title: A combination of (+)-catechin and (-)-epicatechin underlies the in vitro adipogenic action of Labrador tea (Rhododendron groenlandicum), an antidiabetic medicinal plant of the Eastern James Bay Cree pharmacopeia.
abstract: BACKGROUND
  Rhododendron groenlandicum (Oeder) Kron & Judd (Labrador tea) was identified as an antidiabetic plant through an ethnobotanical study carried out with the close collaboration of Cree nations of northern Quebec in Canada.
  
  
  OBJECTIVE
  In a previous study the plant showed glitazone-like activity in a 3T3-L1 adipogenesis bioassay. The current study sought to identify the active compounds responsible for this potential antidiabetic activity using bioassay guided fractionation based upon an in vitro assay that measures the increase of triglycerides content in 3T3-L1 adipocyte.
  
  
  METHODS
  Isolation and identification of the crude extract's active constituents was carried out. The 80% ethanol extract was fractionated using silica gel column chromatography. Preparative HPLC was then used to isolate the constituents. The identity of the isolated compounds was confirmed by UV and mass spectrometry.
  
  
  RESULTS
  Nine chemically distinct fractions were obtained and the adipogenic activity was found in fraction 5 (RGE-5). Quercetins, (+)-catechin and (-)-epicatechin were detected and isolated from this fraction. While (+)-catechin and (-)-epicatechin stimulated adipogenesis (238±26% and 187±21% relative to vehicle control respectively) at concentrations equivalent to their concentrations in the active fraction RGE-5, none afforded biological activity similar to RGE-5 or the plant's crude extract when used alone. When cells were incubated with a mixture of the two compounds, the adipogenic activity was close to that of the crude extract (280.7±27.8 vs 311± 30%).
  
  
  CONCLUSIONS
  Results demonstrate that the mixture of (+)-catechin and (-)-epicatechin is responsible for the adipogenic activity of Labrador tea. This brings further evidence for the antidiabetic potential of R. groenlandicum and provides new opportunities to profile active principles in biological fluids or in traditional preparations.
authors.affiliation: Natural Health Products and Metabolic Diseases Laboratory, Department of Pharmacology, Université de Montréal, Montréal, Québec, Canada; Canadian Institutes of Health Research Team in Aboriginal Antidiabetic Medicines and Montreal Diabetes Research Center, Montreal, Canada; Department of Pharmacognosy, University of Beni-seuf, Beni-seuf, Egypt.
authors.forename: Hoda M
authors.initials: HM
authors.lastname: Eid
authors.affiliation: Natural Health Products and Metabolic Diseases Laboratory, Department of Pharmacology, Université de Montréal, Montréal, Québec, Canada; Canadian Institutes of Health Research Team in Aboriginal Antidiabetic Medicines and Montreal Diabetes Research Center, Montreal, Canada.
authors.forename: Meriem
authors.initials: M
authors.lastname: Ouchfoun
authors.affiliation: Centre for Research in Biotechnology and Biopharmaceuticals, Department of Biology, University of Ottawa, Ottawa, Ontario, Canada; Canadian Institutes of Health Research Team in Aboriginal Antidiabetic Medicines and Montreal Diabetes Research Center, Montreal, Canada.
authors.forename: Ammar
authors.initials: A
authors.lastname: Saleem
authors.affiliation: Centre for Research in Biotechnology and Biopharmaceuticals, Department of Biology, University of Ottawa, Ottawa, Ontario, Canada; Canadian Institutes of Health Research Team in Aboriginal Antidiabetic Medicines and Montreal Diabetes Research Center, Montreal, Canada; Advanced Molecular Studies Department-Institute of Ecology A.C., Xalapa, Veracruz, Mexico.
authors.forename: Jose A
authors.initials: JA
authors.lastname: Guerrero-Analco
authors.affiliation: Centre for Research in Biotechnology and Biopharmaceuticals, Department of Biology, University of Ottawa, Ottawa, Ontario, Canada; Canadian Institutes of Health Research Team in Aboriginal Antidiabetic Medicines and Montreal Diabetes Research Center, Montreal, Canada.
authors.forename: Brendan
authors.initials: B
authors.lastname: Walshe-Roussel
authors.affiliation: Natural Health Products and Metabolic Diseases Laboratory, Department of Pharmacology, Université de Montréal, Montréal, Québec, Canada; Canadian Institutes of Health Research Team in Aboriginal Antidiabetic Medicines and Montreal Diabetes Research Center, Montreal, Canada.
authors.forename: Lina
authors.initials: L
authors.lastname: Musallam
authors.affiliation: Canadian Institutes of Health Research Team in Aboriginal Antidiabetic Medicines and Montreal Diabetes Research Center, Montreal, Canada; Institut de recherche en biologie végétale et Jardin Botanique de Montréal, Université de Montréal, Montréal, Quebec, Canada.
authors.forename: Michel
authors.initials: M
authors.lastname: Rapinski
authors.affiliation: Canadian Institutes of Health Research Team in Aboriginal Antidiabetic Medicines and Montreal Diabetes Research Center, Montreal, Canada; Institut de recherche en biologie végétale et Jardin Botanique de Montréal, Université de Montréal, Montréal, Quebec, Canada.
authors.forename: Alain
authors.initials: A
authors.lastname: Cuerrier
authors.affiliation: Natural Health Products and Metabolic Diseases Laboratory, Department of Pharmacology, Université de Montréal, Montréal, Québec, Canada; Canadian Institutes of Health Research Team in Aboriginal Antidiabetic Medicines and Montreal Diabetes Research Center, Montreal, Canada.
authors.forename: Louis C
authors.initials: LC
authors.lastname: Martineau
authors.affiliation: Centre for Research in Biotechnology and Biopharmaceuticals, Department of Biology, University of Ottawa, Ottawa, Ontario, Canada; Canadian Institutes of Health Research Team in Aboriginal Antidiabetic Medicines and Montreal Diabetes Research Center, Montreal, Canada.
authors.forename: John T
authors.initials: JT
authors.lastname: Arnason
authors.affiliation: Natural Health Products and Metabolic Diseases Laboratory, Department of Pharmacology, Université de Montréal, Montréal, Québec, Canada; Canadian Institutes of Health Research Team in Aboriginal Antidiabetic Medicines and Montreal Diabetes Research Center, Montreal, Canada. Electronic address: pierre.haddad@umontreal.ca.
authors.forename: Pierre S
authors.initials: PS
authors.lastname: Haddad
mesh_terms: D016475:3T3 Cells; D050156:Adipogenesis / Q000187:drug effects*; D000818:Animals; D061006:Bays; D002392:Catechin / Q000494:pharmacology*; D002460:Cell Line; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D029794:Ledum / Q000737:chemistry*; D008519:Medicine, Traditional / Q000379:methods; D051379:Mice; D010936:Plant Extracts / Q000494:pharmacology*; D010946:Plants, Medicinal / Q000737:chemistry; D011792:Quebec; D029793:Rhododendron / Q000737:chemistry*
chemical_list: D007004:Hypoglycemic Agents; D010936:Plant Extracts; D002392:Catechin
keywords: 3T3-L1 adipocytes; Aboriginal traditional medicine; Adipogenesis; Bioassay-guided fractionation; Labrador tea