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

ABSTRACT 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.