title: In vitro inhibition of cytochrome P-450 activities and quantification of constituents in a selection of commercial Rhodiola rosea products.
abstract: BACKGROUND
  Rhodiola rosea L. (Crassulaceae) products are popular natural remedies with a worldwide distribution. Recent studies have revealed potent CYP inhibition by R. rosea extracts both in vitro and in vivo, but information on in vitro CYP inhibition by commercial products are lacking. Variations in commercial R. rosea product quality have also been published.
  
  
  OBJECTIVE
  This study evaluates the variation of in vitro CYP inhibition potential and product quality of six commercially available R. rosea products.
  
  
  METHODS
  Human CYPs isolated from baculovirus-infected cell system were incubated with testosterone (CYP3A4), dextromethorphan (CYP2D6) or phenacetin (CYP1A2). Positive CYP inhibitors ketoconazole (CYP3A4), quinidine (CYP2D6) and β-naphtoflavone (CYP1A2) were used as controls. Quantification of rosavin, rosarin, rosin, tyrosol and salidroside were used to evaluate R. rosea content.
  
  
  RESULTS
  IC50values ranged from 7.2-106.6 μg/mL for CYP3A4, 13.0-186.1 μg/mL for 2D6 and 10.7-116.0 μg/mL for 1A2. The tincture formulation of R. rosea was the strongest inhibitor giving the lowest IC50values of 7.2 ± 0.7, 13 ± 1.7 and 10.7 ± 5.6 μg/mL, respectively. CYP3A4 was significantly more inhibited by the different products than CYP1A2 (p < .05). One of the six products did not contain any rosavin, rosarin or rosin and is not a R. rosea product. Constituent concentrations were not linked to enzyme inhibition.
  
  
  CONCLUSIONS
  The present results show a large variation in inhibitory potential between the products. Several of the products demonstrate similar inhibition levels as the product Arctic Root already proven to inhibit CYP enzyme activity in man.
authors: a Department of Cancer Research and Molecular Medicine, Faculty of Medicine , Norwegian University of Science and Technology (NTNU) , Trondheim , Norway.
authors: Ole Kristian
authors: OK
authors: Thu
authors: a Department of Cancer Research and Molecular Medicine, Faculty of Medicine , Norwegian University of Science and Technology (NTNU) , Trondheim , Norway.
authors: Odd Georg
authors: OG
authors: Nilsen
authors: a Department of Cancer Research and Molecular Medicine, Faculty of Medicine , Norwegian University of Science and Technology (NTNU) , Trondheim , Norway.
authors: Bent
authors: B
authors: Hellum
mesh_terms: D003132:Commerce; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000302:isolation & purification / Q000494:pharmacology*; D006801:Humans; D010936:Plant Extracts / Q000302:isolation & purification / Q000494:pharmacology*; D029771:Rhodiola
chemical_list: D004791:Enzyme Inhibitors; D010936:Plant Extracts; D003577:Cytochrome P-450 Enzyme System
keywords: CYP inhibition; IC50; golden root; quality