Extracts Prepared from Selected High Antioxidant Australian Plants Inhibit Proliferation of HeLa and Caco-2 Carcinoma Cells

Background: High antioxidant foods have been linked to multiple therapeutic properties, including the anticancer and anti-inflammatory properties. Despite this, the anticancer activities of many Australian native plants with high antioxidant capacities are yet to be adequately explored. Materials and Methods: The antiproliferative activity of extracts prepared from the fruits and leaves of a selection of high antioxidant Australian plants against human HeLa cervical and Caco-2 colorectal carcinoma cell lines was examined using MTS assays. Artemia nauplii lethality assays (ALA) were used to evaluate the therapeutic safety of the extracts. Results: Methanolic, aqueous and ethyl acetate extracts prepared from the fruit of Davidsonia pruriens were strong inhibitors of proliferation of HeLa and Caco-2 cells, with IC50 values 169-376 µg/mL. Although Elaeocarpus angustifolia, Kunzea pomifera, Podocarpus elatus and Acronychia acidula fruit extracts also inhibited HeLa and Caco-2 proliferation, they were substantially less potent inhibitors of cell proliferation. Additionally, all of the extracts were determined to be non-toxic in the ALA, and the calculated therapeutic indexes highlighted the potential of the extracts for therapeutic use at effective doses. Conclusion: The D. pruriens extracts were particularly promising inhibitors of HeLa and Caco-2 cell proliferation. Further study is warranted to identify the bioactive components and the mechanism(s) of action.