Molecular weight and anti-tumor activity of the water-soluble polysaccharides isolated by hot water and ultrasonic treatment from the sclerotia and mycelia of Pleurotus tuber-regium

The sclerotia (S) and mycelia (M) of Pleurotus tuber regium were extracted, respectively, by hot water (h) and ultrasonication (s) to yield four water-soluble polysaccharides coded as Sh, Mh, Ss and Ms. All water-soluble polysaccharides were mixture of two fractions that contained predominantly polysaccharides with glucose as the major sugar and galactose and mannose as the minor component. The water-soluble extracts from mycelia seemed to have higher protein content than the ones from sclerotia. The ultrasonicated water extracts (Ms and Ss) contained glycan–chitin complexes with higher weight-average molecular weight (Mw) than that by hot water. Interestingly, the polysaccharides Mh and Sh extracted with hot water, which contained the major fractions with Mw in the range of 40–80×104, exhibited stronger in vivo (Sarcoma 180 solid tumor implanted in BALB/c mice) and in vitro (HL-60 tumor cell culture) anti-tumor activities than that obtained by ultrasonication. In view of these results, the anti-tumor activities of the water-soluble polysaccharides isolated from both sclerotia and mycelia of P. tuber-regium depended on the method of isolation that affected the Mw profile and conponent of the extracts. The effects of moderate Mw and protein content of the polysaccharides on the improvement of the bioactivities could not be negligible.