C-glycosyl flavonoids differ from their O-glycosylated cousins by possessing a stronger carbon-carbon covalent bond between the flavonoid backbone and sugar moiety, but relative rarity in the human diet has led to their neglect in the literature. Accordingly, the fate of dietary C-glycosylated flavonoids in humans is unknown, although such a seemingly minor structural divergence is predicted to strongly modulate their pharmacokinetics and bioactivity. Whilst a variety of mono- and di-C-glycosylated flavones and dihydrochalcones are found in common food crops such as tomatoes and wheat, reviewed in chapter 1, the dietary burden is unusually high in consumers of the popular South African tisane, rooibos tea, due to high concentrations of the unique C-glycosyl dihydrochalcone, aspalathin. Aspalathin is shown to be absorbed as an intact C-glycosyl dihydrochalcone, excreted in low quantities in the urine of human volunteers as a methylated derivative, 3-0- methylaspalathin (3-0-MA), with and without glucuronidation following consumption of green rooibos tea (O.74±0.26 % total dose, n=6). Kinetics ofeOMT-catalysed aspalathin methylation are derived (3-0-MA, App KM 39±5 IlM, App V max 6.67±0.40 Kat mol COMTi), and both human intestinal and hepatic cytosolic fractions also shown to catalyse aspalathin methylation.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:582122 |
| Date | January 2011 |
| Creators | Courts, Fraser Lawrence |
| Publisher | University of Leeds |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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