Ulva compressa, Gelidium microdon, Osmundea pinnatifida, Fucus spiralis and Cystoseira abies-marina from the coast of S. Miguel Island were screened for their in vitro cytotoxicity against HeLa tumour cell line, antioxidant potential and total phenolic content. From each alga, the hexane fraction (HF) of the methanol extract, the methanol residue (MF) and the dichloromethane extract (DE), were obtained and evaluated. The highest antiproliferative activity against HeLa cell line was found in C. abies-marina and F. spiralis DE (IC50 8.8 μg/mL and 10.7 μg/mL, respectively), and presented selective cytotoxicity, when tested against Vero cell line. Fluorescence microscopy studies of the two most active extracts suggest an apoptosis-inducing activity. Concerning the antioxidant activity, high values were found on F. spiralis MF and HF (EC50 0.62 μg/mL and 2.01 μg/mL, respectively), even higher than those obtained for trolox and quercetin. This high antioxidant activity in F. spiralis MF can be explained by its content in phenolic compounds, but not for HF, where the antioxidant compounds must be less polar. These results suggest that some macroalgae
from the Azorean sea have great potential which could be considered for future
applications in medicine, food production or cosmetics industry
