Antioxidant, antiproliferative, genotoxic and cytoprotective effects of the methanolic extract of Padina tetrastromatica on human breast adenocarcinoma and embryonic fibroblast cell lines

The in vitro antioxidant, antiproliferative, genotoxic and cytoprotective effects of the methanolic extract of the seaweed Padina tetrastromatica were assayed using the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, superoxide, nitric oxide and hydroxyl radical scavenging assays, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and comet assays. The methanolic extract of P. tetrastromatica showed considerable antioxidant activity through inhibition of DPPH and hydroxyl radicals, with median inhibitory concentration (IC50) values of 45.57 ± 1.63 and 36.58 ± 2.13 µg/ml, respectively. Treatment of the human breast adenocarcinoma cell line MCF-7 with the methanolic extract, at a concentration range of 0–500 µg/ml, showed considerable antiproliferative effects, with an IC50 value of 125 ± 2.03 µg/ml. The genotoxic and cytoprotective effects of the extract on the human breast adenocarcinoma cell line MCF-7 and the embryonic fibroblast cell line 3T3-L1 were evaluated by the in vitro comet assay, and the extract demonstrated a genotoxic effect on MCF-7 and antigenotoxic and cytoprotective effects on 3T3-L1 cells. The methanolic extract of P. tetrastromatica was more effective in inducing a genotoxic effect in MCF-7 cells and a cytoprotective effect in 3T3-L1 cells, compared with the standard cancer chemotherapy drug doxorubicin, which induced greater DNA damage in the normal 3T3 cells.