CHEMICAL CHARACTERIZATION AND CYTOTOXIC ACTIVITY OF THE HETEROPOLYSACHARIDE FROM Colletotrichum gloeosporioides BIOMASS

Abstract

Colletotrichum gloeosporioides biomass was submitted to ethanolic extraction (78 degrees C, 12 h) to remove low molecular weight compounds followed by hot aqueous extraction (100 degrees C, 4 h, 4x) to obtain polysaccharides. Consecutive freezing/thawing treatments of the aqueous extract yielded a soluble fraction in cold water that was separated on five components (P-I to P-V) by gel exclusion chromatography on Sepharose CL-613. The P-IV was homogeneous on HPSEC/RID, with apparent M-w of 2.8 x 10(4) g mol(-1), Mw/Mn 1.17. 100% of total sugar. The P-IV was composed by galactose (61%), glucose (34%) and mannose (5%). H-1 and C-13 NMR analysis mono- and two-dimensional, homo- (COSY) and heteronuclear (HSQC and HMBC) showed that P-IV is a heteropolysacharide with a main chain constituted by beta-D-galactofuranosidic units (1 -> 5) and (1 -> 6) linked with some of the beta-D-galactofuranosidic (1 -> 6) units substituted in O-3 by alpha-D-glucopiranosidic residues. Cytotoxic assays (MU) indicated that the viability of CHO-K1 cells, when exposed to different heteropolysaccharide concentrations, did not show significant differences when compared to the viability of the negative control (CN), in the experimental times of 24 and 48 hours. These results suggest the possibility of new cytotoxic assays in other normal cell lines as well as in tumor cells.