Distinct structural architectures of mushroom (1 → 3),(1 → 6)-β-D-glucans are associated with different biological responses in breast cancer cells.

Two distinct (1 → 3),(1 → 6)-β-D-glucans, designated GlcEtPp and GlcEtSn-300, were purified from an alkaline extract of the mushroom Lactarius quieticolor and structurally characterized by GC-MS, HPSEC-MALS-RI, and NMR spectroscopy. Structural analysis revealed marked differences in side-chain organization, with GlcEtPp containing O-6 substitutions exclusively by terminal glucosyl units, whereas GlcEtSn-300 exhibited extended (1 → 6)-linked side chains. The fractions also differed in molecular weight and NMR profiles. Their biological effects were evaluated in vitro using non-tumorigenic HB4a and tumorigenic MDA-MB-231 human breast cells. Notably, only GlcEtSn-300 showed comparatively stronger effects on MDA-MB-231 viability and reduced wound closure in the scratch assay, with lower effects observed in HB4a cells under the same conditions. This activity was accompanied by an increased BAX/BCL2 ratio, suggesting a possible apoptosis-related cellular response. Overall, the findings indicate that differences in structural features, including molecular weight and side-chain organization, of (1 → 3),(1 → 6)-β-D-glucans may be associated with distinct biological responses in breast cancer cells and reinforce the importance of detailed structural characterization in studies investigating glucan bioactivity.