Qualitative and quantitative analysis of cyclovirobuxine D and related substances by HPLC-CAD in the active pharmaceutical ingredient of Huangyangning tablets

We have developed a new method using HPLC-CAD (charged aerosol detector) for the quantitative analysis of cyclovirobuxine D and related substances in the API of Huangyangning tablets. The related substances were further studied by HPLC-Q-Exactive coupled with hybrid quadrupole-orbitrap mass spectrometry. A HILIC column of XBridge Amide (4.6 mm×250 mm, 5 μm) was used, and the mobile phase was composed of acetonitrile and 100 mmol·L^-1 ammonium formate (85:15), which was adjusted to pH 2.8 with formic acid. Isocratic mode elution was adopted at a flow rate of 1.1 mL·min^-1. The column temperature was set at 30℃. For CAD, the temperature of atomization and gas pressure were respectively set at 35℃ and 62.2 psi. This method detected and quantified five related substances to cyclovirobuxine D. The results showed that the LOD and LOQ of cyclovirobuxine D was 12.588 ng and 28.323 ng, respectively with an average recovery of 95.74% (RSD=1.79%, n=6). The content of cyclovirobuxine D in 12 batches of API samples provided by three manufacturers was from 79.94% to 88.49%, with an average value of 82.20%. The total content of the five related substances was from 15.99% to 22.15% with an average value of 20.10%, using an external standard method with cyclovirobuxine D as the reference and according to the CAD uniform response to non-volatile substances. The newly developed HPLC-CAD method has advantages in terms of the comprehensiveness of signals from Buxus alkaloids without UV absorption and with high sensitivity to its trace-related substances; the method yields good separation between the components and is compatible with mass spectrometry. It is applicable for the accurate quantitative analysis of main components and related substances in the API of Huangyangning tablets.