ARS | Publication request: Proteins differentially interact with grapefruit furanocoumarins

Submitted to: Florida State Horticultural Society Meeting
Publication Type: Abstract
Publication Acceptance Date: April 1, 2009
Publication Date: April 14, 2009
Citation: Myung, K., Manthey, J.A. 2009. Proteins interact differentially with grapefruit furanocoumarins. Florida State Horticultural Society Meeting. Paper No. HP6.

Technical Abstract: Grapefruit juice (GFJ) interferes with the cytochrome P450 3A4 activity responsible for metabolizing certain medications. This interference is referred to as the "grapefruit-drug interaction". Grapefruit furanocoumarins (FCs), such as 6', 7'-dihydroxybergamottin (DHB) and bergamottin (BM), have been shown to be the main compounds which cause this interaction. Previously, we observed that a number of foods sequester FCs in GFJ. In this study, interactions between macromolecules and GFJ FCs were investigated to determine which food components are responsible for the previously found sequestration. When we removed lipids from corn and salmon by extractions with organic solvents, the resulting defatted corn and salmon powders still sequestered FCs in GFJ, indicating that components responsible for the sequestration are still present in the defatted powders. When water-soluble macromolecules, ie proteins and carbohydrates, were further removed from the defatted corn powder, the binding phenomenon of DHB completely disappeared, but BM binding still occurred. However, the binding of BM to corn residues after successive acid or base hydrolysis was not observed. These results suggest that the components associated with DHB and BM could link to proteins or carbohydrates but not to lipids. Further binding experiments with cellulose, pectin, and purified fungal cell wall showed that these carbohydrates did not interact with GFJ FCs. In contrast, bovine albumin serum and isolated proteins from foods differentially interacted with GFJ FCs, in which tighter interaction with BM occurred, compared to DHB. Overall, our results suggest that the observed sequestration of GFJ FCs by foods is likely due to protein-FC interactions.