Grapefruit. and grapefruit juice. is known to interact with a large number of drugs, usually resulting in adverse effects. These interactions are caused by a class of compounds called furanocoumarins. in particular the compounds bergamott in and dihydroxybergamoftin. These compounds inhibit some forms of an enzyme responsible for breaking down drugs in the body. As the prescribed dose of drugs takes into account how quickly the drug is broken down in the body. this can lead to higher concentrations of the drug in the bloodstream, which in turn can result in unpleasant side effects.