Structure-antioxidant relationship of flavonoids from fermented rooibos

Rooibos tea (Aspalathus linearis) contains different bioactive phenolic Compounds such as dihydrochalcones, flavonols, flavanones, flavones, and flavanols. Flavonoids isolated from rooibos were subjected to different in vitro assays: Trolox equivalent antioxidant activity, LDL oxidation and Fremy's salt assays to determine the total antioxidant activity (TAA), Assay results were compared, and the structure-antioxidant relationship was investigated. A decoupled LDL oxidation test was established with the objective of having an assay adapted more to an in vivo situation. The different in vitro methods were coupled offline to HPLC-DAD. Results from these Coupled offline methods were compared to the TAA to assess the usefulness of the coupling setup.