Brown macroalgae from the Adriatic Sea as a promising source of bioactive nutrients

In the present investigation the acetone extracts of three brown marine macroalgae Dictyota dichotoma, Padaina pavoniaand Sargassum vulgare were tested for antioxidant, antimicrobial and cytotoxic potential. The antioxidant activity was evaluated by free radical scavenging, superoxide anion radical scavenging and reducing power. P. pavonia extract showed more potent free radical scavenging activity (IC50 = 691.56 μg L−1) than D. dichotoma and S. vulgare extracts. Moreover, the tested extracts had effective reducing power and superoxide anion radical scavenging. The total content of phenol and flavonoid in extracts was examined using Folin–Ciocalteu reagent and aluminium chloride method and the obtained values were expressed as pyrocatechol equivalents, and as rutin equivalents, respectively. Further, the antimicrobial potential was determined by a microdilution method. Among the tested species, the extract of D. diichotoma showed the best antimicrobial activity with minimum inhibitory concentration values ranging from 0.156 to 2.5 mg L−1. Finally, the cytotoxic activity was tested using microculture tetrazolium test on the human colon carcinoma LS174 cells, human lung carcinoma A549 cells, malignant melanoma FemX cells and chronic myelogenous leukaemia K562 cells. The extract of D. dichotoma expressed stronger cytotoxic activity toward tested cell lines with IC50 values ranging from 9.76 to 50.96 μg L−1.