Planta Med 2011; 77(14): 1655-1662
DOI: 10.1055/s-0030-1270968
Analytical Studies
Original Papers
© Georg Thieme Verlag KG Stuttgart · New York

Seasonal Variation of Phenolic Constituents and Medicinal Activities of Northern Labrador Tea, Rhododendron tomentosum ssp. subarcticum, an Inuit and Cree First Nations Traditional Medicine

Paleah Black1 , Ammar Saleem1 , Andrew Dunford2 , José Guerrero-Analco1 , Brendan Walshe-Roussel1 , Pierre Haddad3 , Alain Cuerrier4 , John T. Arnason1
  • 1Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
  • 2Nunavut Research Institute, Iqaluit, Nunavut, Canada
  • 3Department of Pharmacology, University of Montreal, Montreal, Quebec, Canada
  • 4Plant Biology Research Institute, University of Montreal, Montreal, Quebec, Canada
Further Information

Publication History

received Nov. 14, 2010 revised March 9, 2011

accepted March 12, 2011

Publication Date:
06 April 2011 (online)


Northern Labrador tea, Rhododendron tomentosum ssp. subarcticum, is one of the most commonly used medicinal plants by Inuit and other First Nations peoples of Canada. The phenolic profile and seasonal variation of this commonly used medicinal plant remains largely unknown. To assess optimal harvesting time, R. tomentosum was collected in accordance with traditional knowledge practices bimonthly throughout the snow-free summer in Iqaluit, Nunavut. The antioxidant potency was measured in a DPPH radical scavenging assay, and the anti-inflammatory activity was determined with a TNF-α production assay. The seasonal variation of phenolic content was assessed with HPLC‐DAD for fifteen of the most abundant phenolic compounds; (+)-catechin, chlorogenic acid, para-coumaric acid, quercetin 3-O-galactoside (hyperoside), quercetin 3-O-glucoside (isoquercitrin), quercetin 3-O-rhamnoside (quercitrin), quercetin pentoside, myricetin, quercetin, 3 procyanidins, and 3 caffeic acid derivatives. The most abundant constituent was (+)-catechin, which made up 19 % of the total weight of characterized phenolics. There was significant seasonal variation in the quantity of all fifteen constituents assessed, whereas there was no seasonal variation of their total sum. The antioxidant activity was positively correlated with phenolic content and negatively correlated with daylight hours. The anti-inflammatory activity was negatively correlated with caffeic acid derivative 1 and daylight hours. Together these results demonstrate that the timing of harvest of R. tomentosum impacts the plant's phenolic content and its antioxidant and anti-inflammatory activities.


John T. Arnason

Centre for Research in Biotechnology and Biopharmaceuticals
Department of Biology, University of Ottawa

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