Physicochemical properties and antitumor activities for sulfated derivatives of lentinan

Five fractions of lentinan, a beta-(1 -> 3)-D-glucan bearing beta-(1 -> 6)-D-glucopyranosyl branches, were treated with chlorosulfonic acid for 90 min at 60 degrees C in pyridine medium to synthesize water-soluble sulfated derivatives having the substitution degree of 1.44-1.76. The C-13 NMR spectra of the sulfated beta-glucans indicated that the C-6 position was preferentially substituted by the sulfate groups. The values of the weight-average molecular weight (M-w), radius of gyration (< S-2 >(1/2)(z)), and intrinsic viscosity ([eta]) of the sulfated lentinan fractions were determined by size-exclusion chromatography with multi-angle laser light scattering (SEC-MALLS) and viscometry in 0.15 M aq NaCl at 25 degrees C, respectively. The dependence of [eta], on M-w for the sulfated lentinan was found to be [eta] = 8.93 x 10(-3) M-w (0.73 +/- 0.02) (mL/g) in 0.15 M aq NaCl (for M-w ranging from 14.6 x 10(4) to 50.4 x 10(4)). On the basis of the Yamakawa-Fujii-Yoshizaki (YFY) theory, the conformational parameters of the sulfated lentinan were calculated as 950 nm(-1) for the molar mass per unit contour length (M-L), 4.8 nm for the persistence length (q), and 13.9 for the characteristic ratio (C-infinity), indicating relatively extended single flexible chains in solution. The sulfated glucan fractions exhibited in vitro antiproliferative activities against sarcoma 180 (S-180) cells, and their inhibition ratios were lower than that of the triple-helix lentinan, but higher than that for the one with single random-coil lentinan chains. (C) 2009 Published by Elsevier Ltd.