title: Labeled content of two furanocoumarins in dietary supplements correlates with neither actual content nor CYP3A inhibitory activity.
abstract: Dietary supplements are a multi-billion dollar business, with yearly profit increases. Allegedly safe, these supplements are marketed to a variety of niches, encompassing claims from immune support to weight loss. Six sports nutrition supplements were acquired that were labeled to contain the furanocoumarin(s) bergamottin and/or 6',7'-dihydroxybergamottin (DHB), both of which are potent irreversible inhibitors of the prominent drug metabolizing enzyme cytochrome P450 3A (CYP3A). Both furanocoumarins are typically present in grapefruit juice, which has been shown to inhibit intestinal CYP3A, perpetrating an increase in the systemic exposure of certain concomitant 'victim' drugs. The acquired supplements were analyzed using ultra-performance liquid chromatography coupled to both a photodiode array (PDA) detector and a triple quadrupole mass spectrometer (MS). Contrary to the product labeling, four of the supplements contained no detectable quantities of either furanocoumarin (LOD 0.060μg/capsule), while two of the supplements contained minimal amounts (one contained 12.13 (±0.23) μg bergamottin and 65.51 (±0.64) μg DHB per capsule; the other contained 2.705 (±0.069) μg bergamottin per capsule and no detectable quantities of DHB). A CYP3A inhibition bioassay was used to assess whether the actual content of the furanocoumarins correlated with CYP3A inhibitory activity. Despite the low amounts of bergamottin and DHB, CYP3A inhibition by the supplements was greater than could be accounted for by the two furanocoumarins. The additional activity suggests the presence of other potent or highly abundant CYP3A inhibitors.
authors.affiliation: Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, PO Box 26170, Greensboro, NC 27402, USA.
authors.forename: Karen M
authors.initials: KM
authors.lastname: VanderMolen
authors.affiliation: Washington State University, College of Pharmacy, PBS 341, PO Box 1495, Spokane, WA 99210-1495, USA; Curriculum in Toxicology, School of Medicine, The University of North Carolina at Chapel Hill, PO Box 7310, Chapel Hill, NC 27599, USA.
authors.forename: Garrett R
authors.initials: GR
authors.lastname: Ainslie
authors.affiliation: Washington State University, College of Pharmacy, PBS 341, PO Box 1495, Spokane, WA 99210-1495, USA; Curriculum in Toxicology, School of Medicine, The University of North Carolina at Chapel Hill, PO Box 7310, Chapel Hill, NC 27599, USA.
authors.forename: Mary F
authors.initials: MF
authors.lastname: Paine
authors.affiliation: Department of Chemistry and Biochemistry, University of North Carolina at Greensboro, PO Box 26170, Greensboro, NC 27402, USA. Electronic address: nicholas_oberlies@uncg.edu.
authors.forename: Nicholas H
authors.initials: NH
authors.lastname: Oberlies
mesh_terms: D001628:Beverages / Q000032:analysis; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D002957:Citrus / Q000737:chemistry; D032083:Citrus paradisi / Q000737:chemistry; D065692:Cytochrome P-450 CYP3A Inhibitors / Q000737:chemistry*; D019587:Dietary Supplements / Q000032:analysis*; D011564:Furocoumarins / Q000737:chemistry*; D013058:Mass Spectrometry / Q000379:methods
chemical_list: D065692:Cytochrome P-450 CYP3A Inhibitors; D011564:Furocoumarins; C068337:bergamottin; C104774:6',7'-dihydroxybergamottin
keywords: Bergamottin; Dietary supplement; Dihydroxybergamottin; Furanocoumarin; Grapefruit juice