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item Manthey, John

Submitted to: Proceedings of Florida State Horticultural Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2006
Publication Date: 2/28/2006
Citation: Manthey, J.A. 2006. HPLC-MS analysis of coumarins and furanocoumarin dimers in immature grapefruit. Proceedings of Florida State Horticultural Society. 118:429-436.

Interpretive Summary: Grapefruit juice contains compounds that influence the metabolism of prescription drugs in humans. These compounds are termed the furanocoumarins. This study investigated the occurrence of these compounds in very young immature grapefruit sampled over two seasons. This study showed that these compounds were present in very early fruit, and that the concentrations of these compounds fluctuated widely during early fruit development. An understanding of the progression of the biosynthesis of the furanocoumarins in developing grapefruit will play an important role in mediating the levels of these compounds through plant breeding and genetic engineering.

Technical Abstract: Furanocoumarin dimers in grapefruit juice are involved in the numerous reported grapefruit/drug interactions. The majority of these compounds putatively occur as conjugates of 6',7'-epoxybergamottin and 6',7'-dihydroxybergamottin, with molecular weights of 708 and 726 amu. These compounds are readily detected by UV (310 nm) and by electrospray ionization mass spectrometry (ESI-MS). Detection by ESI-MS is 10-100 times more sensitive than UV detection, and provides a means of analyzing the trace levels of these compounds in very early season grapefruit. The (furano)coumarin dimers and monomers in 3 varieties (Rio Red, Marsh, and Foster) of grapefruit during the first 4-6 weeks of fruit development were analyzed for 2 seasons (2004 and 2005). Concentration time courses of the monomers in the 3 varieties of grapefruit were generally similar over the 2 seasons. These time courses showed that many of the monomers were transitory, as suggested by their rapid increases in concentrations during the initial stages of cell division, followed by rapid decreases in concentrations accompanying subsequent fruit growth and development. Differences in the time courses of the furanocoumarin dimers in the 2004 and 2005 season fruit suggest that the biosyntheses of these compounds are influenced by environmental and internal growth factors.