Preparative isolation of arylbutanoid‐type phenol [(‐)‐rhododendrin] with peak tailing on conventional C18 column using middle chromatogram isolated gel column coupled with reversed‐phase liquid chromatography

Reversed‐phase liquid chromatography coupled with middle chromatogram isolated gel column was employed for the efficient preparative separation of the arylbutanoid‐type phenol [(‐)‐rhododendrin] from Saxifraga tangutica. Universal C18 (XTerra C18) and XCharge C18 columns were compared for (‐)‐rhododendrin fraction analysis and preparation. Although tailing and overloading occurred on the XTerra C18 column, the positively charged reversed‐phase C18 column (XCharge C18) overcame these drawbacks, allowing for favorable separation resolution, even when loading at a on a preparative scale (3.69 mg per injection). The general separation process was as follows. First, 365.0 mg of crude (‐)‐rhododendrin was enriched from 165 g Saxifraga tangutica extract via a middle chromatogram isolated gel column. Second, separation was performed on an XTerra C18 preparative column, from which 73.8 mg of the target fraction was easily obtained. Finally, the 24.0 mg tailing peak of (‐)‐rhododendrin on XTerra C18 column was selectively purified on the XCharge C18 analytical column. These results demonstrate that the tailing nonalkaloid peaks can be effectively used for preparative isolation on XCharge C18 columns.     

Targeted isolation of 1,1-diphenyl-2-picrylhydrazyl inhibitors from Saxifraga atrata and their antioxidant activities

Saxifraga atrata is an important traditional Tibetan medicine used to treat cough and pneumonia, and has tremendous medicinal potential. In this study, we devised a technique to separate 1,1-diphenyl-2-picrylhydrazyl inhibitors from a methanol extract of S. atrata. The material was first processed using MCI GEL CHP20P medium-pressure liquid chromatography, yielding 1.1 g of the target fraction Fr2. Subsequently, online hydrophilic interaction liquid chromatography-1,1-diphenyl-2-picrylhydrazyl assay was used to identify prospective 1,1-diphenyl-2-picrylhydrazyl inhibitors, and two 1,1-diphenyl-2-picrylhydrazyl inhibitor fractions (Fr24 and Fr25) were identified from Fr2. Then, medium-pressure preparation was continued using an XIon column to separate two 1,1-diphenyl-2-picrylhydrazyl inhibitor fractions (Fr24 and Fr25). The target compound was concentrated in fractions Fr24 and Fr25 using reverse-phase liquid chromatography during further separation procedures. Finally, the purity, structure, and 1,1-diphenyl-2-picrylhydrazyl inhibitory activity of the isolated 1,1-diphenyl-2-picrylhydrazyl inhibitors were determined. Two 1,1-diphenyl-2-picrylhydrazyl inhibitors (adenosine with the half maximal inhibitory concentration of 66.87 ± 14.33 μM and (-)-4-O-(E)-caffeoyl-l -threonic acid with the half maximal inhibitory concentration of 59.06 ± 5.02 μM) were isolated with purities exceeding 95%. The results showed that this technology is effective in the targeted separation of antioxidants from natural products.     

Synthesis of graft copolymer of ethyl cellulose through living polymerization and its self-assembly

Copolymers of ethyl cellulose (EC) with polystyrene (PSt) were synthesized through atom transfer radical polymerization (ATRP). The molecular weight of graft copolymers increased without any trace of the EC macro-initiator, and the polydispersity of the side chains was low. The molecular weight of the side chains increased with the monomer conversion. Kinetic study indicated that the polymerization was first order. The micelle characteristics of the graft copolymer in acetone were investigated using dynamic light scattering (DLS), atom force microscopy (AFM) and transmission electron microscopy (TEM). With increasing the concentration, micelles were gradually formed from the solution. The TEM and AFM images indicated that the micelles had spherical shape and showed core-shell structure.     

Multispectroscopic studies for the identification of archaeological frankincense excavated in the underground palace of Bao'en Temple,Nanjing: near infrared,midinfrared, and Raman spectroscopies

Five resinous incense materials excavated from the underground palace of Bao'en Temple, Nanjing, were studied by a multianalytical approach of near infrared, midinfrared, and Fourier transform Raman spectroscopies. By comparing the multispectroscopic features of five specimens, these incense materials were identified to the same substance. Subsequent analysis and comparison of the ancient incense materials and three modern reference specimens were carried out, and the results indicated that the excavated incense materials were frankincense, with its major component of triterpenoids. This work performs, for the first time, a comprehensive spectroscopic study for the Chinese excavated incense materials, demonstrating that a combined use of near infrared, midinfrared, and Fourier transform Raman spectroscopies is an efficient technique to identify an excavated incense. Copyright © 2012 John Wiley & Sons, Ltd.     

Densely grafting copolymers of ethyl cellulose through atom transfer radical polymerization

Densely grafting copolymers of ethyl cellulose with polystyrene and poly(methyl methacrylate) were synthesized through atom transfer radical polymerization (ATRP). First, the residual hydroxyl groups on the ethyl cellulose reacted with 2‐bromoisobutyrylbromide to yield 2‐bromoisobutyryloxy groups, known to be an efficient initiator for ATRP. Subsequently, the functional ethyl cellulose was used as a macroinitiator in the ATRP of methyl methacrylate and styrene in toluene in conjunction with CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as a catalyst system. The molecular weight of the graft copolymers increased without any trace of the macroinitiator, and the polydispersity was narrow. The molecular weight of the side chains increased with the monomer conversion. A kinetic study indicated that the polymerization was first‐order. The morphology of the densely grafted copolymer in solution was characterized through laser light scattering. The individual densely grafted copolymer molecules were observed through atomic force microscopy, which confirmed the synthesis of the densely grafted copolymer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4099–4108, 2005     

α,α-二溴甲苯引发的苯乙烯原子转移自由基聚合研究

自从Ｍａｔｙｊａｓｚｅｗｓｋｉ等[1,2 ] 发现原子转移自由基聚合 (ＡＴＲＰ)以来 ,寻求新的双多官能引发剂是该领域的重要研究方向之一[3～ 7] .2 0 0 0年 ,我们[8]曾报道了α ,α 二溴乙酸乙酯可作为丙烯酸酯ＡＴＲＰ的双官能引发剂 ,并基于其两端增长的活性聚合性质合成了ＰＳ ｂ ＰＢＡ ｂ ＰＳ和ＰＭＭＡ ｂ ＰＢＡ ｂ ＰＭＭＡ两种三嵌段共聚物 .与此同时 ,Ｈｏｃｋｅｒ等[9] 通过比较氯化苄与α ,α 二氯甲苯引发的苯乙烯ＡＴＲＰ的聚合速度 ,认为α ,α 二氯甲苯是苯乙烯ＡＴＲＰ的双官能引发剂 .当我们参照上述结果 ,用α ,α 二…