Combinatorics-based chemical characterization and bioactivity comparison of different parts of traditional Chinese medicinal plants through LC-Q-TOF-MS/MS, multivariate statistical analysis and bioassay: Marsdenia tenacissima as an example.

Marsdenia tenacissima is a traditional Chinese medicinal plant used for treating cancer, and its main medicinal part is the stem. Considering the resource shortage of M. tenacissima, it is of great significance to improve its utilization efficiency. Steroids and caffeoylquinic acids, the two main components of M. tenacissima, are composed of several basic structures. Based on this rule, a novel strategy of combinatorics-based chemical characterization was proposed to analyze the constituents of roots, stems and leaves of M. tenacissima. Combinatorics was used to generate a compound library for structure alignment, which has the advantages of wide coverage and high specificity. Steroids are composed of four basic parts: core skeleton (C), substituent at position 11 (A), substituent at position 12 (B) and sugar moiety (S). Based on combinatorics, a compound library consisting of 1080 steroids was generated. Diagnostic neutral loss has been used to effectively predict the substituents at position 11 and 12 of steroids, including acetyl, 2-methylpropionyl, tigloyl, 2-methylbutyryl and benzoyl. As a result, 131, 131 and 99 components were detected from the roots, stems and leaves of M. tenacissima, respectively. Principal component analysis (PCA) was used to analyze the differences of roots, stems and leaves, and orthogonal partial least squares-discriminant analysis (OPLS-DA) was further applied to find differential components. Tenacissoside H, a critical indicator component for quality evaluation of the stem, has been proved to be a differential component between roots and stems. Notably, the relative content of tenacissoside H in the roots was significantly higher than that in the stems. The bioactivity comparison showed that roots, stems and leaves of M. tenacissima had similar scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. However, their α-glucosidase inhibitory activity was ranked as leaves > stems > roots. Therefore, besides stems, the other parts of M. tenacissima have potential medicinal value. This study not only helps to develop the resource of M. tenacissima, but also provides a paradigm for the research of other similar medicinal plants.