Wax Composition of Serbian Dianthus spp. (Caryophyllaceae): Identification of New Metabolites and Chemotaxonomic Implications.

Although ethnopharmacologically renowned, wax constituents of Dianthus species were sporadically studied. A combination of GC-MS analysis, synthesis, and chemical transformations enabled the identification of 275 constituents of diethyl-ether washings of aerial parts and/or flowers of six Dianthus taxa (Dianthus carthusianorum, D. deltoides, D. giganteus subsp. banaticus, D. integer subsp. minutiflorus, D. petraeus, and D. superbus) and one Petrorhagia taxon (P. prolifera) from Serbia. Seventeen of these constituents (nonacosyl benzoate, additional 12 benzoates with anteiso-branched 1-alkanols, eicosyl tiglate, triacontane-14,16-dione, dotriacontane-14,16-dione, and tetratriacontane-16,18-dione) and two additional synthesized eicosyl esters (angelate and senecioate) represent completely new compounds. The structures of the tentatively identified ß-ketones were confirmed by analysis of the mass fragmentation of the corresponding pyrazoles and silyl enol ethers obtained by transformations of crude extracts and extract fractions. Silylation allowed the identification of 114 additional constituents, including a completely new natural product (30-methylhentriacontan-1-ol). The results obtained by multivariate statistical analyses showed that the chemical profile of Dianthus taxa's surface waxes is subject to both genetic and ecological factors, whereas the latter seemingly takes a more important role for the studied Dianthus samples.

A new longipinane ketone from Achillea abrotanoides (Vis.) Vis.: chemical transformation of the essential oil enables the identification of a minor constituent.

INTRODUCTION: Minor plant constituents are difficult to identify due to the challenging isolation and acquiring of reliable spectral data. Essential oils abound in such minor constituents that might be of high importance for their (e.g. olfactory) properties. The presence of new minor constituents is usually inferred from gas chromatography mass spectrometry (GC-MS) analyses that provide only a mass spectrum and retention data, which are insufficient to allow a positive identification. OBJECTIVE: To identify a minor unknown constituent of the essential oil of Achillea abrotanoides (Vis.) Vis. (Asteraceae). METHODOLOGY: The application of chemical transformations (oxidation and reduction) performed directly on crude essential-oil samples, followed by preparative chromatography and detailed spectral analysis, to identify a new longipinane ketone from the mentioned sample. RESULTS: GC-MS analyses of the essential oil revealed, among other constituents, the presence of a known rare longipinane alcohol (α-longipinen-7ß-ol) representing 2.5% of the total GC-peak areas, and a related unidentified oxygenated sesquiterpene (3.8%). Interpretation of their mass spectra led to an assumption that the unidentified one could represent α-longipinen-7-one. Oxidation of the entire essential-oil sample by pyridinium chlorochromate confirmed the assumed relationship among the compounds and gave a simplified enriched mixture containing the ketone (ca. 16%). A straightforward chromatographic separation of the ketone was followed by corroboration of its structure by nuclear magnetic resonance (NMR) (one- and two-dimensional), infrared (IR) and MS. CONCLUSIONS: The complementing use of chemical transformations of crude essential oils, chromatographic separations, and detailed spectral analysis could have a more general application in the identification of new natural products.

Diethyl-Ether Flower Washings of Dianthus cruentus Griseb. (Caryophyllaceae): Derivatization Reactions Leading to the Identification of New Wax Constituents.

Some carnation species (Dianthus spp., Caryophyllaceae) exhibit a strong resistance to drought stress that is connected with the increased surface wax formation. Wax composition is unknown for the majority of Dianthus spp. Herein, mass spectral and gas chromatographic data, in combination with synthesis and chemical transformations (transesterification and synthesis of dimethyl disulfide adducts), enabled the identification of 151 constituents of diethyl-ether washings of fresh flowers of Dianthus cruentus Griseb. from Serbia. The flower wax contained, along with the dominant ubiquitous long-chain n-alkanes, homologous series of n- and branched (iso- and anteiso-) long-chain hexyl alkanoates/alkenoates and alkyl/alkenyl benzoates. The branching position in the mentioned hexyl esters was probed by synthesis of esters of three isomeric hexanols that were spectrally characterized (1 H- and 13 C-NMR, IR, MS). The washings also contained long-chain (Z)- and (E)-alkenes (C23 -C35 ) with several different double bond regiochemistries. Fifty-five of these constituents (eight hexyl esters, two benzoates, and forty-five alkenes) were detected for the first time in Plantae, while ten of these represent completely new compounds. The rare occurrence of these wax constituents makes them possible chemotaxonomic markers of this particular Dianthus sp.

Synthesis and Spectral Characterization of Asymmetric Azines Containing a Coumarin Moiety: The Discovery of New Antimicrobial and Antioxidant Agents.

Nine unsymmetrical azines containing a coumarin moiety were prepared by the reaction of the hydrazone of 4-hydroxy-3-acetylcoumarin with differently substituted aromatic aldehydes. The azines were fully spectrally characterized, including a complete assignment of 1 H- and 13 C-NMR resonances, and were assessed for their acute toxicities in the Artemia salina model. Their free radical scavenging activities were tested in the DPPH assay, and in vitro antimicrobial activities were determined against seven bacterial and two fungal strains. The azines containing a p-hydroxyphenyl group were shown to be the most effective antimicrobial agents, and in the case of resistant strains of Staphylococcus aureus and Acinetobacter baumannii, the activity was comparable to that of chloramphenicol. The derivative having a 3,5-dimethoxy-4-hydroxyphenyl group exhibited pronounced antioxidant power reacting rapidly and in 1 : 1 mol ratio with the DPPH radical.