Background: Teucrium Polium and Prosopis Farcta have been traditionally employed in cancer treatment. In this study we evaluated the effects of methanolic extracts of these two plants in HT-29 cells. Methods: IC50s of extracts were obtained via MTT assay and the levels of ROS production, cell death, collapse of mitochondrial membrane potential and Sirt3 enzyme activity were determined. Results: After 48 hours exposure, IC50s for Teucrium and Prosopis extracts were 3 and 2μg/ml, respectively. Extracts induced higher ROS production after 6 hours than after 12 hours. Mitochondrial membrane potential collapse and cell death rate were also increased; Teucrium caused greater cell death than Prosopis. Extracts from both plants increased Sirt3 activity in its normal form, but only Teucrium extract caused a significant increase in activity of Sirt3 enzyme isolated from cancer cells. Conclusion: Teucrium and Prosopis extracts exert anticancer activity via mitochondrial alterations, as exemplified by increased ROS levels, Sirt3 activity and cell death in HT-29 colorectal cancer cells.