Phytochemical Characterization and Mechanistic Insights into the Cytotoxic Effects of Bougainvillea glabra Bract Extract in Caco-2 Colorectal Adenocarcinoma Cells

Bougainvillea glabra Choisy (Nyctaginaceae) is a traditional medicinal plant and a source of betalains and phenolic compounds with potential antioxidant and cytotoxic properties that still remains underexplored. This study characterized a B. glabra extract (BGE) and evaluated its antioxidant capacity, cytotoxic effects, and modulation of intracellular ROS levels in Caco-2 cells. UPLC-MS identified 21 phenolic compounds, including rutin and quercetin, and two major betacyanins. BGE exhibited ABTS radical scavenging activity (156–188 µM TE), reduced intracellular ROS levels under basal and LPS-stimulated conditions, decreased Caco-2 cell viability, and enhanced the cytotoxic effect of cisplatin. These effects were associated with apoptosis- and autophagy-related markers, including p53 and Bcl-2 expression, and differential regulation of genes involved in caspase activation and NF-kB signaling. Overall, BGE exhibited antioxidant and cytotoxic activities, supporting its potential as a source of bioactive compounds for colorectal cancer research.