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

摘要： 从黑节草（Dendrobium candidum Wall．ex Lindl．）分离纯化到三种多糖：黑节草多糖 I，II和III.根据IR、1H及13C NMR、酸水解和O-乙酚基分析，确定它们为一类 O-乙酰葡萄甘露聚糖。由过碘酸氧化、Smith降解、部分酸水解和甲基化分析，证明了它们由几个β-(1→3)D - 甘露吡喃糖基和一个β-(1→4)-D - 葡萄吡喃糖基重复构成主链。支链可能由（l→4)－D-葡萄糖基和其它戊糖基组成，并连接在主链葡萄糖基的 2-、3-或 6-位上。用凝胶层析法测得它们的分子量（MW）为1000 000（I），500 000（II）和120 000（III)。

关键词: 黑节草, 多糖, O-乙酰葡萄甘露聚糖