Abstract:

Objective: To establish the method for determining the contents of polysaccharides and to explore the extraction
technique for polysaccharides from Yunnan orchidaceae plants. Methods: The polysaccharide was extracted with the traditional water
extraction, using glucose as the standard, and the contents of polysaccharides was measured by the phenol-sulfuric acid method. With
the content of polysaccharides as an index, the univariate test were performed to find the optimal extraction technique. Results: A good
linear relationship with a regression equation of A=55.55c（mg/mL）+0.001（r=0.999 8）was achieved when the concentration of glucose
ranged between 0.000 and 0.020 mg/mL. The average recovery rate was 99.7%, and the relative standard deviation was 3.13%（n=6）.
The best conditions of color are as follows, the dosage of phenol and sulphuric acid was 1.0 mL and 7.0 mL respectively, temperature of
color was at 80 ℃, and developing time was 30 minutes. The optimal extraction of polysaccharide was performed by 2 hours soaking
using 1 : 40 volumes of solvent at 70 ℃. Conclusion: The established method is simple and accurate and the optimal extraction
technique shows good reproducibility.

Key words: Orchidaceae plants, polysaccharide, extraction conditions, determination of content, phenol sulfuric acid method