Bioavailability of C-linked dihydrochalcone and flavanone glucosides in humans following ingestion of unfermented and fermented rooibos teas

High-performance liquid chromatography-mass spectrometry (HPLC-MS ⁿ) detected aspalathin and nothofagin, C-glycosides of apigenin and luteolin, and four eriodictyol-C-glycoside isomers in unfermented and fermented rooibos teas. The fermented drink contained 10-fold higher levels of aspalathin and nothofagin and a 4-fold lower eriodictyol-C-glycoside content than the fermented tea. The total flavonoid contents in 500 mL servings of the teas were 84 (fermented) and 159 μmol (unfermented). Following the ingestion of 500 mL of the teas by 10 volunteers, 0-24 h urine and plasma samples were collected for analysis. HPLC-MSⁿ identified eight metabolites in urine. These were O-linked methyl, sulfate, and glucuronide metabolites of aspalathin and an eriodictyolO-sulfate. The main compound excreted was an O-methyl-aspalathin-O- glucuronide (229 nmol) following ingestion of the unfermented drink and eriodictyol-O-sulfate (68 nmol) after ingestion of the fermented beverage. The overall metabolite levels excreted were 82 and 352 nmol, accounting for 0.09 and 0.22% of the flavonoids in the fermented and unfermented drinks, respectively. Most of the aspalathin metabolites were excreted within 5 h of tea consumption, suggesting absorption in the small intestine. Urinary excretion of the eriodictyol-O-sulfate occurred mainly during the 5-12 h collection period, indicative of absorption in the large intestine. Despite exhaustive searches, no flavonoid metabolites were detected in plasma.