Conformational, antioxidant and antibacterial properties of polysaccharides extracted from edible mushrooms of Pleurotus species

Polysaccharide fractions were extracted from three species of edible mushroom belonging to genus Pleurotus: P. florida, P. ostreatus and P. sajor-caju. The cold water, hot water and alkali soluble polysaccharides were precipitated using ethanol. Fractions thus obtained were characterized for presence of specific functional group by vibrational spectroscopy. Spectra of all fractions showed occurrence of several intense overlapped IR bands in the region of 1200-900 cm⁻¹ (mainly C-C and C-O stretching vibrations in pyranoid rings) indicating the presence of polysaccharides as the major component. The (1→3, 1→6) linked β-conformation of the glucans was marked by presence of characteristic IR peaks and spectral similarity with a standard (1→3, 1→6) β-D-glucan in all the fractions. The antioxidant activity of the β-glucan extracts was observed to be variable among the three species. The P. ostreatus NaOH soluble glucans showed the maximum DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity amongst all. The extracted β-glucans exhibited moderate antagonism towards human pathogenic bacteria Yersinia enterocolitica and Salmonella typhi.