Grapefruit juice and St. John’s Wort, a popular herbal supplement, have something in common. Both interfere with the activity of some drugs. It’s easy to find such examples of interactions between the foods and supplements people eat and the drugs they take. But it’s much harder to find out about the chemical interactions that drive those clashes.
An article in the September 27 issue of C&EN is an excellent read into the potential issues when drinking grapefruit juice while on prescription meds. Writer Carmen Drahl points out that “the liver enzyme avenue to drug interactions is by far the most familiar to food-drug interaction aficionados.”
“Liver enzymes known as cytochrome P450s help the body break down drugs, and many foods and herbal remedies contain compounds that alter these enzymes’ activities and thus change the drugs’ potencies.”
Paul F. Hollenberg of the University of Michigan, Ann Arbor, talked at the ACS meeting about his team’s search for a chemical explanation of what’s called the grapefruit juice effect – drinking just a glassful a day can lead to dangerous increases in levels of some drugs, such as Lipitor, in the bloodstream.
“Researchers know that bergamottin, a molecule in grapefruit juice, and its metabolites inactivate a particular cytochrome P450 enzyme known as CYP3A4. Bergamottin molecules work by a process called suicide inactivation: The enzyme transforms them into highly reactive intermediates, which then react with the enzyme.”
“Despite its infamous role in the grapefruit juice effect, bergamottin may not be all bad, Hollenberg said. The problem is that it’s impossible to get a consistent dose of bergamottin in its natural context. People may not consume the same amount of grapefruit or grapefruit juice each day, and different grapefruit crops or juice batches will have different levels of bergamottin.”
“If bergamottin could be administered in a reliable fashion, it might be used to boost the bioavailability of drugs or drug candidates that undergo cytochrome P450 metabolism.”
“As for grapefruit lovers whose medication precludes them from consuming a favorite fruit, Hollenberg says solutions to their problem are in the offing. Researchers are trying several strategies to remove bergamottin from grapefruit juice, such as genetic engineering of grapefruit trees, as well as chemical or photochemical approaches for ridding the juice of bergamottin. “It’s like the idea behind decaffeinated coffee,” he said.”
Click here to read the full article, including the effect of St. John’s Wort, milk thistle, and leafy greens…