Triterpene Acids in Plantago major: Identification, Quantification and Comparison of Different Extraction Methods

Seeds and leaves of cultivated great plantain (Plantago major L.) were extracted with conventional Soxhlet extraction using a variety of solvents and with pilot scale supercritical fluid (CO₂) extraction (SFE-CO₂). Hydroxy pentacyclic triterpene acids (HPTAs), oleanolic acid and ursolic acid, were identified from the SPE purified extracts with LC-(UV)-APCI-MS and quantified with LC-UV. Dried P. major leaves contained 0.07% of oleanolic acid and 0.22% of UA. Seeds had very small amounts of HPTAs, 0.005% of OA and 0.007% of ursolic acid in the oil extracted. SFE-CO₂ extraction without polar modifier was found not to be a suitable technology for the leaf extraction due to the low content of lipophilic and volatile compounds. Soxhlet extraction with diethyl ether and SFE-CO₂ extraction were similar in the efficiency of extracting HPTAs from the seeds.     

Extending the series: synthesis and characterization of a dicationic N-heterocyclic selenium carbene analogue

The room-temperature reaction between the Dipp2DAB ligand, SnCl2, and SeCl4 results in the quantitative formation of a dicationic N-heterocyclic "carbenoid". This represents the first example of a chalcogenium dication that mimics the ubiquitous Arduengo-type carbenes; however, the electronic structure is significantly different.     

Poly(glyceryl glycerol): A multi‐functional hydrophilic polymer for labeling with boronic acids

The synthesis of poly(glyceryl glycerol) (PGG), a polymer featuring a polyethylene oxide backbone and 1,2‐diol groups in every repeating unit, is presented. PGG was prepared by monomer‐activated ring‐opening polymerization of (dl ?1,2‐isopropylidene glyceryl) glycidyl ether, introducing a functional azido‐ or bromo‐head group to each chain. The 1,2‐diol groups, which were released by acidic deprotection, readily reacted with boronic acid derivatives, enabling the attachment of functional moieties under mild aqueous conditions. PGG was conjugated to poly(l ‐lactide) (PLLA) via azide‐alkyne cycloaddition and the resulting copolymer assembled into nanoparticles of 70 nm diameter in aqueous solution. Labeling of the PGG–PLLA particles was achieved by simple mixing with a boronic acid‐functional fluorophore. The labeling efficiency was determined by fluorescence spectroscopy to be 85.5% for boronic acid‐functional rhodamine B compared with 0.2% for plain rhodamine B. The strong interaction of PGG with boronic acids is ascribed to its polyol structure. This study demonstrates the usefulness and versatility of PGG as a hydrophilic polymer for possible biomedical applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1822–1830     

HPLC micro-fractionation coupled to a cell-based assay for automated on-line primary screening of calcium antagonistic components in plant extracts

High performance liquid chromatography (HPLC) micro-fractionation was successfully coupled to an automated ⁴⁵Ca²⁺ uptake assay using GH₄C₁ cells for the separation of natural product extracts and for the primary detection of their calcium antagonistic components. The reliability of the procedure was first established with a reference solution consisting of pure compounds with a known effect on the Ca²⁺ uptake. No loss of activity was observed to occur after HPLC micro-fractionation. Extracts of Peucedanum palustre and Pinus sylvestris, showing high and no inhibition of Ca²⁺ uptake as total extracts, respectively, were analysed and the inhibitory activity of the P. palustre extract could be traced to two components, identified as columbianadin and isoimperatorin. As expected, no significant inhibition was observed with the micro-fractionated P. sylvestris samples. In summary, the procedure was found to be applicable for primary detection of calcium antagonistic components in complex matrices and to significantly reduce the time previously needed for bioactivity-guided isolation.     

Experimental and theoretical investigations of tellurium(IV) diimides and imidotelluroxanes: X-ray structures of B(C6F5)3 adducts of OTe(mu-NtBu)2TeNtBu, [OTe(mu-NtBu)2Te(mu-O)]2 and tBuNH2

The hydrolysis of (t)BuNTe(mu-N(t)Bu)(2)TeN(t)Bu (1) with 1 or 2 equiv of (C(6)F(5))(3)B.H(2)O results in the successive replacement of terminal imido groups by oxo ligands to give the telluroxane-Lewis acid adducts (C(6)F(5))(3)B.OTe(mu-N(t)Bu)(2)TeN(t)Bu (2) and [(C(6)F(5))(3)B.OTe(mu-N(t)Bu)(2)Te(mu-O)](2) (3), which were characterized by multinuclear NMR spectroscopy and X-ray crystallography. The Te=O distance in 2 is 1.870(2) A. The di-adduct 3 involves the association of four (t)()BuNTeO monomers to give a tetramer in which both terminal Te=O groups [d(TeO) = 1.866(3) A] are coordinated to B(C(6)F(5))(3). The central Te(2)O(2) ring in 3 is distinctly unsymmetrical [d(TeO) = 1.912(3) and 2.088(2) A]. The X-ray structure of (C(6)F(5))(3)B.NH(2)(t)()Bu (4), the byproduct of these hydrolysis reactions, is also reported. The geometries and energies of tellurium(IV) diimides and imido telluroxanes were determined using quantum chemical calculations. The calculated energies for the reactions E(NR)(2) + Te(NR)(2) (E = S, Se, Te; R = H, Me, (t)Bu, SiMe(3)) confirm that cyclodimerization of tellurium(IV) diimides is strongly exothermic. In the mixed-chalcogen systems, the cycloaddition is energetically favorable for the Se/Te combination. The calculated energies for the further oligomerization of the dimers XE(mu-NMe)(2)EX (E = Se, Te; X = NMe, O) indicate that the formation of tetramers is strongly exothermic for the tellurium systems but endothermic (X = NMe) or thermoneutral (X = O) for the selenium systems, consistent with experimental observations.     

New upper bounds on the minimum size of covering designs

Let D = {B₁, B₂,…, B_b} be a finite family of k-subsets (called blocks ) of a v-set X(v) = {1, 2,…, v} (with elements called points ). Then D is a (v, k, t) covering design or covering if every t-subset of X(v) is contained in at least one block of D. The number of blocks, b, is the size of the covering, and the minimum size of the covering is called the covering number , denoted C(v, k, t). This article is concerned with new constructions of coverings. The constructions improve many upper bounds on the covering number C(v, k, t) © 1998 John Wiley & Sons, Inc. J Combin Designs 6:21–41, 1998     

Fast-Atom-Bombardment Mass Spectra of Phloroglucinols from Dryopteris Ferns

Fast-atom-bombardment mass spectra of ten phloroglucinol derivatives containing two to six ring units were recorded. The mass spectral behavior of the compounds was quite similar under these conditions. Molecular-weight information was readily available as well as sequential structural data due to extensive fragmentation. Sequential alterations due to the rottlerone change or other analogous decomposition reactions proved to be almost lacking in fast-atom-bombardment mass spectrometry. The negative-ion spectra in general showed better signal-to-noise ratios and more distinct fragment ions.     

Interaction and ionic network formation process between polyamidine and nonlinear optically active dyes

Interactions of phenolic and carboxylic groups containing chromophores (hydroxyarylidene alkanones) with polyamidines were investigated with ultraviolet–visible spectroscopy and dynamic light scattering experiments. Because of the strong basicity of the polyamidines, deprotonation of the chromophores was observed. The ionic network formation process depended on the method of the complex preparation. The step‐by‐step addition of the chromophore to an excess of polyamidine led to the incorporation of the dye molecules inside the polymer coil, and only after this did the interaction of surface functional groups with an additional amount of the low‐molecular‐weight compound lead to network formation. The interaction of the polymer with an excess of the dye initially led to the saturation of amidine groups by chromophore molecules and network formation without the complete destruction of the dye packs. The molecular structure proposed for these complexes was examined with experimental data. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 398–404, 2005