Abstract
Rooibos tea is a well-known beverage characterized by its high level of antioxidative activity and its caffeine-less property. The antioxidative activity and flavonoid composition of the acid precipitates from a rooibos tea extract were examined. The formation of precipitates was absolutely dependent on the acidity of the tea extract below pH 3.3, and hydrochloric acid among some acids employed was the most efficient acid to yield precipitates with high antioxidative activities. The precipitates contained a limited number of flavonoids, including homoorientin, orientin, isovitexin, vitexin, and rutin. These flavonoids exerted as potent antioxidative activities as that of quercetin. Aspalathin, a major chalcone-type flavonoid characteristic to rooibos leaves, was not detected in the acid precipitates. These results indicate that the acid precipitates from a rooibos tea extract may be suitable for the development of supplements which exert functional effects similar to that of rooibos tea itself.
