Isolation and Characterization of Water Soluble Polysaccharides from Isaria cicadae

Isaria cicadae Miquel is an important medicinal food fungus. The crude polysaccharides from I. cicadae were shown to significantly extend the lifespan of fruit flies in our previous study. To understand the underlying mechanism, the composition and structural characterization of polysaccharides from I. cicadae were determined. A water-soluble crude polysaccharide, obtained from a cultured Isaria cicadae by boiling-water extraction and ethanol precipitation, was fractionated by DEAE-Sepharose column chromatography. The isolate gave four polysaccharide fractions termed B-I-1, B-I-2, B-II-1 and B-II-2. The average ratio of Glu: Man: Gla in B-I-2 was 1.28:1.25:1, B-II-1 was 16.08:1:1.95, and B-II-2, was 1:2.43:2.61. B-I-1 was composed of Ara, Xyl and Glu in the ratio of 1:2.36:33.14. GC and FTIR spectra analysis combined with NMR spectroscopic analysis gave preliminary structures of the four polysaccharide fractions, which may provide an elucidation on the action mechanisms of - polysaccharide on fruit flies proliferation