RESUMO
Four manufacturing impurities of D&C Red No. 33 isolated by counter-current chromatography were analyzed by NMR and ESI mass spectrometry. Three of these impurities were reported previously with minimal details of structural determination. All four are structurally related to the main component of the dye. The fourth exhibited an unusual discrepancy between the NMR structure and its chemical formula suggested by ESI-MS results. Structural determination and assignment of the main component and four impurities are discussed as well as resolution of the discrepancy between the NMR and ESI-MS results of the fourth impurity.
RESUMO
High consumer demand has led global food color manufacturers and food companies to dramatically increase the development and use of natural colors. We have previously reported that avocado (Persea americana) seeds, when crushed in the presence of air, develop a red-orange color in a polyphenol oxidase-dependent reaction. The objective of this study was to identify the major colored compound in colored avocado seed extract (CASE). Column chromatography and high performance liquid chromatography were used to isolate the most abundant colored compound in CASE. This compound, henceforth referred to as perseorangin, was a yellow-orange solid. Structural analysis was performed using high-resolution mass spectrometry, and infrared and nuclear magnetic resonance spectroscopy. We determined that perseorangin is a glycosylated benzotropone-containing compound with a molecular formula of C29H30O14. Liquid chromatography with electrospray ionization mass spectrometry-based metabolomic analysis of CASE and uncolored avocado seed extract showed that perseorangin was unique to CASE.
Assuntos
Persea/química , Pigmentos Biológicos/análise , Cromatografia Líquida de Alta Pressão , Espectroscopia de Ressonância Magnética , Conformação Molecular , Persea/metabolismo , Pigmentos Biológicos/isolamento & purificação , Extratos Vegetais/química , Análise de Componente Principal , Sementes/química , Sementes/metabolismo , Espectrometria de Massas por Ionização por ElectrosprayRESUMO
Compounds similar to maitotoxin (MTX) have been isolated from several laboratory strains of the dinoflagellate Gambierdiscus spp. from the Caribbean. Mass spectral results suggest that these compounds differ from MTX by the loss of one sulfate group and, in some cases, the loss of one methyl group with the addition of one degree of unsaturation. NMR experiments, using approximately 50â¯nmol of one of these compounds, have demonstrated that the 9-sulfo group of MTX is still present, suggesting that these compounds are 40-desulfo congeners of MTX.
Assuntos
Dinoflagellida/química , Toxinas Marinhas/química , Oxocinas/química , Região do Caribe , Cromatografia Líquida , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Estrutura MolecularRESUMO
Covering: up to the end of December, 2018 There are still a disturbing number of incorrect natural product structure elucidations reported in the literature. The use of Computer-Assisted Structure Elucidation (CASE) programs can minimize this risk by generating all structures that are consistent with the input data and by ranking these structures in order of probability. They can successfully determine structures for complex natural products, with the possible exception of compounds with very few protons. Current CASE programs utilize mainly 2D COSY and HMBC correlation data for structure generation with a starting assumption that all observed peaks are due to pairs of atoms no more than 3 bonds apart. We discuss these assumptions and the problems that occur when they are violated. We also discuss the advantages and disadvantages of other types of 2D data that could be included at the structure generation stage. Four different CASE programs are described with particular emphasis on how they deal with the presence of longer range correlation peaks. These programs provide only planar skeletal structures. However, a new program that relies on different types of stereospecific NMR data to determine 3D structures is also described. Other types of computer assistance for structure elucidation are discussed, including the increasing use of theoretical DFT calculations to determine 3D structures and to predict chemical shifts. Finally, we suggest possible improvements in these programs and suggest that a challenge match between the developers of current CASE programs would be useful.
Assuntos
Produtos Biológicos/química , Espectroscopia de Ressonância Magnética , Software , Teoria da Densidade Funcional , Estrutura MolecularRESUMO
The present work reports the identification and characterization of a contaminant, 2-(2'-(1,5-naphthyridinyl))-1,3-indanedione (1',5'-naphthyridinophthalone, 1,5NP), in the color additive D&C Yellow No. 10 (U.S.-certifiable form of Quinoline Yellow), together with its quantification in batches of the color additive certified by the U.S. Food and Drug Administration (USFDA). The impurity, which is a compound not previously reported in the literature, was synthesised and characterised for use as a reference material. Test portions from 26 certified batches of D&C Yellow No. 10 submitted to USFDA by four domestic and four foreign manufacturers were analyzed for 1,5NP using high-performance liquid chromatography. The results revealed a wide range of 1,5NP levels across batches, with 18 (69.2%) of the test portions containing amounts from 0.32 to 169.94 µg g-1 while the remaining test portions contained no detectable (<0.07 µg g-1) amounts. Samples of the European and Japanese forms of Quinoline Yellow were also analyzed and found to contain a wide range of 1,5NP levels. The varying levels of 1,5NP in all three forms of Quinoline Yellow suggest that contamination can be significantly decreased or eliminated through manufacturing adjustments. Since 1,5NP is closely related to a D&C Yellow No. 10 contaminant (quinophthalone) that has a USFDA-specified limit of 4 µg g-1 and is a known allergen, assessment of the possible allergenicity of 1,5NP is warranted.
Assuntos
Corantes/química , Aditivos Alimentares/química , Contaminação de Alimentos/análise , Quinolinas/química , Cromatografia Líquida de Alta Pressão , Estrutura MolecularRESUMO
The baobab (Adansonia digitata L.) is a magnificent tree revered throughout Africa and is becoming recognized for its high nutritional and medicinal values. Despite numerous reports on the pharmacological potential, little is known about its chemical compositions. In this study, four hydroxycinnamic acid glycosides (1-4), six iridoid glycosides (5-10), and three phenylethanoid glycosides (11-13) were isolated from the dried baobab fruit pulp. Their structures were determined by means of spectroscopic analyses, including HRMS, 1H and 13C NMR and 2D experiments (COSY, HSQC, HMBC, and ROESY). All 13 compounds isolated were reported for the first time in the genus of Adansonia. An ultra high-performance liquid chromatography high-resolution accurate-mass mass spectrometry (UHPLC HRAM MS) method was used to conduct further investigation of the chemical compositions of the hydro-alcohol baobab fruit pulp extract. Hydroxycinnamic acid glycosides, iridoid glycosides and phenylethanoid glycosides were found to be the main components in baobab fruit pulp.
Assuntos
Adansonia/química , Frutas/química , Glicosídeos/análise , Glicosídeos Iridoides/análise , Extratos Vegetais/química , Ácidos Cumáricos/análise , Álcool Feniletílico/análiseRESUMO
The structure of a novel compound from Adansonia digitata has been elucidated, and its 1 H and 13 C NMR spectra have been assigned employing a variety of one-dimensional and two-dimensional NMR techniques without degradative chemistry. The Advanced Chemistry Development ACD/Structure Elucidator software was important for determining part of this structure that contained a fused bicyclic system with very few hydrogen atoms, which in turn, exhibited essentially no discriminating HMBC connectivities throughout that portion of the molecule. Copyright © 2016 John Wiley & Sons, Ltd.
RESUMO
The commonly occurring, high-cytotoxicity macrolide roridin E has been re-isolated from Stachybotrys chartarum and characterized by 1-D and 2-D NMR spectroscopy. Assignment of the spectral data for roridin E revealed differences from the accepted literature, and spectra are reported herein to aid in future identification. For the first time confirmation of structure was provided by a crystallographic solution for roridin E. Copyright © 2016 John Wiley & Sons, Ltd.
RESUMO
Two new sesquiterpenoid tropolone glycosides, liriosmasides A (1) and B (2), along with two known compounds, secoxyloganin and oplopanpheside C, were isolated from a methanol extract of the roots of Liriosma ovata. The structures of 1 and 2 were elucidated by spectroscopic methods including 1D and 2D NMR and by high-resolution mass spectrometry involving an ultra-high-performance liquid chromatography-quadrupole-orbital ion trap mass spectrometric (UHPLC-Q-Orbitrap MS) method. Compound 1 showed weak inhibitory activity against HIV RNase H.
Assuntos
Glicosídeos/isolamento & purificação , Olacaceae/química , Sesquiterpenos/isolamento & purificação , Tropolona/análogos & derivados , Tropolona/isolamento & purificação , Cromatografia Líquida de Alta Pressão/métodos , Glicosídeos/química , Glicosídeos/farmacologia , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , Peru , Raízes de Plantas/química , Ribonuclease H/antagonistas & inibidores , Sesquiterpenos/química , Sesquiterpenos/farmacologia , Tropolona/química , Tropolona/farmacologiaRESUMO
Three low-level subsidiary color impurities (A, B, and C) often present in batches of the color additive D&C Red No. 33 (R33, Acid Red 33, Colour Index No. 17200) were separated from a portion of R33 by spiral high-speed counter-current chromatography (HSCCC). The separation involved use of a very polar solvent system, 1-BuOH/5mM aq. (NH4)2SO4. Addition of ammonium sulfate to the lower phase forced partition of the components into the upper phase, thereby eliminating the need to add a hydrophobic counterion as was previously required for separations of components from sulfonated dyes. The very polar solvent system used would not have been retained in a conventional multi-layer coil HSCCC instrument, but the spiral configuration enabled retention of the stationary phase, and thus, the separation was possible. A 1g portion of R33 enriched in A, B, and C was separated using the upper phase of the solvent system as the mobile phase. The retention of the stationary phase was 38.1%, and the separation resulted in 4.8 mg of A of >90% purity, 18.3mg of B of >85% purity, and 91 mg of C of 65-72% purity. A second separation of a portion of the C mixture resulted in 7 mg of C of >94% purity. The separated impurities were identified by high-resolution mass spectrometry and NMR spectroscopic techniques as follows: 5-amino-3-biphenyl-3-ylazo-4-hydroxy-naphthalene-2,7-disulfonic acid, A; 5-amino-4-hydroxy-6-phenyl-3-phenylazo-naphthalene-2,7-disulfonic acid, B; and 5-amino-4-hydroxy-3,6-bis-phenylazo-naphthalene-2,7-disulfonic acid, C. The isomers A and B are compounds reported for the first time. Application of the spiral HSCCC method resulted in the additional benefit of yielding 930 mg of the main component of R33, 5-amino-4-hydroxy-3-phenylazo-naphthalene-2,7-disulfonic acid, of >97% purity.
Assuntos
Corantes/análise , Naftalenossulfonatos/análise , Cromatografia Líquida de Alta Pressão , Cor , Distribuição Contracorrente , Interações Hidrofóbicas e Hidrofílicas , Isomerismo , Espectroscopia de Ressonância Magnética , Espectrometria de MassasRESUMO
Specifications in the U.S. Code of Federal Regulations for the color additive FD&C Yellow No. 5 (Color Index No. 19140) limit the level of the tetrasodium salt of 4-[(4',5-disulfo[1,1'-biphenyl]-2-yl)hydrazono]-4,5-dihydro-5-oxo-1-(4-sulfophenyl)-1H-pyrazole-3-carboxylic acid and that of the trisodium salt of 4,4'-[4,5-dihydro-5-oxo-4-[(4-sulfophenyl)hydrazono]-1H-pyrazol-1,3-diyl]bis[benzenesulfonic acid], which are subsidiary colors abbreviated as Pk5 and Pk7, respectively. Small amounts of Pk5 and Pk7 are needed by the U.S. Food and Drug Administration for confirmatory analyses and for development of analytical methods. The present study describes the use of spiral high-speed counter-current chromatography (HSCCC) to separate the closely related minor components Pk5 and Pk7 from a sample of FD&C Yellow No. 5 containing â¼3.5% Pk5 and â¼0.7% Pk7. The separations were performed with highly polar organic/high-ionic strength aqueous two-phase solvent systems that were chosen by applying the recently introduced method known as graphic optimization of partition coefficients (Zeng et al., 2013). Multiple â¼1.0g portions of FD&C Yellow No. 5 (totaling 6.4g dye) were separated, using the upper phase of the solvent system 1-butanol/abs. ethanol/saturated ammonium sulfate/water, 1.7:0.3:1:1, v/v/v/v, as the mobile phase. After removing the ammonium sulfate from the HSCCC-collected fractions, these separations resulted in an enriched dye mixture (â¼160mg) of which Pk5 represented â¼46% and Pk7, â¼21%. Separation of the enriched mixture, this time using the lower phase of that solvent system as the mobile phase, resulted in â¼61mg of Pk5 collected in fractions whose purity ranged from 88.0% to 92.7%. Pk7 (20.7mg, â¼83% purity) was recovered from the upper phase of the column contents. Application of this procedure also resulted in purifying the major component of FD&C Yellow No. 5 to >99% purity. The separated compounds were characterized by high-resolution mass spectrometry and several (1)H and (13)C nuclear magnetic resonance spectroscopic techniques.
Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Corantes/isolamento & purificação , Distribuição Contracorrente/métodos , Espectroscopia de Ressonância Magnética/métodos , Tartrazina/isolamento & purificação , Corantes/química , Espectrometria de Massas/métodos , Concentração Osmolar , Solventes/química , Tartrazina/químicaRESUMO
The present work describes the preparation of two compounds considered to be likely precursors of an impurity present in samples of the color additives D&C Red No. 27 (Color Index 45410:1) and D&C Red No. 28 (Color Index 45410, phloxine B) submitted to the U.S. Food and Drug Administration for batch certification. The two compounds, 2-(2',4'-dihydroxy-3'-bromobenzoyl)-3,4,5,6-tetrachlorobenzoic acid (3BrHBBA) and its 5'-brominated positional isomer (5BrHBBA), both not reported previously, were separated from synthetic mixtures by vortex counter-current chromatography (VCCC). 3BrHBBA was prepared by chemoselective ortho-bromination of the dihydroxybenzoyl moiety. Two portions of the obtained synthetic mixture, 200mg and 210 mg, respectively, were separated by VCCC using two two-phase solvent systems that consisted of hexane-ethyl acetate-methanol-aqueous 0.2% trifluoroacetic acid (TFA) in the volume ratios of 8:2:5:5 and 7:3:5:5, respectively. These separations produced 35 mg and 78 mg of 3BrHBBA, respectively, each product of over 98% purity by HPLC at 254 nm. 5BrHBBA was prepared by monobromination of the dihydroxybenzoyl moiety in the presence of glacial acetic acid. To separate the obtained synthetic mixture, VCCC was performed in the pH-zone-refining mode with a solvent system consisting of hexane-ethyl acetate-methanol-water (6:4:5:5, v/v) and with TFA used as the retainer acid and aqueous ammonia as the eluent base. Separation of a 1-g mixture under these conditions resulted in 142 mg of 5BrHBBA of â¼ 99% purity by HPLC at 254 nm. The isolated compounds were characterized by high-resolution mass spectrometry and proton nuclear magnetic resonance spectroscopy.
Assuntos
Benzoatos/isolamento & purificação , Distribuição Contracorrente/métodos , Benzoatos/química , Cromatografia Líquida de Alta Pressão , Espectroscopia de Ressonância Magnética , Espectrometria de Massas por Ionização por ElectrosprayRESUMO
In developing analytical methods for batch certification of the color additive D&C Green No. 8 (G8), the U.S. Food and Drug Administration needed the trisodium salt of 1,3,6-pyrenetrisulfonic acid (P3S) for use as a reference material. Since P3S was not commercially available, preparative quantities of it were separated from portions of a sample of G8 that contained â¼3.5% P3S. The separations were performed by pH-zone-refining counter-current chromatography using dodecylamine (DA) as the hydrophobic counterion. The added DA enabled partitioning of the polysulfonated components into the organic stationary phase of the two-phase solvent system used, 1-butanol-water (1:1). Thus, a typical separation that involved 20.3g of G8, using sulfuric acid as the retainer acid and 20% DA in the stationary phase and 0.1M sodium hydroxide as the mobile phase, resulted in â¼0.58 g of P3S of greater than 99% purity. The identification and characterization of the separated P3S were performed by elemental analyses, proton nuclear magnetic resonance, high-resolution mass spectrometry, ultra-violet spectra, and high-performance liquid chromatography.
Assuntos
Sulfonatos de Arila/química , Distribuição Contracorrente/métodos , Pirenos/isolamento & purificação , Ácidos Sulfônicos/isolamento & purificação , Aminas/química , Sulfonatos de Arila/normas , Cromatografia Líquida de Alta Pressão , Concentração de Íons de Hidrogênio , Espectrometria de Massas , Ressonância Magnética Nuclear Biomolecular , Pirenos/química , Padrões de Referência , Espectrofotometria Ultravioleta , Ácidos Sulfônicos/químicaRESUMO
Two unknown compounds were previously determined to be potential interferences in liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis of bisphenol A (BPA) in canned infant formula. Both yielded two identical MS/MS transitions to BPA. The identities of the unknowns were investigated using accurate mass LC/MS, LC/MS/MS, and elemental formula and structures proposed. Exact identities were confirmed through purification or synthesis followed by (1)H and (13)C nuclear magnetic resonance (NMR) experiments, as well as comparisons of one unknown with commercial standards. Comparisons of negative ion electrospray ionization (ESI) MS/MS and accurate mass spectra suggested both unknowns to be structurally identical (to BPA and each other). Positive ion ESI spectra confirmed both were larger molecules, suggesting that in the negative mode they likely fragmented to the deprotonated BPA ion in the source [corrected]. Elemental composition of positive ion accurate mass spectra and NMR analysis concluded the unknowns were oxidized forms of the known epoxy can coating monomer, bisphenol A diglycidyl ether (BADGE). One of the unknowns, 2,2-[bis-4-(2,3-dihydroxypropoxy)phenyl]propane, commonly known as BADGE*2H(2)O, is widely reported as an epoxy-phenolic can coating migrant, but has not been suggested to interfere with the MS/MS analysis of BPA. The other unknown, 2-[4-(2,3-dihydroxypropoxy)phenyl]-2-[4'-hydroxyphenyl]propane, or the oxidized form of bisphenol A monoglycidyl ether (BAMGE*H(2)O), has not been previously reported in food or packaging.
Assuntos
Cromatografia Líquida/métodos , Embalagem de Alimentos , Fenóis/química , Propano/análogos & derivados , Propano/química , Espectrometria de Massas em Tandem/métodos , Compostos Benzidrílicos , Fórmulas Infantis/química , Ressonância Magnética Nuclear Biomolecular , Fenóis/análise , Propano/análiseRESUMO
The structures of three complex saponins from the fruit pods of Blighia sapida have been elucidated and their (1)H and (13)C NMR spectra assigned employing a variety of one- and two-dimensional NMR techniques without degradative chemistry. The saponins have either four or six monosaccharide units linked to a triterpene aglycone. High-resolution, proton-coupled-HSQC spectra were important for determining both the identities of the intact monosaccharide units and coupling constants in strongly coupled proton spin systems. These NMR experiments will prove crucial as the complexity of saponin structures reaches the limit that can be determined solely by NMR.
Assuntos
Blighia/química , Saponinas/química , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Saponinas/análise , Triterpenos/análise , Triterpenos/químicaRESUMO
Selective oxidation by bis[(trifluoroacetoxy)iodo]benzene (BTI) provides an effective trap for quenching adducts formed reversibly between dC and an ortho-quinone methide (QM) under physiological conditions. A model adduct generated by 4-methyl-o-QM and 2'-deoxycytidine is rapidly converted by intramolecular cyclization and loss of aromaticity to a characteristic product for quantifying QM alkylation. However, BTI induces a surprising rearrangement driven by overoxidation of a derivative lacking an alkyl substituent at the 4-position of the QM.
Assuntos
Desoxicitidina/química , Indolquinonas/química , Alquilação , Estrutura Molecular , Oxirredução , EstereoisomerismoRESUMO
One new cucurbitane-type triterpenoid glycoside, momordicoside U (1), together with five known cucurbitane-type triterpenoids and related glycosides, 3ß,7 ß,25-trihydroxycucurbita-5,23 (E)-dien-19-al (2), momordicine I (3), momordicine II (4), 3-hydroxycucurbita-5,24-dien-19-al-7,23-di-O-ß-glucopyranoside (5), and kuguaglycoside G (6), were isolated from the whole plant of Momordica charantia. Their structures were determined by chemical and spectroscopic methods. Momordicoside U (1) was evaluated for insulin secretion activity in an in vitro insulin secretion assay and displayed moderate activity.