Cytotoxic and antibacterial potential of Eucalyptus honey: in vitro assessment on human cancer cell lines and bacterial strains

Eucalyptus honey, characterized by its distinct botanical and phytochemical profile, may possess valuable bioactive properties. This study investigated the antibacterial and cytotoxic activities of Eucalyptus honey to assess its therapeutic potential. Melissopalynological analysis identified Eucalyptus camaldulensis as the predominant pollen source (47%). Antibacterial activity was concentration-dependent, with Staphylococcus aureus ATCC 6538p showing the highest susceptibility, producing a 22-mm inhibition zone. Moderate inhibition was observed against Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Bacillus subtilis ATCC 6633, and Enterococcus faecalis ATCC 29212, whereas Micrococcus luteus was resistant. Broth-based assays confirmed strain-dependent inhibitory and bactericidal effects, with MIC50 values ranging from 1.69% to 15.36% and MBC values from 6.25% to 50%. Artificial honey exhibited markedly weaker activity and no bactericidal effect, suggesting the importance of non-sugar constituents. Cytotoxicity was evaluated in six human cancer cell lines (osteosarcoma [MG63], Ewing’s sarcoma [A673], colorectal adenocarcinoma [HT29, SW48], pharyngeal squamous cell carcinoma [2A3], and malignant mesothelioma [CARM-L12 TG3]) using the MTT assay after 48 and 72 h exposure. Pharyngeal carcinoma and osteosarcoma cells were highly sensitive, with 72 h IC50 values of 0.55% and 1.85%, respectively, while malignant mesothelioma cells were resistant. These findings indicate selective cytotoxic and antibacterial potential of Eucalyptus honey.