Studies On Extraction, Purification And Structure Of The Polysaccharides Of Lotus Leaf And Extraction Of Its Flavonoid

Lotus leaf is the leaf of Nelumbl Nuciferea Gacrtn of a department lotus and it is both a Chinese traditional medicine and an edible portion that is promulgated by the National Health Department. Lotus leaf not only contains conventional chemical compositions such as carbohydrate, fat, protein and tannin, but also contains flavonoid and alkaloids that have obvious biology active and physiological functions. At present, researches are mainly focus on flavonoid and alkaloid in Lotus leaf, there are few reports on polysaccharides of Lotus leaf The extraction, isolation, purification as well as its structure of hydro-soluble polysaccharides and flavonoid from Lotus leaf were investigated. The optimal conditions of extracting and precipitating hydro-soluble crude polysaccharides (HSCPS) with ethanol from Lotus leaf were determined. The purification of the hydro-soluble polysaccharides was carried out by DEAE-cellulose chromatography and Sephadex G-200 column chromatography. The compositions and proportions of main monosaccharides of a pure polysaccharide from HSCPS were further identified and the rheological characters were determined. The optimum conditions of different factors for extracting hydro-soluble polysaccharides from Lotus leaf with, hot water by single factor gradient tests and orthogonal design were as follow: extracting temperature 65℃, extracting time 1h, the ratio of solid and liquid 1:25, extracting time 1 time. The efficiency of extracting HSCPS from Lotus leaf would be 9% at these conditions. The conditions of precipitating polysaccharides with ethanol were investigated by double-factorial equal repeated trials with HSCPS concentration and the volume of adding ethanol as two influential factors. The optimal conditions were obtained as follow: concentration of HSCPS shown 4% by saccharometer, adding 4 times ethanol as much as the condensate. Separated and purified by DEAE-cellulose chromatography and Sephadex G-200 column chromatography, a highest content pure acidic polysaccharide (APS) was obtained. Its molecular weight was about 165,000, which was determined by gel-filtration method and HPLC. The results of gel-filtration method and freeze-thawing method showed that APS was a pure polysaccharide. Hydrolyzed completely by acid, APS was mainlycomposed of arabinose except a little of mannose, glucose and galactose by Gas chromatography. The ratio of arabinose, mannose, glucose and galactose was 14:3:3:3.By single factor gradient tests and orthogonal tests, optimum conditions of different factors for extracting flavonoid were obtained. The results showed as follow:ethanol concentration 65%, extracting temperature 30°C, extracting time 1.5h, theratio of solid and liquid 1:25. The efficiency of extracting flavonoid from Lotus leaf would be 17% at these conditions.Furthermore, a functional drink was made from Lotus leaf as primary material.