Abstract:

Polysaccharides were extracted from Gastrodia elata B1 with water and precipitated by ethanol, purified through cetyltrimethylammonium bromide (CTAB) complex method and Sepharose 6-fast flow chromatography. The structural characterization of Gastrodia elata B1 polysaccharides (GPS) was conducted by means of IR and NMR techniques. In simulated chemical reaction system, the scavenging effects of GPS on ·OH and O2· were investigated via Fenton reaction and pyrogallol autoxidation method repectively. Results showed that the optimal extraction technology conditions are as follows: extraction temperature 80 ℃, extraction times 2, solid-liquid ratio 1:40 and using 75% ethanol as precipitant. IR and 1H-NMR analysis indicated that GPS are composed of D-glucopyranose. The 13C-NMR results revealed that GPS are a (1→4) linked α-D-glucan, which is attached by glucosyl side chains at O-6 of the glucosyl residues of main chain. The IC50 of crude GPS and purified GPS to ·OH are 1.18 mg/ml and 1.62 mg/ml respectively, and those O2· are 0.81 mg/ml and 1.03 mg/ml respectively. In conclusion, GPS have a structure of (1→4) linked α-D-glucan with branching residues and certain capacity of scavenging free radicals.

Key words: Gastrodia elata B1, polysaccharides, extraction, structure, free radicals scavenging