A simple and specific quantitative method for determination of dictamnine in Dictamni Cortex by 1H NMR spectroscopy

Abstract

Dictamni Cortex (Baixianpi) is a commonly used medicinal herb in traditional Chinese medicines (TCMs), possessing various bioactivities. Quinoline alkaloids are regarded as one of the main active components in this herb. In the present study, a more convenient, specific and accurate analytical method using ¹H NMR has been developed for the quantitative determination of dictamnine, one of the main active quinoline alkaloids in Dictamni Cortex. In a less crowded region δ 8.0–8.5, the signal of H-5 of dictamnine was well separated from other signals in chloroform-d₁. The quantity of dictamnine was calculated by means of the integral value of H-5 of dictamnine to that of the known amount of internal standard, pyrazine. This assay was precise and reproducible, with RSDs less than 3%. The recovery results of dictamnine were observed between 92.10 and 108.10% and the limit of detection (LOD) and limit of quantitation (LOQ) were 3.3 μg ml⁻¹ and 13.2 μg ml⁻¹, respectively. This newly developed method was proven to be highly accurate, precise and robust, for the determination of dictamnine in Dictamni Cortex. The results obtained from ¹H NMR method were also compared with those from conventional HPLC method, and no remarkable difference was found between these two methods.