Prophylactic Olive Leaf Tea as a Nutraceutical Strategy: Tumor Suppression and Systemic Protection

Olive leaf tea (OLT), rich in phenolics, exhibits antioxidant, anti-inflammatory, and potential anticancer effects; however, the in vivo efficacy remains unclear. This study evaluated the chemopreventive and systemic effects of OLT in a murine Ehrlich Ascites Tumor (EAT) model, with a focus on the treatment timing. OLT was prepared by aqueous infusion and characterized for total phenolic content (TPC: 25.74 mg GAE/g), DPPH scavenging (197.88 µmol TE/g), FRAP activity (81.23 µmol Fe²⁺/g), and LC-MS/MS profile (oleuropein 77.6%). Mice received OLT orally before or after tumor inoculation. Prophylactic OLT reduced EAT cell counts (from 31.48 × 10⁷ to 21.15 × 10⁷), ascites volume (from 4.58 to 2.98 mL), elevated miR-155-5p (14.34-fold), normalized ALT/AST, and restored hepatic antioxidants without histopathological damage. Co-treatment with 5-FU preserved efficacy while reducing hepatotoxicity. In conclusion, OLT provides timing-dependent anticancer and systemic protective effects in the EAT model, supporting its potential as a cost-effective nutraceutical for cancer prevention and adjunctive therapy.