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Potent Natural Immunomodulator, Rice Water-Soluble Polysaccharide Fractions with Anticomplementary Activity¹

¹A part of this work was presented at the Annual Meeting of the Japan Society for Bioscience and Biotechnology and Agrochemistry, Tokyo, April 1999. ²Laboratory of Biochemistry, Department of Biological and Chemical Engineering, Hachinohe National College of Technology, Hachinohe, 039-1192 Japan. ³Corresponding author. E-mail: yama-c@hachinohe-ct.ac.jp. ⁴Present address: Mitsubishi Chemicals Co. Ltd.

Water-soluble polysaccharide fractions, fractionated with ammonium sulfate from the hot-water-extract of rice bran and endosperm, showed a potent anticomplementary activity. As compared with water-soluble polysaccharide isolated from Angelica acutiloba, which is a well-known medicinal herb, the rice fractions showed similar or higher potency. Protease digestion, periodate oxidation, and hydroxylamine treatments indicated that anticomplementary activity is due to polysaccharide moiety rather than protein moiety and the polyphenol moieties, ferulic acid, being an integral component in rice bran proteoglycan. These results suggest that a water-soluble proteoglycan and a polysaccharide in rice modulate complement activity. This is a new example of natural biological response modifiers in food.