Protein sequestration of lipophilic furanocoumarins in grapefruit juice

The sequestration of grapefruit furanocoumarins by foods was investigated by characterizing the binding between these compounds and foods with contrasting protein, fat, and carbohydrate compositions. Individual grapefruit furanocoumarins exhibited contrasting affinities to foods, where the lipophilic bergamottin and several structurally related dimers bound to foods more tightly than the more polar 6',7'-dihydroxybergamottin. From the investigation of different classes of macromolecules in foods, water-soluble proteins were found to be the major constituents responsible for furanocoumarin sequestration. Studies using bovine serum albumin as a model protein demonstrated the dissociation of grapefruit furanocoumarins from the insoluble juice cloud particles and the subsequent formation of water-soluble bovine serum albumin-furanocoumarin complexes. Fluorescence binding assays further demonstrated the binding of bergamottin and 6',7'-dihydroxybergamottin to bovine serum albumin. These results demonstrate that proteins can be sequestration agents of these important dietary furanocoumarins.