Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/21/2012
Publication Date: 1/9/2013
Citation: Myung, K., Manthey, J.A., Narciso, J.A. 2013. Protein Sequestration of Lipophilic Furanocoumarins in Grapefruit Juice. Journal of Agricultural and Food Chemistry. 61:667-673. Interpretive Summary: There is a class of compounds, termed furanocoumarins, that occur in grapefruit juice that interfere with the metabolism of certain prescription drugs. These compounds were shown to preferentially bind to certain foods, and specifically to food proteins. The binding of these compounds to proteins was also shown to occur with bovine serum albumin which is a model for the main transport protein in human blood. This binding raises interesting questions about the possible roles of protein binding in the transport and delivery of these compounds in humans.
Technical Abstract: Our previous discoveries of grapefruit furanocoumarin binding to edible fungi led us to investigate the possible roles of dietary factors in this binding phenomenon. In this present study sequestration of grapefruit furanocoumarins by foods was investigated by characterizing the binding between these compounds and different 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. By investigating 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 support our findings that proteins can be potent sequestration agents of these important dietary furanocoumarins.