title: Walnut leaf extract inhibits PTP1B and enhances glucose-uptake in vitro.
abstract: BACKGROUND
  Walnut, Juglans regia L. (Juglandaceae), is one of the medicinal plants used to treat diabetic symptoms in Austrian folk medicine. The air-dried green leaves are either used as aqueous decoctions or liquor preparations and are consumed on a daily basis. We investigated the hypoglycemic effect of a methanolic Juglans regia leaf extract on glucose uptake, protein tyrosine phosphatase 1B (PTP1B) inhibition and peroxisome proliferator-activated receptor gamma (PPARγ) activation.
  
  
  METHODS
  Hypoglycemic activity was assessed by glucose-uptake in C2C12 myocytes, inhibition of PTP1B and activation of PPARγ. Phytochemical characterization of the extract was carried out by LC-MS and GC-MS.
  
  
  RESULTS
  Methanolic Juglans regia leaf extract enhanced the glucose uptake rate in C2C12 myocytes at concentrations of 25µg/mL compared to untreated cells. This activity may partly be explained by the inhibition of PTP1B but not PPARγ agonism. LC-MS analyses revealed chlorogenic acid (1), 3-p-coumaroylquinic acid (2), a trihydroxynaphthalene-hexoside (3), as well as eight flavonoids (4-11) as main phenolic constituents in the active extract.
  
  
  CONCLUSIONS
  The finding that Juglans regia leaf extract enhances glucose uptake and inhibits PTP1B provides an in vitro-based rationale for the traditional use of walnut leaf preparations against elevated blood-glucose levels.
authors.affiliation: Department of Pharmacognosy, University of Vienna, Althanstraße 14, A-1090 Vienna, Austria.
authors.forename: Anna
authors.initials: A
authors.lastname: Pitschmann
authors.affiliation: Department of Pharmacognosy, University of Vienna, Althanstraße 14, A-1090 Vienna, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Zehl
authors.affiliation: Department of Pharmacognosy, University of Vienna, Althanstraße 14, A-1090 Vienna, Austria.
authors.forename: Atanas G
authors.initials: AG
authors.lastname: Atanasov
authors.affiliation: Department of Pharmacognosy, University of Vienna, Althanstraße 14, A-1090 Vienna, Austria.
authors.forename: Verena M
authors.initials: VM
authors.lastname: Dirsch
authors.affiliation: Department of Pharmacognosy, University of Vienna, Althanstraße 14, A-1090 Vienna, Austria.
authors.forename: Elke
authors.initials: E
authors.lastname: Heiss
authors.affiliation: Department of Pharmacognosy, University of Vienna, Althanstraße 14, A-1090 Vienna, Austria. Electronic address: sabine.glasl@univie.ac.at.
authors.forename: Sabine
authors.initials: S
authors.lastname: Glasl
mesh_terms: D000818:Animals; D002460:Cell Line; D002853:Chromatography, Liquid; D008401:Gas Chromatography-Mass Spectrometry; D005947:Glucose / Q000378:metabolism; D031324:Juglans / Q000737:chemistry*; D013058:Mass Spectrometry; D008519:Medicine, Traditional; D051379:Mice; D018485:Muscle Fibers, Skeletal / Q000187:drug effects* / Q000378:metabolism; D047495:PPAR gamma / Q000187:drug effects / Q000378:metabolism; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D018515:Plant Leaves; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1 / Q000037:antagonists & inhibitors*
chemical_list: D047495:PPAR gamma; D010936:Plant Extracts; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D005947:Glucose
keywords: C2C12 myocytes; Diabetes mellitus; Glucose uptake; Juglans regia; PPARγ agonism; PTP1B inhibition