Quantitative analysis of highly similar salvianolic acids with 1H qNMR for quality control of traditional Chinese medicinal preparation Salvianolate Lyophilized Injection

• We reported a qNMR method for simultaneously determining nine highly similar salvianolic acids including three pairs of diastereomers.
• This method was compared with a HPLC method and the results showed a good agreement between these two methods.
• Comparing to the HPLC method, the qNMR method was easier, faster, more comprehensive, and do not need the rare reference standards thus was more suitable for the quality control of SLI.
• This method was coupled with an advanced statistical analysis to provide data on the quality control of SLI.

Salvianolate Lyophilized Injection (SLI), a traditional Chinese medicinal (TCM) preparation which is used to treat stroke, is composed of multiple salvianolic acids from the aqueous extracts of Salvia miltiorrhiza, and includes mainly protocatechualdehyde, rosmarinic acid, salvianolic acid B, salvianolic acid D, salvianolic acid E, diastereomer of salvianolic acid E, salvianolic acid Y, lithospermic acid and diastereomer of lithospermic acid. It is difficult to quantitatively control the quality of SLI using traditional high performance liquid chromatography due to the highly similar structure of these constituents including three pairs of diastereomers and the lack of commercial resources for most of these constituents as standards. Thus, a highly reproducible, fast, accurate and simple 1H quantitative nuclear magnetic resonance (qNMR) method without the need for calibration curves and complex computation was established by optimizing the solvent system and acquisition parameters to simultaneously determine the nine salvianolic acids and mannitol in SLI. This method was validated and successfully used to determine 10 batches of SLI and the qNMR data were further analyzed with a vector including angle cosine and the partial least squares method for the quality control of SLI. The results indicated that qNMR can be used as a routine method for the quality control of SLI and may have potential in the quantification of diastereomers in other TCM preparations.

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