The Key Role of Sulfation and Branching on Fucoidan Antitumor Activity

There is an urgent need for antitumor bioactive agents with minimal or no side effects over normal adjacent cells. Fucoidan is a marine‐origin polymer with known antitumor activity. However, there are still some concerns about its application due to the inconsistent experimental results, specifically its toxicity over normal cells and the mechanism behind its action. Herein, three fucoidan extracts (FEs) have been tested over normal and breast cancer cell lines. From cytotoxicity results, only one of the extracts shows selective antitumor behavior (at 0.2 mg mL−1), despite similarities in sulfation degree and carbohydrates composition. Although the three FEs present different molecular weights, depolymerization of selected samples discarded Mw as the key factor in the antitumor activity. Significant differences in sulfates position and branching are observed, presenting FE 2 the higher branching degree. Based on all these experimental data, it is believed that these last two properties are the ones that influence the cytotoxic effects of fucoidan extracts. An effective cancer therapeutic strategy relies on the ability to eliminate tumors without damaging surrounding healthy tissues. Due to inconsistent results regarding fucoidan bioactivity, there is the need to characterize which feature(s) is (are) playing the major role. Herein, sulfation and branching seem to be the properties influencing fucoidan antitumor activity.