Contents lists available at ScienceDirect Journal of Ethnopharmacology journal homepage: www.elsevier.com/locate/jep Larix laricina bark, a traditional medicine used by the Cree of Eeyou Istchee: Antioxidant constituents and in vitro permeability across Caco-2 cell monolayers Yi Yong a , Ammar Saleem b , José A. Guerrero-Analco c , Pierre S. Haddad d , Alain Cuerrier e , John T. Arnason b , Cory S. Harris a,b, ⁎ , Tim Johns a a Centre for Indigenous Peoples’ Nutrition and Environment, School of Dietetics and Human Nutrition, McGill University, Macdonald Campus, Sainte-Anne- de-Bellevue, QC, Canada H9X 3V9 b Department of Biology, University of Ottawa, Ottawa, ON, Canada K1N 6C5 c Advanced Molecular Studies-Instituto de Ecología, A.C., Xalapa, Veracruz, México d Natural Health Products and Metabolic Diseases Laboratory, Department of Pharmacology and Montreal Diabetes Research Center, Université de Montréal, P.O. Box 6128, Downtown Postal Station, Montreal, QC, Canada H3C 3J7 e Jardin botanique de Montréal, Institut de recherche en biologie végétale, Université de Montréal, Montréal, QC, Canada H1X 2B2 ARTICLE INFO Keywords: Tamarack Anti-diabetes Rhaponticin Bioavailability Radical scavenging ABSTRACT Ethnopharmacological relevance: Larix laricina, a native tree of North America, is a highly respected medicinal plant used for generations by Indigenous Peoples across its range, including the Cree of northern Québec who use the bark to treat symptoms of diabetes. This study investigates the antioxidant capacity and bioavailability of active constituents identified in L. laricina bark extracts. Materials and methods: (1) Oxygen radical absorbance capacity (ORAC) assay was employed to test antioxidant capacity of organic extracts (80% ethanol) from bark of L. laricina as well as fractions, isolated compounds, and media samples collected during permeability assays. (2) Caco-2 cell monolayer cultures were used to determine the permeability of identified antioxidants, which were quantified in basolateral media samples using liquid chromatography – tandem mass spectrometry (HPLC-ESI-MS/MS). Results: Crude ethanolic extract possessed strong antioxidant potential in vitro (7.1 ± 0.3 Trolox equivalents (TE) μM/mg). Among the 16 L. laricina fractions obtained by chromatographic separation, fraction 10 (F10) showed the highest antioxidant capacity (21.8 ± 1.7 μm TE/mg). Among other identified antioxidants, the stilbene rhaponticin (isolated from F10) was the most potent (24.6 ± 1.1 μm TE/mg). Caco-2 transport studies revealed that none of the identified compounds were detectable in basolateral samples after 2-h treatment with crude extract. In monolayers treated with F10 (60% rhaponticin), small quantities of rhaponticin were increasingly detected over time in basolateral samples with an apparent permeability coefficient (P app ) of 1.86×10 −8 cm/s (0–60 min). To model potential effects on blood redox status, we evaluated the antioxidant capacity of collected basolateral samples and observed enhanced activity over time after exposure to both extract and F10 (75 μg/mL) relative to control. Conclusions: By profiling the antioxidant constituents of L. laricina bark, we identified rhaponticin as the most potent oxygen radical scavenger and observed low permeability in Caco-2 cell monolayers but an increase in basolateral antioxidant capacity. 1. Introduction Larix laricina (Du Roi) K. Koch (Pinaceae) is a tree native to eastern North America, known by the common names Watnagan (Cree), tamarack and larch (English) and mélèze (French). An im- portant medicinal plant of the boreal forest, L. laricina is traditionally used for treating wounds, indigestion, rheumatism, arthritis, colds, ulcers, and skin problems amongst Iroquoiam and Algonquian peoples (Arnason et al., 1981; Farrar, 1995; Marles et al., 2000). The Cree of Eeyou Istchee, Québec, have multiple uses for the plant, from mana- ging cold- and flu-related symptoms to treating burns, boils, cuts, infections and even snow blindness (Marles et al., 2000; Shang et al., http://dx.doi.org/10.1016/j.jep.2016.10.054 Received 18 March 2016; Received in revised form 18 July 2016; Accepted 18 October 2016 ⁎ Corresponding author at: Department of Biology, University of Ottawa, Ottawa, ON, Canada K1N 6N5. E-mail address: charris@uottawa.ca (C.S. Harris). Journal of Ethnopharmacology 194 (2016) 651–657 0378-8741/ © 2016 Elsevier Ireland Ltd. All rights reserved. Available online 21 October 2016 crossmark