Ecology Department of Malaga University, Spain.
In recent decades, polysaccharides isolated from botanical sources (mushrooms, algae, lichens and higher plants) have attracted a great deal of attention in the biomedical arena because of their broad spectrum of therapeutic properties and relatively low toxicity. Within microalgae polysaccharide structural diversity, sulfation of the groups makes up the chain changes its physico-chemical characterization and structural conformation presenting various bioactive, antiviral, anti-inflammatory, anticoagulant, antitumor and immunomodulating properties and may possess strong antioxidant activity. This would indicate that sulfation level and its position in polysaccharide chemical structures determine bioactivity levels. In this regard, polysaccharides have shown the ability to prevent accumulation and activity of free radicals and reactive chemical species, thus acting like protection systems against free radicals and oxidative stress. Furthermore, polysaccharides presenting sulfate groups near glycoside bonds have greater antioxidant activity when reacting with the ABTS•+radical . Recently, algal polysaccharides have also been shown to have anticancer and antitumor properties, in addition to modifying macrophage activity, inducing cytokine production, or stimulating respiratory burst activity of turbot phagocytes. The first line of defence against microbial infection is macrophages. It has previously been shown that polysaccharides of different origin can modulate the functions and activity of macrophages by increasing phagocytosis, microbicidal activity, chemotaxis and antigen presentation to T cells, thus helping in preventive and therapeutic strategies against some diseas. The defence of macrophages against pathogens includes secretions of cytokines such as interleukin 6 (IL-6), tumour necrosis factor α (TNF-α) and mediators of inflammation such as nitric oxide (NO). The major role of TNF-α is the regulation of immune cells; however, it has also been shown to reduce viral replication. Thus, it is clear that polysaccharides extracted from algae have significant therapeutic potential and represent a rich source for future discovery and development of novel compounds of medical value.