Stemmosides C and D, two novel unusual pregnane glycosides from Solenostemma argel: structural elucidation and configurational study by a combined NMR-quantum mechanical strategy

Stemmosides C and D, two novel pregnane glycosides characterized by an unusual C-17 side chain were isolated from the pericarps of Solenostemma argel. In addition, stemmoside D displays an uncommon 14β proton configuration, apparently being the first pregnane isolated from plants known to have a 15 keto, cis CD ring junction. Their structures have been established by ESIMS and NMR experiments. The relative configuration of the molecules was determined using a strategy based on the simulation of ¹H, ¹³C, and J coupling NMR parameters. DFT calculations of ¹H and ¹³C chemical shifts, and of the ¹H homonuclear spin–spin coupling constants were performed with the mPW1PW91 functional using the 6-31G(d,p) basis set on the fully optimized geometries of all the possible stereoisomers.     

New antiproliferative 14,15-secopregnane glycosides from Solenostemma argel

Eight new 14,15-secopregnane glycosides, namely argelosides C-J, possessing two ketal functions involved in three five-membered rings, have been isolated from the hairy seeds of Solenostemma argel. Their structures have been established by MS and NMR experiments, combined with quantum mechanical calculations of the ¹³C chemical shifts for the interpretation of the experimental data. On the basis of the obtained results, the structures of argelosides A and B have been revised. Additionally, the effect of these compounds on the VEGF-induced in Kaposi's sarcoma cell proliferation was evaluated. Results indicated that all the compounds reduced the cell proliferation in a dose-dependent manner.     

A new flavonol glycoside from the aerial parts of Astragalus vulneraria

A new flavonol glycoside, isorhamnetin 3-O-beta-D-apiofuranosyl-(1-->2)-alpha-L-rhamnopyranosyl-(1-->6)]-beta-D-galactopyranoside, and the known diglycoside, isorhamnetin 3-O-alpha-L-rhamnopyranosyl-(1-->6)-beta-D-galactopyranoside were isolated from the aerial parts of Astragalus vulneraria. Characterization of the two compounds was done by spectroscopic methods (1D and 2D NMR, and FAB-MS).     

Phenylethyl Glycosides from Globularia alypum Growing in Turkey

From the leaves of Globularia alypum, three new phenylethyl glycosides, namely galypumosides A (=2‐(3,4‐dihydroxyphenyl)ethyl O‐α‐rhamnopyranosyl‐(1→3)‐4‐O‐[(E)‐caffeoyl]‐6‐O‐[(E)‐p‐coumaroyl]‐β‐glucopyranoside; 1 ), B (=2‐(3,4‐dihydroxyphenyl)ethyl O‐α‐rhamnopyranosyl‐(1→3)‐4‐O‐[(E)‐caffeoyl]‐6‐O‐[(E)‐feruloyl]‐β‐glucopyranoside; 2 ), and C (=2‐(3,4‐dihydroxyphenyl)ethyl O‐α‐rhamnopyranosyl‐(1→3)‐4‐O‐[(E)‐caffeoyl]‐6‐O‐menthiafoloyl‐β‐glucopyranoside; 3 ), were isolated, together with two known phenylethyl glycosides, calceolarioside A and verbascoside. Eight iridoid glucosides, catalpol, globularicisin, globularin, globularidin, globularinin, globularimin, lytanthosalin, and alpinoside, a flavon glycoside, 6‐hydroxyluteolin 7‐O‐sophoroside, a lignan glycoside, syringaresinol 4′‐O‐β‐glucopyranoside, and a phenylpropanoid glycoside, syringin, were also obtained and characterized. The structures of the isolates were elucidated on the basis of 1D‐ and 2D‐NMR experiments as well as HR‐MALDI‐MS.     

Characterisation by liquid chromatography-electrospray tandem mass spectrometry of anthocyanins in extracts of Myrtus communis L. berries used for the preparation of myrtle liqueur

Anthocyanins in extracts of berries of Myrtus communis, prepared following a typical Sardinia myrtle liqueur recipe, were identified and quantified by HPLC coupled with electrospray/tandem mass spectrometry using, respectively, an ion trap and a triple quadrupole mass analyser. The fragmentation patterns of the anthocyanidins were dependent on the MS technique employed, and differed considerably from those previously reported. The anthocyanin profile of five anthocyanin glucosides and four anthocyanin arabinosides, the latter not previously identified in this specie, was specific for myrtle berry extracts. The quantitative compositions of extracts of myrtle berries derived from different geographical areas in Italy were compared.     

Liquid chromatography/tandem mass spectrometry of unusual phenols from Yucca schidigera bark: comparison with other analytical techniques

Qualitative and quantitative analyses of phenolic compounds are of interest for both medicinal and food plants. In the present work, the phenolic fraction from Yucca schidigera, a plant bearing the GRAS (Generally Recognized as Safe) label approved by the US Food and Drug Administration, was studied. Crude extracts of Y. schidigera bark were investigated by liquid chromatography/UV spectrophotometry with diode-array detection, liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) and liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS), in order to develop and optimize simple and rapid techniques to determine both stilbenes and yuccaols for the purposes of quality control of collected material. With optimal LC and MS conditions, stilbenes and yuccaols were quantified with all the proposed methods and the results were compared. Sensitivity was evaluated and the results indicated that MS/MS detection in the multiple reaction monitoring mode is easily applicable to this plant and allows the rapid and direct identification and quantification of these peculiar compounds in crude plant extracts.     

Patavine, a new arylnaphthalene lignan glycoside from shoot cultures of Haplophyllum patavinum

A new arylnaphthalene lignan glycoside, patavine (1), together with five known lignans, justicidin B (2), diphyllin (3), tuberculatin (4), majidine (5), and arabelline (6) were isolated from shoot cultures of Haplophyllum patavinum. The structure of the new compound was elucidated by extensive one-dimensional (1D) and two-dimensional (2D) NMR experiments and mass spectrometry. The cytotoxicity of compounds 1, and 3-6 against LoVo human colon carcinoma cells was investigated.     

Derivatives of pyrido[2,3‐b][1,4]diazepine and of the dipyrido[1,2‐a:2′,3′‐b]imidazole heterocyclic system

With a continuing interest in heteropolycyclic systems which may show biological activities, we studied the reaction of 3‐amino‐2‐(methylamino)pyridine with diethyl 1,3‐acetonedicarboxylate in order to develop pyridodiazepinone derivatives. From the reaction mixture, we separated dipyrido[1,2‐a:2′,3′‐d]imidazole derivatives ( 3 and 4 ) besides two isomeric pyrido[2,3‐b][1,4]diazepine derivatives ( 5 and 6 ) in which the complex structural differentiation was achieved through nmr experiments and chemical evidence. Several attempts to elaborate isomers 5 and 6 have not yet given significant results.     

Profiles analysis of proanthocyanidins in the argun nut (Medemia argun—an ancient Egyptian palm) by LC–ESI–MS/MS

Medemia argun is an ancient palm rich in proanthocyanidins (PACs). These polyphenolic compounds are widely distributed in plants and are an integral part of the human diet. A sensitive high‐performance liquid chromatography and electrospray ionization mass spectrometry (HPLC–ESI–MS) method in the negative ion mode for sequencing these ubiquitous and highly beneficial antioxidants is described in order to profile different PACs in M. argun nuts. The analytical protocol based on tandem mass spectrometry was used to sequence dimers, trimers, tetramers and pentamers with different A‐type, B‐type and A/B‐type linkages. Diagnostic ions resulting from heterocyclic ring fission and retro‐Diels–Alder reaction of flavan‐3‐ol provided information on the hydroxylation pattern and the type of interflavan bond. The sequences were discovered through ions derived from quinone methide cleavage of the interflavan bond. The identification of PACs linkages through LC–MSⁿ eliminates a number of tedious separation steps. The method was successfully applied to give a view of PAC profile in M. argun nuts. M. argun nuts contained 636.88 mg/g PACs (as equivalent of (þ)‐catechin). The data obtained in our research show that M. argun is a rich source of hydrolyzable PACs. Copyright © 2014 John Wiley & Sons, Ltd.     

Vaporization study of the SbBr3 system by the torsion—effusion method

Vapor pressures of solid antimony tribromide were measured by the torsion—effusion technique. The values obtained can be expressed by the equation log P(atm) = (9.3 ± 1.3) ? (4.4 ± 0.5)/T in the temperature range 324–368 K.The standard heat of vaporization was derived by second- and third-law treatment of the data and compared with values reported in the literature. The value ΔH⁰_vap (298 K) = 19.5 ± 0.5 kcal mole^?1 was derived.