Metabolomic and quality discrimination of Stemona tuberosa radix extracts using LC-MSn

Stemona tuberosa has been used as an antitussive medicine and insecticidal agent since the 6th century A.D. With the understanding of alkaloids as the active compounds, previous studies showed that profiles of alkaloids varied significantly, which raised the issue of quality control. Our study firstly demonstrated a considerable intraspecific chemical variation of S. tuberosa using chemometric methods (Principle Component Analysis and Heatmap) based on data from liquid chromatography – mass spectrometry (LC-MSn). This variation could reflect potential chemotypes, rather than the geographical origins of the samples. Qualities of 23 samples collected from China and Vietnam were evaluated by the amounts of antitussive alkaloids (neotuberostemonine, neostenine, croomine, stemoninine, tuberostemonine and tuberostemonine H) and croomine, an alkaloid responsible for the negative effects. Chemical fingerprints of extracts from crude source material, granules and decoction of S. tuberosa were determined and the dose equivalence between granules and decoction was found to be similar. Extracts with methanol resulted in the formation of alkaloidal artifacts and it is suggested that in future studies other solvents, such as water should be used in Stemona alkaloids extraction. The discovery of the considerable chemical variation and the relatively high abundance of croomine in some samples, raises serious concerns about the quality standards of the commercialized products from S. tuberosa. Manufactures should ensure they have sources of S. tuberosa that have the appropriate levels of the antitussive alkaloids and low levels of croomine.