Phenolic Compounds of Plants of the Scutellaria L. Genus. Distribution, Structure, and Properties

Information on flavones, flavanones, flavanonols, flavonols, chalcones, isoflavones, biflavonoids, lignoflavonoids, and lignane glycosides and stilbenes isolated from plants of the Scutellaria L. genus was systematized and reviewed. A list of 208 phenolic compounds was given according to flavonoid type with an indication of the plant sources, structures, and physicochemical properties and citations of the original articles.     

Complete 1H and 13C NMR spectral assignment of cis- and trans- 3-(2-[2-(4-methylphenyl)ethenyl]phenyl])sydnones

1H and 13C NMR spectra of cis- and trans-3-(2-[2-(4-methylphenyl)ethenyl]phenyl])sydnones, the first stilbene-substituted mezoionic oxadiazolium rings, were fully assigned combining the information in various solvents, such as deuterated benzene, acetone and chloroform, using 2D NMR techniques.     

Effects of fluorine atoms on the optical nonlinear response of stilbene derivatives

The effect of fluorine atoms on the second-order optical nonlinear response of 4-nitro-4′-methoxy-trans-stilbene and polyene derivatives containing up to three double bonds (n=1, 2, 3) has been investigated within a semiempirical context (PM3 Hamiltonian). Experimental data reported in literature indicate a β_vec(SHG) value of 34, 47 and 76 (×10⁻³⁰ esu) for n=1, 2, 3, respectively, at 0.65 eV in CHCl₃ solutions. Our calculations show that fluorinating the nitrophenyl group the β_vec(SHG) is doubled. Further increase in the second-order nonlinear response can be obtained fluorinating the CC bond linkers between the aromatic moieties.Besides, the effect of different donor-acceptor pairs has been studied and the results interpreted in the two-state model context.Some results concerning the third-harmonic generation (THG), γ (THG), are presented, and a possible interpretation proposed.     

Mammalian Arginase Inhibitory Activity of Methanolic Extracts and Isolated Compounds from Cyperus Species

Polyphenolic enriched extracts from two species of Cyperus, Cyperus glomeratus and Cyperus thunbergii, possess mammalian arginase inhibitory capacities, with the percentage inhibition ranging from 80% to 95% at 100 µg/mL and 40% to 64% at 10 µg/mL. Phytochemical investigation of these species led to the isolation and identification of two new natural stilbene oligomers named thunbergin A-B (1–2), together with three other stilbenes, trans-resveratrol (3), trans-scirpusin A (4), trans-cyperusphenol A (6), and two flavonoids, aureusidin (5) and luteolin (7), which were isolated for the first time from C. thunbergii and C. glomeratus. Structures were established on the basis of the spectroscopic data from MS and NMR experiments. The arginase inhibitory activity of compounds 1–7 was evaluated through an in vitro arginase inhibitory assay using purified liver bovine arginase. As a result, five compounds (1, 4–7) showed significant inhibition of arginase, with IC₅₀ values between 17.6 and 60.6 µM, in the range of those of the natural arginase inhibitor piceatannol (12.6 µM). In addition, methanolic extract from Cyperus thunbergii exhibited an endothelium and NO-dependent vasorelaxant effect on thoracic aortic rings from rats and improved endothelial dysfunction in an adjuvant-induced arthritis rat model.     

Gnetifolin L and O, Two Dimeric Stilbenes from Gnetum Montanum

GnetuI)1monlanlImgr0wsinthes0uthernpart0fChinaandhasbeenusedf0rthetreatment0fbronchitisandarthritisinf0lkmedicinel.Previously,aninvestigationofthisspeciesledt0theis0lationofs0meaIkal0idsanddibenzyletherderivatives2.lnourstudies,tenc0mp0nentsincludingresveratr0l,is0rhapontigenin,daucoster0l,O-sitosterol,stearicacid,gnetif0linE,gnet0l,is0rhapontigenin-3-O-6-gluc0pyra(-)8-viniferinandgnetifolinCwere0btainedfromthisplant'.Inthefurtherstudy,f0urnewdimericstilbenesnamedgnetif0IinMandN',gnetifoli…     

Regioselective reductive demethoxylation of 3,4,5-trimethoxystilbenes

Selective removal of the 4-methoxy group of 3,4,5-trimethoxystilbenes was performed under electron transfer conditions from Na metal in THF. Careful control of reaction conditions and quenching procedure allowed the synthesis of either (E)-3,5-dimethoxystilbenes or 3,5-dimethoxybibenzyls.     

Negative ion electrospray high‐resolution tandem mass spectrometry of polyphenols

Representative compounds with a 1,3‐dihydroxybenzene substructure belonging to different important polyphenol classes (stilbenes, flavones, isoflavones, flavonols, flavanones, flavanols, phloroglucinols, anthraquinones and bisanthraquinones) were investigated based on detailed high‐resolution tandem mass spectrometry measurements with an Orbitrap system under negative ion electrospray conditions. The mass spectral behaviour of these compound classes was compared among each other not only with respect to previously described losses of CO, CH₂CO and C₃O₂ but also concerning the loss of CO₂ and successive specific fragmentations. Furthermore, some unusual fragmentations such as the loss of a methyl radical during mass spectral decomposition are discussed. The obtained results demonstrate both similarities and differences in their mass spectral fragmentation under MSⁿ conditions, allowing a characterization of the corresponding compound type. Copyright © 2015 John Wiley & Sons, Ltd.