Carboxymethylated β-glucans from mushroom sclerotium of Pleurotus tuber-regium as novel water-soluble anti-tumor agent

Six hot alkali extracts (HAE-1 to HAE-6) of mushroom (1→3)-β-glucans from the sclerotia of Pleurotus tuber-regium having different molecular weight (Mw) ranging from 1×104 to 42×104 were carboxymethylated to give their corresponding water-soluble derivatives (CMHAE-1 to CMHAE-6) with Mw ranged from 2.08×104 to 53.2×104. In general, the CMHAE β-glucans had higher water solubility and higher in vivo (Sarcoma 180 solid tumor implanted on BALB/c mice) as well as in vitro (HL-60 tumor cell culture) anti-tumor activity than the native HAE β-glucans. From ELISA assay of cytokines, CMHAE fractions could increase production of tumor necrosis factor alpha (TNF-α) in mouse plasma stimulated by lipopolysaccharide (LPS). It was postulated that a more expanded flexible chain of these novel CMHAE β-glucans might account for their in vivo and in vitro anti-tumor activities.