# Pharmacological and Cosmeceutical Potential of Seaweed Beach-Casts of Macaronesia
## 3 Results and Discussion
### Anticancer Activity
Figure 2: Cell survival of a cytotoxic assay against DU-145 prostate cancer cell line of different samples tested at two concentrations (20 \(\upmu\)g/mL and 50 \(\upmu\)g/mL). Adriamycin at 5.43 \(\upmu\)g/mL was used as reference. a 46% inhibition; unlike the present study, they were assayed at a rather high concentration of 200 ug/mL of pure polysaccharide [47]. Another study, employing brown alga collected in the Persian Gulf, showed a weak antiproliferative effect on the T47D cell line (IC\({}_{50}\) 99.9 ug/mL) and on the T47D tamoxifen-resistant cell line (IC\({}_{50}\) 143 ug/mL)[48], which may indicate differences in metabolites profiles of these species and in extraction methods compared with those evaluated in this study. The cytotoxic activity of the samples against the HT29 cancer colon cell line was also studied. Some growth inhibition activity at 20 ug/mL and 50 ug/mL was recorded for just five samples (1.E; 1.M; 1.E.1; 1.E.2 and 13.E.1), with cell survival data varying from 65% to 2%, corresponding to a cell growth inhibition of 35% to 98% (Figure 4). The best sample was 1.M.1, which displayed an IC\({}_{50}\) value of 24.4 ug/mL and a selectivity index of 2.43 (Tables 2 and 3). Extracts of the tropical seaweed _Pylaiella littoralis_ exhibited, in a dose-dependent manner, a clear antiproliferative activity against HT29 cells, with 55% inhibition when tested at 50 ug/mL, a result which in the present work achieved much better results for samples 1.E.1 and 1.E.2, and similar for samples 1.E and 13.E.1 at the same concentration; the IC\({}_{50}\) value of 28 ug/mL reported by those authors is between the results reported herein for samples 1.M.1 and 1.E.2. [41]. The in vitro results against the tumor cell lines studied were quite interesting, not only because 38% of the tested samples exhibit IC\({}_{50}\) values below 25 ug/mL, which means very promising samples with high to moderate cytotoxic activity, but also because of their high activity against several cancer cell lines. For example, samples 1.M.1 and 1.E.1 exhibited cytotoxic activity against at least three tumor cell lines with IC\({}_{50}\) values lower than 25 ug/mL. The best results were against NCI H1299 lung cancer, with four samples presenting IC\({}_{50}\) values lower than 14 ug/mL (1.M.1, 1.E.2, 11.E and 12.E), followed by T47D breast cancer with two samples with IC\({}_{50}\) lower than 16.5 ug/mL (1.E.2 and 1.M), all of them with SI values higher than 4.2. For the other two cancer cell lines (DU-145 prostate and HT29 colon cancer cell lines), the lowest IC\({}_{50}\) values were around 23-25 ug/mL. It should be noted that of the 38 SI values calculated, 65.8% were higher than 2, which indicated samples with a highly selective cytotoxic action, being much more active against the tumor cell lines than against the nontumor cell line employed. Figure 4: Cell survival of a cytotoxic assay against the HT29 colon cancer cell line of different samples tested at two concentrations (20 ug/mL and 50 ug/mL). Adriamycin at 5.43 ug/mL was used as reference. These results demonstrated that macroalgae can be attractive sources of potential anticancer compounds, with many references also supporting this claim [49], such as the 22-membered cyclic lactone lobophorolide, isolated from _Lobophora variegata_, one of the main components of the beach-cast samples with highest activity (beach-casts 1, 11 and 12), which was extremely active at low concentration against human the HCT-116 colon cell line (IC\({}_{50}\) = 0.03 \(\upmu\)g/mL) [50]. Furthermore, the different beach-casts evaluated here also showed large seaweed species composition variability within beach-casts, although those identified as _L. variegata_ mono-specific, which occurred with a certain degree of frequency, displayed very attractive results.