Letter to the Editor Seaweeds: Some Pharmaco-Immunological Effects

Seaweed is a sea plant that is found in every sea or ocean and may belong to one of several groups of multicellular seaweeds such as the red, the green, and the brown seaweeds. Seaweeds are consumed by people living in coastal areas, particularly in East Asia including Japan, China, Korea, Taiwan, and Thailand and are rarely eaten by people in the western countries. Seaweeds, as an important source of trace minerals, have been frequently used as an herbal medicine to suppress inflammation and also used for the treatment of various diseases such as allergy, cancer, ulcers, arthritis, and hypotension (1-5). Therefore, extracts of seaweeds, especially the brown seaweeds, could be utilized as a good natural source of a possible food supplement and is consumed as an anti-inflammatory agent in the pharmaceutical industry to treat some immunologic disorders and allergic diseases (1). Several studies from various countries indicate an increasing prevalence of allergic diseases and asthma in the last decades (6,7). Also, studies have demonstrated a relationship between dietary factors and allergic diseases, particularly with high fatty acid foods, fruits, and antioxidants (1,8- 10). Hyaluronidase, an enzyme which cleaves hyaluronic acid in the extracellular matrix of connective tissue, is also known to be involved in allergic inflammation (11). Antiallergic agents may have a strong inhibitory effect on the activation of hyaluronidase (12). A wide variety of seaweeds, specially the brown ones, with polyphenol and phlorotannin contents were assessed for their antihyaluronidase activity, as antiallergic agents (12,13). However, the inhibitory effect on hyaluronidase may be related to the high molecular weight of phlorotannin, since the higher the molecular weight of phlorotanin, the higher its inhibitory effect on the sulphation of compounds present in the crude extract of seaweeds (12,14). Another study investigated the effect of alginic acid, a naturally occurring hydrophilic colloidal polysaccharide obtained from a different species of brown seaweeds (Phaeophyceae), on the mast cell-mediated anaphylactic and inflammatory reactions (15). The results depicted that alginic acid oligosaccharide suppresses Th2 development and IgE secretion by inducing interleukin (IL)-12 secretion (16). Furthermore the results of an epidemiological study showed that higher dietary ingestion of seaweed may diminish the prevalence of allergic rhinitis in Japanese female young adults (1). Indeed, the dietary fiber in the seaweed, fucoidan, modulates the function of immune cells including macrophages, natural killer (NK) cells, lymphocytes and neutrophils (17,18). Therefore, fucoidan upon inhibition of class switching in B lymphocytes, blocks IgE production and its might clarify its beneficial effect in the treatment of allergic diseases and a reduction in the prevalence of allergic rhinitis in this group (19).