Characterization of Cross-flow Ultrafiltration Fractions from Maitake Medicinal Mushroom, Grifoia frondosa (Agaricomycetes), Reveals Distinct Cytotoxicity in Tumor Cells

beta-glucans from Basidiomycetes like Grifola frondosa (the maitake mushroom) are well known for their health benefits. Polysaccharide preparations from medicinal mushrooms such as G. frondosa have been successfully tested in a vast number of studies. Many mushroom extracts have been developed and today are merchandized for use medicinally and commercially. Studies could show that, in particular, chemical structural features such as the molecular size of beta-glucans significantly influence their bioactivity. Thus it is highly important to explore the composition and structural properties of beta-glucans extracted from medicinal mushrooms and their effects on human tumor cell viability. Our study focuses on the molecular weight cutoff distribution of beta-glucans in hot water-based extracts from maitake mushrooms. Cross-flow ultrafiltration was applied to obtain 5 fractions of different molecular size. beta-glucan content was quantified using an enzyme-based test kit, specialized to 1,3-1,6-beta-glucans. Here we show that only small amounts of beta-glucans with a high molecular weight (>100 kDa) could be detected from an aqueous extract of G. frondosa. The main compounds encompass substances with a low molecular weight (<5 kDa), composing about 35% of the whole extract. In addition, tumor cell viability studies demonstrate significant cytotoxic potential in 2 different solid cancer cell types for the fraction with a high molecular weight (>100 kDa) and for 1 fraction with a low molecular weight (5-10 kDa). In summary, our experiments prove that cross-flow ultrafiltration serves as a quick and easy method for dividing crude aqueous mushroom extracts into different molecular-weight fractions that inhibit tumor cell viability in vitro.