HMBC Spectra Research Articles

Yeast Glycogen Synthase Kinase-3β Pathway Inhibitors from an Organic Extract of Streptomyces sp.

Investigation of a microbial fermentation organic extract of Streptomyces sp. H7667 led to the isolation of three new imides, 3-[(5E)-5-methyl-4-oxo-2-hydroxy-5-octenyl]glutarimide (1), 2-amino-N-2'-(phenylacetyl)propanimide (5), and 2-amino-N-(2'-(cyclohex-2''-enyl)acetyl)acetimide (6), and one new isoflavonoid glycoside, 6-O-methyl-7-O-alpha-rhamnopyranosyldaidzein (7), along with four known compounds. Their structures were elucidated by HRESIMS, 1H and 13C NMR, COSY, HMQC, HMBC, and NOESY spectra. Compounds 1-8 were evaluated for their inhibitory activities in the yeast glycogen synthase kinase-3beta assay.

Profiling of Iris germanica extracts by LC-PDA-MS and off-line microprobe NMR

The roots of German iris (Iris germanica L., Iridaceae) have been traditionally used for various topical applications including the treatment of sores and freckles [1]. Characteristic constituents of the root are isoflavones which reportedly show anti-inflammatory and anti-oxidative properties [1] [2]. For these reasons iris root extracts are used as cosmetic ingredients. Lipophilic and polar extracts of iris root were submitted to a phytochemical profiling by semi-preparative HPLC and off-line NMR measurements in a 1mm TXI microprobe (active volume 5µL) [3]. A total of 18 compounds were purified in sub-milligram to milligram amounts via two successive chromatographic steps on a SunFire column (10×150mm; 5µm, Waters) with a gradient of acetonitrile in water containing 0.1% HCOOH. The compounds were identified as isoflavones, isoflavone glycosides and acetovanilllone by analysis of on-line MS and PDA, and off-line NMR data including HSQC and HMBC spectra. The activity of the isolated compounds on the proliferation of endothelial cells is currently being investigated. The example demonstrates the applicability of the off-line HPLC microprobe NMR approach as a robust means for a rapid chemical and biological characterization of the constituents of plant extracts.

Novel Secondary Metabolites, Spirosorbicillinols A, B, and C, from a Fungus

In our searching program for novel sorbicillin related compounds, three novel compounds, spirosorbicillinols A (1), B (2), and C (3), were isolated from the fermentation broth of the USF-4860 strain isolated from a soil sample. The planar structures of compounds 1-3 were determined from spectroscopic evidence and degradation reaction, and that of 1 was the same as that of 2. The relative stereochemistries of compounds 1-3 were determined by (1)H-(1)H coupling constants, the elucidation of HMBC and NOESY spectra in detail. 1 and 2 were stereoisomers at C8 position, each other. We propose that compounds 1 and 2 were formed by exo and endo intermolecular Diels-Alder reaction between sorbicillinol as a diene and scytolide (proposed precursor-1) as a dienophile, respectively. Similarly, we propose that compound 3 was formed by an endo intermolecular Diels-Alder reaction between sorbicillinol and proposed precursor-2.

New Iridoid Esters from the Roots of Patrinia scabiosaefolia

were established by the HMBC spectrum. Correlations between the signals at δ 6.88 (H-6)/6.31 (H-7) and δ 45.4 (C-9), δ 2.81 (H-9) and δ 67.2 (C-10) confirmed that the isolated hydroxymethyl group was connected to C-8. In addition, correlations between signals δ 6.24 (H-1) and δ 172.0 (C-1'), δ 4.87 (H-11a)/4.65 (H-11b) and δ 172.8 (C-1) indicated that the isovaleryloxy group was connected to C-1 and C-4, respec-tively. The positions of the methoxy groups at C-3 and C-8 were confirmed by cross peaks between δ 3.44 (OCH

New Dibenzofurans from the Branches of Distylium racemosum Sieb. et Zucc

correlation with this carbon (134.5 ppm) in its HMBC spectrum. The methyl proton (H-11) in the ring B showed a NOESY peak with H-8 aromatic proton, which in turn showed NOESY correlation with anomeric proton (H-1') of a sugar moiety, thereby suggesting the sugar residue is placed at C-7 position. This was further confirmed by HMBC correlation observed between H-1' and C-7. The

A pair of taxoids from the needles of Taxus canadensis

A pair of taxoids were isolated from the needles of Taxus canadensis, which were identified as 2,10-diacetyl-5(Z)-cinnamoylphototaxicin II (1), a new taxoid, and 2,10-diacetyl-5(E)-cinnamoylphototaxicin II (2), a known one, by spectroscopic methods including 1H, 13C NMR, HSQC, HMBC, NOESY, and mass spectra.

Structure analysis of an acidic polysaccharide isolated from green tea

An acidic polysaccharide (ATPS-2) was isolated and purified from coarse green tea. ATPS-2 with peak molecular weight of 4430 Da was composed of rhamnose, arabinose, galactose and galacturonic acid. Structure features of the purified ATPS-2 were investigated by a combination of chemical and instrumental analysis, such as periodate oxidation, Smith degradation, 1H NMR, 13C NMR, COSY, HSQC, HMBC and ROESY spectrum. It was found that ATPS-2 was a pectic polysaccharide. The backbone proved to consist of the smooth region of α-1,4-D-galactopyranosyluronan blocks interconnected by 1,2-linked rhamnose residues involved in the linear sugar chain. The ramified hairy regions were shown to contain the following of the backbone: →4)-α-D-GalpA-(1 → 2)-α-L-Rhap-(1 → 4)α-D-GalpA-(1→ and the side chains attached to the residues of rhamnopyranose of these fragments. The backbone galacturonic acid residues of ATPS-2 were partially O-methyl esterified and acetylated. The side chains contain linear and branched α-L-Araf and β-D-Galp residues.

NMR Study on a Novel Mucin from Jellyfish in Natural Abundance, Qniumucin from Aurelia aurita

A novel mucin (qniumucin), which we recently discovered in jellyfish, was investigated by several NMR techniques. Almost all the peaks in the (13)C and proton NMR spectra were satisfactorily assigned to the amino acids in the main chain and to the bridging GalNAc, the major sugar in the saccharide branches. The amino acid sequence in the tandem repeat part (-VVETTAAP-) was reconfirmed by the cross-peaks between alpha protons and carbonyl carbons in the HMBC spectrum. A connectivity analysis around the O-glycoside bond (GalNAc-Thr) was also performed, and detailed information on the local configuration was obtained by the DPFGSE-NOE-HSD technique. The strategy and the results described in this paper can be extended to the structural analysis of general O-glycan chains, which are more complex than the present mucin. NMR analyses reveal the simple structure of qniumucin extracted by the present protocol, and the homogeneity and purity of qniumucin are probably the result of it being extracted from jellyfish, a primitive animal.

NMR Investigation of Aniline Oligomers Produced in the Early Stages of Oxidative Polymerization of Aniline

The products obtained within early stages of the oxidative polymerization of aniline in solutions of various weak organic acids or in water, and aniline oligomers produced by the oxidation of aniline and aniline-(15)N in acetic acid (0.4 M) with a limited amount of oxidant were analyzed using 1H, 13C, and 15N 1D and 2D NMR spectroscopy and 1H PFG NMR. Such products are virtually identical in all cases, according to 1H NMR. They are always a mixture of products, among which one of them is prominent. Both native and neutralized forms of the products were examined. As shown by a combination of 1H DQF COSY, 1H NOESY, 1H-(13)C and 1H-(15)N HSQC, and 1H-(13)C and 1H-(15)N HMBC spectra, both forms of this product contain an oligoaniline moiety ended mostly by phenylamino groups. In a significant amount, the chains contain--either as an inner or terminal group--an unexpected six-member ring with an oxygen-containing substituted quinoneimine structure. The most probable structure of the major product is given. The difference between the native and neutralized forms of the product was examined. It is shown that the oligomeric chains, in particular quinoneimine units of the former one, are protonated. Both forms of the product exhibit a slight paramagnetism, and contain about 2x10(-9) mol g(-1) of unpaired electron spins.

Complete assignments of 1H and 13C NMR data for new dibenzocyclooctadiene lignans from Kadsura oblongifolia

Two new dibenzocyclooctadiene lignans, named kadoblongifolins A (1) and B (2), and one new natural product dibenzocyclooctadiene lignan, named kadoblongifolin C (3), were isolated from the stems of Kadsura oblongifolia (K. oblongifolia), together with five known ones, schizanrin F (4), propinquanin C (5), schisantherin G (6), heteroclitin Q (7), kadsurarin (8). The structures of these new lignans were elucidated by a combination of high-resolution electron ionization mass spectrometry (HR-EI-MS), (1)H NMR, (13)C NMR, HMQC, HMBC, and NOESY spectra.

Microbial transformation of epothilone A by Aspergillus niger AS 3.739

The microbiological transformation of epothilone A (1) by Aspergillus niger AS 3.739 afforded four main metabolites. Their structures were elucidated by 1H, 13C NMR and HSQC, COSY, HMBC, and NOESY spectra as trans-12,13-hydroxylated epothilone A (2), cis-12,13-hydroxylated epothilone A (3), trans-12,15-epoxidated epothilone A (4), and cis-12,15-epoxidated epothilone A (5). All four compounds were firstly found based on their stereochemistry. These new compounds displayed cytotoxicity against human breast carcinoma cells MCF-7 with IC50 9.88 μg/ml of 2, 2.52 μg/ml of 3, 9.88 μg/ml of 4, and 5.68 μg/ml of 5.

1H and 13C NMR Spectral Study of Some 2r-Aryl-6c-phenylthian-4-ones, Their 1-Oxides and 1,1-Dioxides

ABSTRACT Four 2r-aryl-6c-phenylthian-4-ones 1b−1e and their 1-oxides 2b−2e and 1,1-dioxides 3b−3e have been newly synthesized. 1H and 13C NMR spectra have been recorded for all these compounds and 2r,6c-diphenylthian-4-one 1-oxide 2a. 13C NMR spectrum has been recorded for the sulfone 3a of 1a. For selected compounds 1H-1H COSY, HSQC, HMBC, and NOESY spectra have been recorded. The vicinal proton–proton coupling constants suggest that in all these compounds, the heterocyclic ring adopts chair conformation with equatorial orientations of the aryl and phenyl groups. Proton and carbon chemical shifts suggest that in the sulfoxides, the S=O bond is axial and enhances the J aa value by some special effect. The S = O bond causes a significant upfield shift even on carbons without hydrogens. Significant solvent shifts also were observed.

New Alkaloids from Oryza sativa cv. Heugjinjubyeo Bran

) was also deduced from both the carbon signals at δ 166.13 and δ 51.55. The location of the carbomethoxy group was determined to be at the C-5 position in dihydrobenzofuran moiety by HMBC spectrum. The methylenedioxy protons at δ 6.73 were correlated with two carbon peaks at δ 145.05 and δ 145.72 on a benzodioxine moiety in selective HMBC long range spectrum.

Production of uremic toxin methylguanidine from creatinine via creatol on activated carbon

The mixture of creatinine, activated charcoal and water was stirred. As a result the conversion of creatinine into two products was observed. 1H, 13C NMR and HMBC spectra were recorded and the chemical shifts assigned. Two uremic toxins: creatol and N-methylguanidine were identified. To interpret the NMR data obtained, the optimum structure of creatol, which can exist in the forms of seven tautomers, has been calculated using the DFT B3LYP/6-311G(2d,p) method. The influence of the solvent was described by the polarizable continuum model (PCM). The calculated energy of the most energetically stable tautomeric form A is lower by 12.2, 16.9, 33.8, 81.5, 106.3, 130.4 kJ/mol in water than that of the tautomers B– G, respectively, which suggests that the A form of creatol should prevail in solution. In DMSO, the calculated energy of the most energetically stable tautomeric form A is lower than that of both D and B and the remaining tautomeric forms ( C, E– G) are less energetically stable. Subsequently, we sought the correlations between the experimental and the calculated chemical shifts of protons and carbons-13 for the forms – A, B (in water) and A, B, D (in DMSO) – of creatol. The population of the A tautomer is predominant in both H 2O and DMSO. We have also recorded the spectra of creatol and N-methylguanidine at different pH. Our data are complete enough to be used in the analysis of body fluids.

Structural elucidation and immuno-stimulating activity of an acidic heteropolysaccharide (TAPA1) from Tremella aurantialba

A novel acidic heteropolysaccharide (TAPA1) was purified from hot water extracts of Tremella aurantialba fruiting bodies by DEAE-Sepharose Fast Flow and Sephacryl S-500 High-Resolution Chromatography. The heteropolysaccharide had a molecular weight of ca. 1.35 × 10 6 Da, and a carbohydrate content estimated to be ∼98.7% by the phenol–sulfuric acid method. It was composed mainly of d-mannose, d-xylose, and d-glucuronic acid in the ratio of ca. 5:4:1, along with trace amounts of d-galacturonic acid and d-glucose. Monosaccharide compositional analysis and GC–MS of methylated derivatives, combined with 1H and 13C NMR spectroscopies (including COSY, TOCSY, NOESY, HSQC, and HMBC spectra), revealed TAPA1 to consist of an α-(1→3)-linked mannopyranosyl backbone, partially substituted at position 4 with xylose side chains, and at position 2 with side chains composed of either xylose, mannose, and glucuronic acid or of xylose and mannose. Bioactivity testing showed that TAPA1 stimulated the proliferation of mouse spleen lymphocytes in vitro.

New phragmalin-type limonoids from Swietenia macrophylla King

Abstract The fruit of Swietenia macrophylla is commonly known as “sky fruit”. The fruit, which contains flavonoids and saponins, is processed commercially into a wide range of health foods and healthcare products. The fruit concentrate is used traditionally to improve blood circulation and impart a healthy skin. In this paper, we describe the isolation and structure elucidation of three new phragmalin ortho esters, named swietephragmin H-J ( 1 – 3 ), and a new polyhydroxylated phragmalin, named swietemacrophine ( 4 ), from the leaves of S. macrophylla . The structures of the compounds were elucidated by spectroscopic methods, including HRESIMS, 1 H NMR, 13 C NMR, DEPT, 1 H– 1 H COSY, HMQC, HMBC and NOESY spectra. This is the first report of phragmalin ortho esters and a polyhydroxylated phragmalin from this plant.

Suppressing One‐Bond Correlations in HMBC Spectra: Improved Performance for the BIRD–HMBC Pulse Sequence

An improved version of the BIRD-HMBC experiment is proposed. In comparison to the original version, the filtering (suppression of (1) J(CH) signals) is accomplished using a double tuned G-BIRD filter positioned in the middle of the long-range correlations evolution period. Compensation of offset dependence by replacing the rectangular 180 degree pulses with the broadband inversion pulses (BIPs), with superior inversion performance and improved tolerance to B(1) field inhomogeneity, significantly improves the sensitivity of the original BIRD-HMBC experiment. For usual one-bond coupling constants ranges (115-180 Hz), optimal results are easily obtained by adjusting the delays, delta, of the BIRD elements to an average J value. For larger ranges (e.g. 110-260 Hz), the use of a double tuned G-BIRD filter allows excellent suppression degrees for all types of one-bond constants present in a molecule, superior to the original scheme and other purging schemes. These attributes make the improved version of the BIRD-HMBC experiment a valuable and robust tool for rapid spectral analysis and rapid checks of molecular skeletons with a minimum spectrometer time.

Hydrogen bonds in phenylboronic acids with polyoxaalkyl substituents at ortho-position

Phenylboronic acids with polyoxaalkyl substituents at ortho position were synthesized from the corresponding bromides. Structures in solid state, determined by single crystal X-ray diffraction, reveal the presence of inter- and intramolecular hydrogen bonds. Presence of several oxygen atoms in oxaalkyl chains enables the formation of intramolecular hydrogen bonds by B(OH) 2 group with different oxygen centers which lead to the formation of bifurcated hydrogen bonds. Investigated compounds were characterized by 1H, 13C, 11B and 17O NMR spectroscopy in solution. Assignment of 1H and 13C signals was made on the basis of HSQC and HMBC spectra. 17O NMR spectra show that in acetonitrile solution hydrogen bonds with solvent molecules are predominant.

Clean HMBC: Suppression of strong-coupling induced artifacts in HMBC spectra

A new experiment, clean HMBC, is introduced for suppression of strong-coupling induced artifacts in HMBC spectra. The culprits of these artifacts are an inherent shortcoming of low-pass J filters in the presence of strong coupling and the 1H π pulse in the middle of the evolution period aimed at suppressing evolution under heteronuclear J couplings and 1H chemical shifts. A π pulse causes coherence transfer in strongly coupled spin systems and, as is well known in e.g., homonuclear J spectra, this leads to peaks that would not be there in the absence of strong coupling. Similar artifacts occur in HMBC spectra, but they have apparently been overlooked, presumably because they have been assigned to inefficiency of low-pass J filters or not noticed because of a coarse digital resolution in the spectra. Clean HMBC is the HMBC technique of choice for molecules notorious for strong coupling among protons, such as carbohydrates, and the new technique is demonstrated on D-mannose. Finally, a fundamental difference between HMBC and H2BC explains why strong-coupling artifacts are much less of a problem in the latter type of spectra.

Steroidal Saponins from the Seeds of Hyoscyamus Niger L.

Ten steroidal saponins have been isolated form the seeds of Hyoscyamus niger L. for the first time and their structures have been elucidated. Seven saponins belong to spirostane series, two are furostane-type and one is pregnane glycoside. Hyoscyamosides B, C and C2 are new steroidal saponins, which have never been reported before in literature. Complete assignments of the 1H and 13C NMR chemical shifts for all these glycosides were achieved by means of one- and two-dimensional NMR techniques, including 1H–1H COSY, HSQC, HMBC and ROESY spectra.