Cytotoxic effect of a mannogalactoglucan extracted from Agaricus bisporus on HepG2 cells

•A mannogalactoglucan (RK2-Ab) from Agaricus bisporus was structurally characterized;.•The main chain is formed mainly by α-d-Galp and β-d-Glcp units (1→6)-linked;.•Main chain is 2-O- and/or 4-O-substitued by β-d-Manp non-reducing end units;.•RK2-Ab reduced cellular viability of HepG2 cells;.•Antitumor activity by inducing apoptosis by the mitochondrial death pathway. A mannogalactoglucan (RK2-Ab; Mw 1.8×104gmol−1) composed by Man (27.3%), Gal (24.4%) and Glc (48.3%) was extracted and characterized from Agaricus bisporus, and its biological activity was evaluated on human hepatocarcinoma cells (HepG2). The partially-O-methylated alditol acetates together with the NMR data suggest the main chain to be composed of α-d-Galp (32.8%) and β-d-Glcp (37.0%) units (1→6)-linked, with β-d-Manp (14.6%), as non-reducing end units, substituting the side chains at O-2 (α-d-Galp units; 3.3%) and O-2 and O-4 (β-d-Glcp units; 3.6%). (1→2)-linked β-d-Glcp (2.7%) and β-d-Manp (6.0%) can also be observed. RK2-Ab reduced cellular viability of HepG2 cells, by both, the MTT and lactate dehydrogenase release assays, promoted the increase of cytochrome c release and decrease of ATP content. Suggesting that the mannogalactoglucan from A. bisporus may have antitumor activity by inducing apoptosis by the mitochondrial death pathway, and could be used in cancer therapy.