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Introduction: Symphytum officinale L. (comfrey, Boraginaceae) is a cultivated or spontaneously growing medicinal plant that is traditionally used for the treatment of bone fractures, hematomas, muscle pains and joint pains. A wide range of topical preparations and dried roots for ex tempore applications are marketed in European drug stores or pharmacies.Objective: The aim of this study was to perform the qualitative and quantitative analysis of pyrrolizidine alkaloids (PAs) and phenolic compounds in the hydroethanolic extracts of 16 commercial comfrey root batches purchased from 12 different European countries. Methods: Liquid chromatography hyphenated with high-resolution tandem mass spectrometry (LC-HRMS/MS) was used for the profiling of PAs and phenolic compounds, whereas LC-MS/MS and liquid chromatography with diode array detection (LC-DAD) were used for their quantification.Results: 20 PAs (i.e. intermedine, lycopsamine, acetylintermedine, acetyllycopsamine, symphytine, symphytine-N-oxide), 17 phenolic compounds (i.e. caffeic and rosmarinic acids, rabdosiin, globoidnan A, globoidnan B) and 9 nonphenolic compounds (sugars, organic and fatty acids) were fully or partly annotated in the analysed samples. In addition, the quantitative analyses revealed that globoidnan B, rabdosiin and globoidnan A are new phenolic markers that can be used together with rosmarinic acid and PAs for the quality control of commercial comfrey root batches.Conclusions: This study brings new insights into the phytochemical complexity of S. officinale, revealing not only numerous toxic PAs, but also a significant number of valuable phenolic compounds that could contribute to the bioactivities of comfreybased preparations.

Comfrey Symphytum officinale L. (true comfrey) and S. × uplandicum Nyman (a hybrid between S. asperum Lepech × S. officinale L., Russian comfrey) are used externally for the treatment of pain, inflammation and swelling of muscles and joints in degenerative arthritis, in acute myalgia, sprains, contusions and strains after accidents. Besides plant secondary compounds associated with beneficial activities (e.g. rosmarinic acid and allantoin) comfrey forms also toxic pyrrolizidine alkaloids (PA). To improve further breeding and study the genetic relationships of a comfrey collection, a sample set of 219 S. officinale and 5 hybrid plants of S. × uplandicum were analysed with 34 SNP markers by KASP (Kompetitive Allele Specific PCR), developed from a next generation sequencing approach of three different individuals of S. officinale. In parallel, the plants were analysed for the polyphenol rosmarinic acid, the purine derivative allantoin, and the toxic pyrrolizidine alkaloids. Besides the two beneficial compounds, further 13 polyphenols and 10 purine derivatives were determined. The plants were grouped into six distinct genetic clusters. Rosmarinic acid was not linked to any of the clusters, while one cluster was distinctively different for some compounds, amongst them allantoin and globoidnan A. Also linked to a certain genetic cluster was a low content of PA, which could become a valuable gene pool for minimizing PA content by breeding. A subset of the samples was analysed in a second year again where rosmarinic acid and allantoin showed a medium stability, while globoidnan A was completely unstable.

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Comfrey (Symphytum officinale L.) roots are well-known bioactive ingredients included in various cosmeceutical and pharmaceutical preparations. In this study, the influence of the post-harvest storage on the chemico-biological potential of roots collected from different European regions and stored for up to six months was investigated. Total phenolic content (TPC) and total phenolic acid content (TPAC) were spectrophotometrically estimated, whereas the levels of individual phenolic and pyrrolizidine alkaloidal markers were determined by HPLC-DAD and HPLC-MS/MS, respectively. The changes in the biological potential was tracked via antioxidant (DPPH, ABTS, CUPRAC, and FRAP) and anti-enzymatic (cholinesterase, tyrosinase, glucosidase, and amylase) assays. TPC and TPAC varied from 6.48–16.57 mg GAE/g d.w. root and from 2.67–9.03 mg CAE/g, respectively. The concentration of the four phenolics (rosmarinic acid, globoidnan A, globoidnan B, rabdosiin) and six pyrrolizidine alkaloids generally showed maximum values at 1–3 months, after which their levels significantly decreased. With respect to the bioassays, the samples showed a wide range of antioxidant and anti-enzymatic effects; however, a direct storage time–bioactivity relationship was not observed. Similar conclusions were also revealed by the multivariate and correlation analyses. Our study could improve the current knowledge of the shelf-life properties of comfrey-based products and enhance their industrial exploitation.