Portuguese macroalgae as a source of bioactive compounds with selective anticancer activity against breast cancer cells.

Marine-derived natural products are promising sources of new anticancer agents, but the bioactivity of Portuguese macroalgae and halophytes remains insufficiently explored. This study aimed to identify extracts with selective antiproliferative activity against breast cancer cells using environmentally sustainable extraction methods. Crude extracts were prepared by ultrasound-assisted extraction with water or 10% dimethyl sulfoxide (DMSO) and screened in human MCF-7 breast adenocarcinoma cells using the sulforhodamine B (SRB) assay after 48 h of exposure. Active extracts were subsequently evaluated in non-tumorigenic MCF-12A breast epithelial cells, and half-maximal effective concentrations (EC50) were determined from concentration-response curves. Of 48 crude extracts screened, 21 inhibited MCF-7 cell proliferation in a concentration-dependent manner and were selected for further evaluation. Three extracts derived from the brown macroalgae Bifurcaria bifurcata II and Ericaria selaginoides-two aqueous and one DMSO-based-showed selective activity against MCF-7 cells without detectable inhibition of MCF-12A cells within the corresponding concentration ranges. These findings identify Portuguese macroalgae as promising sources of selectively active anticancer metabolites and support further phytochemical characterization and mechanistic investigation using sustainable bioprospecting approaches.