Viet Nam is recognized internationally as one of the countries that has the world’s highest
biodiversity with various types of forest, swamps, river and stream, sea, etc. Located in the center of the
South East Asia, Viet Nam’s total coastline is about 3260 km long as the west border of the East Sea with the
area of over 1,000,000 km2, it is one of the world’s most important seas having various and abundant algae.
There are about 6000 identified species of seaweed in the world and they are divided into 3 main seaweed,
divisions in terms of pigment: green algae (Chlorophytes), brown algae (Pheophytes) and red algae
(Rhodophytes). Algae plays an important role in sea creature resources. They are being widely exploited,
raised and used more and more by human in food and industry. According to research results, Viet Nam now
explores nearly 1000 seaweed species, 143 of which are brown algae (Phaeophyta) that have large, long
individual size as well as large number capacity. Therefore, brown algae are considered as a valuable raw
material of the present and the future of agriculture, drug manufacturing industry, functional food and
cosmetic. In the drug manufacturing industry, brown algae are used as the main raw material to extract
compounds that have biological activity with large application capacity.
Marine brown algae, representatives of the class Phaeophyceae, are known as a rich source of unique
polysaccharides. Among them, alginic acids and alginates have found various technical applications, whereas
sulfated polysaccharides (fucoidans) are intensively studied in view of their various promising biological
activities, mainly anticoagulant and antitumor ones. Fucoidans are sulfate polysaccharides derived from
marine brown seaweed containing mainly fucose and sulfate groups with other residues such as galactose,
xylose, glucose, manose and uronic acids. Fucoidans were reported to possess various biological effects in
vitro and in vivo such as anti-inflammatory, anticoagulant, antithrombotic, antiviral including anti-HIV,
immunomodulatory, antioxidant and antitumor.
Thanks to the variety of chemical structure and having many interesting biological activities,
fucoidan has been strongly researched. Elucidation of fine chemical structure of fucoidans is complicated as
fucoidan preparations are often mixtures of structurally different sulfated polysaccharides. These usually
have branched non-regular structures and contain different monosaccharides and noncarbohydrate
substituents (sulfate and acetate groups). Fucoidans from algae belonging to the family Sargassaceae have
especially complex structures, but are attractive since these algae are readily available from natural
populations. Fucoidan from brown algae belongs to Sargassum, Hormophysa and Turbinaria, has
complicated chemical structure but is very appealing to activity as well as its application and available in the
nature. Although many researches in order to identify fucoidan’s sophisticated structure are published, only
few results find out the regularity of fucoidan’s structure such as the association among sugar residues bases,
embranchment, the position of sulfate bases and other monosaccharide molecules. Up to now, most of the
researches on biological activity have been carried out on crude fucoidan. Therefore, the relationship
between structure and biological activity of fucoidan in reality, up to now, has not been cleared. To help the
research on effect mechanism of fucoidan on biological cells and using fucoidan to prepare medicines,
accurate identification of fucoidan’s chemical structure is the first decision and attracting many scientists
around the world. Therefore, I have chosen the topic: “Structural characteristics and biological activities of
fucoidans extracted from selected vietnamese brown seaweeds”.