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Introduction: Quantitative (1)H-NMR (qNMR) is a well-established method for quantitative analysis and purity tests. Applications have been reported in many areas, such as natural products, foods and beverages, metabolites, pharmaceuticals and agriculture. The characteristics of quantitative estimation without relying on special target reference substances make qNMR especially suitable for purity tests of chemical compounds and natural products. Ginsenosides are a special group of natural products drawing broad attention, and are considered to be the main bioactive principles behind the claims of ginsengs efficacy. The purity of ginsenosides is usually determined by conventional chromatographic methods, although these may not be ideal due to the response of detectors to discriminate between analytes and impurities and the long run times involved., Objective: To establish a qNMR method for purity tests of six dammarane-type ginsenoside standards., Methods: Several experimental parameters were optimised for the quantification, including relaxation delay (D1), the transmitter frequency offset (O1P) and power level for pre-saturation (PL9). The method was validated and the purity of the six ginsenoside standards was tested. Also, the results of the qNMR method were further validated by comparison with those of high performance liquid chromatography., Conclusion: The qNMR method was rapid, specific and accurate, thus providing a practical and reliable protocol for the purity analysis of ginsenoside standards., (Copyright © 2014 John Wiley & Sons, Ltd.)

This paper utilized a quantitative (1)H nuclear magnetic resonance (qHNMR) method for assessing the purity of iridoids and secoiridoids. The method was fully validated, including specificity, linearity, accuracy, precision, reproducibility, and robustness. For optimization of experimental conditions, several experimental parameters were investigated, including relaxation delay (D1), scan numbers (NS) and power length (PL1). The quantification was based on the area ratios of H-3 from analytes relative to aromatic protons from 1,4-dinitrobenzene (internal standard) with methanol-d4 as solvent. Five iridoids and secoiridoids (sweroside, swertiamarin, gentiopicroside, geniposide, genipin) were analyzed. Furthermore, the results were validated by the high performance liquid chromatography coupled with ultraviolet detection (HPLC-UV) method. It can be concluded that the qHNMR method was simple, rapid, and accurate, providing a reliable and superior method for assessing the purity of iridoids and secoiridoids., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A comprehensive two-dimensional HPLC system with an immobilized liposome chromatography (ILC) column in conjunction with an RP column (in tandem) was developed for the screening and analysis of the membrane-permeable compounds in a traditional Chinese medicine prescription Longdan Xiegan Decoction (LXD). More than 50 components in LXD were resolved using the developed separation system. Eight flavonoids and two iridoids were identified interacting with the ILC column; a system that mimics biomembranes. The results show that the developed comprehensive two-dimensional chromatography system can be used for identifying membrane permeable natural products in complex matrixes such as extracts of traditional Chinese medicine prescriptions.