Abstract: In order to obtain the optimum condition of the extraction and shrimp larvae toxicities of the polysaccharide from Dendrobium moniliforme from Huohan, the effect of the extraction times, extracting time, solid-liquid ratio and extraction temperature on the yield of the polysaccharides from the stems of D.moniliforme were investigated by single factor experiments and orthogonal experiments, and shrimp larvae toxicity of the polysaccharide was evaluated by corrected mortality. The decreasing order of the four influencing factors affecting the polysaccharide yield were successively extraction temperature, extracting time, solid-liquid ratio and extraction times. The orthogonal experimental results showed that the optimal condition were extraction temperature, 60℃; solid-liquid ration, 1∶ 40; extracting time, 2 h and extraction times, 3.Being administered for 4 h, 8 h and 12 h, the LD50 values of the crude were 1.03, 0.66 and 0.38 mg/mL respectively. Under this condition, the polysaccharide content was 25.24%.Remarkable shrimp larvae toxicity was showed by the polysaccharide of wilding D. moniliforme from huoshan.

Key words: Dendrobium moniliforme (Linn.)Sw., polysaccharide, shrimp larvae toxicity, corrected mortality