Chromatographic fingerprints analysis and determination of seven components in Danmu preparations by HPLC-DAD/QTOF-MS

Background: Danmu preparations (Danmu Capsule and Danmu Syrup), which are made from Nauclea officinalis stem extracts, have good clinical efficacy in acute tonsillitis, acute pharyngitis and upper respiratory tract infection. However, there is currently no reliable and systematic method to control the quality of these two Danmu preparations.

Methods: Using high-performance liquid chromatography (HPLC) coupled with diode array detection (DAD), the fingerprints of the Danmu preparations were established at 250 nm to comprehensively investigate the stability of preparation process. The chemical constituents in the Danmu preparations were separated and identified by HPLC coupled with quadrupole-time-of-flight high-definition mass spectrometry (HPLC-Q-TOF-MS). And seven major components were simultaneously determined at dual wavelengths (250 nm, 326 nm).

Results: The results of HPLC fingerprint similarity evaluation showed that the similarity values of 25 batches of Danmu preparations were more than 0.993. Twenty-three compounds, including 10 alkaloids, 6 phenolic acids, 2 iridoids, and 5 unknown compounds, were identified or tentatively characterized according to the retention times and MS/MS fragment patterns of compounds. The developed assay method of seven components was validated with acceptable linearity, precision, repeatability, stability and recovery. The contents of strictosamide belonging to alkaloids as the most abundant constituent in Danmu Capsule and Danmu Syrup were 43,681.20-99,652.49 μg/g and 1567.83-2427.25 μg/mL respectively. The contents of protocatechuic acid which were the highest in measured phenolic acids were 2633.01-7739.78 μg/g in Danmu Capsule and 192.05-448.71 μg/mL in Danmu Syrup, respectively. As an iridoid, the contents of sweroside in Danmu Capsule and Danmu Syrup were 1573.82-2789.81 μg/g and 70.32-182.81 μg/mL, respectively.

Conclusion: The established qualitative analysis method of fingerprint can be used to attain standardization, uniformity and stability of the preparation process. Meanwhile, the quantitative analysis in this study can be used as an accurate assay method for preparations.