Rapid Preparation of Low-Molecular-Weight Fucoidan Using a Plasma-Liquid Interface Process

Fucoidan is a polysaccharide extracted from seaweed such as kelp and <i>mozuku</i> (Nemacystus decipiens). Unlike other polysaccharides, fucoidan is characterized by being rich in sulfate groups. Fucoidan is known to exhibit physiological activities such as induction of apoptosis, anti-blood coagulation, anti-tumor, anti-virus, and anti-allergic effects when ingested in the body. Because of these features, fucoidan is used as a source material for supplements. At present, however, commercially available fucoidan supplements show only limited physiological efficacy. One of the reasons is poor intestinal absorption of as extracted fucoidan which has extremely large molecular weight ranging from tens of thousands to millions. According to recent research on fucoidan, low-molecular-weight (LMW) fucoidan has been revealed to have much more pronounced physiological activities than high-molecular weight one. LMW fucoidan at present is generally prepared with depolymerization using hydrolysis or enzymatic reactions, which are time- and/or energy-consuming processes. Consequently, LMW fucoidan supplements becomes expensive. To overcome this cost issue, we have examined possibility of preparation of LMW fucoidan using low-temperature atmospheric pressure plasma as a cost-effective alternative to conventional depolymerization processes. In this work, DBD plasma of argon gas was generated on aqueous solution containing as-received fucoidan extracted from Macrocystis pyrifera (Sigma-Aldrich). The molecular weight of the fucoidan, which was investigated by GPC, was reduced from 10⁴-10⁵ down to 10³ within 10 min. This depolymerization rate is much faster than conventional hydrolysis which takes longer time of several hours. Faster and stronger depolymerization of fucoidan is known to reduce content of sulfated groups which is indispensable for having physiological activity. FTIR investigation on our samples indicated that our process does not cause significant removal and/or destruction of sulfated groups.<br/>Acknowledgements: This work was supported by JSPS/MEXT KAKENHI (19H01888), JST OPERA (JPMJOP1843), and JST A-STEP (JPMJTR20UK).