Optimization of experimental parameters for quantitative NMR (qNMR) and its application in quantitative analysis of traditional Chinese medicines / 药学学报

Quantitative NMR (qNMR) is a technology based on the principle of NMR. This technology does not need the references of the determined components, which supplies a solution for the problem of reference scarcity in the quantitative analysis of traditional Chinese medicines. Moreover, this technology has the advantages of easy operation, non-destructiveness for the determined sample, high accuracy and repeatability, in comparison with HPLC, LC-MS and GC-MS. NMR technology has achieved quantum leap in sensitivity and accuracy with the development of NMR hardware. In addition, the choice of appropriate experimental parameters of the pre-treatment and measurement procedure as well as the post-acquisition processing is also important for obtaining high-quality and reproducible NMR spectra. This review summarizes the principle of qHNMR, the various experimental parameters affecting the accuracy and the precision of qHNMR, such as signal to noise ratio, relaxation delay, pulse width, acquisition time, window function, phase correction and baseline correction, and their corresponding optimized methods. Moreover, the application of qHNMR in the fields of quantitation of single or multi-components of traditional Chinese medicines, the purity detection of references, and the quality analysis of foods has been discussed. In addition, the existing questions and the future application prospects of qNMR in natural product areas are also presented.

Quality standard study on Vigna radiata / 中国中药杂志

In order to control the quality of Vigna radiata, the quality control method and standard were established in this study. The tests of water content, ash and ethanol-soluble extractives of V. radiata were carried out according to the methods recoded in appendix of Chinese Pharmacopeia (2010 edition, volume 1). The TLC method was established by using vitexin and isovitexin as references, and a mixture of acetate-method-water (10: 1.7 : 1.3) as the developing solvent system on GF254 thin layer plate. The contents of vitexin and isovitexin were determined by HPLC on a Prevail C18 (4.6 mm x 250 mm, 5 microm) column, using acetonitrile: water (23 : 77) as mobile phase at a flow rate of 1.0 mL x min(-1). The column temperature is 30 degrees C and the detection wavelength is 337 nm. As a result, vitexin, isovitexin and the other constituents were well separated on TLC detected under the UV light (254 nm). The methodology validation for the assay of vitexin and isovitexin presented that they were in good linear correlation in the ranges of 6.12-98 mg x L(-1) and 6.85-109.6 mg x L(-1), with the regression equations of Y = 46.213X - 7.100 (r = 1.000) and Y = 54.515X + 6.829 (r = 1.000), and the average recoveries were 98.2% (RSD 1.9%) and 97.2% (RSD 0.79%), respectively. The content ranges of vitexin and isovitexin from 25 different batches of V. radiata were 1.076-2.062 mg x g(1) and 1.127-2.303 mg x g(-1), respectively. suggesting that the qualities of V. radiata are relatively stable. The ethanol-soluble extractives, water content and total ash of 25 samples varied in the ranges of 13.27% - 18.46%, 9.59% - 12.43% and 2.63% - 3.53%, respectively. All of the above data proved that the established quality of control method V. radiata is specific and accurate, which can be used for the quality control of this drug.