A review on fucoidan antitumor strategies: From a biological active agent to a structural component of fucoidan-based systems

•Fucoidan is a sulfated polysaccharide with different biological activities.•Its antitumor potential has been mainly studied as a soluble bioactive agent.•Chemical features influence the mechanisms of action and efficacy of antitumor approaches.•In recent years, fucoidan-based systems, namely for drug delivery have been developed. Due to the severe side-effects and the toxicity to healthy tissues, cancer treatments based in chemotherapy have not fully achieved the desire outcomes so far. The use of natural compound may be of great value to develop better tolerated therapies. Fucoidan is a marine sulfated polysaccharide extracted from brown algae that, besides other biological activities, has been reported to present interesting anti-cancer potential. This review briefly introduces fucoidan chemical structure, physicochemical properties and the above-mentioned biological feature. Fucoidan usage as soluble agent presents promising results herein described for different types of cancer. Trying to enhance and optimize fucoidan usage in the cancer field, different systems, namely drug delivery, have been recently developed to target different types of cancers. This aspect will be presented in detail, highlighting the role of fucoidan on their reported or envisaged performance.