Rapid Identification of Alkaloids in the Rhizomes of Corydalis decumbens by Molecular Networking Base on HPLC-Q-TOF-MS/MS

The molecular network technology based on LC-MS/MS has attracted more and more attention in the research field of natural products, but the research reports in the field of natural products of Chinese herbs are very limited. In this research, a method of high performance liquid chromatography-quadrupole-time of flight mass spectrometry (HPLC-Q-TOF-MS/MS) combined with molecular networking was developed for systematically and rapidly analyzing alkaloids in 75% ethanol extract of the rhizomes of Corydalis decumbens. Chromategraphic separation was performed on a Tnature C18 column (4.6 mm×250 mm×5 μm). Acetonitrile and 0.5% (volume fraction) formic acid solution were used as the mobile phase for gradient elution with the flow rate of 1 mL/min. The MS analysis was carried out by the electrospray ionization (ESI) source at positive ion mode. The MS/MS data of the rhizomes of Corydalis decumbens extract was converted on the platform of Global Natural Products Social Molecular Networking (GNPS) platform, and clusters were established according to the similarity of fragment ions, thus obtaining a molecular network. According to the comparison of chromategraphic retention time, accurate molecular mass, characteristic fragment ions, MS/MS cracking rules and literatures, seven alkaloid types of particle clusters were identified in the molecular network, including protopine-type, protoberberine-type, tetrahydroprotoberberine-type, phthalide, simple isoquinoline, aporphine and benzylisoquinoline alkaloids, and their structures were identified respectively. The qualitative analysis results showed that 52 compounds were identified and speculated in the rhizomes of Corydalis decumbens, including 21 potential new compounds, and 6 compounds were found in the rhizomes of Corydalis decumbens for the first time. The technology of visualization of molecular networks based on data from high performance liquid chromatography-mass spectrometry combines the high efficiency separation capabilities of high performance liquid chromatography with the high sensitivity and selectivity of mass spectrometry and intuitive advantages of molecular network analysis of big data. Through the visual display of fragment ions, the aggregation and distribution of fragment ions are clearly displayed, and the interaction between molecules is intuitively searched. The alkaloids in the rhizomes of Corydalis decumbens can be quickly and accurately identified, which is the basis for further research on the pharmacodynamic substances. At the same time, the study provides reference for the identification of natural products in traditional Chinese herbs.