Abstract: Three polysaccharides, named candiduman I, II and III, have been isolated and purified from Dendrobium candidum. They were shown to be 1iomo-geneous by electrophoresis and gel chromatography. According to IR,1H and 13C NMR, acid hydrolysis and determination of 0-acetyl group, they were identified as the 0-acetylglucomannan. From the results of Smith degradation, partial acid hydrolysis and methylation analysis, it was concluded that the polysaccharides possessed backbone consisting of repeating some 8-(l-3)-linked D-mannopyranosyi residues and one β-(l-4) -linked D-glucopyranosyi residue, and probably possessed branched chains consisting of β-(l-4) -linked D-glucopyranosyi residues and p-pentose end groups. Side chains are atta-ched to 2-, 3-, or 6- of D-glucopyranosyi, residues of backbone. Their average molecular weights were estimated to be ca. 1 000 000(I ), 500 000(II), 120 000 (III) respectively by gel chromatography.

Key words: Dendrobium candidum