Comprehensive identification of polyphenolic metabolites in aspen knotwood by combination of 2D NMR and HPLC-HRMS.

INTRODUCTION: European aspen (Populus tremula L.) knotwood contains large amounts of polyphenolic metabolites, mainly flavonoids, and can be considered as a promising industrial-scale source of valuable bioactive compounds. Valorization of knotwood extractives requires detailed information on their chemical composition and a relevant analytical methodology. OBJECTIVE: This study proposes combined analytical strategy for non-targeted screening and identification of polyphenolic plant metabolites and is aimed at comprehensive characterization of knotwood extractives. MATERIALS AND METHODS: Aspen knotwood acetone extract with determined antioxidant activity was an object of the study. Two-dimensional NMR spectroscopy with Structure Elucidator expert system was used for preliminary search of major components and specific structures. Liquid chromatography-high-resolution mass spectrometry (HPLC-HRMS) with data-dependent MS/MS spectra acquisition was used as a complementary technique providing molecular-level characterization and identification of the detected metabolites. RESULTS: Twenty-eight phenolic metabolites were found and identified. Among them, flavonoids, aromadendrin and naringenin, as well as their glycosylated derivatives (mainly O-glucosides) and methyl ethers, dominated. Taxifolin and its 7-O-glucoside were detected as minor components. Other detected compounds are represented by p-coumaric acid and its rutinoside and small amounts of glycosylated ferulic acid. Nineteen of the detected compounds were discovered in aspen knotwood for the first time. The results were confirmed by preparative isolation of individual compounds and NMR studies. CONCLUSION: The proposed analytical strategy based on 2D NMR and HPLC-HRMS can be considered a powerful tool in the analysis of plant extractives and allowed for the identification and semi-quantification of a large number of polyphenols in aspen knotwood.

Mucolytic Drugs Ambroxol and Bromhexine: Transformation under Aqueous Chlorination Conditions.

Bromhexine and ambroxol are among the mucolytic drugs most widely used to treat acute and chronic respiratory diseases. Entering the municipal wastewater and undergoing transformations during disinfection with active chlorine, these compounds can produce nitrogen- and bromine-containing disinfection by-products (DBPs) that are dangerous for aquatic ecosystems. In the present study, primary and deep degradation products of ambroxol and bromhexine obtained in model aquatic chlorination experiments were studied via the combination of high-performance liquid and gas chromatography with high-resolution mass spectrometry. It was shown that at the initial stages, the reactions of cyclization, hydroxylation, chlorination, electrophilic ipso-substitution of bromine atoms with chlorine, and oxidative N-dealkylation occur. Along with known metabolites, a number of novel primary DBPs were tentatively identified based on their elemental compositions and tandem mass spectra. Deep degradation of bromhexine and ambroxol gives twenty-four identified volatile and semi-volatile compounds of six classes, among which trihalomethanes account for more than 50%. The specific class of bromhexine- and ambroxol-related DBPs are bromine-containing haloanilines. Seven of them, including methoxy derivatives, were first discovered in the present study. One more novel class of DBPs associated with bromhexine and ambroxol is represented by halogenated indazoles formed through dealkylation of the primary transformation products containing pyrazoline or tetrahydropyrimidine cycle in their structure.

Analysis of pentacyclic triterpenoids and phytosterols in cloudberry (Rubus chamaemorus L.) by LC-MS/MS.

Cloudberry (Rubus chamaemorus L.) is a plant rich in various biologically active compounds. In this work, the composition and concentrations of pentacyclic triterpenoids (PCTs) and phytosterols in various parts of cloudberries were studied using high-performance liquid chromatography-tandem mass spectrometry by multiple reaction monitoring mode (MRM, targeted analysis) and precursor ion scan mode (non-targeted analysis and semi-quantitative determination). Moderately polar fractions of cloudberry leaves, sepals and berries extracts are rich in ß-sitosterol glycoside and various triterpenoid acids, among which tormentic acid (∼190-1800 µg/g dw part of cloudberries) and its hydroxyl derivatives (∼3.1-470 µg/g dw part of cloudberries) predominate. Non-polar fractions are characterised by the presence of amyrins (0.76-110 µg/g dw part of cloudberries), ß-sitosterol (62-750 µg/g dw part of cloudberries) and ß-sitosterol glycoside (∼92-360 µg/g dw sepals).

Polycommunin A, a dihydrocinnamoyl bibenzyl isolated from the moss Polýtrichum commúne, and its antioxidant activity.

A novel polyphenolic compound named Polycommunin A (1) was discovered in the aerial part of the common haircap moss (Polýtrichum commune) widely spread in boreal and temperate climate zones. Aqueous ethanol and extraction of the plant material with further isolation of polyphenolic fraction and preparative HPLC separation allowed obtaining individual compound and identifying it as dimeric dihydrocinnamoyl bibenzyl by NMR spectroscopy and high-resolution tandem mass spectrometry. Polycommunin A demonstrated high in vitro antioxidant activity determined by FRAP and PCL assays and comparable to that of Trolox and Quercetin.