Rooibos leaves and fine stems (Aspalathus linearis; Fabaceae) are increasingly enjoyed as herbal tea, largely in fermented (oxidised) red-brown form, but also in unfermented (unoxidised) green form. Rooibos is rich in antioxidant polyphenols, with the dihydrochalcone, aspalathin, as a major active ingredient. We used Caenorhabditis elegans as model organism to investigate the effect of rooibos extracts against oxidative stress in vivo. In a high glucose environment, C. elegans treated with rooibos extract exhibited an extended lifespan. Furthermore, green rooibos was a more potent antioxidant than red rooibos, probably due to its substantially higher aspalathin content. In addition, rooibos decreased acute oxidative damage caused by the superoxide anion radical generator, juglone, with aspalathin playing a major role in improving the survival rate of C. elegans. Quantitative real-time PCR results demonstrated that aspalathin targets stress and ageing related genes, reducing the endogenous intracellular level of ROS. These findings suggest that rooibos increases stress resistance and promotes longevity under stress, probably mediated via a regulation of the DAF-16/FOXO insulin-like signalling pathway, supporting some of the health claims put forward for rooibos tea.
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