| Respondin(TM) is a proprietary immune builder developed by Ocean Nutrition Canada Ltd. from extracts of the green microalgae Chlorella pyrenoidosa. Early studies have shown that high molecular weight polysaccharides or perhaps polysaccharide-protein complexes are responsible for the immunoactivity of Respondin(TM), but there have been no detailed studies on the structures of the polysaccharides. The complex mixture present in crude extracts of Chlorella pyrenoidosa was fractionated by graded ethanol precipitation, followed by other techniques. An unique arabinogalactan was isolated after ethanol fractional precipitation, SEC and CTAB precipitation of Respondin(TM). The repeating unit of the arabinogalactan was unambiguously established as →2)-alpha-L-Araf-(1 → 3)-[alpha-L-Araf-(1 → 4)]-beta- D-Galp-(1→ by a combination of sugar analysis, GLC-MS data for (S)-2-octyl glycosides, chemical shift data, 1JC,H values for anomeric carbons, COSY, TOCSY, HSQC, HMBC and NOESY. Arabinogalactans are important constituents of plant cell walls, but the structure of this arabinogalactan is different from any of those reported previously. 3-O-Methylgalactose was found in one immunoactive polysaccharide, but the structure of this polysaccharide could not be completely determined. Another polysaccharide containing both arabinose and galactose was partially purified. This mixture, together with the fully characterized arabinogalactan, appear to have synergistic immunoactivity. |
