Therapeutic effects of several medicinal plants and vegetables, which are commonly used as food and in folk medicine against many disease, are well known. Antioxidant capacities of Heracleum persicum Desf., Prangos ferulacea (L.) Lindl., Chaerophyllum macropodum Boiss. species from Apiaceae family were evaluated by determining their effects on DPPH radical scavenging, and lipid peroxidation inhibition, as well as their total phenolic contents. Potential natural glutathione-S-transferase inhibitors have gained great importance in the last decade especially because of the role of glutathione-S-transferases in developing resistance to chemotherapy. Selected plants were therefore further investigated for their influence on the activity of glutathione-S-transferase enzyme. In comparing antioxidant capacities, P. ferulacea was found to be a better antioxidant than the other two plants in the family, with 50% inhibitory concentration values as 0.242 and 0.152mg/ml for DPPH radical scavenging and lipid peroxidation inhibition, respectively. The same plants were also evaluated for their effects on GST activities and among the studied plants, P. ferulacea was the most efficient inhibitor with IC₅₀ value of 79.25μg/ml for GST. C. macropodum and H. persicum were less effective antioxidants than P. ferulacea with IC₅₀ values of 0.623 and 0.438mg/ml for DPPH radical scavenging, respectively, however, they could also be considered as potential GST inhibitors.