Glutathione reductase (GR, E.C. 22.214.171.124), a flavoenzyme, is responsible for recycling of oxidized glutathione disulfide. This study was performed in two main sections. In the first GR was purified from bovine liver by affinity column chromatography and the purification rate and specific activity of the enzyme were calculated as 1832-fold and 141 EU/mg protein, respectively. The subunit molecular weight of the enzyme was determined as 55 kDa by means of SDS-PAGE. The second section isolated natural components of Arum rupicola Boiss. var. rupicola using column chromatography. The isolation protocol for this plant was performed with a series of different-sized columns with hexane-ethyl acetate. According to the thin-layer chromatography plate, seven substances (R1-R7) were isolated. Our study's aim was to find new activators or inhibitors for GR activity. With this aim, all isolated substances were tested for GR activity. R6 showed competitive inhibition, while R4 had noncompetitive inhibition of GR activity. R1 played a role as an activator of GR activity. The inhibitory activity percentage vs. concentration graph was plotted. Values of IC50 for R4 and R6 were calculated as 0.193 mg/mL and 3.98 mu g/mL, respectively, from the equation of this graph.