2D Nuclear Magnetic Resonance Spectra Research Articles

Revision of structures of acridone alkaloids from natural sources

AbstractThe reported chemical structures of tricyclic acridone alkaloids (1–6) from Severinia buxifolia and Pleiospermium alatum were reinvestigated through a comparison of the nuclear magnetic resonance (NMR) spectral data of similar compounds and a comprehensive study of their two‐dimensional (2D) NMR spectra. The structures of 1–5 were further confirmed by a comparison of their spectral data with those of the authentic samples and standards. The different chemical shifts caused by substituted functional groups in the tricyclic acridones were summarized according to the results in the present study. Furthermore, the synthetic compound 10 (N‐methyl‐1,3‐dihydroxy‐4,5,6‐trimethoxyacridine‐9‐one) has not been reported from any natural sources in the previous literature. In addition, the chemical structures of macranthanine (21) and 7‐hydroxy‐noracronycine (22) from Glycosmis macrantha were also revised.

Supramolecular Cages Based on a Silver Complex as Adaptable Hosts for Poly-Aromatic Hydrocarbons.

In this work, an L-shaped silver complex, AgLClO4 (L = 2,3-bis[3-(pyridin-2-yl)-1H-pyrazol-1-yl·methyl]quinoxaline), M, is found to be adaptable enough to host a range of medium and large aromatic hydrocarbons including several polycyclic aromatic hydrocarbons (PAHs). The transformation of M from as-synthesized closed (nonporous) crystalline to at least three types of open phase structures in the presence of different aromatic hydrocarbons enables the adaptable binding of M to these aromatics. In essence, M can rearrange its cavities to fit the different sizes and shapes of the guest molecules in the manner that is infeasible with cage compounds or coordination networks. Single-crystal and powder X-ray diffraction confirm the adaptable structures of the resulting host-guest complexes, M·nG (G= guest, n= 0.5 or 0.75). Detailed 1D and 2D nuclear magnetic resonance spectra, along with the fluorescence spectroscopy, reveal that the host-guest complexes feature similar chemical compositions in the solution, but are in the states of rapid exchange in and outside the cages. Such an adaptability of M provides insights into the strength of host-guest interactions and enables a new class of adsorptive molecular materials that can bind a large number of aromatics, specifically PAHs.

Inverse or direct detect experiments and probes: Which are “best” for in-vivo NMR research of 13C enriched organisms?

In-vivo Nuclear Magnetic Resonance (NMR) spectroscopy is a unique and powerful approach for understanding sublethal toxicity, recovery, and elucidating a contaminant’s toxic mode of action. However, magnetic susceptibility distortions caused by the organisms, along with sample complexity, lead to broad and overlapping 1D NMR spectra. As such, 2D NMR in combination with 13C enrichment (to increase signal) is a requirement for metabolite assignment and monitoring using high field in-vivo flow based NMR. Despite this, it is not clear which NMR experiment and probe combinations are the most appropriate for such studies. In terms of experiments, 1H–13C Heteronuclear Single Quantum Coherence (HSQC) and 13C–1H Heteronuclear Correlation Spectroscopy (HETCOR) experiments are logical choices for molecular fingerprinting. HSQC uses 1H for detection and thus will be the most sensitive, while HETCOR uses 13C for detection, which benefits from improved spectral dispersion (i.e. a larger chemical shift range) and avoids detection of the huge in-vivo water signal which can be problematic in HSQC. NMR probes are available in two variations, inverse (inner coil 1H) which is best suited to 1H detection and observe (inner coil 13C) which is ideal for 13C detection. To further complicate matters, the low biomass in many aquatic organisms makes cryoprobes desirable, however, changing cryoprobes is time prohibitive, requiring at least a day to warmup and cool down, meaning only a single probe can be used to monitor “real-time” in-vivo responses. The key questions become: Is it best to use HSQC on an inverse cryoprobe and accept a compromised HETCOR? Or is it best to use HETCOR on an observe cryoprobe and accept a compromised HSQC? Here these questions are explored using living 13C enriched Daphnia as the test case. The number of metabolites identified across the different probe/experiment combinations are compared over a range of experiment times. Finally, the probes/experiments are compared to monitor an anoxic stress response. Both probes and experiments prove to be quite robust, albeit HSQC identified slightly more metabolites in most cases. HETCOR did nearly as-well and because of the lack of water complications would be the most accessible approach for researchers to apply in-vivo NMR to 13C enriched organisms, both in terms of experimental setup and flow system design. This said, when using an optimized flow system, HSQC did identify the most metabolites and an inverse probe design offers the most potential for 1H-only approaches which are continuously being developed and have the potential to eventually overcome the current limitation that requires 13C enriched organisms.

A comparison of non-uniform sampling and model-based analysis of NMR spectra for reaction monitoring.

Nuclear magnetic resonance (NMR) spectroscopy is widely used for applications in the field of reaction and process monitoring. When complex reaction mixtures are studied, NMR spectra often suffer from low resolution and overlapping peaks, which places high demands on the method used to acquire or to analyse the NMR spectra. This work presents two NMR methods that help overcome these challenges: 2D non-uniform sampling (NUS) and a recently proposed model-based fitting approach for the analysis of 1D NMR spectra. We use the reaction of glycerol with acetic acid as it produces five reaction products that are all chemically similar and, hence, challenging to distinguish. The reaction was measured on a high-field 400 MHz NMR spectrometer with a 2D NUS-heteronuclear single quantum coherence (HSQC) and a conventional 1D 1 H NMR sequence. We show that comparable results can be obtained using both 2D and 1D methods, if the 2D volume integrals of the 2D NUS-HSQC NMR spectra are calibrated. Further, we monitor the same reaction on a low-field 43 MHz benchtop NMR spectrometer and analyse the acquired 1D 1 H NMR spectra with the model-based approach and with partial least-squares regression (PLS-R), both trained using a single, calibrated data set. Both methods achieve results that are in good quantitative agreement with the high-field data. However, the model-based method was found to be less sensitive to the training data set used than PLS-R and, hence, was more robust when the reaction conditions differed from that of the training data.

Assessment of Astaxanthin Accumulation in Hepatocytes of Atlantic Salmon Fed Different Diets Using NMR Spectroscopy.

This study aimed to assess the astaxanthin (Ax) accumulation in hepatocytes isolated from farmed Atlantic salmon fed different diets (rich marine, poor, poor with marine phospholipids (MPL) and poor with docosahexaenoic acid (DHA)). Nuclear magnetic resonance (NMR) spectroscopy was used for the Ax detection and quantification. The use of the 13C-enriched Ax allowed the assessment of short-time Ax metabolism. The substitution of fish oil and meal in fish feed on plant analogs and the addition of MPL caused further catabolism and decrease of Ax accumulation in hepatocytes from 17 to about 6 mg/kg or to almost zero in the case of DHA addition. Signals assignment of the native and 13C-enriched astaxanthin in acetone were performed using 1D and 2D NMR spectra.

Furoic acid derivatives from the endophytic fungus Coniothyrium sp.

The endophytic fungus Coniothyrium sp. was isolated from leaves of Quercus robur. Fermentation of this fungus on solid rice medium yielded two new furoic acid derivatives (1 and 2) and two additional known compounds. The structures of the new compounds were determined by extensive analysis of 1D and 2D nuclear magnetic resonance spectra as well as high-resolution mass spectrometry data. Compound 1, containing three aromatic chromophores attached by rotatable sigma bonds and a chirality center in benzylic position, was found to be a scalemic mixture with an excess of the (S) enantiomer, the absolute configuration of which was elucidated as by the solution time-dependent density functional theory-electronic circular dichroism approach. The ωB97X/TZVP PCM/MeCN and SOGGA11-X/TZVP SMD/MeCN methods were used for geometry reoptimization to reproduce the solution conformational ensemble. All isolated compounds were tested for their cytotoxicity but proved to be inactive.

Low-field benchtop NMR spectroscopy: status and prospects in natural product analysis†.

Since a couple of years, low-field (LF) nuclear magnetic resonance (NMR) spectrometers (40-100 MHz) have re-entered the market. They are used for various purposes including analyses of natural products. Similar to high-field instruments (300-1200 MHz), modern LF instruments can measure multiple nuclei and record two-dimensional (2D) NMR spectra. To review the commercial availability as well as applications, advantages, limitations, and prospects of LF-NMR spectrometers for the purpose of natural products analysis. Commercial LF instruments were compared. A literature search was performed for articles using and discussing modern LF-NMR. Next, the articles relevant to natural products were read and summarised. Seventy articles were reviewed. Most appeared in 2018 and 2019. Low costs and ease of operation are most often mentioned as reasons for using LF-NMR. As the spectral resolution of LF instruments is limited, they are not used for structure elucidation of new natural products but rather applied for quality control (QC), forensics, food and health research, process control and teaching. Chemometric data handling is valuable. LF-NMR is a rapidly developing niche and new instruments keep being introduced.

Structural Analysis of Nuclear Spin Clusters via 2D Nanoscale Nuclear Magnetic Resonance Spectroscopy

Abstract2D nuclear magnetic resonance (NMR) is essential in molecular structure determination. The nitrogen vacancy (NV) center in diamond is proposed and developed as an outstanding quantum sensor to realize NMR in nanoscale. In this work, a scheme for 2D nanoscale NMR spectroscopy is developed based on quantum controls on an NV center. A proof‐of‐principle experiment on a target of two coupled nuclear spins in diamond is carried out. A correlation spectroscopy (COSY) like sequence is used to acquire the data on time domain, which is then converted to frequency domain with the fast Fourier transform. With the 2D NMR spectrum, the structure and location of the set of nuclear spin are resolved. This work marks a fundamental step toward resolving the structure of a single molecule.

A procedure for calibration transfer of DOSY NMR measurements: An example of molecular weight of heparin preparations

AbstractCalibration transfer is commonly used for spectra obtained on different spectrometers or other conditions. This paper reports a multivariate transfer approach for 2D diffusion‐ordered spectroscopy (DOSY) measurements among high‐resolution nuclear magnetic resonance (NMR) spectrometers on the basis of partial least squares (PLS) regression. As the test system previously published quantitative model to predict molecular weight of heparin, low molecular weight heparin (LMWH) was used.For multivariate modeling, piecewise direct standardization (PDS) and direct standardization (DS) were employed. PDS showed the best performance for estimating heparin molecular weight resulting in a significant decrease in root mean square error of prediction (RMSEP) from 647 and 393 Da without standardization to 513 and 135 Da when PDS was applied for heparin and LMWH, respectively. DS is not recommended for high‐resolution NMR data.The study showed the success of standardization procedure in cases when multivariate models have to be applied to the 2D NMR spectra recorded on different NMR spectrometers. The proposed approach appears to be a valuable achievement towards application of transfer models also to 2D NMR data.

Conformational Studies on Two FtsZ Targeting Cyclic Peptides

Two FtsZ targeting cyclic peptides 1 (Ac-[Orn-Leu-Met-Asp]-Ala-Phe-Arg-Ser-NH2) and 2 (Ac-Ser-Leu-Met-[Asp-Ala-Phe-Arg-Orn]-NH2) were found to be inhibitors of FtsZ polymerization, that makes them excellent starting point for the future development of a new class of antimicrobials. We investigated their solution structure by means of nuclear magnetic resonance (NMR) and molecular dynamic simulations (MD). Deep analysis of 2D NMR spectra (COSY, TOCSY and NOESY), recorded in DMSO-d6, allowed the assignments of all peptide signals and suggested the presence of strong turn structures. We also noticed that the guanidine group of Arg significantly affects the spectral properties and the chromatographic behavior of these peptides depending on whether it makes part of the cycle or not. MD simulations allowed to investigate the conformational preference of the two cyclic peptides and to associate diversity in their structure and dynamics to their different behavior. In particular, peptide 1 showed enhanced flexibility and structural variance with respect to peptide 2.

Differences in the composition of hip and knee synovial fluid in osteoarthritis: a nuclear magnetic resonance (NMR) spectroscopy study of metabolic profiles

The hip and knee joints differ biomechanically in terms of contact stresses, fluid lubrication and wear patterns. These differences may be reflected in the synovial fluid (SF) composition of the two joints, but the nature of these differences remains unknown. The objective was to identify differences in osteoarthritic hip and knee SF metabolites using metabolic profiling with Nuclear Magnetic Resonance (NMR) spectroscopy. Twenty-four SF samples (12 hip, 12 knee) were collected from patients with end-stage osteoarthritis (ESOA) undergoing hip/knee arthroplasty. Samples were matched for age, gender, ethnicity and had similar medical comorbidities. NMR spectroscopy was used to analyse the metabolites present in each sample. Principal Component Analysis and Orthogonal Partial Least Squares Discriminant Analysis were undertaken to investigate metabolic differences between the groups. Metabolites were identified using 2D NMR spectra, statistical spectroscopy and by comparison to entries in published databases. There were significant differences in the metabolic profile between the groups. Four metabolites were found in significantly greater quantities in the knee group compared to the hip group (N-acetylated molecules, glycosaminoglycans, citrate and glutamine). This is the first study to indicate differences in the metabolic profile of hip and knee SF in ESOA. The identified metabolites can broadly be grouped into those involved in collagen degradation, the tricarboxylic acid cycle and oxidative metabolism in diseased joints. These findings may represent a combination of intra and extra-articular factors.

Separation of Unprecedented Degradants of Domperidone by Ultra-Performance Convergence Chromatography and Their Structure Elucidation.

Domperidone, a gastroprokinetic agent, is a common drug to treat emesis. It was subjected to acid, base-mediated hydrolysis, peroxide-mediated oxidation, photolysis and thermal degradation according to ICH guidelines to observe stability of the selected drug under the stress conditions. Although the drug is resistant to base hydrolysis, photolysis and thermal stressors, two degradants (DP-ISO1 and DP-ISO2) were formed in acid mediated hydrolysis. Oxidation with hydrogen peroxide also resulted in one product (DP-OX). All three degradants were isolated from the crude reaction mixture by preparative high-performance liquid chromatography and supercritical fluid chromatography. Structures of isolated compounds were unambiguously characterized as 5-chloro-1-(1-(3-(6-chloro-2-oxo-2,3-dihydro-1H-benzo[d]imidazol-1-yl)propyl)piperidin-4-yl)-1,3-dihydro-2H-benzo[d]imidazol-2-one (DP-ISO1), 5-chloro-1-(3-(4-(5-chloro-2-oxo-2,3-dihydro-1H-benzo[d]imidazol-1-yl)piperidin-1-yl)propyl)-1,3-dihydro-2H-benzo[d]imidazol-2-one (DP-ISO2), 4-(5-chloro-2-oxo-2,3-dihydro-1H-benzo[d]imidazol-1-yl)-1-(3-(2-oxo-2,3-dihydro-1H-benzo[d]imidazol-1-yl)propyl)piperidine 1-oxide (DP-OX) by analysis of mass spectrometry, 1D and 2D nuclear magnetic resonance spectra. To the best of our knowledge, DP-ISO1 and DP-ISO2 are new and DP-OX was previously reported as domperidone impurity.

Fast quantitative 2D NMR for metabolomics and lipidomics: A tutorial.

Nuclear magnetic resonance (NMR) is a well-known analytical technique for the analysis of complex mixtures. Its quantitative capability makes it ideally suited to metabolomics or lipidomics studies involving large sample collections of complex biological samples. To overcome the ubiquitous limitation of spectral overcrowding when recording 1D NMR spectra on such samples, the acquisition of 2D NMR spectra allows a better separation between overlapped resonances while yielding accurate quantitative data when appropriate analytical protocols are implemented. Moreover, the experiment duration can be considerably reduced by applying fast acquisition methods. Here, we describe the general workflow to acquire fast quantitative 2D NMR spectra in the "omics" context. It is illustrated on three representative and complementary experiments: UF COSY, ZF-TOCSY with nonuniform sampling, and HSQC with nonuniform sampling. After giving some details and recommendations on how to apply this protocol, its implementation in the case of targeted and untargeted metabolomics/lipidomics studies is described.

1 H-15 N HMBC NMR as a tool for rapid identification of isomeric azaindoles: The case of 5F-MDMB-P7AICA.

The high frequency of the synthetic cannabinoid receptor agonists (SCRAs) emergence renders this group of new psychoactive compounds particularly demanding in terms of detection, identification, and responding. Without the available reference material, one of the specific problems is differentiation and structure elucidation of constitutional isomers. Herein, we report a simple and efficient flow chart diagram applicable for a rapid nuclear magnetic resonance (NMR) identification and differentiation between azaindoles, 4-, 5-, 6-, and 7-azaindole, which is a common structural motif of synthetic cannabinoids. The flow chart diagram is based on 1 H NMR and 1 H-15 N NMR spectra, and to prove the concept, it has been tested on 5F-MDMB-P7AICA (1). Spectral and analytical data including standard 1D and 2D NMR spectra, gas chromatography-mass spectrometry (GC-MS), Fourier transform infrared-attenuated total reflectant (FTIR-ATR), Raman, melting point, and combustion analysis are provided for compound 1.

Isolation and characterization of collagen type I crosslink from skin: high-resolution NMR reveals diastereomers of hydroxylysinonorleucine crosslink

Skin is made up of mainly collagen type I and its structure is stabilised by the formation of covalent immature and mature crosslinks. In this study, collagen immature crosslink hydroxylysinonorleucine (HLNL) was isolated from bovine skin in high purity using two sequential purification steps. These consisted of preparative fibrous cellulose and size exclusion chromatography. The purified crosslink was then analysed using tandem mass spectrometry and high-resolution nuclear magnetic resonance(NMR) spectroscopy. The mass of singly and doubly charged ions of HLNL was 292.1865 and 146.5970m/z and their optimised fragmentation energy was 17keV and 5keV, respectively. The 13C NMR of HLNL showed a doubled-up peak at 67.84 and 67.91ppm which corroborated a diastereomeric form of collagen immature crosslink HLNL and both are chiroptically indistinguishable. The chemical structure was fully resolved using 1H, 13C and DEPT-135 high-resolution NMR spectroscopy and compared with other previous studies. We also obtained for the first time the 2D NMR spectra COSY and HSQC of HLNL. We therefore suggested that collagen organization into specific fibrils' orientation may be affected by the different configuration of these diastereomers of HLNL.

Assessing the potential of quantitative 2D HSQC NMR in 13C enriched living organisms.

In vivo Nuclear Magnetic Resonance (NMR) spectroscopy has great potential to interpret the biochemical response of organisms to their environment, thus making it an essential tool in understanding toxic mechanisms. However, magnetic susceptibility distortions lead to 1D NMR spectra of living organisms with lines that are too broad to identify and quantify metabolites, necessitating the use of 2D 1H-13C Heteronuclear Single Quantum Coherence (HSQC) as a primary tool. While quantitative 2D HSQC is well established, to our knowledge it has yet to be applied in vivo. This study represents a simple pilot study that compares two of the most popular quantitative 2D HSQC approaches to determine if quantitative results can be directly obtained in vivo in isotopically enriched Daphnia magna (water flea). The results show the perfect-HSQC experiment performs very well in vivo, but the decoupling scheme used is critical for accurate quantitation. An improved decoupling approach derived using optimal control theory is presented here that improves the accuracy of metabolite concentrations that can be extracted in vivo down to micromolar concentrations. When combined with 2D Electronic Reference To access In vivo Concentrations (ERETIC) protocols, the protocol allows for the direct extraction of in vivo metabolite concentrations without the use of internal standards that can be detrimental to living organisms. Extracting absolute metabolic concentrations in vivo is an important first step and should, for example, be important for the parameterization as well as the validation of metabolic flux models in the future.

Fast Quantitative 2D NMR for Untargeted and Targeted Metabolomics.

Nuclear magnetic resonance (NMR) spectroscopy exhibits a great potential for the quantitative analysis of complex biological samples such as those encountered in metabolomics. To overcome the ubiquitous problem of overlapping peaks in 1D NMR spectra of complex mixtures, acquisition of 2D NMR spectra allows a better separation between overlapped resonances while yielding accurate quantitative data when appropriate analytical protocols are implemented. The experiment duration can be made compatible with high-throughput studies on large sample collections by relying on fast acquisition methods. Here, we describe the general metabolomics workflow to acquire fast quantitative 2D NMR data with a focus on targeted or untargeted analyses.

Nuclear and Electron Magnetic Resonance Spectroscopies of Atomically Precise Gold Nanoclusters

Atomically precise gold nanoclusters display properties that are unseen in larger nanoparticles. When the number of gold atoms is sufficiently small, the clusters exhibit molecular properties. Their study requires extensive use of classic molecular physical chemistry and, thus, methods such as vibrational spectroscopies, electrochemistry, density functional theory and molecular dynamics calculations, and of course nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopies. NMR and EPR studies have been mostly carried out on the benchmark, stable molecules Au25(SR)18, Au38(SR)24, Au102(SR)44, and Au144(SR)60 (where SR = thiolate). In this Account, we showcase examples primarily taken from our previous and ongoing NMR and EPR studies, which we hope will trigger further interest in the use of these sensitive, though often underutilized, techniques. Indeed, 1D and 2D NMR spectra of pure, atomically precise clusters can be very detailed and informative. Molecular clusters are molecules and, thus, have discrete energy levels and undergo stepwise oxidation or reduction. The effect of the charge state on the chemical shifts and line shapes is a function of the ligand type (ligands differ due to specific bonds with different Au atom types) and the position of the chemical group along the ligand backbone: for groups near the Au core, they can be very dramatic. Ligand-protected gold clusters are hard-soft molecules where a hard metal core is surrounded by a dynamic molecular layer. The latter provides a nanoenvironment that interfaces the cluster core with the surrounding environment and can be permeated by molecules and ions. NMR spectroscopy is especially useful to assess its structure. For example, the data show that whereas long alkanethiolates form bundles, shorter chains exhibit more conformational freedom and are quite folded. NMR spectroscopy allows studying diastereotopic effects and provides information on possible hydrogen bonds of ligands with sulfur or surface gold atoms. EPR spectroscopy is a very precise technique to check and characterize the magnetic state of gold clusters or clusters doped with foreign-metal atoms. Electron nuclear double resonance (ENDOR) provides a powerful tool to assess the interaction of an unpaired electron with nuclei, as we showed for 197Au and 1H. It can be used as a sensitive probe of the spin-density distribution in nanoclusters: for example, it showed that the singly occupied molecular orbital may span outside the Au core by nearly 6 Å. Solid-state EPR spectroscopy has provided compelling evidence that the specific ligands and the crystallinity degree are very important factors in determining the interactions between clusters in the solid state. Depending on the condition, paramagnetic, superparamagnetic, ferromagnetic, or antiferromagnetic behavior can be observed. Time-resolved EPR was successfully tested to determine the efficiency of singlet-oxygen generation via sensitization of Au25 clusters. This Account thus demonstrates some of the remarkable insights that can be gained into the properties of atomically precise clusters through detailed NMR and EPR studies.

Application of High-Resolution NMR and GC-MS to Study Hydrocarbon Oils Derived from Noncatalytic Thermal Transformation of e-Waste Plastics.

The increases in the volumes of electronic waste have become an aggravating environmental, economic, and social health issue in recent times. This study investigates the conversion of e-waste plastics into hydrocarbon oils via noncatalytic thermal transformation followed by an in-depth characterization of these oils using diverse analytical techniques such as gas chromatography–mass spectrometry (GC–MS), Fourier transform infrared (FTIR) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy. In particular, NMR spectroscopy is a key analytical tool utilized in this study to gain a comprehensive insight into the chemical nature of the resultant oils along with a semiquantitative investigation of the changes in their composition over a temperature range of 800–1200 °C. The one-dimensional (1D) 1H and two-dimensional (2D) heteronuclear single-quantum correlation spectra were acquired for the oils, wherein the 2D NMR spectrum provided improved resolution of peaks to address the overlaps encountered in the 1D spectrum. The experimental results obtained from GC–MS, FTIR spectroscopy, and NMR spectroscopy were found to align well with each other. The oils produced in this study have a high calorific value of 38.27 MJ/kg and thus may find use in several applications. A detailed mechanism for the thermal degradation of styrene acrylonitrile plastics and the formation of major products is elucidated in this study.

Morin as a Preservative for Delaying Senescence of Banana.

Banana is a climacteric fruit with desirable palatability and high nutritional value. It ripens rapidly accompanied with metabolite changes during postharvest storage. In this work, morin was applied to treat banana to delay senescence. Nuclear magnetic resonance (NMR) spectroscopy was used to monitor the changes of metabolite composition and levels in banana. The results showed that morin significantly delayed the changes of color and firmness. 1D and 2D NMR spectra reflected that the levels and composition of metabolites were changed with the senescence initiation. The principal component analysis revealed that the first principal components responsible for banana senescence were carbohydrates, amino acids, lipids and phenolics. Morin treatment delayed the transformation of starch to glucose, fructose and sucrose, accelerated the accumulations of alanine and γ-Amino-butyrate (GABA), postponed the generations of valine and l-aspartic acid, suppressed the degradation of saponin a. It indicated that morin was effective in delaying banana senescence.