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영어

Many natural polysaccharides and derivatives isolated from various organisms such as marine seaweeds, mushrooms, plants, and microorganisms have attracted considerable attention in recent years as a rich and promising source of bioactive natural compounds in the fields of pharmacology and health beneficial foods due to their diverse biological activities, including antioxidant, antitumor, immunomodulatory, anti-inflammation, anticoagulant and antithrombotic, antibacterial, and antiviral activities. Among natural polysaccharides, sulfated polysaccharides (SPS) that contain hemi-ester sulfate groups in their sugar residues are commonly found in three major groups of marine algae, red algae (Rhodophyta), brown algae (Phaeophyta) and green algae (Chlorophyta). The major SPS of red algae are galactans commercially known as agar and carrageenan, and those of brown algae are fucans, including fucoidan, ascophyllan, sargassan, and glucuronoxylofucan. In contrast to those of red and green algae, the major SPS of green algae are more heterogeneous in sugar compositions, three main groups are glucuronoxylorhamnans, glucuronoxylorhamnogalactans and xyloarabinogalactans. Apart from industrial uses, these algal polysaccharides have emerged in recent years as a rich and important source of bioactive natural compounds, due to their diverse pharmacological activities including immune-modulatory, anticoagulant, antithrombotic, anti-mutagenic, antioxidant, anti-inflammatory, antitumour, antiprotozoal, antimicrobial, antiviral activities, etc, which are prerequisites of pharmaceutical and medicinal applications. For example, fucoidans, one of the most extensively studied SPS isolated from brown seaweeds, are known to exhibit a wide range of physiological and biological activities, thus medically useful activities, such as anti-inflammatory, antiviral, anticoagulant, antitumor, antioxidant, and antiangiogenesis activities. For these reasons, production and applications of these acidic polysaccharides as therapeutic agents have been increasingly important topics of intensive researches. Anticoagulating and antithrombotic activities are among the most widely studied properties of SPS for alternative sources of heparinoid-active compounds as therapeutic agents, due to several side effects of currently used heparin. Many SPS isolated from marine seaweeds have been reported for their antiviral activities against animal viruses, such as HSV types 1 and 2, human immunodeficiency virus type-1 (HIV-1), influenza virus, and human cytomegalovirus (HCMV). Although the use of these polysaccharides and oligosaccharides as drugs is in its infancy, currently, some are already in various phases of clinical trials as microbicides. An Undaria pinnatifida extract comprising predorminantly sulfated galactofucan was patented for its in vivo antiviral activity including HSV-1. Therefore, the potential of these SPS derived from marine algae as therapeutic agents in, e.g. antiviral medication, cancer therapy or blood clotting surveillance, becomes of great interest. Generally, these biological activities are related to structure, composition and sulphate substitution of polysaccharide macromolecules. However, it is now commonly accepted that the structures and chemical composition, including sugar composition, degree of sulfation, and molecular mass of these algal polysaccharides vary depending on the algal species, their harvesting time and regions of cultivation as well and thus must give rise to variation in the degree of most biological and pharmacological activities. Therefore, the SPS of Korean seaweeds may have different structures and thus different bioactivities from those of similar seaweeds harvested in other countries. In this context, in the course of our long-term research goal in searching for new and especially carbohydrate-based drug candidates and/or health beneficial foods materials from natural compounds, we have isolated and purified sulphated polysaccharides (SPS) from Korean seaweeds, Undaria pinnatifida and Capsosiphon fulvescens, and characterized their structures and biological activities such as immunomodulating, antiviral, anticoagulant, and antitumor activities. On the other hand, in spite of their potential as biologically active compounds, the high molecular mass and viscous nature of polysaccharides has hampered their application especially as a therapeutic agent. Therefore, a reliable SPS-degrading enzyme preparation would be highly desirable to obtain low-molecular weight oligosaccharides and thereby help overcome these problems. However, available data on, for example, purified fucoidanases remain scarce and no convenient commercial sources with fucoidanolytic activity are yet available for the degradation of these polysaccharides. Recently, we isolated and identified a marine bacterial strain that degrades the fucoidan (MF, Miyeokgui fucoidan) that we purified from the sporophyll of Korean Undaria pinnatifida. Subsequently, we purified this enzyme and produced low-molecular weight galactofuco-oligosaccharides (LMFOs), ranging from 1,389 to 3,749 Da and evaluated and compared their pharmacological activities, including immunomodulating, antiviral, anticoagulant, and antitumor activities, to those of intact high-molecular weight fucoidan, MF. Meanwhile, we have been working on other polysacchardies isolated from hyaluronic acids (HA), mushrooms, and plants like mulberry fruits. Some data on the structures and biological activities including immunomodulating, anti-inflammatory and anti-asthma, and anti-obesity effects of these polysaccharides will be discussed as well. (Recent publications on structures and biological activities of polysaccharides and oligosaccharides)