Polysaccharides from Platycodon grandiflorum
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POLYSACCHARIDES FROM Platycodon grandiflorum
Wei Liu,1* Hua Liu,1 and Meiyan Han2
UDC 547.917
In this work, polysaccharides from the roots of Platycodon grandiflorum (PGPs) were extracted with hot water. After removal of proteins, pigments, and salt, the purified PGPs were isolated using DEAE-Cellulose 52, yielding three fractions. Fractions were further isolated by Sephadex G-100, and their elementary compositions, molecular weights, IR spectra, and 1H NMR spectra were obtained. Keywords: Platycodon grandiflorum, polysaccharides, extraction, purication, characterization. Platycodon grandiflorum is known as a medicinal plant for thousands of years in China. There are many reports on the pharmacological activities of Platycodon grandiflorum, which include hepatoprotective [1], expectorant [2], and enhanced insulin sensitivity effects [3]. Pharmacological studies have shown that the polysaccharides of Platycodon grandiflorum have antitumor and immune-enhancing activities [4, 5]. Hence, the polysaccharides of Platycodon grandiflorum are of great interest to researchers. Most reports on the polysaccharides of Platycodon grandiflorum have concentrated on the pharmacological aspects of these compounds. Only few reports have described methods for the extraction of the polysaccharides, and none has described the isolation or identification of these compounds. Therefore, we attempted to establish a method to isolate and quantitate the polysaccharides of Platycodon grandiflorum, as well as to determine their monosaccharide compositions and elucidate their structures. We expect this study will provide a basis for future research and application of these polysaccharides. The polysaccharides from the roots of Platycodon grandiflorum were extracted. The polysaccharide content was determined by the anthrone-sulfuric acid method combined with the 3,5-dinitrosalicylic acid (DNS) method. The anthronesulfuric acid method [6] was used to determine the total sugar content of crude polysaccharides, and the DNS method was used to determine the monosaccharide content. The content of Platycodon grandiflorum polysaccharides (PGPs) was 95.55% and the extraction yield was 42.51%. The neutral polysaccharide, eluted with distilled water, was named PGPN. The acidic polysaccharides, eluted by the stepwise addition of NaCl solutions of different concentrations, were named PGPA1, PGPA2, and PGPA3. The elution peak of PGPA2 was not collected because the content of this compound was too low. The other three fractions were further isolated by Sephadex G-100 column chromatography. The average molecular weights of PGPN, PGPA1, and PGPN3, determined by Sephadex G-200 column chromatography, were 10233, 4677, and 23442 g/mol, respectively. According to the results of TLC and GC analysis, the carbohydrate portion of PGPN contained fructose, glucose, and galactose in a ratio of 3.1:1.1:1. PGPA1 was composed of fructose and galactose in a ratio of 2.7:1, and PGPA3 contained xylose and galactose in a ratio of 3.4:1. PGPN and PGPA1 exhibited a broad intense pe
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