Effect of green microalgal extracts exhibiting antibacterial activity on viability of human malignant and non-malignant cells

Microalgae have been investigated for their ability to produce metabolites that exhibit antibacterial activity. However, as research on antibacterial activity progresses, the effect of microalgal extracts on mammalian cells needs to be also assessed. The in vitro effect of microalgal extracts with demonstrated antibacterial activity against the human opportunistic pathogen Staphylococcus aureus was examined on the viability of non-malignant (MCF10A and 184B5 cells) and malignant human cell lines (A2780 and MCF7). Direct cell counts indicated that the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) proliferation assay was found to under/overestimate cell viability when specific microalgal extracts and/or concentrations were tested. From direct cell counts, the viability of non-malignant cells was not reduced after exposure to the extracts, whereas the viability of malignant cells was affected by specific microalgal extracts and concentrations. The results suggest that green microalgae are worthy of further investigation as potential sources of antibiotics, since they did not show a negative effect on the non-malignant cell lines, MCF10A and 184B5. Additional studies should evaluate the compounds responsible for the anti-proliferative activity of specific microalgal extracts observed on the malignant cells A2780 and MCF7.