Hydroxypropylation confers cytotoxic activity to (1→3), (1→6)-β-D-glucans against B16-F10 murine melanoma cells

Mushroom-derived (1→3),(1→6)-β-D-glucans exhibit diverse biological activities, including effects relevant to cancer research, which may be modulated through chemical modification. In the present study, sequential hydroxypropylations were performed on a highly purified (1→3),(1→6)-β-D-glucan (NM-Glc) from the mushroom Lactarius quieticolor to generate derivatives with distinct structural characteristics (HP1 and HP2). The derivatives were characterized by NMR, GC-MS, and SEC-MALS-RI, which suggested preferential hydroxypropyl substitution at the O-6 and O-4 positions. Each sample (NM-Glc (unmodified glucan; Mw 1.26 × 10⁵ g.mol^-1), HP1 (Mw 4.02 × 10⁴ g.mol^-1, MS: 0.70, DS_Frac: 0.38, DS_Sub: 0.57), and HP2 (Mw 5.66 × 10⁴ g.mol^-1, MS: 0.94, DS_Frac: 0.47, DS_Sub: 0.83) was evaluated for its biological effects on B16-F10 murine melanoma cells at 10, 100, and 1000 μg.mL^-1. NM-Glc did not exhibit significant cytotoxicity toward tumor cells under the evaluated conditions, whereas the hydroxypropyl-modified glucans exhibited cytotoxicity at 100 and 1000 μg.mL^-1 and reduced cell adhesion to the substrate (observed only for HP2 at 1000 μg.mL^-1). Acridine orange/ethidium bromide (AO/EB) staining revealed an increased proportion of apoptotic-like cells following treatment with HP1 and HP2, with HP2 producing the most pronounced effects. Therefore, hydroxypropylation is a promising strategy to generate (1→3),(1→6)-β-D-glucans capable of reducing melanoma cell viability in vitro.