Interaction of proteins with grapefruit furanocoumarins

Abstract

Grapefruit or 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.” Previously, we observed that a number of foods sequester many of the furanocoumarins (FCs) in GFJ. In this study, the 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 the FCs in GFJ. Further binding experiments with cellulose and pectin showed that these carbohydrates did not interact with GFJ FCs. In contrast, isolated proteins from salmon differentially interacted with GFJ FCs, in which tighter interactions with bergamottin occurred, compared to 6´,7´-dihydroxybergamottin. Overall, our results suggest that the previously observed sequestration of GFJ FCs by foods is likely due to protein–FC interactions.