Analysis of four pentacyclic triterpenoid acids in several bioactive botanicals with gas and liquid chromatography and mass spectrometry detection

Several pentacyclic triterpenoid acids including betulinic, oleanolic, and ursolic acids were reported to have health beneficial properties such as antiviral and anti‐inflammatory properties, as well as the capability to inhibit “in vitro” the development of various cancer cell types. For this reason betulinic, oleanolic, and ursolic acids are used as neutraceuticals. For the analysis of the pentacyclic triterpenoid acids in complex plant materials, an improved scheme was developed, involving a qualitative screening using silylation and gas chromatography with mass spectrometry analysis, followed by quantitation using a novel liquid chromatography with tandem mass spectrometry procedure. The use of the two methods provides more reliable information regarding the plant materials with unknown composition. Besides betulinic, oleanolic, and ursolic acids that were analyzed, by this procedure a fourth pentacyclic triterpenoid acid was identified and quantitated that was not previously reported to be present in plants. This acid has been identified as 3β‐3‐hydroxy‐lupa‐18,20(29)‐dien‐28‐oic acid. The newly identified acid has a structure as a derivative of lupane, although lupane with a double bond in the 18‐position was not previously reported as present in plants. The new liquid chromatography with tandem mass spectrometry procedure developed for this study offers a very low limit of quantitation, excellent precision, and robustness. Rosemary was found to contain the largest levels of pentacyclic triterpenoid acids among all the analyzed botanicals.     

Facile synthesis of 6,6,8,6,6-ring fused pentacyclic heterocycles: annelation of quinolines to quinoxalines under PTC condition

An efficient and simple synthesis of pentacyclic quinolonoquinoxalinooxazocines in a one-pot sequence has been performed by unique application of phase transfer catalysis. Preparative simplicity and conceptual novelty of the methodology offer an attractive general application for the synthesis of novel quinoline antibiotics.     

Novel biotransformation of pentacyclic triterpenoid acids by Nocardia sp. NRRL 5646

Six pentacyclic triterpene acids, ursolic acid, oleanolic acid, betulinic acid, 23-hydroxybetulinic acid, glycyrrhetinic acid, and senegenin, were metabolized by the microbe Nocardia sp. NRRL 5646 to selectively furnish their corresponding 28-methyl esters. Notably, ursolic acid (1) was converted to oleanolic acid methyl ester (4) via two intermediates, oleanolic acid (2), and ursolic acid methyl ester (3), which are formed by participation of ‘retro-biosynthetic’ methyl migration from C-19 to C-20. Senegenin (11) was selectively converted to a nortriterpene methyl ester, senegenic acid methyl ester (12), via an unprecedented C-C bond cleavage. The stereochemical assignments of compounds 11 and 12 were made unambiguously for the first time using 2D NMR spectroscopy.     

Selective mono-and diamination of polyfluorinated benzenes and pyridines with liquid ammonia

Amination of pentafluoropyridine, 2,3,5,6-tetrafluoropyridine, 4-chlorotetrafluoropyridine, 3,5-dichlorotrifluoropyridine, octafluorotoluene, α,α,α,2,3,5,6-heptafluorotoluene, decafluoro-m-xylene, decafluorobiphenyl, hexafluorobenzene, and pentafluorobenzene with liquid ammonia was investigated. Bis-aminodefluorination temperatures for the majority of substrates were shown to exceed significantly the corresponding temperatures of monoaminodefluorination. The optimal conditions for selective preparation of mono-and diaminopolyfluoro(het)arenes were elucidated. An efficient method for isolation of particular polyfluorophenylenediamines from product mixtures formed in nonselective reactions of pentafluorobenzene and hexafluorobenzene with aqueous ammonia based on complexation with a crown ether is proposed. Dedicated to the memory of Academician N. N. Vorozhtsov on the occasion of his 100th anniversary. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2163–2170, November, 2007.     

Complete assignments of 1H and 13C NMR spectral data for three new triterpenoid saponins from Ilex hainanensis Merr

Three new oleanane-type triterpenoid saponins, ilexhainanoside C, D and E, all with 24, 28-dioic acid groups, were isolated from the leaves of Ilex hainanensis. They were 3beta-hydroxyolean-12-ene-24, 28-dioic acid-28-O-beta-D-glucopyranoside(1), 3beta, 19alpha-dihydroxyolean-12-ene-24, 28-dioic acid-28-O-beta-D-glucopyranoside(2) and 3beta, 29-dihydroxyolean-12-ene-24, 28-dioic acid-28-O-beta-D-glucopyranoside(3). The structures of these three new compounds were elucidated and complete assignments of the (1)H and (13)C NMR spectroscopic data were achieved by 1D and 2D NMR experiments [heteronuclear single quantum coherence (HSQC), HMBC and rotational nuclear Overhauser effect spectroscopy (ROESY)].     

Complete assignments of 1H and 13C NMR spectroscopic data for two new triterpenoid saponins from Ilex hainanensis

Two novel unsaturated E-ring pentacyclic triterpenoid saponins, ilexhainanoside A and ilexhainanoside B, were isolated from the leaves of Ilex hainanensis. Their chemical structures were determined by MS, NMR spectroscopy and chemical analysis. Complete assignments of the 1H and 13C NMR spectroscopic data were achieved by 1D and 2D NMR experiments (HSQC, HMBC, ROESY and 1H-1H COSY).     

Structure elucidation and complete NMR spectral assignments of two new oleanane‐type pentacyclic triterpenoid saponins from the husks of Xanthoceras sorbifolia Bunge

Two new saponins were isolated from husks of Xanthoceras sorbifolia Bunge and their structures were elucidated as 3‐O‐[β‐D‐galactopyranosyl(1→2)]‐α‐L‐arabinofuranosyl(1→3)‐β‐D‐methyl glucuronic acid‐21‐O‐(3,4‐diangeloyl)‐α‐L‐rhamnose‐3β, 16α, 21β, 22α, 28β‐pentahydroxyl‐22‐acetoxy‐olean‐12‐ene(1) and 3‐O‐[β‐D‐galactopyranosyl(1→2)]‐α‐L‐arabinofuranosyl(1→3)‐β‐D‐methyl glucuronic acid‐21,22‐O‐diangeloyl‐3β,15α,16α,21β,22α,28β‐hexahydroxyl‐olean‐12‐ene(2) on the basis of 1D and 2D NMR (including ¹H, ¹³C‐NMR, ¹H? ¹H COSY, HSQC, HMBC and DEPT), ESI‐MS spectrometry and chemical methods. Copyright © 2009 John Wiley & Sons, Ltd.     

Complete assignments of (1)H and (13)C NMR spectroscopic data for two new triterpenoid saponins from Ilex pernyi

Ilexpernoside A and ilexpernoside B, two new pentacyclic C(4)-nortriterpenoid saponins, were isolated from the leaves of Ilex pernyi Franch. Their chemical structures were determined by MS, NMR spectroscopy and chemical analysis. Complete assignments of the (1)H and (13)C NMR spectroscopic data were achieved by 1D and 2D NMR experiments (HSQC, HMBC, (1)H-(1)H COSY and NOESY).     

A facile and convenient method for synthesis of alkyl thiocyanates under homogeneous phase transfer catalyst conditions

A simple and environmentally friendly method is described for the efficient conversion of alkyl halide to alkyl thiocyanate using tetrabutylammonium bromide （TBAB） as a phase transfer catalyst. The reactions occur in water and furnish the corresponding alkyl thiocyanate in high yields. No evidence for the formation of isothiocyanates as by-product of the reaction was observed and the products were obtained in pure form without further purification.     

A novel and facile synthesis of 4-arylquinolin-2(1H)-ones under metal-free conditions

A novel and facile synthesis of 4-arylquinolin-2(1H)-ones without metal catalysis has been developed. This reaction involved cyclization/elimination steps and was performed under metal-free conditions using inexpensive reagents such as NaI, selectfluor and KOH.     

A conformational NMR analysis of methymycin aglycones: complete and unambiguous assignments of stereochemically diverse glycosylated methymycin analogs by 1D and 2D NMR techniques and molecular modeling

The ¹H and ¹³C NMR spectra of 10‐deoxymethynolide (1), 8.9‐dihydro‐10‐deoxymethynolide (2) and its glycosylated derivatives (3–9) were analyzed using gradient‐selected NMR techniques, including 1D TOCSY, gCOSY, 1D NOESY (DPFGSENOE), NOESY, gHMBC, gHSQC and gHSQC‐TOCSY. The NMR spectral parameters (chemical shifts and coupling constants) of 1–9 were determined by iterative analysis. For the first time, complete and unambiguous assignment of the ¹H NMR spectrum of 10‐deoxymethynolide (1) has been achieved in CDCl₃, CD₃OD and C₆D₆ solvents. The ¹H NMR spectrum of 8,9‐dihydro‐10‐deoxymethynolide (2) was recorded in CDCl₃, (CD₃)₂CO and CD₃OD solutions to determine the conformation. NMR‐based conformational analysis of 1 and 2 in conjugation with molecular modeling concluded that the 12‐membered ring of the macrolactones may predominantly exist in a single stable conformation in all solvents examined. In all cases, a change in solvent caused only small changes in chemical shifts and coupling constants, suggesting that all glycosylated methymycin analogs exist with similar conformations of the aglycone ring in solution. Copyright © 2013 John Wiley & Sons, Ltd.     

Facile preparation of a symmetric hexavalent oleanolic acid/per-O-methylated α-cyclodextrin conjugate with two conformations in solution and unambiguous NMR analysis

A newly synthesized hexavalent oleanolic acid/per-O-methylated α-cyclodextrin conjugate shows significant differences in NMR spectra with previously synthesized analogs. Characterization of the product by ¹H NMR, ¹³C NMR, COSY, HSQC, HMBC, TOCSY, NOE, and ROESY experiments were performed. Detailed investigations revealed that the compound has two conformations in solution and the ratio of them was 1:1. Further variable-temperature NMR study revealed that the two conformations were stable at temperature range of 273–323 K in CDCl₃ solution.     

2D NMR analysis for unambiguous structural elucidation of phenolic compounds formed through reaction between (+)‐catechin and glyoxylic acid

Various phenolic compounds were synthesized in an aqueous–alcoholic solution containing (+)‐catechin and glyoxylic acid which was used as a model of fruit‐derived food browning that usually occurs during aging. After purification by semi‐preparative HPLC, the isolated compounds were subjected to homo‐ and heteronuclear proton and carbon NMR analysis including COSY, TOCSY, ROESY, HSQC and HMBC techniques. These experiments allowed the structural elucidation and complete ¹H and ¹³C NMR assignment of the isolated compounds. The strategies followed for the assignment of all proton and carbon resonances in addition to the linkage site determination are discussed. Copyright © 2002 John Wiley & Sons, Ltd.     

Cloning, expression, and sequence analysis of diaminopropionate ammonia lyase gene from a nonvirulentsalmonella typhimurium PU011

Background: Seeds ofLathyrus sativus, a legume plant, contain 3-oxalyl and 2,3-dioxalyl DAP (O-DAP), neurotoxins which when consumed causes Neurolathyrism or Osteolathyrism, in humans, affecting nervous system and bone formation respectively. Some microorganisms viz virulent and non-virulentSalmonella typhimurium, Salmonella typhi and Pseudomonad have been shown to detoxifyL-α,β-diaminopropionate (DAP), the immediate precursor of O-DAP. Result: The gene coding for diaminopropionate ammonia lyase (DAPAL) which detoxifies DAP was cloned from nonvirulentS. typhimurium PU011 intoEscherichia coli DH5α and the nucleotides sequenced (1212 bp). Whereas the specific enzyme activity of DAPAL obtained from recombinantE. coli PU018 was 0.346 U/mg, the specific activity of the enzyme from nonvirulentS. typhimurium PU011 was 0.351 U/mg. The DAPAL corresponding to 43 kDa protein was found both in nonvirulentS. typhimurium PU011 andE. coli PU018. The Km value was found to be 0.740 mM and 0.680 mM forS. typhimurium PU011 and 0.741 mM and 0.683 mM forE. coli PU018 when grown in minimal medium (MM+DAP) andL. sativus seed extracts respectively, indicating that both of them were capable of utilizing the neurotoxins present inL. sativus seeds. The biomass, enzyme production and the effect of pH and temperature on DAPAL enzyme activity from both non-virulentS. typhimurium PU011 andE. coli PU018 were found to be similar. Conclusion: The recombinantE. coli PU018 as well as non-virulentS. typhimurium PU011 are as good as pathogenicS. typhimurium in detoxifying DAP, the immediate precursor of O-DAP present inL. sativus seeds.     

Reaction products of dichlorodiorganostannanes with sodium in liquid ammonia: In-situ investigations with Sn NMR spectroscopy and usage as intermediates for the synthesis of tetraorganostannanes

Dichlorodibutylstannane, dichlorodioctylstannane and dichlorodiphenylstannane were reacted with different amounts of sodium in liquid ammonia. At a molar ratio of R₂SnCl₂/Na of 1:2, polystannanes precipitated, in some cases accompanied by cyclic oligostannanes. The products resulting from mixtures with R₂SnCl₂/Na ratios of 1:3 to 1:10 were soluble and, hence, could be studied in-situ in liquid ammonia with ¹¹⁹Sn NMR spectroscopy. The compounds obtained, tin hydrides of the type R₂SnH⁻ and in certain cases distannides of the composition R₄Sn₂²⁻, formed essentially independent of the R₂SnCl₂/Na ratio; this, in contrast to views expressed in the literature. Our experiments showed that the chemical structure of the in-situ generated species did not permit to draw conclusions about the composition of the reaction products with bromoethane and vice versa - a practice commonly described. Furthermore, we observed migration of the butyl groups both in-situ during the reaction of dichlorodibutylstannane with sodium in liquid ammonia, as well as in the final reaction product. By contrast in the case of the phenyl substituent, migration was detected not during the chemical event in liquid ammonia, but only in the compounds formed. These observations imply a different mechanism for butyl and phenyl group migration.     

Selective cleavage of protonated penetratin and its substitutes under low‐energy collision‐induced dissociation condition

An understanding of the dissociation of penetratin is important for improving its metabolic stability and cargo‐delivery efficiency. In this study, we describe the selective cleavage of the K15–K16 amide bond of penetratin under the low‐energy collision‐induced dissociation condition in mass spectrometry. A variety of penetratin substitutes have been studied in which key basic amino acids have been substituted within the sequence. The calculated structure indicates that an α‐helix structure prevents the fragmentation of the central peptide domain and the side chain of lysine is involved in the proton translocation process. Copyright © 2010 John Wiley & Sons, Ltd.     

Copper/Schiff-base complex immobilized on amine functionalized silica mesoporous magnetic nanoparticles under solvent-free condition: A facile and new avenue for the synthesis of thiazolidin-4-ones

A copper/Schiff-base complex supported on amine-functionalized silica mesoporous magnetic nanoparticles was prepared as novel magnetically interphase nanoparticles and its morphology and structure were evaluated using Fourier transform infrared spectroscopy, X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, thermogravimetric analysis, zeta potential, and a vibrating sample magnetometer. The catalytic activity of the synthesized nanoparticles was evaluated for the synthesis of thiazolidine-4-ones.     

Stability of dye-sensitized solar cell under reverse bias condition: Resonance Raman spectroscopy combined with spectrally resolved analysis by transmittance and efficiency mapping

In this work, resonance Raman spectroscopy (RRS) together with a spectrally resolved analysis by transmittance and efficiency mapping (SATEM) have been applied as a powerful tool to detect and to understand deeply the degradation mechanisms suffered by a series-connected dye-sensitized solar cell (DSC) in a module under real working condition. When shadowing phenomena occur on the module, the shadowed cell works as a load rather than as a generator and suffers reverse bias (RB) condition that induces a progressive degradation until the complete device⬢s breakdown. The reported analysis follows the degradation processes involving both the electrolyte solution and the sensitizer during the aging time. In particular, polyiodides formation has been pointed out as crucial triiodide depletion mechanism in the electrolyte solution leading to a strong unbalance in the redox couple and to a slowdown in dye regeneration process. The final device breakdown occurs when hydrogen production within the electrolyte solution causes the breaking of the sealing and the partial electrolyte leakage from the active area. RRS demonstrated the irreversible structural changes suffered by dye molecules during this final stage by identifying the main degradation products. Finally, a spectrally resolved comparison between incident to photon current conversion efficiency (IPCE) for photo (PE) and counter electrode (CE) illumination were used, along with transmittance analysis, in order to derive detailed information about the structural modification suffered by the cell constituents. The combination between SATEM and RRS techniques exhaustively provided a deep comprehension of the DSC degradation processes by giving a route to further stabilize the devices for a feasible next commercialization.