Inhibition of RPA32 and Cytotoxic Effects of the Carnivorous Plant <i>Sarracenia purpurea</i> Root Extract in Non-Small-Cell Lung Cancer Cells

The carnivorous plant <i>Sarracenia purpurea</i> has been traditionally used in various ethnobotanical applications, including treatments for type 2 diabetes and tuberculosis-like symptoms. This study investigates the cytotoxic effects of <i>S. purpurea</i> root extract (Sp-R) on human non-small-cell lung cancer (NSCLC) cell lines, including H1975, H838, and A549, focusing on its impact on cell survival, apoptosis, proliferation, and migration. Additionally, its ability to inhibit the single-stranded DNA-binding activity of human RPA32 (huRPA32), a key protein in DNA replication, was evaluated. Extracts from different plant parts (leaf, stem, and root) were prepared using various solvents (water, methanol, ethanol, and acetone) and screened for apoptosis-inducing potential using the chromatin condensation assay. Among these, the acetone-extracted root fraction (Sp-R-A) exhibited the most potent pro-apoptotic effects. The MTT assay demonstrated a dose-dependent cytotoxic effect on NSCLC cells, with IC₅₀ values of 33.74 μg/mL for H1975, 60.79 μg/mL for H838, and 66.52 μg/mL for A549. Migration and clonogenic assays further revealed that Sp-R-A significantly inhibited cancer cell migration and colony formation in a dose-dependent manner. Moreover, Sp-R-A enhanced apoptosis when combined with the EGFR inhibitor afatinib, suggesting a potential synergistic effect. The electrophoretic mobility shift assay confirmed that Sp-R-A significantly inhibited the DNA-binding activity of huRPA32, with an IC₅₀ of 13.6 μg/mL. AlphaFold structural prediction and molecular docking studies indicated that major bioactive compounds in <i>S. purpurea</i>, including α-amyrin, ursolic acid, and betulinaldehyde, strongly interact with the DNA-binding domain of huRPA32, potentially contributing to its inhibitory effect. Overall, these findings suggest that huRPA32 is a potential molecular target of Sp-R-A and the anticancer potential of <i>S. purpurea</i> root extract against NSCLC is highlighted, supporting further investigation into its therapeutic applications.