Heteronuclear Multiple Bond Correlation Spectroscopy Research Articles

1H and 13C NMR spectral assignments for low-concentration bile acids in biological samples

Bile acids are the main body of enterohepatic circulation in vivo. They have essential functions such as emulsifying fat, bacteriostasis and regulating multiple metabolic pathways as signal molecules. However, the assignments of NMR signals for some low-concentration bile acids are still needed. This study combined 1D nuclear magnetic resonance (NMR) and 2D NMR techniques including 1H–1H correlation spectroscopy (COSY), 1H–1H total correlation spectroscopy (TOCSY), 1H J-resolved spectroscopy (J-Res), 1H–13C heteronuclear single quantum coherence spectroscopy (HSQC), and 1H–13C heteronuclear multiple bond correlation spectroscopy (HMBC) to assign the 1H and 13C signals of six bile acids in aqueous solution at physiological pH (∼7.4) and nine bile acids in methanol. These data are of importance to the NMR-based studies on lipid digestion, absorption, and metabolism.

Major Carotenoids of Meiothermus ruber Are Deinoxanthin Glucoside Esters, Not Meiothermoxanthin Glucoside Esters

Meiothermus ruber DSMZ 1279T was isolated from a hot spring in Kamchatka and was red in color. The major carotenoid present was reported to be 1'-(β-d-glucopyranosyloxy)-3,4,3',4'-tetradehydro-1',2'-dihydro-β,ψ-caroten-2-one after saponification (Burgess et al. J. Nat. Prod. 1999, 62, 859-863). In this study, we purified the major carotenoids in this species without saponification. We then reidentified the major carotenoids present using spectroscopic data, including electronic circular dichroism (ECD), 1H NMR, rotating-frame nuclear Overhauser effect spectroscopy (ROESY), 13C NMR, heteronuclear single-quantum correlation spectroscopy (HSQC), heteronuclear multiple-bond correlation spectroscopy (HMBC), and MS, and enzymatic hydrolysis of fatty acid moieties and found deinoxanthin glucoside iso fatty acid esters. The bound fatty acids present included four iso types, and their composition differed from cellular lipids. Moreover, the previously identified carotenoid glucoside was a saponification artifact of deinoxanthin glucoside esters. Ketomyxocoxanthin glucoside esters and 1'-hydroxytorulene glucoside esters were also present. On the basis of the identification of carotenoids and the whole genome sequence of M.ruber, we propose a carotenoid biosynthetic pathway and note the corresponding genes.

Steroid glycosides isolated from Paris polyphylla var. chinensis aerial parts and paris saponin II induces G1/S-phase MCF-7 cell cycle arrest

In our previous research on Vietnamese medicinal plants, we found that the ethanolic extract of the aerial parts of Paris polyphylla var. chinensis exhibited cytotoxic effects in vitro in the MCF-7 human cancer cell line. Here, we used combined chromatographic separations to isolate six compounds including a new steroid glycoside, paripoloside A (3), and five known compounds, from the butanol extract of the aerial parts of P. polyphylla. We unambiguously elucidated their structures based on spectroscopic data (proton and carbon-13 nuclear magnetic resonance, heteronuclear single quantum coherence, heteronuclear multiple bond correlation, correlation spectroscopy, and high-resolution electrospray ionization mass spectroscopy data), and chemical reactions. Among the isolated compounds, paris saponin II (PSII) had the strongest cytotoxic effects against MCF-7 breast cancer cells. Interestingly, PSII significantly increased the expression of p53, p21, p27, and Bax protein levels and significantly suppressed the expression of cyclin D1 and retinoblastoma protein. These data suggest that PSII may induce G1/S phase cell cycle arrest and apoptosis pathway development in MCF-7 cells. Furthermore, the MCF-7 breast cancer cells mechanism of PSII was also investigated using molecular docking. Together, our results demonstrate that isolated compounds from P. polyphylla are promising candidates as breast cancer inhibitors.

In vitro anticancer and antibacterial potentials of selected medicinal plants and isolation and characterization of a natural compound from Withania coagulans.

In the current study, five different plants, Syzygium Cumini, Fagonia cretica, Acacia modesta, Withania coagulans, and Olea europaea aqueous extracts were prepared and applied against the anticancer and antibacterial activities. It was observed that O.Europaea extract shows the highest anticancer activity with cell viability of 21.5%. All the five plants extract was also used against the inhibition of Bacillus subtilis where O.Europaea extract shows a promising inhibitory activity of 3.2cm followed by W.coagulans. Furthermore, W.coagulans was subjected to the process of column chromatography as a result a withanolide was isolated. The fast atom bombardment mass spectrometry (FAB-MS) and high resolution fast atom bombardment (HRFAB-MS) [M+1] indicated molecular weight at m/z 453 and molecular formula C28H37O5. The UV-Vis. spectrum shows absorbance at 210nm suggesting the presence of conjugated system, and Fourier-transform infrared spectroscopy (FTIR) was recorded to explore the functional groups. Similarly, 1D and 2D NMR spectroscopy techniques such as 1H, 13C NMR, correlation spectroscopy (COSY-45°), heteronuclear single quantum correlation (HSQC), heteronuclear multiple bond correlation (HMBC) and Nuclear Overhauser effect Spectroscopy (NOESY) techniques was carried out to determine the unknown natural product. The collective data of all these techniques established the structure of the unknown compound and recognized as a withanolide.

Unusual ent-Kaurane Diterpenes from the Coffea Cultivar S288 Coffee Beans and Molecular Docking to α-Glucosidase.

A total of 11 new (1-11) and 2 known (12 and 13) ent-kaurane diterpene derivatives were identified from the roasted beans of Coffea cultivar S288. Their structures were established by extensive spectroscopic analysis, including one- and two-dimensional nuclear magnetic resonance (heteronuclear single-quantum correlation, heteronuclear multiple-bond correlation, correlation spectroscopy, and rotating-frame Overhauser enhancement spectroscopy), high-resolution electrospray ionization mass spectrometry, and X-ray analyses. Cafespirone acid A (1) represents the first example of diterpene featuring a spirocyclic skeleton constructed from a 6/6/5 tricyclic system. Cafeane acid A (2) possesses a 6/6/6/5 tetracyclic system as a result of the C/D ring rearrangement. Furthermore, compounds 1-12 were evaluated for their α-glucosidase inhibitory activity. The results showed that compounds 2, 4, 5, 6, 7, 10, and 11 had a moderate inhibitory effect on α-glucosidase, and half-maximal inhibitory concentration values of compounds 4, 6, 7, and 10 were 18.76 ± 1.46, 4.88 ± 0.03, 12.35 ± 0.91, and 12.64 ± 0.59 μM, respectively, compared to the positive control acarbose (60.71 ± 16.45 μM). Additionally, the molecular docking experiments showed that the carbonyl group at C-19 of compounds 4, 6, and 7 formed strong hydrogen bonds with ARG315, which may make them have moderate inhibitory activity.

Hybridized Fe/Ru-SiMWCNT-ionic liquid nanofluid for CO2 conversion into carbamate using superoxide ion

Suppressing the nucleophilic susceptibility of ionic liquids based nanofluid is necessary for energy storage and superoxide ion (O2•−) utilization. This study reports the development of novel pseudocapacitive Fe/Ru-SiMWCNT nanofluid comprising of Fe3O4, RuO2, SiO2, and MWCNT hybridized phases. The Fe/Ru-SiMWCNT nanohybrid possessed CO2 and O2 sorption capability, as confirmed from the temperature-programmed desorption experiments. Detailed spectroscopy techniques characterize the Fe/Ru-SiMWCNT nanohybrid component's physicochemical and morphological properties. The novel ionic liquid (IL) based nanofluid index is Fe/Ru-SiMWCNT/1-(2-methoxyethyl)-1-methylpyrrolidinium tris(pentafluoroethyl) trifluorophosphate. Therefore, stable O2•− was generated therein at −0.445 V vs Ag/AgCl and recorded long-term stability for 2 days with 87.31 % efficiency. Moreover, the O2•− mediated CO2 conversion to C2O62− at −0.54 V vs Ag/AgCl with 97.90 % energy efficiency. Also, the normalized exchange current density in the nanofluid was 2.20 mA/cm2, which is higher than 1.94 mA/cm2 observed in the IL counterpart. The high normalized exchange current density is due to Fe/Ru-SiMWCNT nanohybrid phase's pseudocapacitance. Accordingly, this pseudocapacitive capability enables converting O2 and CO2 in the nanofluid with lower activation overpotential of −0.305 and −0.460 V vs Ag/AgCl, respectively. In contrast, the conversion of O2 and CO2 in the IL required higher activation overpotential of −0.826 and −1.013 V vs Ag/AgCl, respectively. The electrolysis of O2/CO2 in the nanofluid containing diethanolamine at −1.564 V vs Ag/AgCl, 60 °C and 1.0 h produced methyl 2-hydroxyethyl (methyl) carbamate as the primary product. The heteronuclear multiple bond correlation spectroscopy analysis finally elucidated the carbamate structure by two strong correlations between the protons and carbons in the vicinity of three and four bonds apart. Therefore, this study highlights the control design of electrochemically stable IL-based nanofluids robust for reactive oxygen species, energy storage and conversion.

Activating Magnesium Electrolytes through Chemical Generation of Free Chloride and Removal of Trace Water.

Mg batteries are attractive next-generation energy storage systems due to their high natural abundance, inexpensive cost, and high theoretical capacity compared to conventional Li-ion based systems. The high energy density is achieved by electrodeposition and stripping of a Mg metal anode and requires the development of effective electrolytes enabled by a mechanistic understanding of the charge-transfer mechanism. The magnesium aluminum chloride complex (MACC) electrolyte is a good model system to study the mechanism as the solution phase speciation is known. Previously, we reported that minor addition of Mg(HMDS)2 to the MACC electrolyte causes significant improvement in the Mg deposition and stripping voltammetry resulting in good Coulombic efficiency on cycle one and, therefore, negating the need for electrochemical conditioning. To determine the cause of the improved electrochemistry, here we probe the speciation of the electrolyte after Mg(HMDS)2 addition using Raman spectroscopy, 27Al nuclear magnetic resonance spectroscopy, and 1H-29Si heteronuclear multiple bond correlation spectroscopy on MACC + Mg(HMDS)2 at various Mg(HMDS)2 concentrations. Mg(HMDS)2 scavenges trace H2O, but it also reacts with MACC complexes, namely, AlCl4-, to form free Cl-. We suggest that although both the removal of H2O and the formation of free Cl- improve electrochemistry by altering the speciation at the interface, the latter has a profound effect on electrodeposition and stripping of Mg.

Incorporated diffusion ordered heteronuclear multiple bond correlation spectroscopy, 3D iDOSY-HMBC. Merging of diffusion delay with long polarization transfer delay of HMBC

3D iDOSY-HMBC pulse sequences allow the simplification of HMBC data of mixtures via separation in the diffusion domain. The presented methods utilize incorporated DOSY approach, iDOSY, where the existing delays of the basic pulse sequence are utilized for diffusion attenuation. In the simplest form of the proposed 3D iDOSY-HMBC sequences, no extra delays or RF-pulses were required, only two diffusion gradients were added within HMBC polarization transfer delay.

6-Nitro-7-tosylquinazolin-4(3H)-one

Sulfones are important building blocks in the construction of biologically active molecules or functional materials. The sulfonyl functional group in sulfones is so versatile that it can act as either a nucleophile, an electrophile, or a radical in different organic reactions. Recently, quinazoline sulfones have been used to build asymmetrical ether derivatives as inhibitors of signaling pathways governed by tyrosine kinases and the epidermal growth factor-receptor. In this paper, we report a facile synthesis of a novel quinazoline sulfone, 6-nitro-7-tosylquinazolin-4(3H)-one (III), using the modified protocol from 7-chloro-6-nitroquinazolin-4(3H)-one (I) and sodium p-toluenesulfinate (II). The structure of the title compound III was determined using mass-spectrometry, FT-IR, 1H-NMR, 13C-NMR, DEPT, HSQC (Heteronuclear single quantum coherence), HMBC (Heteronuclear Multiple Bond Correlation Spectroscopy) spectroscopies, and PXRD analysis.

183 W NMR Spectroscopy Guides the Search for Tungsten Alkylidyne Catalysts for Alkyne Metathesis.

Triarylsilanolates are privileged ancillary ligands for molybdenum alkylidyne catalysts for alkyne metathesis but lead to disappointing results and poor stability in the tungsten series. 1H,183W heteronuclear multiple bond correlation spectroscopy, exploiting a favorable 5 J‐coupling between the 183W center and the peripheral protons on the alkylidyne cap, revealed that these ligands upregulate the Lewis acidity to an extent that the tungstenacyclobutadiene formed in the initial [2+2] cycloaddition step is over‐stabilized and the catalytic turnover brought to a halt. Guided by the 183W NMR shifts as a proxy for the Lewis acidity of the central atom and by an accompanying chemical shift tensor analysis of the alkylidyne unit, the ligand design was revisited and a more strongly π‐donating all‐alkoxide ligand prepared. The new expanded chelate complex has a tempered Lewis acidity and outperforms the classical Schrock catalyst, carrying monodentate tert‐butoxy ligands, in terms of rate and functional‐group compatibility.

183W NMR Spectroscopy Guides the Search for Tungsten Alkylidyne Catalysts for Alkyne Metathesis

AbstractTriarylsilanolates are privileged ancillary ligands for molybdenum alkylidyne catalysts for alkyne metathesis but lead to disappointing results and poor stability in the tungsten series. 1H,183W heteronuclear multiple bond correlation spectroscopy, exploiting a favorable 5J‐coupling between the 183W center and the peripheral protons on the alkylidyne cap, revealed that these ligands upregulate the Lewis acidity to an extent that the tungstenacyclobutadiene formed in the initial [2+2] cycloaddition step is over‐stabilized and the catalytic turnover brought to a halt. Guided by the 183W NMR shifts as a proxy for the Lewis acidity of the central atom and by an accompanying chemical shift tensor analysis of the alkylidyne unit, the ligand design was revisited and a more strongly π‐donating all‐alkoxide ligand prepared. The new expanded chelate complex has a tempered Lewis acidity and outperforms the classical Schrock catalyst, carrying monodentate tert‐butoxy ligands, in terms of rate and functional‐group compatibility.

Synthesis of anti-4-phenoxyphenylaminoglyoxime and its some transition metal complexes: Spectral, DFT, electrochemical and anticancer activity studies

anti-4-phenoxyphenylaminoglyoxime (LH2) was synthesized starting from 4-aminodiphenylether and anti-chloroglyoxime in absolute ethanol. Then, mononuclear complexes [Ni(II) and Cu(II)] of LH2 were synthesized with the metal:ligand ratio of 1:2. The LH2 and its complexes [Ni(LH)2 and Cu(LH)2] were characterized by elemental analysis, FT-IR, Raman, UV–vis, thermogravimetric analysis (TGA), 1H NMR, 13C NMR, heteronuclear multiple bond correlation (HMBC) spectroscopy and theoretical DFT studies. Also, redox properties of the ligand and its complexes were investigated by cyclic voltammetry in DMSO solution at room temperature. Conformational space was scanned with molecular mechanic simulations and then the possible stable conformers of LH2 ligand were determined by B3LYP/6–311++G (d,p) level calculations. The Ni(LH)2 and Cu(LH)2 metal complexes were modeled theoretically using B3LYP/LanL2DZ level. The theoretical vibrational frequencies were calculated by using optimization calculation levels. The NMR parameters of LH2 ligand, Cu(LH)2 and Ni(LH)2 metal complexes were calculated at mPW1PW91/6-311 + G (2d,p) level. Theoretically calculated values were compared with the related experimental values. The DFT calculation results have been used to predict and interpret the molecular structures of LH2 ligand and its complexes. The geometry around nickel in Ni(LH)2 and around cupper in Cu(LH)2 complex are almost square planar. In addition, we evaluated the efficacy of LH2 ligand and its Ni(LH)2 and Cu(LH)2 complexes in the breast adenocarcinoma cell line (MCF7). Our data showed that the metal compounds affect positively the cytotoxic activity of the ligand (LH2). The metal complexes, especially Ni(LH)2 complex, exhibited noteworthy biological activity against the viability of MCF7 cells.

Enhancing computer-assisted structure elucidation with DFT analysis of J-couplings.

Computer-assisted structure elucidation (CASE) is the class of expert systems that derives molecular structures primarily from one-dimensional and two-dimensional nuclear magnetic resonance data. Contemporary CASE systems, including Advanced Chemistry Development/Structure Elucidator (ACD/SE), consider cross-peaks in heteronuclear multiple bond coherence (HMBC) and correlation spectroscopy (COSY) spectra as two- or three-bond correlations by default. However, four and more bond correlations (nonstandard correlations [NSCs]) could be present in these spectra too. The indiscriminate addition of NSCs to the CASE computations is prohibitively expensive. To address this problem, the ACD/SE program performs a logical analysis of observed correlations and determines the minimum number of NSCs. Guided by this information, a more efficient fuzzy structure generation (FSG) algorithm is subsequently applied. Until now, the FSG algorithm was utilized without any verification of the reliability of found NSCs. Here, we report a verification method for NSCs based on the relationship between NSCs and J-couplings computed with high accuracy density functional theory (DFT) methods. We used the example of strychnine to show that 41 (32%) of 8-Hz HMBC cross-peaks were NSCs and were consistent with 4-6 JCH couplings greater than 0.3 Hz. This cutoff value was largely confirmed by the analysis of NSCs in 11 real-world natural products elucidated by ACD/SE. Additionally, utilizing the example of the CASE study of cleospinol A, we showed that the DFT-computed J-couplings of NSCs can distinctively differentiate the correct structure among six proposed isomers. The proposed approach of NSC verification should further improve the robustness of CASE analysis and can help reveal potential problems with reported experimental data.

Chromatographic isolation and structural elucidation of secondary metabolites from the soil-inhabiting fungus Aspergillus fumigatus 3T-EGY

Eight compounds were isolated and identified from the soil-inhabiting fungus Aspergillus fumigatus 3T-EGY, namely, stearic acid (1), α-linolenic acid (2), physcion (3), di-(2-ethylhexyl) phthalate (4), 2,4,5,17-tetramethoxy pradimicin lactone (5), 3,5-dihydroxy-7-O-α-rhamnopyranoyl-2H-chromen-2-one (6), juglanthraquinone A-5-O-d-rhodosamine-(4′→1″)-2-deoxy-d-glucose (4″→1″′)-cinerulose B (7), and micropeptin (8). Their structures were determined on the basis of one-dimensional (1D-) and two-dimensional nuclear magnetic resonance (2D-NMR) [1H-, 13C-NMR, 1H-1H COSY (COrrelated SpectroscopY), and 1H-13C HMBC (Heteronuclear Multiple Bond Correlation) spectroscopy]. Compound 7 showed moderate in vitro antimicrobial activity against three pathogenic strains with inhibition zones values were ranged from 9.0 to 10.66 mm compared to neomycin as a positive control with inhibition zones values were ranged from 14.0 to 19.0 mm.

Heteronuclear Single–Quantum Correlation Spectroscopy (HSQC) and Heteronuclear Multiple– Bond Correlation Spectroscopy (HMBC) Comparative Study on Malignant and Benign Human Cancer Cells and Tissues with the Passage of time under Synchrotron Radiation

Heteronuclear Single–Quantum Correlation Spectroscopy (HSQC) and Heteronuclear Multiple– Bond Correlation Spectroscopy (HMBC) Comparative Study on Malignant and Benign Human Cancer Cells and Tissues with the Passage of time under Synchrotron Radiation

Correlation Spectroscopy (COSY), Exclusive Correlation Spectroscopy (ECOSY), Total Correlation Spectroscopy (TOCSY), Incredible Natural-Abundance Double-Quantum Transfer Experiment (INADEQUATE), Heteronuclear Single-Quantum Correlation Spectroscopy (HSQC), Heteronuclear Multiple-Bond Correlation Spectroscopy (HMBC), Nuclear Overhauser Effect Spectroscopy (NOESY) and Rotating Frame Nuclear Overhauser Effect Spectroscopy (ROESY) Comparative Study on Malignant and Benign Human Cancer Cells and Tissues Under Synchrotron Radiation

In the current study, we have experimentally and comparatively investigated and compared malignant human cancer cells and tissues before and after irradiating of synchrotron radiation using Correlation Spectroscopy (COSY), Exclusive Correlation Spectroscopy (ECOSY), Total Correlation Spectroscopy (TOCSY), Incredible Natural-Abundance Double-Quantum Transfer Experiment (INADEQUATE), Heteronuclear Single-Quantum Correlation Spectroscopy (HSQC), Heteronuclear Multiple-Bond Correlation Spectroscopy (HMBC), Nuclear Overhauser Effect Spectroscopy (NOESY) and Rotating Frame Nuclear Overhauser Effect Spectroscopy (ROESY).

The isolation and structural elucidation of a new iridoid glycoside from Cymbaria dahurica L.

Abstract A new iridoid glycoside, namely, cymdahoside A (1), together with two known ones, 2 and 3, were isolated from the EtOAc extract of Cymbaria dahurica. The structure elucidation of 1 was carried out by one-dimensional (1D) NMR (1H and 13C NMR) and 2D NMR (correlation spectroscopy, heteronuclear single-quantum coherence, heteronuclear multiple-bond correlation and nuclear Overhauser effect spectroscopy) spectral analyses.

Heteronuclear Correlation Experiments Such as Heteronuclear Single-Quantum Correlation Spectroscopy (HSQC), Heteronuclear Multiple-Quantum Correlation Spectroscopy (HMQC) and Heteronuclear Multiple-Bond Correlation Spectroscopy (HMBC) Comparative Study On Malignant and Benign Human Endocrinology and Thyroid Cancer Cells and Tissues Under Synchrotron Radiation

Heteronuclear Correlation Experiments Such as Heteronuclear Single-Quantum Correlation Spectroscopy (HSQC), Heteronuclear Multiple-Quantum Correlation Spectroscopy (HMQC) and Heteronuclear Multiple-Bond Correlation Spectroscopy (HMBC) Comparative Study On Malignant and Benign Human Endocrinology and Thyroid Cancer Cells and Tissues Under Synchrotron Radiation

Regioisomeric Preference in Ring-Opening Polymerization of 3',5'-Cyclic Phosphoesters of Functional Thymidine DNA Analogues.

Regioregularity is a crucial property in the synthesis of DNA analogues, as natural DNA is synthesized exclusively in the 5' to 3' direction. We have focused our attention on the determination of the regioisomeric distribution of poly(3',5'-cyclic 3-(3-butenyl) thymidine ethylphosphate)s obtained from the ring-opening polymerization of (R)-3',5'-cyclic 3-(3-butenyl) thymidine ethylphosphate. The regioisomeric preference was investigated by comparison to synthesized model compounds of 3',3'-, 3',5'-, and 5',5'-linkages, where the model 3'-phosphoester linkages were to the secondary alcohol of 3-hydroxytetrahydrofuran and the model 5'-linkages derived from coupling to the primary alcohol of tetrahydrofurfuryl alcohol. From the 31P resonance frequency assignments of those small molecule model compounds, 31P NMR spectra revealed the major connectivity in the polymer backbone to be 3',5'-linkages, with ≤30% of other isomeric forms. Model reactions employing a series of alcohol initiators imparting various degrees of steric hindrance, to mimic the increased steric hindrance of the propagating alcohol relative to the initiator, were then conducted to afford the corresponding ring-opened unimer adducts and to gain understanding of the regioselectivity during the ring-opening polymerization. 1H-31P heteronuclear multiple-bond correlation spectroscopy showed ethanol and 4-methoxybenzyl alcohol initiation to yield only the P-O5' bond cleavage product, whereas attack by isopropyl alcohol upon (R)-3',5'-cyclic 3-(3-butenyl) thymidine ethylphosphate afforded both P-O3' and P-O5' bond cleavage products, supporting our hypothesis that the increased steric hindrance of the propagating species dictates the regioselectivity of the P-O bond cleavage. Further model reactions suggested that the P-O5' bond cleavage products can be detected upon the formation of dimers during the ring-opening polymerization. Overall, this work provides a fundamental understanding of the polymerization behavior of six-membered cyclic phosphoesters and broadens the scope of DNA analogues from the ring-opening polymerization of 3',5'-cyclic phosphoesters.

A novel approach to correlation spectroscopy (COSY), exclusive correlation spectroscopy (ECOSY), total correlation spectroscopy (TOCSY), incredible natural–abundance double–quantum transfer experiment (INADEQUATE), heteronuclear single–quantum correlation spectroscopy (HSQC), heteronuclear multiple–bond correlation spectroscopy (HMBC), nuclear overhauser effect spectroscopy (NOESY) and rotating frame nuclear overhauser effect spectroscopy (ROESY) comparative study on malignant and benign human cancer cells and tissues under synchrotron radiation

A novel approach to correlation spectroscopy (COSY), exclusive correlation spectroscopy (ECOSY), total correlation spectroscopy (TOCSY), incredible natural–abundance double–quantum transfer experiment (INADEQUATE), heteronuclear single–quantum correlation spectroscopy (HSQC), heteronuclear multiple–bond correlation spectroscopy (HMBC), nuclear overhauser effect spectroscopy (NOESY) and rotating frame nuclear overhauser effect spectroscopy (ROESY) comparative study on malignant and benign human cancer cells and tissues under synchrotron radiation