Isolation and characterization of a new antitumor polysaccharide, KS-2, extracted from culture mycelia of Lentinus edodes.

A new antitumor and antiviral substance, KS-2, was prepared by ethanol precipitation of the hot water extract of culture mycelia of Lentinus edodes KSLE 007. It was further purified by ECTEOLA-cellulose and Sephadex G-100 column chromatography based on the interferon-inducing activity. Its homogeneity was revealed by CsCl density gradient centrifugation, electrophoresis on cellulose acetate and Sephadex G-100 and ECTEOLA-cellulose column chromatography. KS-2 is mainly composed of alpha-linked mannose and contains a small amount of peptide which consists of serine, threonine and alanine with residual amounts of the other amino acids. The estimated molecular weight of KS-2 is between 6.0 X 10(4) and 9.5 X 10(4). KS-2 suppressed the growth of EHRLICH as well as Sarcoma-180 tumors in mice when given either orally or intraperitoneally. It is also capable of inducing an interferon in mice when dosed orally or intraperitoneally. The acute LD50 of KS-2 was found to be extremely low, more than 12,500 mg/kg when administered orally to mice.