Evaluation of Prunus africana Bark Extract-Induced Apoptotic Activities and Associated Signaling Pathways in Selected Breast Cancer Cells

Breast cancer remains the most prevalent malignancy among middle-aged and elderly women with underlying health conditions, with triple-negative breast cancer (TNBC) representing a notably aggressive subtype associated with poorer clinical outcomes. Prunus africana (P. africana) has been reported to contain bioactive compounds with notable antioxidant and anticancer properties. Bark extracts obtained using water, as well as single (100%) and binary (50% v/v) solvents of methanol and ethanol (MeOH-100, EtOH-100, MeOH-50, and EtOH-50), were evaluated for their antioxidant activity, apoptosis-inducing effects, and modulation of signaling pathways in selected breast cancer cell lines. Antioxidant activity was measured via FRAP, DPPH radical scavenging, and TEAC assays; cytotoxic activity and pathway modulation were assessed using MTS, human apoptosis, and phospho-RTK array assays. While the EtOH-100 extract presented the lowest extraction yield of 3.22%, it showed the highest total phenolic (505.96 mg GAE/g) and total flavonoid (2.53 mg RU/g) contents and antioxidant activities (2.25 mM Fe2+/g and 311.68 mM TE/g), and the lowest EC50 (0.21 mg/mL), comparable to ascorbic acid (0.18 mg/mL). EtOH-100 also notably induced apoptosis in HCC1806 as shown by increased cleaved caspase-3, HSP60, and HSP27 expression, and sustained catalase levels. Phospho-RTK array analysis revealed early silencing of HGF and transient upregulation of EGF and Insulin R following EtOH-100 extract treatment, suggesting modulation of oncogenic signaling. These findings highlight the therapeutic potential of P. africana, particularly the EtOH-100 extract, as a viable treatment for TNBC.