Manuka Honey-induced Cytotoxicity against MCF7 Breast Cancer Cells is Correlated to Total Phenol Content and Antioxidant Power

Aims: To investigate the relations between total polyphenols content, antioxidant power and Manuka honey cytotoxicity towards MCF-7 cells.

Study Design: In vitro study.

Place and Duration of Study: Department of Chemistry, University of Crete in partnership with the School of Biomedical Sciences, Ulster University, 09/ 2014 – 09/ 2015.

Methodology: Manuka honey (UMF 5+,10+, 15+ and 18+) were examined for total phenols content using the Folin-Ciocalteu method with results expressed as mg gallic acid equivalents per kg honey (mg GAE/kg). Antioxidant power was evaluated using the Ferric Reducing Antioxidant Power “FRAP” method and expressed as mg GAE/kg. Honey cytotoxicity was examined with MCF-7 breast cancer cells cultured with RPMI 1640 supplemented with charcoals stripped serum and viability was monitored using the MTT assay.

Results: The total phenols content for Manuka honey ranged from 1367±152 mg GAE/kg for UMF 5+ honey to 2358 ±79 mg GAE/ kg for UMF 18+ honey. The antioxidant power for Manuka honey ranged from 170±22 mg GAE/kg for UMF 5+ honey rising to 266±21 mg GAE/kg for UMF 18+ honey. Manuka honey showed dose-dependent cytotoxicity towards MCF-7 cells after 24 hrs. treatment. The concentration of honey which produces 50% inhibitory activity (IC50) ranged from 4.7% (w/v) for UMF 5+ honey to 2.2% (w/v) for UMF 18+ honey. The cytotoxicity of Manuka honey was highly correlated with, values for the total phenols content (R2=0.99) and antioxidant power (R2=0.95) of Manuka.

Conclusion: Manuka honey is cytotoxic to MCF-7 breast cancer cells in vitro and the effects are correlated with the total phenols content and antioxidant power.