2D Nuclear Magnetic Resonance Spectroscopy Research Articles

Chemical and Biological Characterization of the Ethyl Acetate Fraction from the Red Sea Marine Sponge Hymedesmia sp.

Hymedesmiidae is one of the largest families of marine sponges and stands out as an exceptional source of variable metabolites with diverse biological activities. In this study, the ethyl acetate fraction (HE) of a Hymedesmia sp. marine sponge from the Red Sea, Egypt, was analyzed for the first time using Ultra-performance liquid chromatography electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) analysis. The analysis tentatively identified 29 compounds in this fraction, including the isolation and identification of six compounds (two pyrimidine nucleosides, one purine, and two pyrimidine bases in addition to one cerebroside) for the first time. The structures of the isolated compounds were established by 1D and 2D NMR (nuclear magnetic resonance), MS (mass spectrometry), and IR (infrared) spectroscopy. Furthermore, the cytotoxic, antioxidant, and antimicrobial activities of the ethyl acetate fraction were evaluated in vitro. The fraction exhibited strong DPPH scavenging activity with an IC50 of 78.7 µg/mL, compared to ascorbic acid as a positive control with an IC50 of 10.6 µg/mL. It also demonstrated significant cytotoxic activity with IC50 values of 13.5 µg/mL and 25.3 µg/mL against HCT-116 and HEP-2 cell lines, respectively, compared to vinblastine as a positive control with IC50 values of 2.34 µg/mL and 6.61 µg/mL against HCT-116 and HEP-2, respectively. Additionally, the ethyl acetate fraction displayed promising antibacterial activity against S. aureus with a MIC value of 62.5 µg/mL, compared to ciprofloxacin as a positive control with MIC values of 1.56 µg/mL for Gram-positive bacteria and 3.125 µg/mL for Gram-negative bacteria. It also exhibited activity against E. coli and P. aeruginosa with MIC values of 250 µg/mL and 500 µg/mL, respectively. Briefly, this is the first report on the biological activities and secondary metabolite content of the ethyl acetate fraction of Hymedesmia sp. marine sponge, emphasizing the potential for further research against resistant bacterial and fungal strains, as well as different cancer cell lines. The ethyl acetate fraction of Hymedesmia sp. is a promising source of safe and unique natural drugs with potential therapeutic and pharmaceutical benefits.

Parallel β-Sheet Structure and Structural Heterogeneity Detected within Q11 Self-Assembling Peptide Nanofibers.

Q11 peptide nanofibers are used as a biomaterial for applications such as antigen presentation and tissue engineering, yet detailed knowledge of molecular-level structure has not been reported. The Q11 peptide sequence was designed using heuristics-based patterning of hydrophobic and polar amino acids with oppositely charged amino acids placed at opposite ends of the sequence to promote antiparallel β-sheet formation. In this work, we employed solid-state nuclear magnetic resonance spectroscopy (NMR) to evaluate whether the molecular organization within Q11 self-assembled peptide nanofibers is consistent with the expectations of the peptide designers. We discovered that Q11 forms a distribution of molecular structures. NMR data from two-dimensional (2D) 13C-13C dipolar-assisted rotational resonance indicate that the K3 and E9 residues between Q11 β-strands are spatially proximate (within ∼0.6 nm). Frequency-selective rotational echo double resonance (fsREDOR) on K3 Nζ and E9 Cδ-labeled sites showed that approximately 9% of the sites are close enough for salt bridge formation to occur. Surprisingly, dipolar recoupling measurements revealed that Q11 peptides do not assemble into antiparallel β-sheets as expected, and structural analysis using Fourier-transform infrared spectroscopy and 2D NMR alone can be misleading. 13C PITHIRDS-CT dipolar recoupling measurements showed that the most abundant structure consists of parallel β-sheets, in contrast to the expected antiparallel β-sheet structure. Structural heterogeneity was detected from 15N{13C} REDOR measurements, with approximately 22% of β-strands having antiparallel nearest neighbors. We cannot propose a complete structural model of Q11 nanofibers because of the complexity involved when examining structurally heterogeneous samples using NMR. Altogether, our results show that while heuristics-based patterning is effective in promoting β-sheet formation, designing a peptide sequence to form a targeted β-strand arrangement remains challenging.

Identification of major degradation products of Clorsulon drug substance including its degradation pathways by high resolution mass spectrometry and NMR

Clorsulon is an effective anthelmintic drug substance extensively used in the treatment of parasitic infestations in both cattle and sheep. An in-depth investigation of Clorsulon’s degradation products (DPs) was carried out through forced degradation study to comprehend its degradation path. A total of eight degradation products were separated under various stress degradation conditions. Structural elucidation of these DPs was conducted using ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS), and their fragmentation patterns were compared to that of the parent compound. Adequate amount of DP-4 was isolated and purified by semi-preparative high-performance liquid chromatography (HPLC) methods. Subsequently, it was examined in detail using both 1D and 2D NMR (nuclear magnetic resonance spectroscopy). Most probable mechanistic pathways for the formation of degradation products under various stress degradation conditions were proposed to better understand the degradation profile. Based on the results of the stress study, Clorsulon drug substance was found to be unstable under photolytic and oxidative conditions. Understanding Clorsulon's degradation pathway is essential for determining shelf-life prediction of the finished product, safety and efficacy assurance, and guiding the development of stable, high-quality formulations.

Analysis of <i>cis</i>-isomer-enriched dihydroquercetin sample by 1D and 2D NMR spectroscopy

Introduction. The structure of dihydroquercetin (DHQ) is characterized by two chiral centers at positions 2 and 3 of the benzopyran cycle, resulting in possible diastereomers: trans- and cis-isomers. Therefore, the development of methods for qualitative and quantitative control of DHQ diastereomers in analyzed samples is essential for patient safety management. Nuclear magnetic resonance (NMR) spectroscopy is one of the physicochemical methods that can be used for this purpose.Aim. The study objective was to accumulate the analytical and structural characteristics of cis-DHQ by NMR spectroscopy of the spheroidal form of this flavonoid (DHQs).Materials and Methods. 1D 1H, 1H,1H-COSY, 1H,1H-NOESY, and 1H,13C-HSQC NMR spectra were acquired at 298 K on an 800 MHz NMR spectrometer equipped with a TXI triple resonance probe. The number of scans was 32. The mixing time in the NOESY experiment was 400 ms. The 1H and 13C were analyzed using CcpNmr software. The dihedral angles were calculated by applying the Karplus equation.Results and discussion. In trans-DHQ, the chemical shift values for H2 and H3 are 4.93 ppm and 4.52 ppm, respectively, and in cis-DHQ they are 5.31 ppm and 4.20 ppm, respectively. The spin-spin coupling constants between H2 and H3 of trans- and cis-DHQ are 12.00 Hz and 2.40 Hz, respectively. Thus, the dihedral angles for the trans- and cis-isomers are 154° and 64°, respectively. We found that DHQs contains 12.5 % of the cis-isomer.Conclusion. Our experiments confirmed that NMR spectroscopy can discriminate between trans- and cis-DHQ based on the chemical shift values for the cross-peaks of H2 and H3. The second major finding was that this method can be considered as a more selective quantitative analysis than HPLC with UV detection without reference. One of the most important results of this study for drug development is the updated information on the structural parameters of DHQ diastereomers in the liquid phase.

Isolation, characterization, identification and quantification of 6-F oxyphenisatin dipropionate, a novel illegal additive, from a fruit-flavored jelly

ObjectiveThis study is aimed to screen, identify and detect illegal additives from healthcare products which claim or imply to have weight-loss effects. MethodUltra-high performance liquid chromatography-quadruple-time-of-flight mass spectroscopy (UPLC-Q-TOF/MS) was employed to perform non-targeted screening of illegal additives from a total of 26 batches of healthcare products with weight-loss effects. A novel oxyphenisatin dipropionate analog was discovered in a fruit-flavored jelly that was not clearly labeled as containing added drugs. After being separated and purified by silica gel column chromatography, the analog was unambiguously characterized by one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) spectroscopies. The molecular structure of the analog was finally identified by comparing the spectra of the analog with those of suspected candidates prepared by de novo synthesis strategy. Thereafter, a sensitive and precise reversed phase ultra performance liquid chromatography coupled with photodiode array (UPLC-PDA) detection method was developed and verified for the determination of the analog in 15 batches of real samples. ResultsIn the MS/MS spectra, the signal intensity of mass/charge ratios (m/z, 242 and 214) of the novel analog fragments was highly similar to that of mass/charge ratios (m/z, 224 and 196) of oxyphenisatin dipropionate fragments. Additionally, the 1D NMR spectrum of the analog was completely consistent with that of one of the suspected candidates prepared by the de novo synthesis strategy. Based on the above analysis, the structure of the analog was determined as 3,3-bis[4'-(propionyloxy)phenyl]-6-fluoro-2-oxoindoline, which was briefly named 6-F oxyphenisatin dipropionate. A developed quantitative method showed good linearity (R2 > 0.999) in a concentration range of 1.0–100 μg/mL. The limits of detection (LOD) and quantification (LOQ) for the analog was 3 mg/kg and 10 mg/kg, respectively. The average recoveries of the analog from spiked three different matrix samples in low (1 time of LOQ), medium (2 times of LOQ), and high (10 times of LOQ) concentrations were varied from 93.9 % to 107.8 % with a precision of 0.03–1.56 %. Results of quantitative analysis in 15 batches of healthcare products revealed that the content of 6-F oxyphenisatin dipropionate in a fruit-flavored jelly and a solid beverage was 118 mg/kg and 330 mg/kg, respectively. ConclusionIn terms of its structure, 6-F oxyphenisatin dipropionate replaces hydrogen atom by the fluorine atom at position 6 on the indolinone fragment in oxyphenisatin dipropionate. To our best knowledge, 6-F oxyphenisatin dipropionate has never been detected as an illegal additive in foods. Such illegal addition of the analog to foods is more concealing, thus the supervision and testing departments should attach great importance to its application in food markets.

New indole derivatives from endophytic fungus Colletotruchum sp. HK-08 originated from leaves of Nerium indicum

ObjectiveTo study secondary metabolites from endophytic fungus Colletotruchum sp. HK-08 originated from the leaves of Nerium indicum. MethodsThe compounds were isolated by various column chromatographic techniques, and their structures were elucidated by spectroscopic techniques [high resolution electrospray ionization mass spectroscopy (HRESIMS), one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance spectroscopy (NMR)], as well as comparison with literature data. The Ellman method was used to determine the acetylcholinesterase (AChE) inhibitory activity. ResultsFour indole derivatives were identified from Colletotruchum sp. HK-08, including 6′-hydroxymonaspiloindole (1), 2-(2-oxoindolin-3-yl)ethyl 2-(4-hydroxyphenyl) acetate (2), 2-(2-oxoindolin-3-yl)ethyl 2-(2-hydroxyphenyl)acetate (3), and monaspiloindole (4). Compound 4 presented weak AChE inhibitory activity with IC50 value of (69.30 ± 6.27) μmol/L [tacrine as the positive control, with IC50 value of (0.61 ± 0.07) μmol/L]. ConclusionCompounds 1–3 were new compounds, and compound 4 had weak AChE inhibitory activity.

Bioprospection of Tenellins Produced by the Entomopathogenic Fungus Beauveria neobassiana.

Fungi are known as prolific producers of bioactive secondary metabolites with applications across various fields, including infectious diseases, as well as in biological control. However, some of the well-known species are still underexplored. Our current study evaluated the production of secondary metabolites by the entomopathogenic fungus Beauveria neobassiana from Thailand. The fermentation of this fungus in a liquid medium, followed by preparative high-performance liquid chromatography (HPLC) purification, resulted in the isolation of a new tenellin congener, namely pretenellin C (1), together with five known derivatives (2-6). Their chemical structures were elucidated by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy in combination with high-resolution electrospray ionization mass spectrometry (HR-ESI-MS). We evaluated the antimicrobial and cytotoxic activities from all isolated compounds, as well as their inhibitory properties on biofilm formation by Staphylococcus aureus. Generally, tenellins displayed varying antibiofilm and cytotoxic effects, allowing us to propose preliminary structure-activity relationships (SARs). Among the tested compounds, prototenellin D (2) exhibited the most prominent antibiofilm activity, while its 2-pyridone congener, tenellin (4), demonstrated potent cytotoxic activity against all tested cell lines. Given the fact that the biological activities of the tenellins have so far been neglected in the past, our study could provide a good starting point to establish more concise structure-activity relationships in the near future.

Phytochemical and chemotaxonomic study on Thymus quinquecostatus Cêlak

Seventeen compounds, including one sesquiterpene (1), two diterpenoids (2 and 3), four monoterpenes (4–7), one phenolic acid (8), seven flavonoids (9–15), one lignan (16), and one sterol (17), have been isolated from the whole herb of Thymus quinquecostatus Cêlak., Lamiaceae. Among them, compounds 1–3, 9, 10, 12, 14, 15, and 16 were isolated from the genus Thymus for the first time; and compounds 5–7 were first isolated from this plant. Their structures were determined using 1D and 2D nuclear magnetic resonance (NMR) spectroscopy and compared with known data. To the best of our knowledge, their chemotaxonomic significance was explored in the present study for the first time.

Intracellular pyruvate-lactate-alanine cycling detected using real-time nuclear magnetic resonance spectroscopy of live cells and isolated mitochondria.

Pyruvate, an end product of glycolysis, is a master fuel for cellular energy. A portion of cytosolic pyruvate is transported into mitochondria, while the remaining portion is converted reversibly into lactate and alanine. It is suggested that cytosolic lactate and alanine are transported and metabolized inside mitochondria. However, such a mechanism continues to be a topic of intense debate and investigation. As a part of gaining insight into the metabolic fate of the cytosolic lactate and alanine; in this study, the metabolism of mouse skeletal myoblast cells (C2C12) and their isolated mitochondria was probed utilizing stable isotope-labeled forms of the three glycolysis products, viz. [3-13 C1 ]pyruvate, [3-13 C1 ]lactate, and [3-13 C1 ]alanine, as substrates. The uptake and metabolism of each substrate was monitored, separately, in real-time using 1 H-13 C 2D nuclear magnetic resonance (NMR) spectroscopy. The dynamic variation of the levels of the substrates and their metabolic products were quantitated as a function of time. The results demonstrate that all three substrates were transported into mitochondria, and each substrate was metabolized to form the other two metabolites, reversibly. These results provide direct evidence for intracellular pyruvate-lactate-alanine cycling, in which lactate and alanine produced by the cytosolic pyruvate are transported into mitochondria and converted back to pyruvate. Such a mechanism suggests a role for lactate and alanine to replenish mitochondrial pyruvate, the primary source for adenosine triphosphate (ATP) synthesis through oxidative phosphorylation and the electron transport chain. The results highlight the potential of real-time NMR spectroscopy for gaining new insights into cellular and subcellular functions.

Impact of Extraction Method on the Structure of Lignin from Ball-Milled Hardwood.

Understanding the structure of hardwoods can permit better valorization of lignin by enabling the optimization of green, high-yield extraction protocols that preserve the structure of wood biopolymers. To that end, a mild protocol was applied for the extraction of lignin from ball-milled birch. This made it possible to understand the differences in the extractability of lignin in each extraction step. The fractions were extensively characterized using 1D and 2D nuclear magnetic resonance spectroscopy, size exclusion chromatography, and pyrolysis-gas chromatography-mass spectrometry. This comprehensive characterization highlighted that lignin populations extracted by warm water, alkali, and ionic liquid/ethanol diverged in structural features including subunit composition, interunit linkage content, and the abundance of oxidized moieties. Moreover, ether- and ester-type lignin-carbohydrate complexes were identified in the different extracts. Irrespective of whether natively present in the wood or artificially formed during extraction, these complexes play an important role in the extractability of lignin from ball-milled hardwood. Our results contribute to the further improvement of lignin extraction strategies, for both understanding lignin as present in the lignocellulosic matrix and for dedicated lignin valorization efforts.

Structure elucidation and gene cluster of the O-antigen of Shewanella xiamenensis strain DCB-2-1 containing an amide of d-glucuronic acid with d-alanine and its bonding with U, Cr and V

The aim of this work was to examine the structure and gene cluster of O-OPS of S. xiamenensis strain DCB-2-1 and survey its conceivability for chelating uranyl, chromate and vanadate ions from solution. O-polysaccharide (OPS, O-antigen) was isolated from the lipopolysaccharide of Shewanella xiamenensis DCB-2-1 and studied by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy and sugar analysis. The following structure of the brunched pentasaccharide was established: [Display omitted] where d-β-GlcpA(d-Ala) is d-glucuronic acid acylated with NH group of d-Ala. The OPS structure established is unique among known bacterial polysaccharide structures. Interestingly, that dN-(d-glucuronoyl)-d-alanine derivative is not found in bacterial polysaccharides early.The O-antigen gene cluster of Shewanella xiamenensis strain DCB-2-1 has been sequenced. The gene functions were tentatively assigned by comparison with sequences in the available databases and found to be in agreement with the OPS structure. Based on the analysis of the IR spectra of the isolated polysaccharide DCB-2-1 and the products of its interaction with UO2(NO3)2 ∗ 6H2O, NH4VO3 and K2Cr2O7, a method of binding them can be proposed. Laboratory experiments show that the use of polysaccharide can be effective in removing uranyl, chromate and vanadate from solution.

Type I Lipoteichoic Acid (LTA) Purification by Hydrophobic Interaction Chromatography and Structural Analysis by 2D Nuclear Magnetic Resonance (NMR) Spectroscopy.

Type I lipoteichoic acid (LTA) is a glycerolphosphate polymer found in the cell envelope of diverse Gram-positive bacteria. The glycerolphosphate backbone is often further decorated with D-alanine and/or sugar residues. Here, we provide details of a 1-butanol extraction and purification method of type I LTA by hydrophobic interaction chromatography. The protocol has been adapted from methods originally described by Fischer et al. (Eur J Biochem 133:523-530, 1983) and further optimized by Morath et al. (J Exp Med 193:393-397, 2001). We also present information on a 2D nuclear magnetic resonance (NMR) analysis method to gain chemical and structural information of the purified LTA material.

Isolation and Structural Characterization of a major degradation product of Ambrisentan using Q-TOF-MS, NMR and FTIR

Ambrisentan, an endothelin receptor antagonist, is subjected to forced degradation under neutral hydrolytic conditions, leading to a potential unknown impurity. This neutral degradation product (DP) has been detected using reverse-phase ultra-performance liquid chromatography (UPLC), where it has eluted at 1.24 relative retention time to the Ambrisentan peak. DP was isolated using semi-preparative HPLC from the degradation mixture. Later, the structure of DP was elucidated using high-resolution mass spectrometry, 2D Nuclear magnetic resonance spectroscopy (NMR), and Fourier transformed infrared spectroscopy (FTIR) spectroscopic techniques and characterized as 2-(2,2- diphenylvinyloxy)-4,6-dimethylpyrimidine.

Anti-inflammatory activity via NO production inhibition of compounds from Vietnamese Lycopodium casuarinoides Spring

In our investigation of the methanol extract derived from the aerial parts of Vietnamese Lycopodium casuarinoides Spring, we successfully isolated two novel secondary metabolites: 3β,21α,24-trihydroxyserrat-14-en-29-yl-E-4′-hydroxy-3′-methoxycinnamate (1) and lycocasuarinol A (2), and eight known compounds, namely α-onocerin (3), salcolin A (4), salcolin B (5), (2 R,3 R)-dihydrokaempferol (6), apigenin (7), huperzinine (8), 4-methoxycinnamic acid (9), and (E)-p-coumaric acid (10). The structural elucidation of these compounds was accomplished through high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) and one-dimensional (1D) and two-dimensional (2D) nuclear magnetic resonance (NMR) spectroscopy techniques. All isolates were tested for their potential to inhibit nitric oxide (NO) production in lipopolysaccharide (LPS)-induced RAW264.7 cells. Notably, the flavonoids (2 R,3 R)-dihydrokaempferol (6) and apigenin (7) exhibited significant inhibitory activity against NO production, with IC50 values of 3.4 µM and 3.0 µM, respectively. These values surpassed the inhibition observed with the positive control, celastrol. Furthermore, a comparison of the guaiacyl glyceryls salcolin A (4) and salcolin B (5), differing in their threo-β- and erythro-guaiacyl glyceryl moieties, revealed potential structure-activity relationships. These findings suggest that the extract from Lycopodium casuarinoides and its phytochemical constituents hold promise as potential anti-inflammatory agents

DIBENZOCYCLOOCTADIENE LIGNANS ISOLATED FROM THE ROOTS OF SCHISANDRA CAULIFLORA AND THEIR NITRIC OXIDE INHIBITION ACTIVITY ON LPS STIMULATED RAW 264.7 CELLS

Objectives: To isolate and determine the chemical structure of some compounds from the roots of Schisandra Cauliflora and their inhibitory activity on nitric oxide production. Methods: The roots of Schisandra cauliflora, which were collected in Vinh Phuc in April 2022, were processed before being extracted and isolated to obtain compounds. Compounds structures were elucidated based on extensive spectroscopic analyses, including 1D- and 2D-nuclear magnetic resonance spectroscopy (NMR), mass spectrometry (HR-ESI-MS), and CD spectra. The obtained compounds were evaluated for inhibitory activity on nitric oxide production on LPS stimulated RAW 264.7 cells. Results and conclusion: From the methanol extract of the roots of Schisandra cauliflora, three dibenzocyclooctadiene lignans were isolated, including ananonin J, ananolignan F, and ananolignan C. Their structures were elucidated. All the compounds inhibited nitric oxide productions on LPS stimulated RAW 264.7 cells with IC50 values of 45.24 ± 1.46, 41.32 ± 1.45, and 48.71 ± 1.34µM, respectively, compared to that of the positive control of dexamethasone (IC50 14.20 ± 0.54µM). This is the first time these lignan compounds have been isolated from the roots of Schisandra cauliflora.

Evaluating performance of CrCl3-catalyzed ethanol pretreatment of poplar on cellulose conversion

As green and effective depolymerization processes, CrCl3 and CrCl3-catalyzed ethanol pretreatment were comprehensively investigated to improve cellulose conversion from pretreated residues in poplar in the present study. The influence of pretreatment temperature on delignification, structural characteristics of lignin, and the yield of glucose and ethanol was comparatively analyzed to emphasize the synergy effect of CrCl3 and ethanol solvent. Particularly, CrCl3-catalyzed ethanol pretreatment at 200 °C resulted in the pretreated substrates with >94% removal of hemicellulose and lignin, consequently reaching 88.88% and 56.11% yields of glucose and ethanol, respectively. Lignin's structural change was observed by Gel permeation chromatography and 2D nuclear magnetic resonance spectroscopy and its relationship with the efficiency of enzymatic hydrolysis and fermentation was determined. Results indicated that the increased pretreatment temperature enhanced the lignin depolymerization with smaller molecular weight, fewer β-O-4 linkages, and higher S/G ratio, especially in CrCl3-catalyzed ethanol pretreatment, which was positively associated with poplar cellulose conversion. In addition to offering a comprehensive illustration of the sugar/ethanol generation during CrCl3-catalyzed organosolv pretreatment, this work also provided theoretical support for biofuel and biochemical production from poplar.

Chemical Constituents from Ficus sagittifolia Stem Bark and Their Antimicrobial Activities.

The phytochemical investigation of the ethylacetate fraction of an ethanolic extract obtained from the stem bark of Ficus sagittifolia (Moraceae) led to the isolation of four flavonoids: (2R)-eriodictyol (1), 2'- hydroxygenistein (2), erycibenin A (3), and genistein (4); a dihydrobenzofuran: moracin P (5); a coumarin: peucedanol (6); and an apocarotenoid terpenoid: dihydrophaseic acid (7). These were identified via 1D and 2D nuclear magnetic resonance spectroscopy (NMR) and ultra-high-resolution liquid chromatography-quadrupole time-of-flight mass spectroscopy (UHPLC-QTOF MS). Moracin P (5) is being reported for the first time in the genus Ficus, while the others are known compounds (1-4 and 6-7) isolated previously from the genus but being reported for the first time from the species F. sagittifolia. Their antimicrobial activity against various pathogens (five bacteria: Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, and Salmonella typhi; two fungi: Aspergillus niger and Candida albicans) was tested. The mixture of genistein and moracin P (4+5) exhibited strong activity against K. pneumoniae (MIC < 0.0039 mg/mL), whereas dihydrophaseic acid (7) was the most active against P. aeruginosa and A. niger (MIC = 0.0078 and <0.0039 mg/mL, respectively). These compounds might be considered potential antimicrobial agents with the potential to be starting points for the development of antimicrobial drugs.

Molecular Characterization and Quantification of Saponins from Sugar Beet (Beta vulgaris ssp. vulgaris var. altissima)

Consumer demand for sustainably and ecologically produced food has grown in recent years. However, for numerous reasons, this demand has not always been met. New solutions are still being sought, particularly in the area of emulsifiers, an integral ingredient of many food products. The biggest challenge is the limited scope of application offered by current alternatives. While some progress has been made using foam active quillaja saponins, they are neither pleasant‐tasting nor sustainably produced. Only very little is known about other alternatives, and especially the behavior of saponins, particularly on a molecular level, is not very well understood. Moreover, it is often not known which parts of a plant contain the highest levels of saponins and are therefore most suitable for extraction.To expand the current level of knowledge about emulsifying and foam active extracts, saponin extracts were made from oat bran, beetroot as well as sugar beet and characterized in close cooperation with the Department of Food Physics and Meat Science at the University of Hohenheim. Measurements conducted on these extracts showed that foam activity is a good indicator of their emulsifying ability. The most promising one ‐ sugar beet extract ‐ was examined in more detail using taste dilution analysis, which revealed saponin fractions with a slight off‐taste and high foam activity. A series of eight saponins was obtained from these fractions and further characterized, together with three commercially available ones that were identified using non‐targeted screening. The unequivocal identification and structure elucidation was performed using a combination of liquid chromatography‐tandem mass spectrometry (LC‐MS/MS) and both one‐dimensional (1D) and two‐dimensional (2D) nuclear magnetic resonance (NMR) spectroscopy. For most substances, this was the first time that a complete assignment of 1H and 13C NMR signals had been made. All of these saponins possess taste recognition values above 1000 μmol/L, which is higher than most values for the taste‐ active saponins reported in the literature. The foam activity of these substances was measured using a self‐developed small‐scale foam activity assay. It was measured for different concentrations of saponins in a buffer solution. The foam activity of numerous other saponins was also determined, resulting in the most comprehensive overview of the foam activities of individual saponins.In addition to these isolation and characterization activities, an LC‐MS/MS method of performing simultaneous quantitative analyses of all the obtained sugar beet saponins was developed and validated. These were quantified in several sugar beet varieties (root and leaves), different sugar beet compartments, and side streams originating during the sugar beet converting process. Great variations in mass fractions were found in these materials, ranging from 862 mg/kg to 2,452 mg/kg for the various sugar beet root varieties and from 907 mg/kg to 5,398 mg/kg for the sugar beet leave varieties. Sugar beet fiber was identified as the best saponin source, with a total saponin quantity of 12.7 g/kg, followed by dried sugar beet pulp, with a total quantity of 10.3 g/kg. As a by‐product stream, dried sugar beet pulp is highly suitable for the sustainable manufacture of saponins.The results obtained are of key significance to the utilization of sugar beet saponins as well as saponins extracted from other plant materials or by‐product streams for use as food additives.

Non-uniformly sampled 2D NMR Spectroscopy reconstruction based on Low Rank Hankel Matrix Fast Tri-Factorization and Non-convex Factorization

Nuclear magnetic resonance (NMR) spectroscopy is widely used in chemistry and medicine to research the composition of matter and the spatial structure of proteins. However, NMR signals with larger sizes and higher dimensions are slower to acquire. Therefore, Non-Uniform Sampling (NUS) methods are used to speed up the acquisition of NMR signals, and some mathematical algorithms are used to recover the original NMR signals from the NUS data. In recent years, low-rank Hankel matrix completion is proved to recover NMR data with less error. However, it requires singular value decomposition (SVD) with high computational complexity in each iteration, which is not suitable for reconstructing signals with large sizes. In this paper, we propose a Fast Tri-Factorization (FTF) method to decompose the low-rank Hankel matrix into three small-scale matrices, and it convert the original problem into a matrix nuclear norm minimization problem on the small-scale matrix to mitigate high computation cost of multiple SVDs. Furthermore, the factor matrix size remains constant for different size of the Hankel matrices. We further replace the low-rank constraint with Non-convex Factorization (NF) to avoid the time-consuming SVD in each iteration. Numerical experiments show that the proposed method can significantly speed up the NMR reconstruction compared with several existing algorithms while ensuring the reconstruction accuracy.

Amesia hispanica sp. nov., Producer of the Antifungal Class of Antibiotics Dactylfungins.

During a study of the diversity of soilborne fungi from Spain, a strain belonging to the family Chaetomiaceae (Sordariales) was isolated. The multigene phylogenetic inference using five DNA loci showed that this strain represents an undescribed species of the genus Amesia, herein introduced as A. hispanica sp. nov. Investigation of its secondary metabolome led to the isolation of two new derivatives (2 and 3) of the known antifungal antibiotic dactylfungin A (1), together with the known compound cochliodinol (4). The planar structures of 1-4 were determined by ultrahigh performance liquid chromatography coupled with diode array detection and ion mobility tandem mass spectrometry (UHPLC-DAD-IM-MS/MS) and extensive 1D and 2D nuclear magnetic resonance (NMR) spectroscopy after isolation by HPLC. All isolated secondary metabolites were tested for their antimicrobial and cytotoxic activities. Dactylfungin A (1) showed selective and strong antifungal activity against some of the tested human pathogens (Aspergillus fumigatus and Cryptococcus neoformans). The additional hydroxyl group in 2 resulted in the loss of activity against C. neoformans but still retained the inhibition of As. fumigatus in a lower concentration than that of the respective control, without showing any cytotoxic effects. In contrast, 25″-dehydroxy-dactylfungin A (3) exhibited improved activity against yeasts (Schizosaccharomyces pombe and Rhodotorula glutinis) than 1 and 2, but resulted in the appearance of slight cytotoxicity. The present study exemplifies how even in a well-studied taxonomic group such as the Chaetomiaceae, the investigation of novel taxa still brings chemistry novelty, as demonstrated in this first report of this antibiotic class for chaetomiaceous and sordarialean taxa.