Abstract: Background and Objective: The discovery of traditional plants with some medicinal properties, verifying their biological targets and the bioassay guided standardization of their active components are the particular interest of diverse research groups recently. These efforts may help to revise the therapy modalities with natural product supplements. In this context, the possible biological targets of plants, namely Heliotropium europaeum, Carlina oligocephala and Echinops ritro, with no known medicinal value but recognized for their region specific traditional use, were evaluated. Here, the biological targets were enzymes of the antioxidant and xenobiotic defense mechanisms, with roles on inflammatory response. Materials and Methods: Cytotoxicity analyses were performed by using human promyelocytic (HL60) and chronic myelogenous leukemia (K562) cells for circulating models and breast adenocarcinoma (MCF7) cells for epithelial model to evaluate the non-toxic dose range of extracts by virtue of XTT and trypan blue. The target aimed effectiveness of these plants were determined with dose response profiles and IC50 values against glutathione peroxidase (GPX), glutathione transferase (GST), catalase (CAT) and superoxide dismutase (SOD) targets, as well as their capacity to reduce free radicals (DPPH) and non-radical hydrogen peroxide (H2O2). For standardization purposes, all extract concentrations were brought to 23.81 mg L–1 GAE and dilutions were made from these stocks. The IC50 values were determined by nonlinear regression analysis, with sigmoidal dose-response 4-parameter logistic equation. Results: The results showed that the best DPPH and H2O2 scavenging was observed with E. ritro extracts. On the contrary, the best enzyme inhibition profile was observed with H. europaeum against CAT, SOD, GPX and GST targets. Among the enzymes evaluated, all plants with different fractions also exerted strong GPX and CAT inhibition. Conclusion: The enzyme profiling of extracts may reveal the medicinal value of herbal remedies, by identifying their effects on cellular targets. In addition to define how reasonable the use of plants in traditional and complementary medicine (TCM) practices, these efforts may help to improve the standardized supplement preparations to benefit therapeutics with reduced efficiency due to inference with cellular defense and drug resistance enzymes, or both.