HPLC-MS analysis of coumarins and furanocoumarin dimers in immature grapefruit

John A. Manthey

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 three varieties (Rio Red, Marsh, and Foster) of grapefruit during the first 4-6 weeks of fruit development were analyzed for two seasons (2004 and 2005). Concentration time courses of the monomers in the three varieties of grapefruit were generally similar over the two 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.

Keywords


grapefruit juice; psoralens; coumarins; grapefruit/drug interaction; time course; dimers; hplc-pda

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283