Purity assessment of ginsenoside Rg1 using quantitative ¹H nuclear magnetic resonance

Area of Science:

• Phytochemistry
• Analytical Chemistry
• Traditional Chinese Medicine

Background:

• Ginseng herbs (Panax ginseng, P. notoginseng, P. quinquefolius) are popular traditional Chinese medicines and natural products.
• Accurate quantification of ginsenoside Rg1 is crucial for quality control.
• High-performance liquid chromatography with ultraviolet detection (HPLC-UV) is commonly used but can introduce errors due to detector selectivity.

Purpose of the Study:

• To apply quantitative nuclear magnetic resonance (qNMR) for accurate purity assessment of ginsenoside Rg1 chemical reference substance (CRS).
• To compare qNMR results with manufacturer-reported purity and other chromatographic methods.

Main Methods:

• Quantitative nuclear magnetic resonance (qNMR) using phenylmethyl phthalate as an internal standard.
• Optimization of qNMR parameters (relaxation delay, scans, windowing) and data processing (Lorentz/Gauss deconvolution).
• Method validation for sensitivity, linearity, precision, and accuracy.

Main Results:

• The developed qNMR method demonstrated acceptable validation parameters.
• The purity of commercial Rg1 CRS was determined to be 90.34±0.21% by qNMR.
• This qNMR-determined purity was significantly lower than the manufacturer's claim (>98.0% by HPLC-UV).

Conclusions:

• qNMR provides a more accurate assessment of Rg1 CRS purity compared to HPLC-UV.
• Common LC-based methods (HPLC-UV, HPLC-ELSD, LC-MS) may overestimate Rg1 CRS purity.
• The accuracy of LC-based methods is influenced by sample loading and impurity properties.