Urtica Fissa Polysaccharide: Isolation, Activities And Structure Characterization

Nettle plants have been widely used as folk medicine for a long history. Related literatures have reported that nettle (Urtica) is a common botanical medicine and nettle polysaccharide is effective in anti-inflammatory,it is meaningful and valuable to further study of the polysaccharide from Urtica.In this study, Urtica fissa was choosed for following research. Comparing the polysaccharide content in extracts of Urtica collected from three different areas,results showed Urtica fissa from Guizhou was the highest in polysaccharide content.Based on our previous preparation of Urtica fissa polysaccharide in laboratory, we developed a large-scale process to manufacture polysaccharide for using as therapeutic agent. Urtica fissa roots and stems were preextracted with ethanol to remove coloured materials and then extracted with boiling water. The aqueous extract was ultrafilted to remove small molecular substances using an ultrafiltion system including a pump and a hollow fiber microporous membrane cartridge with molecular weight cutoff 5000, the concentrated fraction was lyophilized to obtain the crude polysaccharide fraction. The percentage of total sugar in crude fraction was determined by phenol-sulfuric acid method, the reducing saccharide (including oligo or monosaccharides) content was determined by DNS method, the percentage of polysaccharide in crude fraction was calculated based on percentage of total sugar minus that of reducing sugars. The results showed that polysaccharide was the main component in crude fraction.To investigate the anti - inflammatory and analgesic effect of polysaccharide, cotton pellets granuloma model and the twisting- body and thermal - plate methods were used. The results showed that polysaccharide fraction of Urtica fissa had significant inhibitory effect on cotton pellets granuloma in rats, but less significant analgesic effect on heat - induced pain or acetic acid - induced pain. The crude polysaccharide was treated by Sevage method to remove protein and purified by chromatography on DEAE- Cellulose,DEAE-Sephadex A-25 and Sepharose 6B to obtain purified four polysaccharides. The homogeneity was analyzed using electrophoresis and HPLC. One of purified polysaccharide (20B) was further studied on its physico-chemical properties and structural characterization using 1DNMR and 2DNMR. Polysaccharide is composed of D-arabinofuranosyl, D-galactopyranosyl, D-glucopyranosyl residues. Molecular weights were determined to be Mn 4140, Mw 5118 and Mz 6356. The main 1H- and 13C-signals, anomeric proton configurations were determined as possible by various 1H-1H and 1H-13C correlation experiments such as DQF-COSY, TOCSY and HSQC. The sequence of sugar residues was established from analysis of HMBC spectrum. Results showed that the structure of polysaccharide 20B may be expressed as follows:...