Amino Nitrogen Atom Research Articles

Synthesis, Spectroscopy and Biological Studies of Copper and Silver Complexes Derived from 2-Substituted Amino Propanoic Acid

Synthesis of copper and silver complexes were prepared from novel Schiff base ligand. These synthesized ligand and their metal complexes were characterized by elemental analysis, FT-IR, 1H NMR, UV-Vis and Mass spectrometry. The coordination of amino nitrogen, phenolic oxygen, and carboxylato oxygen atoms is shown by the infrared spectra.The Schiff bases and its complexes were screened for their in vitro antibacterial and antifungal studies against the bacteria Pseudomonas Aeruginosa (PA, Gram -ve), Bacillus Cirroflagellosus (BC, Gram +ve), Penicillium Notatium (PN) and Aspergillus Niger (AN) strains. The results of the antibacterial investigation show that the copper and silver complexes possess more potent bactericide and fungicide properties than the ligand.

The facile preparation of polydopamine-modified sepiolite and its adsorption properties and microscopic mechanism for cadmium ion

Natural sepiolite (SEP) has the characteristics of cation exchange, abundant reserves, low cost, and environmental friendliness, but its adsorption capacity for heavy metal pollutants is limited. Because polydopamine (PDA) molecules contain rich functional groups such as phenolic and amino groups, in the present work, dopamine and natural sepiolite were utilized as raw materials to prepare polydopamine-modified sepiolite composite (SEP/PDA) by simple co-precipitation method. According to Langmuir isotherm model, the maximum adsorption capacity of SEP/PDA for Cd2+ can reach 203.21 mg/g at 298 K. At the initial concentration of 100 mg/L, the adsorption capacity was 2.9 times that of natural sepiolite. The composite material has good reusability and anti-cationic interference performance and has 100 % removal ability of low concentration Cd2+ in actual electroplating wastewater. Density Functional Theory (DFT) calculations were performed to obtain the electronic structure information. To elucidate the microscopic mechanism, molecular surface analyses, Interaction Region Indicator (IRI), Atom In Molecules (AIM) theory, Bond Order Density (BOD), and Electron Localization Function (ELF) were conducted. These analyses revealed that the amino nitrogen and phenolic oxygen atoms in the dopamine molecules donate lone pair electrons to coordinate with cadmium ions. Polydopamine, which possesses multiple oxidation states, contains catechol, quinone, and indole or a lesser extend pyrrole groups that can complex with cadmium ions, resulting in the formation of a surface complex. This coordination significantly enhances the adsorption properties of the SEP/PDA composite.

Isolation and characterisation of zinc‐chelating peptides from tilapia (Oreochromis niloticus) protein hydrolysate

SummaryThis study aimed to isolate and characterise zinc‐chelating peptides from tilapia (Oreochromis niloticus) protein hydrolysate. The hydrolysate was fractionated using a multi‐ultrafiltration technique, yielding peptide fractions with molecular weights between 0.5 and 5 kDa. These fractions were further purified using immobilised metal ion affinity chromatography (IMAC‐Zn2+) and reverse high‐performance liquid chromatography (RP‐HPLC). Among the fractions obtained, the peptide fraction F211 exhibited a zinc‐binding capacity of 76.26 ± 2.46 mg g−1. Sequence analysis indicated that zinc binding occurred at amino acids on the F21 peptide and at valine or glutamate residues on the F22 peptide fraction. Structural characterisation revealed that amino nitrogen and oxygen atoms from carboxylate groups were the primary binding sites for Zn2+. Additionally, the zinc–peptide complex demonstrated strong thermal stability, which is significant for potential applications in food processing and storage, where maintaining the integrity of nutritional supplements under varying temperature conditions is crucial. These findings provide a feasible approach for the separation and purification of zinc‐binding peptides from tilapia protein hydrolysates and contribute to the understanding of the binding mechanisms between zinc and peptides.

Chitosan encapsulation soy peptide–calcium promotes calcium absorption and bone health of rats fed a low calcium diet

Calcium deficiency is considered widespread globally, and discovering calcium with high bioavailability is one of the keys to solving calcium deficiency. This study prepared a calcium delivery system with chitosan and soy peptide and investigated its characteristics, ability to promote calcium absorption, and effects on bone health. The experiment results reveal that chitosan encapsulates soybean peptide–calcium (COS–SPs–Ca) with carboxyl oxygen atoms, amino nitrogen atoms, and phosphate ions, which has a slow-release effect in simulated gastrointestinal digestion. In calcium-deficient rats, COS–SPs–Ca has beneficial effects on serum biochemical parameters, bone biomechanics, and bone microarchitecture, and significantly up-regulated the gene expression of TRPV5, TRPV6, PepT1, and Calbindin-D9k in the small intestine. These results suggest that COS–SPs–Ca is a promising calcium supplement.

Characterization, in vitro antioxidant activity and stability of cattle bone collagen peptides‑selenium chelate

In this study, cattle bone collagen peptides–selenium chelate (CCP-Se) was prepared and its structure, oxidation resistance and stability were characterized. The selenium binding capacity was 33.65 ± 0.13 mg/g by optimized preparation conditions. Structural analysis showed that selenium ions bound mainly to the amino nitrogen, carboxyl oxygen and hydroxyl oxygen atoms of the cattle bone collagen peptide (CCP). The microstructure and particle size analyses showed that the particle size of CCP-Se was increased and formed a regular and compact crystal structure compared with CCP. Additionally, CCP-Se exhibited excellent antioxidant activity. Stability analysis showed that CCP-Se was stable in thermal processing, simulated in vitro digestion and acid/alkali tolerance tests. The intestinal selenium permeability of CCP-Se was significantly better than sodium selenite (p < 0.05). This study provides reference for the high-value application of cattle bone and suggests the potential of CCP-Se as a new effective selenium supplement.

Bifunctional hyper-cross-linked polymer with phosphorylated-amidoximated groups for efficient uranium extraction from water

Designing and developing a uranium adsorbent with high adsorption capacity and good selectivity is highly significant. We synthesized a novel hyper-cross-linked polymer adsorbent with bifunctional groups, (PHCP-4-AO), such as phosphate and amidoxime groups, via simple Scholl reaction and subsequent functionalization for the first time highly efficient extraction of U(VI) from aqueous solution. Due to its unique molecular structure design, it can enhance the selectivity and adsorption capacity of uranium by using two different functional groups. The maximum uranium adsorption capacity of PHCP-4-AO was 424.33 mg/g, which was higher than the single-functional group phosphorylated (PHCP-4) (315.43 mg/g) and amidoximated (HCP-4-AO) (260.38 mg/g) adsorbents. The combination of phosphate and amidoxime groups improves the adsorption effect. PHCP-4-AO has good selectivity and affinity for uranyl ions. In simulated wastewater, the Kd of PHCP-4-AO for uranium was 7266.3 mL/g, which was more than 15 times that of other ions. After three adsorption–desorption cycles, the adsorption capacity of PHCP-4-AO can still be maintained above 300.00 mg/g. Through XPS analysis, it is speculated that the sorption of uranium by PHCP-4-AO is owing to the lone pair electrons found on the oxygen atom of the phosphate groups, as well as the oxime oxygen and amino nitrogen atoms of the amidoxime groups entering the uranium’s empty orbit to form the coordination bonds. These findings demonstrated that this new hyper-cross-linked polymer could be considered as a valuable material in the extraction and recovery of uranium from uranium-containing aqueous solutions.

Enhancing U(VI) removal from highly acidic wastewater through the synergistic effect of diethylenetriaminepenta(methylenephosphonic) acid and meso-SiO2 on nanosized γ-Fe2O3

Wastewater from uranium mining activities is highly acidic and contains uranium, thereby posing severe risks to the ecological environment and human health. Accordingly, uranium purification is extremely crucial. Herein, we delicately designed a novel adsorbent of diethylenetriaminepenta(methylenephosphonic) acid (DTPMP) and meso-SiO2 modified γ-Fe2O3 (γ-Fe2O3@SiO2@DTPMP, denoted as FSD), and found that the adsorbent can remarkably boost the removal performance of U(VI) under highly acidic conditions. The removal efficiencies of U(VI) by FSD are 90.26 % and 99.81 % in strong acidic solutions of pH = 1.0 and pH = 2.0, respectively, which are much higher than most of the reported adsorbents. Importantly, FSD exhibits high adsorption capacity (51.45 mg/g) and excellent anti-interference, even the wastewater stream contained a lot of organic substances (e.g., fulvic acid), cations (e.g., K+, Na+, Mg2+, NH4+, Zn2+, Co2+, etc.), radioactive nuclides (e.g., Cs+ and Sr2+). After five cycles, the adsorption efficiency and desorption efficiency of FSD only reduced by 8.83 % and 9.61 %, respectively, which are mainly attributed to the unique structures and good chemical stability of FSD. The removal of U(VI) by FSD is a heterogeneous adsorption process which is dominated by chemical adsorption, mainly involving surface coordination complexation. Multiwfn wavefunction and VMD programs based on density functional theory (DFT) further analyzed and visualized the interaction sites and relative strengths of reactions. The results of detailed characterization analysis and theoretical calculations confirmed that the highly efficient U(VI) removal by FSD is mainly ascribed to the strong coordination of the phosphate groups and amino nitrogen atoms in DTPMP with UO22+. Therefore, this study provides a promising strategy for the removal of U(VI) in strongly acidic wastewater.

Production of novel mung bean peptides-based zinc supplement: Process optimization, chelation mechanism, and stability assessment in vitro

To realize the add value of protein resources from mung bean processing by-products, mung bean peptides-zinc chelate (MBP-Zn), a novel zinc supplement, was synthesized in the present study. Under the optimized process conditions (MBP concentration of 6%, pH 5.0, mass ratio of MBP to zinc salt of 2:1, temperature of 60 °C and time of 80 min), the zinc chelation rate of MBP-Zn reached up to 98.15%. Integrating the results of Fourier transform infrared spectroscopy and amino acid profiles, it is inferred that zinc ions may bind to MBP via carboxy oxygen, amino nitrogen, and sulfhydryl sulfur atoms. The incorporation of zinc ions dramatically changed the structure of the chelate, as evidenced by the blue shift and attenuation of the original UV and fluorescence spectra. The morphological analysis revealed that Zn2+ induced cross-linking of peptides, forming enlarged nanoparticles that fragmented the original smooth surface of MBP. Surprisingly, the superior stability of MBP-Zn over the conventional zinc supplement ZnSO4 was confirmed, regardless of pH and temperature variations, or simulated gastrointestinal digestion circumstances. These findings pave the way for the large-scale production of mung bean peptide-based zinc supplements as nutraceuticals in the food industry.

Lactobacillus helveticus-Derived Whey-Calcium Chelate Promotes Calcium Absorption and Bone Health of Rats Fed a Low-Calcium Diet.

This study investigated the characteristics of Lactobacillus helveticus-derived whey-calcium chelate (LHWCC) and its effect on the calcium absorption and bone health of rats. Fourier-transform infrared spectroscopy showed that carboxyl oxygen atoms, amino nitrogen atoms, and phosphate ions were the major binding sites with calcium in LHWCC, which has a sustained release effect in simulated in vitro digestion. LHWCC had beneficial effects on serum biochemical parameters, bone biomechanics, and the morphological indexes of the bones of calcium-deficient rats when fed at a dose of 40 mg Ca/kg BW for 7 weeks. In contrast to the inorganic calcium supplement, LHWCC significantly upregulated the gene expression of transient receptor potential cation V5 (TRPV5), TRPV6, PepT1, calcium-binding protein-D9k (Calbindin-D9k), and a calcium pump (plasma membrane Ca-ATPase, PMCA1b), leading to promotion of the calcium absorption rate, whereas Ca3(PO4)2 only upregulated the TRPV6 channel in vivo. These findings illustrate the potential of LHWCC as an organic calcium supplement.

Glycated Walnut Meal Peptide-Calcium Chelates: Preparation, Characterization, and Stability.

Finding stable and bioavailable calcium supplements is crucial for addressing calcium deficiency. In this study, glycated peptide-calcium chelates (WMPHs-COS-Ca) were prepared from walnut meal protein hydrolysates (WMPHs) and chitosan oligosaccharides (COSs) through the Maillard reaction, and the structural properties and stability of the WMPHs-COS-Ca were characterized. The results showed that WMPHs and COSs exhibited high binding affinities, with a glycation degree of 64.82%. After glycation, Asp, Lys, and Arg decreased by 2.07%, 0.46%, and 1.06%, respectively, which indicated that these three amino acids are involved in the Maillard reaction. In addition, compared with the WMPHs, the emulsifying ability and emulsion stability of the WMPHs-COS increased by 10.16 mg2/g and 52.73 min, respectively, suggesting that WMPHs-COS have better processing characteristics. After chelation with calcium ions, the calcium chelation rate of peptides with molecular weights less than 1 kDa was the highest (64.88%), and the optimized preparation conditions were 5:1 w/w for WMPH-COS/CaCl2s, with a temperature of 50 °C, a chelation time of 50 min, and a pH of 7.0. Scanning electron microscopy showed that the "bridging role" of WMPHs-COS changed to a loose structure. UV-vis spectroscopy and Fourier transform infrared spectrometry results indicated that the amino nitrogen atoms, carboxyl oxygen atoms, and carbon oxygen atoms in WMPHs-COS chelated with calcium ions, forming WMPHs-COS-Ca. Moreover, WMPHs-COS-Ca was relatively stable at high temperatures and under acidic and alkaline environmental and digestion conditions in the gastrointestinal tract, indicating that WMPHs-COS-Ca have a greater degree of bioavailability.

Multi-Scale Insight into Inhibition Mechanism of Benzo Derivatives in Chemical Mechanical Polishing of Copper Film Based on Experiments and Theoretical Calculations

To protect the copper (Cu) surfaces from corrosion during the chemical mechanical polishing (CMP), selecting appropriate inhibitors are critical. Benzo and its derivatives are potential superior inhibitors due to their diverse heteroatoms and environmentally friendliness. In this study, benzothiazole (ABT), 2-benzothiazolamine (2-ABT) and 2-aminobenzimidazole (2-ABI) were used as inhibitors to investigate the effect of molecular structure on the inhibition performance through experimental and theoretical calculation. With the addition of inhibitors, the removal rates were all inhibited effectively and the inhibition efficiency was in the following order: 2-ABI > 2-ABT > ABT. Electrochemical experiments and surface morphology tests demonstrated that the inhibitors could prevent corrosion by forming dense passivation film on Cu surfaces with a high inhibition efficiency of 88%, 94% and 95%, and improve the surface quality after CMP. Calculation results revealed that the introduction of amino groups (–NH2) and nitrogen(N) atom into five-membered ring enhanced the inhibition effect due to the larger adsorption energy, stronger ability to contribute electrons and denser passivation film which consistent with the experiment. Such study confirms the benzimidazole derivatives are potentially inhibitor for Cu film CMP and provides a new reference to design and select novel inhibitors.

Synthesis and crystal structure of a bench-stable pyridinium ketene hemiaminal: 1-(1-eth-oxy-ethen-yl)-2-[meth-yl(phen-yl)amino]-pyridin-1-ium tri-fluoro-methane-sulfonate.

The novel bench-stable N-quaternized ketene N,O-acetal, C16H19N2O+·CF3O3S-, was synthesized and its structure determined. The title compound is a rare example of a pyridinium ketene hemiaminal for which a crystal structure has been determined, joining the 2-chloro-1-(1-ethyoxyethen-yl)pyridin-1-ium tri-fluoro-methane-sulfonate salt from which it was synthesized. The cationic species of the title compound can be defined by three individually planar fragments assembling into a non-coplanar cation. The phenyl substituent extending from the amino nitro-gen atom and the ethyoxyvinyl substituent extending from the pyridine N atom are oriented on the same side of the mol-ecule and maintain the closest coplanar relationship of the three fragments. Supra-molecular inter-actions are dominated by C-H⋯O inter-actions from the cation to the SO3 side of the tri-fluoro-methane-sulfonate anion, forming a two-dimensional substructure.

Development, characterization and in vivo zinc absorption capacity of a novel soy meal hydrolysate-zinc complexes.

Zinc is an essential trace element for the human body. Recently, a novel Zn-binding peptide, Lys-Tyr-Lys-Arg-Gln-Arg-Trp (PP), was purified and identified from soy protein hydrolysates with high Zn-binding capacity (83.21 ± 2.65%) by our previous study. The preparation of soy meal hydrolysates (SMHs)-Zn complexes is convenient and low-cost, while PP (Lys-Tyr-Lys-Arg-Gln-Arg-Trp)-Zn complexes have a higher coordination rate but a relatively high cost. The aim of this study was to investigate the effect of soy meal hydrolysates (SMHs)-Zn complexes on zinc absorption in mice model, and synthetic soy peptide (PP)-Zn complexes with high Zn-binding capacity were used as control. Firstly, SMHs were prepared by enzymolysis, and the PP (Lys-Tyr-Lys-Arg-Gln-Arg-Trp) were synthesized based on previous studies. The binding mechanism of soy hydrolysates and zinc was analyzed by spectral analysis. Furthermore, the cytotoxicity of the SMHs-Zn complexes was also studied using the CCK-8 method. The effect of zinc absorption was evaluated based on Zn content, total protein and albumin content, relevant enzyme system, and the PeT1 and ZnT1 mRNA expression levels. The result showed that zinc was bound with carboxyl oxygen and amino nitrogen atoms on SMHs, with hydrophobic and electrostatic interactions as auxiliary stabilizing forces. SMHs-Zn were proved to have great solubility and a small particle size at different pH values, and it showed a beneficial effect on Caco-2 cells growth. Moreover, it was proved that SMHs-Zn and PP-Zn could increase the levels of zinc and the activity of Zn-related enzymes in mice. SMHs-Zn possessed higher PepT1 and ZnT1 mRNA expression levels than PP-Zn in the small intestine. SMHs-Zn with a lower Zn-binding capacity had similar effects on zinc absorption in mice as PP-Zn, suggesting that the bioavailability of peptide-zinc complexes in mice was not completely dependent on their Zn-binding capacity, but may also be related to the amino acid composition.

Preparation, structure characterization, and stability analysis of peptide-calcium complex derived from porcine nasal cartilage type II collagen.

Porcine nasal cartilage type II collagen-derived peptides (PNCPs) may be complexed with calcium to provide a highly bioavailable, low-cost, and effective calcium food supplement. However, the calcium-binding characteristics of PNCPs have not yet been investigated. In the present study, calcium-binding peptides were derived from porcine nasal cartilage type II collagen and the resulting PNCPs-Ca complex was characterized. The study reveals that the calcium-binding capacity of PNCPs is closely related to enzymatic hydrolysis conditions. The highest calcium-binding capacity of PNCPs was observed at a hydrolysis time of 4 h, temperature of 40 °C, enzyme dosage of 1%, and solid-to-liquid ratio of 1:10. Scanning electron microscopy and energy dispersive X-ray spectroscopy revealed that the PNCPs had a pronounced capacity for calcium binding, with the PNCPs-Ca complex exhibiting a clustered structure consisting of aggregated spherical particles. Fourier-transform infrared spectroscopy, fluorescence spectroscopy, X-ray diffraction, dynamic light scattering, amino acid composition, and molecular weight distribution analyses all indicated that the PNCPs and calcium complexed via the carboxyl oxygen and amino nitrogen atoms, leading to the formation of a β-sheet structure during the chelation process. In addition, the stability of the PNCPs-Ca complex was maintained over a range of pH values consistent with those found in the human gastrointestinal tract, facilitating calcium absorption. These research findings suggest the feasibility of converting by-products from livestock processing into calcium-binding peptides, providing a scientific basis for the development of novel calcium supplements and the potential reduction of resource waste. © 2023 Society of Chemical Industry.

Synthesis, characterization, crystal structures and biological activity of molybdenum complexes derived from bis(acetylacetonato)dioxomolybdenum(VI) and Schiff bases

Reaction of bis(acetylacetonato)dioxomolybdenum(VI) with 4-fluoro-2-((pyridin-2-ylmethylene)amino)phenol and 3-methyl-2-((pyridin-2-ylmethylene)amino)phenol, respectively in methanol afforded two new molybdenum complexes [MoO2L1] and [MoO2L2], where L1 and L2 are the dianionic form of 3-(((5-fluoro-2-hydroxyphenyl)amino)(pyridin-2-yl)methyl)pentane-2,4-dione (H2L1) and 3-(((2-hydroxy-6-methylphenyl)amino)(pyridin-2-yl)methyl)pentane-2,4-dione (H2L2). Both complexes have been characterized by elemental analysis, IR, UV–Vis, 1H and 13C NMR spectra. Molecular structures of the complexes have been determined by X-ray crystallography. In the complexes, the ligands coordinated to the Mo atoms via pyridine nitrogen, amino nitrogen, phenolate oxygen, and enolate oxygen atoms. The octahedral coordination of the Mo atoms is furnished by two oxido oxygen atoms. The complexes were evaluated for their antibacterial activities on Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas fluorescens, and antifungal activities on Candida albicans and Aspergillus niger, and gave interesting results.

Casein calcium-binding peptides: Preparation, characterization, and promotion of calcium uptake in Caco-2 cell monolayers

In this study, casein calcium-binding peptides were isolated from casein hydrolysate using calcium-peptide binding properties and their banding properties were characterized. Subsequently, the promoted calcium absorption abilities of casein calcium-binding peptides in the Caco-2 cells monolayers were investigated. Amino acid composition analysis showed that casein calcium-binding peptide-calcium chelate are rich in Glu, Ser, and Asp, with a significant increase in proportion compared to the casein hydrolysate. Molecular weight analysis showed that approximately 90 % of the casein calcium-binding peptides are oligopeptides. Thirty-seven peptide sequences were identified by mass spectrometry, and the presence, quantity, and position of some specific amino acid residues were found to correlate with calcium-binding ability. Additionally, calcium-peptide binding properties were characterized by using Ultraviolet-Visible spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy, which indicated that calcium ions were mainly chelated with the amino nitrogen atoms and oxygen atoms on the carboxyl group of casein calcium-binding peptides, thus forming chelate with porous microstructures. Compared with the control group, the casein calcium-binding peptides treatment group showed a significant increase in calcium transport at 30, 60, 120 and 180 min, respectively, by 44.25 %, 31.21 %, 20.67 % and 24.08 %. Therefore, casein calcium-binding peptides are expected to be used as dietary calcium supplements.

Effects of fullerene C60 with antihypoxants

BACKGROUND: Drug improvement is often carried out with the help of chemical modifications that improve the receptor action or transport of drugs to their target tissues.&#x0D; AIM: The aim of this study was to investigate the effect of combinations of C60 fullerene with amtizol, 2-amino-4-acetylthiazolo[5,4-b]indole, metaprot, metaprot base, and rutin on antihypoxic activities in a model of acute hypoxia with hypercapnia.&#x0D; MATERIALS AND METHODS: Several compounds with mono-, bi-, and tricyclic structures were examined separately or combined with C60 fullerene. All compounds, except for rutin, were synthesized at the Department of Pharmacology of the S.M. Kirov Military Medical Academy and contain active amino groups, nitrogen, and sulfur atoms in the cycles: amtizol (3,5-diamino-1,2,4-thiadiazole), VM-606 (2-amino-4-acetylthiazolo[5,4-b]indole), Metaprot (2-ethylthiobenzimidazole hydrobromide monohydrate), and Metaprot base. All compounds demonstrated antihypoxic activity. Hypobaric hypoxia was simulated in a flow pressure chamber by lifting animals to a height of 10,000 m at a speed of 50 m/s and exposure for 60 min. The preparations were administered intraperitoneally 60 min before the experiment. The protective effect was evaluated by the average life expectancy at altitude. Hypoxia with hypercapnia was assessed on male white mice weighing 2022 g, which were placed in 200 mL glass jars with hermetic lids, which were lowered under water to prevent air leakage. The studied preparations and their complexes with fullerene in the form of a thin suspension with Tween-80 were administered intraperitoneally min before hypoxia. The lifespan of the animals was recorded.&#x0D; RESULTS: The formation of the complex and its properties depend on the development of a donoracceptor bond between the drug and fullerene. An increase in the bioavailability of amtizol in the form of a complex with C60 fullerene increased the antihypoxic activity of the mixture by 40%. For the first time, dynamic curves of the activities of amtizol and 2-amino-4-acetylthiazolo[5,4-b]indole depending on time were obtained in a model of hypercapnic hypoxia.&#x0D; CONCLUSION: Fullerene C60 enhances the antihypoxic activity of the studied compounds due to an increase in the bioavailability of the antihypoxant caused by the microporation of tissue membranes due to the action of fullerene C60.

Divergent Asymmetric Total Synthesis of (-)-Voacafricines A and B.

A divergent asymmetric total synthesis of voacafricines A and B, hexacyclic monoterpene indole alkaloids, has been accomplished featuring the following key steps: a) a catalyst-controlled asymmetric Pictet-Spengler reaction of 6-methoxytryptamine with a chiral α-ketoester affording a 1,1-disubstituted tetrahydro-β-carboline in excellent yield and diastereoselectivity; b) oxidative cleavage of a 3,5-disubstituted cyclopentene furnishing a dialdehyde intermediate, which was effectively differentiated through spontaneous cyclization with the neighboring hydroxy and secondary amine functions; c) intramolecular nucleophilic addition of a tertiary amino nitrogen atom to the in situ generated oxonium species generating stereoselectively an unprecedented 8-alkyl octahydro-2H-5,8-methanofuro[2,3-b]azepin-8-ium motif bearing five contiguous stereocenters. The synthesis confirmed the absolute configuration of these two natural products.

Divergent Asymmetric Total Synthesis of (−)‐Voacafricines A and B

AbstractA divergent asymmetric total synthesis of voacafricines A and B, hexacyclic monoterpene indole alkaloids, has been accomplished featuring the following key steps: a) a catalyst‐controlled asymmetric Pictet–Spengler reaction of 6‐methoxytryptamine with a chiral α‐ketoester affording a 1,1‐disubstituted tetrahydro‐β‐carboline in excellent yield and diastereoselectivity; b) oxidative cleavage of a 3,5‐disubstituted cyclopentene furnishing a dialdehyde intermediate, which was effectively differentiated through spontaneous cyclization with the neighboring hydroxy and secondary amine functions; c) intramolecular nucleophilic addition of a tertiary amino nitrogen atom to the in situ generated oxonium species generating stereoselectively an unprecedented 8‐alkyl octahydro‐2H‐5,8‐methanofuro[2,3‐b]azepin‐8‐ium motif bearing five contiguous stereocenters. The synthesis confirmed the absolute configuration of these two natural products.

Process Optimization, Structural Characterization, and Calcium Release Rate Evaluation of Mung Bean Peptides-Calcium Chelate

To reduce grievous ecological environment pollution and protein resource waste during mung bean starch production, mung bean peptides-calcium chelate (MBP-Ca) was synthesized as a novel and efficient calcium supplement. Under the optimal conditions (pH = 6, temperature = 45 °C, mass ratio of mung bean peptides (MBP)/CaCl2 = 4:1, MBP concentration = 20 mg/mL, time = 60 min), the obtained MBP-Ca achieved a calcium chelating rate of 86.26%. MBP-Ca, different from MBP, was a new compound rich in glutamic acid (32.74%) and aspartic acid (15.10%). Calcium ions could bind to MBP mainly through carboxyl oxygen, carbonyl oxygen, and amino nitrogen atoms to form MBP-Ca. Calcium ions-induced intra- and intermolecular interactions caused the folding and aggregation of MBP. After the chelation reaction between calcium ions and MBP, the percentage of β-sheet in the secondary structure of MBP increased by 1.90%, the size of the peptides increased by 124.42 nm, and the dense and smooth surface structure of MBP was transformed into fragmented and coarse blocks. Under different temperatures, pH, and gastrointestinal simulated digestion conditions, MBP-Ca exhibited an increased calcium release rate compared with the conventional calcium supplement CaCl2. Overall, MBP-Ca showed promise as an alternative dietary calcium supplement with good calcium absorption and bioavailability.