Tissue-specific metabolite profiling of Fallopia multiflora (Heshouwu) and Fallopia multiflora var. angulata by mass spectrometry imaging and laser microdissection combined with UPLC-Q/TOF-MS.

Heshouwu, derived from root tubers of Fallopia multiflora (Thunb.) Harald., is a well-known herb used for millennia in traditional Chinese medicine. However, different forms of root tubers of Heshouwu have occurred in current Chinese herbal market and used in clinic, although it is still unknown whether their quality is consistent. In the present study, a mass spectrometry imaging and laser microdissection combined with UPLC-Q/TOF-MS were therefore used for the metabolite profiling on the whole and different parts of root tubers of F. multiflora and F. multiflora var. angulata. Our results suggested that the character of "woody heart" root tubers of F. multiflora was similar to that of F. multiflora var. angulata, but the latter had more phloem fibers and larger diameter vessel in the normal vascular bundle. Moreover, 140 compounds including stilbenes, anthraquinones, phenolic acids, naphthalenes, and other compounds were identified or putatively characterized from F. multiflora and F. multiflora var. angulata. Both unsupervised principal component analysis (PCA) and supervised Orthogonal Partial Least Squares Discrimination Analysis (OPLS-DA) multivariate statistics allowed discriminating F. multiflora and F. multiflora var. angulata. And a total of 32 potential markers were identified. The tissue-specific study indicated that the compounds in the phelloderm of F. multiflora and F. multiflora var. angulata were the most abundant. This is the first study on metabolite profiling and comparison of root tubers between F. multiflora and F. multiflora var. angulata, which would provide reasonable basis for further quality evaluation and safe medication of F. multiflora.