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Plant metabolite profiling reveals the diversity of secondary or specialized metabolites in the plant kingdom with its hundreds of thousands of species. Specialized plant metabolites constitute a vast class of chemicals posing significant challenges in analytical chemistry. In order to be of maximum scientific relevance, reports dealing with these compounds and their source species must be transparent, make use of standards and reference materials, and be based on correctly and traceably identified plant material. Essential aspects in qualitative plant metabolite profiling include: (i) critical review of previous literature and a reasoned sampling strategy; (ii) transparent plant sampling with wild material documented by vouchers in public herbaria and, optimally, seed banks; (iii) if possible, inclusion of generally available reference plant material; (iv) transparent, documented state-of-the art chemical analysis, ideally including chemical reference standards; (v) testing for artefacts during preparative extraction and isolation, using gentle analytical methods; (vi) careful chemical data interpretation, avoiding over- and misinterpretation and taking into account phytochemical complexity when assigning identification confidence levels, and (vii) taking all previous scientific knowledge into account in reporting the scientific data. From the current stage of the phytochemical literature, selected comments and suggestions are given. In the past, proposed revisions of botanical taxonomy were sometimes based on metabolite profiles, but this approach ("chemosystematics" or "chemotaxonomy") is outdated due to the advent of DNA sequence-based phylogenies. In contrast, systematic comparisons of plant metabolite profiles in a known phylogenetic framework remain relevant. This approach, known as chemophenetics, allows characterizing species and clades based on their array of specialized metabolites, aids in deducing the evolution of biosynthetic pathways and coevolution, and can serve in identifying new sources of rare and economically interesting natural products. [Display omitted] • Plant metabolic profiling and reporting on it are challenging. • Botanical, phytochemical, and analytical pitfalls are discussed. • Artefact formation as well as botanical and chemical misassignments are problematic. • Data interpretation of chemophenetic/chemosystematic papers is often poor. • Recommendations for authors and editors are given. [ABSTRACT FROM AUTHOR]

Seven diarylheptanoids and three 3-keto-steroids were detected in the acetone extract obtained from Zostera marina L. collected at the coast of the German Baltic Sea. The identified diarylheptanoids encompassed tricyclic diarylheptanoids, tetracyclic diarylheptanoids, and dimers of cyclic diarylheptanoids. During the whole growing season, tetracyclic diarylheptanoids were occurring in higher concentrations than other subclasses of diarylheptanoids. Concentrations of tricyclic diarylheptanoids were higher than the ones of dimeric cyclic diarylheptanoids, except in winter. All detected diarylheptanoids showed similar seasonal trends: the contents displayed an increasing tendency from September to a peak in autumn, and then dropped until the end of winter. In spring and summer diarylheptanoid contents were relatively low and showed fluctuating patterns. Additionally, we investigated how the gradual drying of the plants affected the contents of phenolic compounds and diarylheptanoids. To this end, daily samples of air-drying plants were taken; starting from fresh, living green leaves to completely dry, brown leaves. The results revealed that phenolic compounds were gradually decomposing, whereas the amounts of diarylheptanoids were increasing during the drying process. Three 3-keto-steroids, which have already been described from other sources, are described for the first time as metabolites of Z. marina. [Display omitted] • 3-Ketosteroids were detected in Zostera marina for the first time. • Seasonal variation of diarylheptanoids differed from seasonal variation of phenolics. • Drying experiments showed increases of diarylheptanoids during the drying process. • In contrast, the levels of phenolics decreased during drying. [ABSTRACT FROM AUTHOR]

• Zostera marina L. (Zosteraceae) yielded the cyclic diarylheptanoid cymodienol. • Also a previously undescribed diaryheptanoid, isotedarene A was found. • This compound is closely related to tedarene A, previously described from a sponge. • Structures were established by MS and extensive 1D and 2D NMR experiments. A first phytochemical investigation of apolar natural products of the seagrass Zostera marina L. (Zosteraceae) yielded cymodienol, a cyclic diarylheptanoid so far only known from the seagrass Cymodocea nodosa (Ucria) Asch. (Cymodoceaceae) and a previously undescribed diaryheptanoid, isotedearene A, which is closely related to tedarene A, a natural product previously described from the neotropic sponge Tedania ignis (Duchassaing & Michelotti, 1864) (Tedaniidae). Structures were established by mass spectrometry and extensive 1D and 2D NMR experiments. [ABSTRACT FROM AUTHOR]

Extracellular DNA (exDNA) widely occurs in the environment due to release by either cell lysis or active secretion. The role of exDNA in plant-soil interactions has been investigated and inhibitory effects on the growth of conspecific individuals by their self-DNA have been reported. Transcriptome analysis in the model plant Arabidopsis thaliana showed a clear recognition by the plant roots of self- and nonself-exDNA, with inhibition occurring only after exposure to the former. In this study, an untargeted metabolomics approach was used to assess at molecular level the plant reactions to exDNA exposure. Thus, the effects on the metabolites profile of A. thaliana after exposure to self- and nonself-exDNA from plants and fish, were studied by NMR, LC-MS, chemometrics and molecular networking analyses. Results show that self-DNA significantly induces the accumulation of RNA constituents (nucleobases, ribonucleosides, dinucleotide and trinucleotide oligomers). Interestingly, AMP and GMP are found along with their cyclic analogues cAMP and cGMP, and in form of cyclic dimers (c-di-AMP and c-di-GMP). Also methylated adenosine monophosphate (m6AMP) and the dimeric dinucleotide N-methyladenylyl-(3'→5') cytidine (m6ApC) increased only in the self-DNA treatment. Such striking evidence of self-DNA effects highlights a major role of exDNA in plant sensing of its environment. Metabolomics and molecular networking of Arabidopsis thaliana showed differential and specific accumulation of RNA constituents and analogues only after exposure to the plant self-DNA. [Display omitted] • Arabidopsis thaliana metabolites during self- and nonself-DNA exposure are analysed. • Combined approach of NMR, LC-MS, chemometrics and molecular networking is used. • Self-DNA exposure induced a significant accumulation of specific RNA constituents. • Cyclic AMP and GMP, and N6 methylated adenosine occur only in self-DNA treatment. • This is the first metabolomic study on different effects of self- and nonself-exDNA. [ABSTRACT FROM AUTHOR]

[Display omitted] Leontodon tenuiflorus (Gaudin) Rchb. yielded ixerisoside D, sonchuside A , and the previously undescribed 4,6-O-dihypocretenoyl-D-glucopyranoside. This is the first report of a hypocretenoid from Leontodon section Asterothrix. • Three sesquiterpenoids were isolated from Leontodon tenuiflorus. • These are the first sesquiterpenoids from Leontodon section Asterothrix. • Ixerisoside D and sonchuside A were also reported from other taxa of the Cichorieae. • 4,6- O -Dihypocretenoyl-D-glucopyranoside has been found for the first time. • Chemophenetic implications of the findings are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Simplexide is a glycolipid of marine origin, endowed with immunological properties, composed of a long chain secondary alcohol glycosylated by an α-d-glucosyl-(1→4)-β-d-galactosyl disaccharide residue. Herein we describe the preparation of a fluorescent derivative of simplexide, labeled at position 6 of the distal glucose with a dansyl group, as a probe for future studies on the mechanism by which simplexide affects the immune system. Fluorescent simplexide was prepared from a 6″-amino functionalized compound, which in turn was obtained through a highly efficient glycosylation between the preformed activated disaccharide and the long chain secondary alcohol 18-pentatriacontanol. [Copyright &y& Elsevier]

Abstract: Terpioside B (2a), a unique glycolipid containing two fucose residues in the furanose form in its pentasaccharide chain, was isolated from the marine sponge Terpios sp. Its complete stereostructure was solved by interpretation of mass spectrometric and NMR data along with CD and GG–MS analyses of its degradation products. Terpioside B is a potent inhibitor against LPS-induced NO release, and is considerably more active than simpler glycosphingolipids such as terpioside A and monoglucosylceramide. [Copyright &y& Elsevier]

Abstract: Tedanol, a new brominated and sulfated pimarane diterpene was isolated from the Caribbean sponge Tedania ignis. Structure of tedanol was elucidated by mass spectroscopy and extensive NMR studies (including spectral simulation), and its absolute configuration was determined using the Mosher method. Tedanol showed a potent anti-inflammatory activity at 1mg/kg evaluated in vivo in a mouse model of inflammation. After a single intraperitoneal administration, tedanol significantly reduced both the acute and the subchronic phases of carrageenan-induced inflammation. The anti-inflammatory activity was coupled with a strong inhibition of COX-2 expression, inhibition of cellular infiltration measured as mieloperoxidase (MPO) levels, and inhibition of iNOS expression. These features make tedanol a promising template for the development of new anti-inflammatory molecules with low gastrointestinal toxicity. [Copyright &y& Elsevier]

Seasonal variations of phenolic compounds, in leaves of Zostera marina L. from the Baltic Sea near Kiel/Germany were investigated. Dominant compounds were mono- and disulfated flavonoids and phenylpropanoic acids, in particular luteolin 7,3ʹ- O -disulfate and diosmetin 7- O -sulfate as well as rosmarinic acid, a dimeric phenylpropanoid. All detected sulfated flavones showed similar seasonal trends: there were two significant concentration peaks in June and November. Moreover, two geographically distinct flavonoid chemotypes were identified based on their respective main flavonoid; one chemotype was characterized by the prevalence of luteolin 7,3ʹ- O -disulfate (German Baltic Sea), and the other by the prevalence of diosmetin 7- O -sulfate (Norwegian North Sea). Furthermore, an undescribed tetrameric phenylpropanoid, 7ʹʹ,8ʹʹ-didehydrosalvianolic acid B, was isolated and its structure was established by extensive NMR, MS, and CD experiments. This compound inhibited activity of Na+/K+-ATPase in the micro-molar range without any cytotoxic effects against human cancer and normal cells. [Display omitted] • In Baltic Zostera marina four phenolic acids and eight flavonoids were identified. • 7ʹʹ,8ʹʹ-didehydrosalvianolic acid B was isolated and characterized. • The compound inhibits activity of Na+/K + -ATPase in the micro-molar range. • Seasonal variation of phenolics was quantitatively analyzed by UHPLC. • Two chemotypes were characterized based on their dominant flavonoids. [ABSTRACT FROM AUTHOR]

Abstract: CD and NMR studies on heterochiral oligodeoxynucleotides (d/l-ODNs) forming quadruplex structures are reported. Heterochiral ODNs, based on sequence TGGGGT, are able to form stable either right- or left-handed quadruplexes depending on d/l ratio and residues position. Results suggest that the 3′-end and the core of the G-run are more important than the 5′-end in determining the quadruplex handness. Particularly, oligonucleotide TDGDGLGLGDTD (L34) at low temperatures forms a well-defined left-handed quadruplex, notwithstanding it is mostly composed by natural d residues. This structure is characterized by three all-anti G-tetrads and one all-syn G-tetrad. [Copyright &y& Elsevier]

Abstract: Corrugoside (1a), a new immunostimulatory triglycosilated α-galactoglycosphingolipid, was isolated from the marine sponge Axinella corrugata, and its structure determined by spectral analysis and chemical degradation. Compound 1a activated murine NKT cells in vitro, with a potency of about 2logs lower than that of αGalCer. Four stereoisomeric glycosphingolipids (2a–2d) were also obtained, β-glucosylceramides bearing unusual endoperoxide and allylic hydroperoxide functionalities on the sphinganine chain. They were shown to be photooxidation artifacts of the known glycosphingolipids 3, also present in the sponge. A possible role of compound 3 as a singlet oxygen scavenger to protect the organism from oxidative damage is proposed. [Copyright &y& Elsevier]

Abstract: A concise synthesis of α-sulfatide 1, an analogue of natural glycolipid antigens with potential anti-tumor activity, was performed. Two different approaches to the α-glycosidic bond were explored, resulting in a high yield and excellent stereoselectivity. Compound 1 combines the structural features of sulfated β-GalCer (sulfatide) and α-GalCer, which activate specific T cells. α-Sulfatide 1 was stimulatory for CD1d-restricted semi-invariant Natural Killer T (iNKT) cell clones, although less potent than α-GalCer, while it was not recognized by CD1a-restricted sulfatide-specific T cells. [Copyright &y& Elsevier]

Sodium dithionite, which is known to cause dehalogenation of α-halo carbonyl compounds, also induces dehalogenation of protected 2-iodo-2-deoxyglycosides. Combined with the well-known iodonium-mediated haloalkoxylation, this reaction provides an easy, mild and highly stereoselective route for preparation of 2-deoxy-α-glycosides from glycals. [Copyright &y& Elsevier]

Four undescribed lignans and two undescribed sesquiterpenic acids, together with three known compounds (hypochoeroside C, hypochoeroside D, and 5- O -caffeoylshikimic acid) were isolated from the roots of Hypochaeris radicata subsp. neapolitana (Asteraceae, Cichorieae). The lignans were identified as 4-(3,4-dihydroxybenzyl)-2-(3,4-dihydroxyphenyl)tetrahydrofuran-3-carboxy- O -β-D-glucopyranoside, 4-(3,4-dihydroxybenzyl)-2-(3,4-dihydroxyphenyl)tetrahydrofuran-3-carboxy- O -β-D-glucopyranosyl-2′- O -methacrylate, (7 S ,8 R ,8′ R)-7-(3,4-dihydroxyphenyl)-3′,4′-dihydroxy-7,8,7′,8′-tetrahydronaphtho [8,8′-c]furan-1(3H)-one, and (7 S ,8 R ,8′ R)-7-(3,4-dihydroxyphenyl)-3′,4′-dihydroxy-8'-(hydroxymethyl)-7,8,7′,8′-tetrahydronaphthalen-8-carboxylic acid. The two sesquiterpenic acids were identified as the ring open precursors of hypochoerosides C and D. Structures were elucidated using NMR and HRMS. Absolute configurations of (7 S ,8 R ,8′ R)-7-(3,4-dihydroxyphenyl)-3′,4′-dihydroxy-7,8,7′,8′-tetrahydronaphtho [8,8′-c]furan-1(3H)-one and (7 S ,8 R ,8′ R)-7-(3,4-dihydroxyphenyl)-3′,4′-dihydroxy-8'-(hydroxymethyl)-7,8,7′,8′-tetrahydronaphthalen-8-carboxylic acid were determined using electronic circular dichroism (ECD) spectroscopy. 4-(3,4-dihydroxybenzyl)-2-(3,4-dihydroxyphenyl)tetrahydrofuran-3-carboxy- O -β-D-glucopyranoside was evaluated for its anti-proliferative activity against myeloma cell lines MM1S, U266, and NCI-H929 and showed cytotoxicity at 100 mM against MM1S strain. No neurotoxicity was observed for major compounds 4-(3,4-dihydroxybenzyl)-2-(3,4-dihydroxyphenyl)tetrahydrofuran-3-carboxy- O -β-D-glucopyranoside, hypochoeroside C, and hypochoeroside D in a fluorescence assay measuring neurite outgrowth in dorsal root ganglion (DRG) neurons. Additionally, compounds 4-(3,4-dihydroxybenzyl)-2-(3,4-dihydroxyphenyl)tetrahydrofuran-3-carboxy- O -β-D-glucopyranoside, hypochoeroside C, hypochoeroside D, and hypochoerosidic acid D were quantified in unstressed and drought-stressed plants using HPLC-DAD. Drought-stressed plants were found to contain lower concentrations of the lignan 4-(3,4-dihydroxybenzyl)-2-(3,4-dihydroxyphenyl)tetrahydrofuran-3-carboxy- O -β-D-glucopyranoside and sesquiterpene lactone hypochoeroside C. Image 1 • Four undescribed lignans were discovered in H. radicata subsp. neapolitana. • Additionally, two undescribed sesquiterpenic acids were found. • Structures were elucidated using ECD, NMR, and HRMS. • None of the tested compounds displayed neurotoxicity. • Drought-stressed plants contained lower concentrations of natural products. [ABSTRACT FROM AUTHOR]