Physicochemical properties and antitumor activities of water-soluble native and sulfated hyperbranched mushroom polysaccharides

Abstract

A water-soluble hyperbranched β-glucan, coded as TM3b, extracted from sclerotia of an edible fungus ( Pleurotus tuber-regium) was fractioned into eight fractions coded as F1–F8 by a nonsolvent addition method. Five fractions were treated with chlorosulfonic acid at 35 °C to synthesize successfully sulfated derivatives coded as S-F2, S-F3, S-F4, S-F5, and S-F8 with degree of substitution of 0.28–0.54. The 13C NMR results of these sulfated β-glucans indicated that while the C-6 position was fully substituted, C-2, C-3, and C-4 were only partially substituted by the sulfate groups. The weight-average molecular weights ( M w) and intrinsic viscosities ([ η]) of the native and sulfated TM3b fractions were determined using multi-angle laser light scattering and viscometry in 0.15 M aq NaCl at 25 °C, respectively. The dependences of [ η] on M w for TM3b and sulfated TM3b were found to be [ η ] = 0.18 M w 0.28 ± 0.03 ( M w range from 3.30 × 10 4 to 3.90 × 10 7) and [ η ] = 2.24 × 10 - 2 M w 0.52 ± 0.06 ( M w range from 3.24 × 10 4 to 3.15 × 10 5) in 0.15 M aq NaCl at 25 °C, respectively. It revealed that both the native TM3b and its sulfated derivatives exist in a spherical chain conformation in 0.15 M aq NaCl. Furthermore, the native and sulfated TM3b fractions showed potent antitumor activities in vivo and in vitro. The sulfated derivatives exhibited relatively higher in vitro antitumor activity against human hepatic cancer cell line HepG2 than the native TM3b. Water solubility and introduction of sulfate groups were the main factors in enhancing the antitumor activities.