Targeted Isolation of Neuroprotective Dicoumaroyl Neolignans and Lignans from Sageretia theezans Using in Silico Molecular Network Annotation Propagation-Based Dereplication

Abstract

The integration of LC-MS/MS molecular networking and in silico MS/MS fragmentation is an emerging method for dereplication of natural products. In the present study, a targeted isolation of natural products using a new in silico-based annotation tool named Network Annotation Propagation (NAP) is described. NAP improves accuracy of in silico fragmentation analyses by reranking candidate structures based on the network topology from MS/MS-based molecular networking. Annotation for the MS/MS spectral network of the Sageratia theezans twig extract was performed using NAP, and most molecular families within the network, including the known triterpenoids 1-7, could be putatively annotated, without relying on any previous reports of molecules from this species. Based on the in silico dereplication results, molecules were prioritized for isolation. In total, six dicoumaroyl 8- O-4' neolignans (8-13) and three dicoumaroyl lignans (14-16) were isolated from the twigs of S. theezans and structurally characterized by spectroscopic analyses. Isolates were evaluated for their neuroprotective activity, and compounds 14-16 showed potent protective effects against glutamate-induced oxidative stress in mouse HT22 cells at a concentration of 12.5 μM.

Characterization of Anti-Inflammatory and Antioxidant Constituents from Scutellaria baicalensis Using LC-MS Coupled with a Bioassay Method

“…Molecular networking is established through networking the chemical and structural similarity relationships between metabolites based on the similarity of their MS/MS fragments. Thus, metabolites with similar scaffolds can be grouped into clusters, confirming structural similarity [2,3,6]. This suggests the possibility of identification for unidentified nodes, if their spectra or the spectra of surrounding nodes are known by reference.…”

“…The crude MeOH extract was partitioned into n-hexane, EtOAc, n-BuOH, and H 2 O layers by liquid-liquid separation. The EtOAc layer was further subjected to column chromatography over silica gel and C 18 -reversed phase silica gel to obtain eight compounds (1)(2)(3)(4)(5)(6)(7)(8). Similarly, the n-BuOH layer was successively separated by multicolumn chromatography to yield one compound (9).…”

“…Recently, molecular networking was introduced in drug development and metabolomics, particularly for natural products containing hundreds of components [8]. Molecular networking is mainly conjugated for prioritization specific structures that are expected to be active [2][3][4] and for annotation of bioactive extracts in natural products [5,9].…”

Metabolic and metagenomic profiling of hydrocarbon-degrading microorganisms obtained from the deep biosphere of the Gulf of México

“…Nonetheless, we included authentic standards (analyzed under the same conditions as our samples) with the aim to enrich the molecular network, and these when analyzed showed a correct spectral match, thereby suggesting that the relative low annotation noted is related to the absence of such metabolites within public spectral libraries. To overcome this limitation, we applied in silico structure prediction (i.e., NAP) to obtain in silico fragmentation-based metabolite annotation as reported by others (da Silva et al 2018, Kang et al 2018, Kang et al 2019. This type of analysis allows us to annotate (by a consensus candidate structure) most of the nodes (or metabolites) within the global molecular network and to assign a chemical ontology to each annotated metabolite as per ClassyFire (Djoumbou Feunang et al 2016).…”

“…This platform analyzes the MS/MS or MS2 spectral data, and based on fragmentation pattern similarity generates molecular networks whereby compound dereplication, through spectral library matching, enriches the networks allowing to infer molecular families. Molecular networking has been successfully implemented to globally visualize the metabolome derived from individual and grouped bacterial strains (Floros et al 2016), study small molecules within a specific pathway (Vizcaino et al 2014), and for targeted-isolation of new chemical entities (Kang et al 2018), among others.…”