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CPP1b is a pectic polysaccharide isolated from Codonopsis pilosula, and it possesses potent antitumor activity. In this study, a HNO3-Na2SeO3 method was performed to synthesize selenium-CPP1b (sCPP1b). The effects of BaCl2 usage amount and HNO3 concentration on the yield and selenium content of sCPP1b were investigated by single-factor experiments. Reaction time, reaction temperature and the ratio of polysaccharide to Na2SeO3 were optimized by orthogonal experimental design at three levels of each of the three factors (L9(3)(4)) based on antitumor activity, selenium content and yield of sCPP1b. Our results showed that 5h of reaction time, 60°C of reaction temperature, and 2:2 ratio of polysaccharide to Na2SeO3 were the optimal selenylation modification conditions. The validation experiments completed under the optimal conditions gave the mean selenium content and yield of sCPP1b were 478.17μg/g (RSD=5.7%) and 595mg/g (RSD=1.6%), respectively. Selenylation modification can significantly increase the antitumor activity of CPP1b in vitro. The structural characterization of sCPP1b was further characterized by Fourier-transform infrared spectroscopy, thermogravimetric analysis, and high-performance gel permeation chromatography coupled with multi-angle laser light scattering. These structure analysis results indicated that sCPP1b has been successfully selenylation modified with similar structure to polysaccharide of CPP1b., (Copyright © 2014 Elsevier B.V. All rights reserved.)

A pectic polysaccharide (CPP1b) was at first isolated from Codonopsis pilosula. Sugar analysis revealed that CPP1b is composed of rhamnose (Rha), arabinose (Ara), galactose (Gal) and galacturonic acid (GalA) with a molar ratio of 0.25:0.12:0.13:2.51. The result of esterification assay showed that about 46.7±0.4% of carboxylic groups in GalA residues existed as methyl ester. Combined with chemical and spectroscopic analyses, a preliminary structure of CPP1b was proposed as follows: 1,4-linked α-D-GalpA and 1,4-linked α-D-GalpA6Me interspersed with rare 1,2-linked β-L-Rhap, 1,2,6-linked α-D-Galp and terminal α-L-Arap. CPP1b had an average molar mass and root-mean square radius (RMS) of 1.45×10(5) Da and 29.7 nm, respectively, and presented a linear random coil conformation in 0.9% NaCl. The ultrastructure of CPP1b was further investigated by transmission electron microscope (TEM) and scanning electron microscope (SEM). CPP1b exhibited obvious cytotoxicity to human lung adenocarcinoma A549 cells in a dose- and time-dependent manner., (Copyright © 2013 Elsevier Ltd. All rights reserved.)