A quantitative ¹H nuclear magnetic resonance (qHNMR) method for assessing the purity of iridoids and secoiridoids

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.