Among modern day metabolic diseases, obesity has reached epidemic proportions worldwide and novel therapeutic support strategies are urgently needed. Adipocytes are interesting targets in this context. Using ethnobotanical and bioassay screening techniques, we have identified two Boreal Forest plants used by the James Bay Cree that potently inhibit adipogenesis, namely ALNUS INCANA ssp. RUGOSA (Speckled Alder) and POPULUS BALSAMIFERA (Balsam Poplar). The mode of action of this inhibitory activity was reported in a companion paper. The current study report the results of a classical bioassay-guided fractionation approach aimed at identifying the active principles responsible for the inhibition of adipogenesis, as measured using triglyceride accumulation in the 3T3-L1 adipocyte model cell line. The glycosides oregonin and salicortin were isolated and identified as the respective active principles for ALNUS INCANA and POPULUS BALSAMIFERA. These compounds thus offer promise as novel agents to mitigate the incidence or the progression of obesity.