Oligosaccharide fractions, a neutral fraction NOSP and three anionic fractions OSP3, OSP2, and OSP1, have been obtained from porphyran digested with enzymes of Arthrobacter sp. S-22, and examined for in vitro antitumor activity against WI-38 VA-13 cells. However, they did not inhibit growth of WI-38 VA-13 cells. In contrast, the sulfated disaccharide fraction, OSP1, showed considerable antitumor activity against Ehrlich ascites and Meth-A fibrosarcoma. Furthermore, OSP1 significantly enhanced the phagocytosis of macrophages when intraperitoneally administered.
