Joanna Cosgrove03.01.09
Squashing the 'Grapefruit Effect'
Mushroom appears to override the dreaded grapefruit-drug interaction.
By Joanna Cosgrove
Online Editor
“Grapefruit juice possesses many nutritional features, including many potentially cardioprotective compounds, that are important in improving human health [however] grapefruit consumption has been decreased over years, threatening the citrus industry in the U.S., and the reduction in consumption is largely related to grapefruit-drug interactions,” commented Kyung Myung, PhD, of the U.S. Citrus and Subtropical Products Laboratory, Agricultural Research Service, U.S. Department of Agriculture in Winter Haven, FL.
Dr. Myung explained that a class of phenolic compounds called furanocoumarins (FCs)—naturally present not only in grapefruits but also pummelos, limes and lemons—are responsible for grapefruit-drug interactions. The compounds can inhibit a specific enzyme responsible for metabolizing some medications, which can result in an overdose of the medication. “Our initial approach to solving this problem was to discover fungi capable of modifying the grapefruit juice FCs, and thus, inactivate them as enzyme inhibitors,” he said, adding that the use of microorganisms or their enzymes to modify food properties is a common practice throughout the food industry.
Edible mushrooms are divided into two major fungal groups, ascomycetes and basidiomycetes. The objectives of this study were to examine whether edible fungi, including two ascomycetes, Morchella esculenta and Monascus purpureus, and two basidiomycetes, Pleurotus sapidus and Agaricus bisporus, could remove FCs in grapefruit juice and to evaluate whether the removal could be affected by different factors, i.e., pH of grapefruit juice, sources of grapefruit juice (fresh versus concentrate), and fungal materials (wet versus dry).
Dr. Myung and his team are not the first who have attempted to remove FCs from grapefruit juice using chemical, physical and microbiological methods. According to published studies from 2006, other researchers have used a series of chemical extractions, ultraviolet radiation and heat to degrade FCs in grapefruit juice. The use of “autoclaved fungus to absorb and remove FCs” in grapefruit juice is another area that’s also been explored. Dr. Myung’s team made use of a previously established method, which enabled them to complete their study within a relatively short timeframe.
The team discovered that many fungi exhibited passive adsorption of the FCs from grapefruit juice. “This was not the active (enzyme catalyzed) process that we were looking for, but this passive process did appear to significantly lower the concentrations of the FCs in grapefruit juice,” he said. “It became apparent to us that this passive binding might be useful for the removal of these compounds from grapefruit juice on an industrial scale. Because of the potential application of these findings to food production, we switched our research to edible fungi.”
It wasn’t long before the team’s focus came to rest on the Morchella esculenta mushroom, more commonly known as the morel. “Aspergillus niger and Morchella esculenta are categorized within the same fungal group, the ascomycetes. So, it was reasonably thought that using an edible fungus similar to the Aspergillus, which was shown to be previously effective, would be a good follow-up approach to produce food-grade FC-free grapefruit juice,” said Dr. Myung.
He added that the team’s selection and success with the morel mushroom was not made so consumers would be able to replicate the technique in an at-home application. Rather, he said they were looking for a model for an industrial-scale application. “We think this is the initial step for an industrial application to develop FC-free grapefruit juice [and] we are focusing on identifying the constituents in fungal hyphae that are responsible for the binding with the FC,” he said. “Once these constituents are identified, we hope to transfer this information to a grapefruit juice processor as a means to ultimately remove the FC from grapefruit juice, and thus make a grapefruit juice that is free of the drug interactions.”
A full account of the team’s research, which began in September 2007 and concluded in February 2008, was published in The Journal of Agricultural and Food Chemistry (November 24, 2008, Vol. 56, No. 24).