allergies, clastogen suppression, the inhibition of X-ray-induced cell transformation, the suppression of lipid peroxide accumulation, and as an anti-HIV activity. Nutritionally, rooibos tea is recognized as a wellbalanced beverage because of its high content of minerals including potassium, sodium, calcium, and magnesium 7) besides its caffeine-less property. Additionally, rooibos tea contains many flavonoids, which exhibit a potent antioxidative activity. Rooibos leaves also contain a unique chalcone-type flavonoid, aspalathin, and it is found in abundance in unfermented tea, but not in its fermented form. This means that the fermentation process causes an extensive degradation or a conversion of aspalathin. Therefore, it is important to evaluate the antioxidative activity and flavonoid composition in rooibos tea products. Recently, Yamamoto has reported that rooibos tea has an immunopotentiating activity in the culture system 日本家政学会誌 Vol. 61 No.11 717 ~ 723 (2010)