Structural characterization and discrimination of Paris polyphylla var. yunnanensis by a molecular networking strategy coupled with ultra-high-performance liquid chromatography with quadrupole time-of-flight mass spectrometry

Exploration of the profiles of steroidal saponins from Rhizoma Paridis and their metabolites in rats by UPLC-Q-TOF-MS/MS

INTRODUCTION

Steroidal saponins characterised by intricate chemical structures are the main active components of a well-known traditional Chinese medicine (TCM) Rhizoma Paridis. The metabolic profiles of steroidal saponins in vivo remain largely unexplored, despite their renowned antitumor, immunostimulating, and haemostatic activity.

OBJECTIVE

To perform a comprehensive analysis of the chemical constituents of Rhizoma Paridis total saponins (RPTS) and their metabolites in rats after oral administration.

METHOD

The chemical constituents of RPTS and their metabolites were analysed using ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS/MS).

RESULTS

A reliable UPLC-Q-TOF-MS/MS method was established, and a total of 142 compounds were identified in RPTS. Specifically, diosgenin-type saponins showed the diagnostic ions at m/z 415.32, 397.31, 283.25, 271.21, and 253.20, whereas pennogenin-type saponins exhibited the diagnostic ions at m/z 413.31, 395.30, and 251.20. Based on the characteristic fragments and standard substances, 15 specific metabolites were further identified in the faeces, urine, plasma, and bile of rats. The metabolic pathways of RPTS, including phase I reactions (de-glycosylation and oxidation) and phase II reactions (glucuronidation), were explored and summarised, and the enrichment of metabolites was characterised by multivariate statistical analysis.

CONCLUSION

The intricate RPTS could be transformed into relatively simple metabolites in rats through de-glycosylation, which provides a reference for further metabolic studies and screening of active ingredients for TCM.

Unraveling the serial glycosylation in the biosynthesis of steroidal saponins in the medicinal plant Paris polyphylla and their antifungal action

Sugar-sugar glycosyltransferases play important roles in constructing complex and bioactive saponins. Here, we characterized a series of UDP-glycosyltransferases responsible for biosynthesizing the branched sugar chain of bioactive steroidal saponins from a widely known medicinal plant Paris polyphylla var. yunnanensis. Among them, a 2'-O-rhamnosyltransferase and three 6'-O-glucosyltrasferases catalyzed a cascade of glycosylation to produce steroidal diglycosides and triglycosides, respectively. These UDP-glycosyltransferases showed astonishing substrate promiscuity, resulting in the generation of a panel of 24 terpenoid glycosides including 15 previously undescribed compounds. A mutant library containing 44 variants was constructed based on the identification of critical residues by molecular docking simulations and protein model alignments, and a mutant UGT91AH1Y187A with increased catalytic efficiency was obtained. The steroidal saponins exhibited remarkable antifungal activity against four widespread strains of human pathogenic fungi attributed to ergosterol-dependent damage of fungal cell membranes, and 2'-O-rhamnosylation appeared to correlate with strong antifungal effects. The findings elucidated the biosynthetic machinery for their production of steroidal saponins and revealed their potential as new antifungal agents.

Ultra-high-performance liquid chromatography combined with electrospray ionization quadrupole time-of-flight mass spectrometry and molecular networking analysis to investigate the chemodiversity of bioactive extracts of Annona jahnii Saff. fungi from the Brazilian Amazon

RATIONALE

Annona species are of interest for the isolation of bioactive molecules; however, studies of Annona jahnii Saff. are limited. The exploration of bioactive metabolites of endophytes isolated from this species is unprecedented and allows the preservation of the host plant, in addition to enabling the discovery of compounds with promising biological activities.

METHODS

Ethyl acetate extracts from the cultured media of five fungi were obtained. The antioxidant capacity of the extracts was measured using the 1,1-diphenyl-2-picrylhydrazyl free radical method. Antimicrobial activity was determined using the microdilution method in broth in 96-well plates. The exploration of the metabolic profile of the extracts and dereplication of the compounds were performed using ultra-high-performance liquid chromatography/electrospray ionization/tandem mass spectrometry (UHPLC/ESI-MS/MS) combined with analysis using molecular networking (MN).

RESULTS

A total of 1818 MS features were detected in the five selected extracts, of which 39 compounds were putatively identified. The secondary metabolites with the highest abundance were alkaloids, naphthopyrons, and cytochalasins. Other secondary metabolites include fumonisins, coumarin, and a meroterpenoid. Most of these compounds are related to specific biological properties such as antioxidant, anti-inflammatory, antimicrobial, antiviral, and antitumor activities. Extracts F398 and F403 showed inhibitory activity of the four pathogens tested. Extracts F475 and F506 did not inhibit the growth of Staphylococcus aureus, and F407 did not inhibit the growth of Escherichia coli in addition to having potent antioxidant activity, with IC₅₀ values of 10 μg/mL or less.

CONCLUSIONS

The use of UHPLC/ESI-MS/MS data combined with MN proved useful in the dereplication of bioactive molecules of complex extracts that are still unexplored. These initial investigations should significantly assist in further research and increase the efficiency and speed in the discovery of new sources of secondary metabolites and new natural products.

A Mass Spectrometry Based Metabolite Profiling Workflow for Selecting Abundant Specific Markers and Their Structurally Related Multi-Component Signatures in Traditional Chinese Medicine Multi-Herb Formulae

In Traditional Chinese Medicine (TCM), herbal preparations often consist of a mixture of herbs. Their quality control is challenging because every single herb contains hundreds of components (secondary metabolites). A typical 10 herb TCM formula was selected to develop an innovative strategy for its comprehensive chemical characterization and to study the specific contribution of each herb to the formula in an exploratory manner. Metabolite profiling of the TCM formula and the extract of each single herb were acquired with liquid chromatography coupled to high-resolution mass spectrometry for qualitative analyses, and to evaporative light scattering detection (ELSD) for semi-quantitative evaluation. The acquired data were organized as a feature-based molecular network (FBMN) which provided a comprehensive view of all types of secondary metabolites and their occurrence in the formula and all single herbs. These features were annotated by combining MS/MS-based in silico spectral match, manual evaluation of the structural consistency in the FBMN clusters, and taxonomy information. ELSD detection was used as a filter to select the most abundant features. At least one marker per herb was highlighted based on its specificity and abundance. A single large-scale fractionation from the enriched formula enabled the isolation and formal identification of most of them. The obtained markers allowed an improved annotation of associated features by manually propagating this information through the FBMN. These data were incorporated in the high-resolution metabolite profiling of the formula, which highlighted specific series of related components to each individual herb markers. These series of components, named multi-component signatures, may serve to improve the traceability of each herb in the formula. Altogether, the strategy provided highly informative compositional data of the TCM formula and detailed visualizations of the contribution of each herb by FBMN, filtered feature maps, and reconstituted chromatogram traces of all components linked to each specific marker. This comprehensive MS-based analytical workflow allowed a generic and unbiased selection of specific and abundant markers and the identification of multiple related sub-markers. This exploratory approach could serve as a starting point to develop more simple and targeted quality control methods with adapted marker specificity selection criteria to given TCM formula.