71 research outputs found
NAUCLEFOLININE: A NEW ALKALOID FROM THE ROOTS OF NAUCLEA LATIFOLIA
ABSTRACT. A novel indole alkaloid, nauclefolinine (1) and five known triterpenic compounds, rotundic acid (2), α-L-rhamnoquinovic acid (3), 3-O-β-D-glucopyranosyl-β-sitosterol (4), squalene (5) and sitosterol-3-O-6'-stearoyl-β-D-glucopyranoside (6) have been isolated from the roots of Nauclea latifolia
The Three Pillars of Natural Product Dereplication. Alkaloids from the Bulbs of Urceolina peruviana (C. Presl) J.F. Macbr. as a Preliminary Test Case
The role and importance of the identification of natural products are discussed in the perspective of the study of secondary metabolites. The rapid identification of already reported compounds, or structural dereplication, is recognized as a key element in natural product chemistry. The biological taxonomy of metabolite producing organisms, the knowledge of metabolite molecular structures, and the availability of metabolite spectroscopic signatures are considered as the three pillars of structural dereplication. The role and the construction of databases is illustrated by references to the KNApSAcK, UNPD, CSEARCH, and COCONUT databases, and by the importance of calculated taxonomic and spectroscopic data as substitutes for missing or lost original ones. Two NMR-based tools, the PNMRNP database that derives from UNPD, and KnapsackSearch, a database generator that provides taxonomically focused libraries of compounds, are proposed to the community of natural product chemists. The study of the alkaloids from Urceolina peruviana, a plant from the Andes used in traditional medicine for antibacterial and anticancer actions, has given the opportunity to test different approaches to dereplication, favoring the use of publicly available data sources
Coupled Blind Signal Separation and Spectroscopic Database Fitting of the Mid Infrared PAH Features
The aromatic infrared bands (AIBs) observed in the mid infrared spectrum are
attributed to Polycyclic Aromatic Hydrocarbons (PAHs). We observe the NGC
7023-North West (NW) PDR in the mid-infrared (10 - 19.5 micron) using the
Infrared Spectrometer (IRS), on board Spitzer. Clear variations are observed in
the spectra, most notably the ratio of the 11.0 to 11.2 micron bands, the peak
position of the 11.2 and 12.0 micron bands, and the degree of asymmetry of the
11.2 micron band. The observed variations appear to change as a function of
position within the PDR. We aim to explain these variations by a change in the
abundances of the emitting components of the PDR. A Blind Signal Separation
(BSS) method, i.e. a Non-Negative Matrix Factorization algorithm is applied to
separate the observed spectrum into components. Using the NASA Ames PAH IR
Spectroscopic Database, these extracted signals are fit. The observed signals
alone were also fit using the database and these components are compared to the
BSS components. Three component signals were extracted from the observation
using BSS. We attribute the three signals to ionized PAHs, neutral PAHs, and
Very Small Grains (VSGs). The fit of the BSS extracted spectra with the PAH
database further confirms the attribution to ionized and neutral PAHs and
provides confidence in both methods for producing reliable results. The 11.0
micron feature is attributed to PAH cations while the 11.2 micron band is
attributed to neutral PAHs. The VSG signal shows a characteristically
asymmetric broad feature at 11.3 micron with an extended red wing. By combining
the NASA Ames PAH IR Spectroscopic Database fit with the BSS method, the
independent results of each method can be confirmed and some limitations of
each method are overcome
Computer-assisted methods for molecular structure elucidation: realizing a spectroscopist's dream
NMReDATA, a standard to report the NMR assignment and parameters of organic compounds
The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link. Open access articleEven though NMR has found countless applications in the field of small molecule characterization, there is no standard file for the NMR data relevant to structure characterization of small molecules. A file format is introduced to associate the NMR parameters extracted from 1D and 2D spectra of organic compounds to the assigned chemical structure. These NMR parameters, which we shall call NMReDATA, include chemical shift values, signal integrals, intensities, multiplicities, scalar coupling constants, lists of 2D correlations, relaxation times and diffusion rates. The file format is an extension of the existing SDF (Structure Data Format), which is compatible with the commonly used MOL format. The association of an NMReDATA file with the raw and spectral data from which it originates constitutes an NMR record. This format is easily readable by humans and computers and provides a simple and efficient way for disseminating results of structural chemistry investigations, automating the verification of published result, and for assisting the constitution of highly needed open-source structural databases
Blind Separation of Analytes in Nuclear Magnetic Resonance Spectroscopy and Mass Spectrometry: Sparseness-Based Robust Multicomponent Analysis
Model-Free Analysis of Mixtures by NMR Using Blind Source Separation
International audienc
Détermination assistée par ordinateur de la structure des molécules organiques
La spectroscopie de Résonance Magnétique Nucléaire offre un moyen unique de déterminer des relations de proximité entre atomes par le biais des expériences de corrélation. L'analyse
structurale de petites molécules organiques s'en trouve extrêmement facilitée. Des programmes informatiques peuvent utiliser directement les informations de corrélation pour déduire des
structures. Le fonctionnement et l'usage d'un tel programme, LSD (Logic for Structure Determination), sont détaillés sur un exemple, l'acide gibberellique
A new method for spin-spin coupling patterns analysis in high resolution NMR spectroscopy
International audienc
A new method for spin-spin coupling patterns analysis in high resolution NMR spectroscopy
The measurement of scalar coupling constants is a problem of general importance in liquid state Nuclear Magnetic Resonance and for which many solutions have been proposed. A transformation
algorithm applied to time domain data was used to achieve this goal. It yields multiplicity as a function of possible J values. The effectiveness of the method is demonstrated on
m-bromonitrobenzene, a molecule whose 1H NMR spectrum exhibits hard to measure small couplings
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