Constellation, le dépôt institutionnel de l'Université du Québec à Chicoutimi

Résumé

Labrador tea (Ledum groenlandicum Retzius) is an ericaceae widely distributed in North America. The leaves and twigs were used in Native American traditional medicine to treat several inflammatory pathologies such as asthma, rheumatisms and burns. Reactive oxygen species as well as reactive nitrogen species such as nitric oxide (NO) contribute significantly to these pathologies. In this study, the antioxidant, anti-inflammatory and anticancer activities of crude methanol extracts of leaves and twigs from Ledum groenlandicum were investigated. Both extracts showed a strong antioxidant activity using the ORAC method and a cell based-assay. Moreover, the twig and leaf extracts showed significant anti-inflammatory activity, inhibiting NO release, respectively, by 28 and 17% at 25 μg/ml in LPS-stimulated RAW 264.7 macrophages. In comparison, N(G)-nitro-l-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, reduced NO release by 24% at 25 μg/ml. The twig extract was also found to be active against DLD-1 colon carcinoma and A-549 lung carcinoma cells, with IC50 values of 43 ± 1 and 65 ± 8 μg/ml, respectively. The bioguided study of the twig extract resulted in the isolation and identification of ursolic acid, a known triterpene. Ursolic acid was active against DLD-1 (IC50: 9.3 ± 0.3 μM) and A-549 (IC50: 8.9 ± 0.2 μM), suggesting it is, in part, responsible of the anticancer activity of the twig extract.