Polysaccharides from the gum exudates of Astragalus species Tragacantha section plants are extracted and modified into water-soluble fractions free from small molecular impurities. Such polysaccharide fractions upon parenteral administration inhibit specific tumors and viruses in mammals away from the site of injection, presumably by immunostimulatory effects. These polysaccharide fractions show no toxicity upon parenteral administration.
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