[structure: see text] A new indole alkaloid, arboflorine, possessing a novel pentacyclic carbon skeleton and incorporating a third nitrogen atom was obtained from the Malayan Kopsia arborea. The structure was established by spectroscopic analysis, and a possible biogenetic pathway from a preakuammicine-type precursor is presented.
Calcium borate nanoparticles have been synthesized by a thermal treatment method via facile co-precipitation. Differences of annealing temperature and annealing time and their effects on crystal structure, particle size, size distribution and thermal stability of nanoparticles were investigated. The formation of calcium borate compound was characterized by X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), and Thermogravimetry (TGA). The XRD patterns revealed that the co-precipitated samples annealed at 700 °C for 3 h annealing time formed an amorphous structure and the transformation into a crystalline structure only occurred after 5 h annealing time. It was found that the samples annealed at 900 °C are mostly metaborate (CaB(2)O(4)) nanoparticles and tetraborate (CaB(4)O(7)) nanoparticles only observed at 970 °C, which was confirmed by FTIR. The TEM images indicated that with increasing the annealing time and temperature, the average particle size increases. TGA analysis confirmed the thermal stability of the annealed samples at higher temperatures.
Lumusidines A-D, bisindole alkaloids of the macroline-macroline type, and one of the macroline-pleiocarpamine type, villalstonidine F, were isolated from the stem-bark extract of Alstonia macrophylla (Apocynaceae). The structures and absolute configurations of these alkaloids were established using NMR, MS, and X-ray diffraction analyses.
Oligostilbenoids (e.g., ampelopsin F, viniferin, pallidol) result from homogeneous or heterogeneous coupling of monomeric stilbenoid units, leading to various chemical structures. Oligostilbenoid synthesis is regio- and stereocontrolled. To tackle this regio- and stereocontrol, a supramolecular chemistry approach is required that can be achieved by quantum chemistry. The stability of noncovalent π-stacks, formed between two stilbenoid units prior to oxidation, is accurately evaluated with density functional theory (DFT) including dispersive effects (within the DFT-D formalism). These noncovalent arrangements drive the regiocontrol. The rest of the chemical pathway is a succession of dearomatization and rearomatization stages. The thermodynamics and kinetics of the processes are calculated with classical hybrid functionals. This study allows discrimination between the two main possible chemical pathways, namely, radical-neutral and radical-radical reactions. The former appears more likely, thermodynamics and kinetics being in perfect agreement with the experimental 1:2 ratio obtained for ampelopsin F:pallidol analogues, respectively.
A new coumarin, 8,4''-dihydroxy-3'',4''-dihydrocapnolactone-2',3'-diol (1) and two known triterpenes, 5(6)-gluten-3-one (2) and 5(6)-gluten-3alpha-ol (3) were isolated from the leaves of Micromelum minutum (Rutaceae) collected from Sepilok, Sabah, Malaysia and their structures were characterized by spectroscopic methods.
Pogostemon cablin, originating in Malaysia and India, is cultivated in southern China including Guangdong and Hainan Province, which was called GuangHuoXiang to differentiate it from the HuoXiang of the north, the species Agastache rugosa, that it resembles. Essential oil of P. cablin mainly contributes to the pharmacological activities and the therapeutic properties of the essential oils are directly correlated with their qualitative and quantitative composition. For controlling the quality, standard fingerprint of P. cablin collected from different regions was developed by using GC-MS. Nine compounds including beta-patchoulene, caryophyllene, alpha-guaiene, seychellene, beta-guaiene, delta-guaiene, spathulenol, patchouli alcohol and pogostone were identified among 10 main peaks in P. cablin. Hierarchical clustering analysis based on characteristics of 10 investigated peaks in GC profiles showed that 18 samples were divided into three main clusters, patchouliol-type, pogostone-type and an interim-type, which was the one between the two chemotypes. The simulative mean chromatogram for the three types P. cablin was generated using the Computer Aided Similarity Evaluation System. The fingerprint can help to distinguish the substitute or adulterant, and further assess the differences of P. cablin grown in various areas of China.
A series of hitherto unreported anthracene-embedded dispirooxindoles has been synthesized via a one-pot three-component 1,3-dipolar cycloaddition reaction of an azomethine ylide, generated in situ from the reaction of isatin and sarcosine to 10-benzylideneanthracen-9(10H)-one as a dipolarophile in 1-butyl-3-methylimidazolium bromide([bmim]Br), an ionic liquid. This reaction proceeded regio- and diastereoselectively, in good to excellent yields.
Novel series of 2-(4,6-dimethoxy,1,3,5-triazin-2-yl) amino acid ester derivatives were synthesized using simple one pot method in methanol. The products were obtained in high yields and purities as observed from their spectral data, elemental analyses, GC-MS and X-ray crystallographic analysis. The B3LYP/6-311G(d,p) calculated molecular structures are well correlated with the geometrical parameters obtained from the X-ray analyses. The spectroscopic properties such as IR vibrational modes, NMR chemical shifts and UV-Vis electronic transitions were discussed both experimentally and theoretically. The IR vibrational frequencies showed good correlations with the experimental data (R(2)=0.9961-0.9995). The electronic spectra were assigned based on the TD-DFT results. Intense electronic transition band is calculated at 198.1nm (f=0.1389), 204.2nm (f=0.2053), 205.0 (f=0.1704) and 205.7 (0.2971) for compounds 6a-i, respectively. The molecular orbital energy levels contributed in the longest wavelength transition band were explained. For all compounds, the experimental wavelengths showed red shifts compared to the calculations due to the solvent effect. The NMR chemical shifts were calculated using GIAO method. The NBO analyses were performed to predict the stabilization energies due to the electron delocalization processes occur in the studied systems.
The rational design of 4-hydroxycoumarins with tailor-made antioxidant activities is required nowadays due to the wide variety of pharmacologically significant, structurally interesting of coumarins and researcher orientation toward green chemistry and natural products. A simple and unique coumarins have been achieved by reaction of 4-hydroxycoumarin with aromatic aldehyde accompanied with the creation of a macromolecules have 2-aminothiazolidin-4-one. The molecular structures of the compounds were characterized by the Fourier transformation infrared and Nuclear magnetic resonance spectroscopies, in addition to CHN analysis. The scavenging abilities of new compounds against stable DPPH radical (DPPH•) and hydrogen peroxide were done and the results show that the compounds exhibited high antioxidant activates.
Hindered phenols find a wide variety of applications across many different industry sectors. Butylated hydroxytoluene (BHT) is a most commonly used antioxidant recognized as safe for use in foods containing fats, pharmaceuticals, petroleum products, rubber and oil industries. In the past two decades, there has been growing interest in finding novel antioxidants to meet the requirements of these industries. To accelerate the antioxidant discovery process, researchers have designed and synthesized a series of BHT derivatives targeting to improve its antioxidant properties to be having a wide range of antioxidant activities markedly enhanced radical scavenging ability and other physical properties. Accordingly, some structure-activity relationships and rational design strategies for antioxidants based on BHT structure have been suggested and applied in practice. We have identified 14 very sensitive parameters, which may play a major role on the antioxidant performance of BHT. In this review, we attempt to summarize the current knowledge on this topic, which is of significance in selecting and designing novel antioxidants using a well-known antioxidant BHT as a building-block molecule. Our strategy involved investigation on understanding the chemistry behind the antioxidant activities of BHT, whether through hydrogen or electron transfer mechanism to enable promising anti-oxidant candidates to be synthesized.
A new sesquiterpene, scodopin, and a mixture of three tryptamine-type alkaloids, scorodocarpines A-C, were isolated from the fruits of Scorodocarpus borneensis, together with a known hemisynthetic sesquiterpene, cadalene-beta-carboxylic acid, which was isolated from the bark. The structures of the new compounds were elucidated by interpretation of spectral data, especially tandem mass spectrometry for the alkaloid mixture.
In a continuation of our study of the Rutaceae, detailed chemical investigation on Micromelum minutum (Rutaceae) collected from Sepilok, Sabah, Malaysia gave four new coumarins. The structures of the coumarins have been fully characterised by spectroscopic methods as 3",4"-dihydrocapnolactone 1, 2',3'-epoxyisocapnolactone 2, 8-hydroxyisocapnolactone-2',3'-diol 3 and 8-hydroxy-3",4"-dihydrocapnolactone-2',3'-diol 4.
The ethanol extract of the leaves of Tabernaemontana divaricata (double flower variety) provided a total of 23 alkaloids, including the new aspidosperma alkaloids, taberhanine, voafinine, N-methylvoafinine, voafinidine, voalenine and the new bisindole alkaloid, conophyllinine in addition to the previously known, biologically active bisindole, conophylline and its congener, conofoline. The structures of the new alkaloids were established by spectroscopic methods. The preparation and characterization of the corresponding quinones of the biologically active bisindoles are also described in relation to a structure-activity study of these compounds with respect to their action in stimulating insulin expression.
In this study, simultaneous adsorption of cationic dyes was investigated by using binary component solutions. Thiourea-modified poly(acrylonitrile-co-acrylic acid) (TMPAA) polymer was used as an adsorbent for uptake of cationic dyes (malachite green, MG and methylene blue, MB) from aqueous solution in a binary system. Adsorption tests revealed that TMPAA presented high adsorption of MG and MB at higher pH and higher dye concentrations. It suggested that there are strong electrostatic attractions between the surface functional groups of the adsorbent and cationic dyes. The equilibrium analyses explain that both extended Langmuir and extended models are suitable for the description of adsorption data in the binary system. An antagonistic effect was found, probably due to triangular (MG) and linear (MB) molecular structures that mutually hinder the adsorption of both dyes on TMPAA. Besides, the kinetic studies for sorption of MG and MB dyes onto adsorbent were better represented by a pseudo-second-order model, which demonstrates chemisorption between the polymeric TMPAA adsorbent and dye molecules. According to experimental findings, TMPAA is an attractive adsorbent for treatment of wastewater containing multiple cationic dyes.
Different fractions of fully hydrogenated soybean oil (FHSBO) in soybean oil (10-30% w/w) and the addition of 1% salt (sodium chloride) were used to investigate the effect of high-pressure treatments (HP) on the crystallization behaviors and physical properties of the binary mixtures. Sample microstructure, solid fat content (SFC), thermal and rheological properties were analyzed and compared against a control sample (crystallized under atmospheric condition). The crystallization temperature (Ts) of all model fats under isobaric conditions increased quadratically with pressure until reaching a pressure threshold. As a result of this change, the sample induction time of crystallization (tc) shifted from a range of 2.74-0.82 min to 0.72-0.43 min when sample crystallized above the pressure threshold under adiabatic conditions. At the high solid mass fraction, the addition of salt reduced the pressure threshold to induce crystallization during adiabatic compression. An increase in pressure significantly reduced mean cluster diameter in relation to the reduction of tc regardless of the solid mass fraction. In contrast, the sample macrostructural properties (SFC, storage modulus) were influenced more significantly by solid mass fractions rather than pressure levels. The creation of lipid gel was observed in the HP samples at 10% FHSBO. The changes in crystallization behaviors indicated that high-pressure treatments were more likely to influence crystallization mechanisms at low solid mass fraction.
Rechargeable zinc-air batteries are deemed as the most feasible alternative to replace lithium-ion batteries in various applications. Among battery components, separators play a crucial role in the commercial realization of rechargeable zinc-air batteries, especially from the viewpoint of preventing zincate (Zn(OH)42-) ion crossover from the zinc anode to the air cathode. In this study, a new hydroxide exchange membrane for zinc-air batteries was synthesized using poly (2,6-dimethyl-1,4-phenylene oxide) (PPO) as the base polymer. PPO was quaternized using three tertiary amines, including trimethylamine (TMA), 1-methylpyrolidine (MPY), and 1-methylimidazole (MIM), and casted into separator films. The successful synthesis process was confirmed by proton nuclear magnetic resonance and Fourier-transform infrared spectroscopy, while their thermal stability was examined using thermogravimetric analysis. Besides, their water/electrolyte absorption capacity and dimensional change, induced by the electrolyte uptake, were studied. Ionic conductivity of PPO-TMA, PPO-MPY, and PPO-MIM was determined using electrochemical impedance spectroscopy to be 0.17, 0.16, and 0.003 mS/cm, respectively. Zincate crossover evaluation tests revealed very low zincate diffusion coefficient of 1.13 × 10-8, and 0.28 × 10-8 cm2/min for PPO-TMA, and PPO-MPY, respectively. Moreover, galvanostatic discharge performance of the primary batteries assembled using PPO-TMA and PPO-MPY as initial battery tests showed a high specific discharge capacity and specific power of ~800 mAh/gZn and 1000 mWh/gZn, respectively. Low zincate crossover and high discharge capacity of these separator membranes makes them potential materials to be used in zinc-air batteries.
A series of twenty-six analogs of benzimidazole based oxadiazole have been synthesized and evaluated against alpha-glycosidase enzyme. Most the analogs showed excellent to good inhibitory potential. Among the screened analogs, analog 1, 2, 3 and 14 with IC50 values 4.6 ± 0.1, 9.50 ± 0.3, 2.6 ± 0.1 and 9.30 ± 0.4 µM respectively showedexcellent inhibitory potential than reference drug acarbose (IC50 = 38.45 ± 0.80 µM). Some of the analogs like 19, 21, 22 and 23 with methyl and methoxy substituent on phenyl ring show hydrophobic interaction and were found with no inhibitory potential. The binding interactions between synthesized analogs and ligands protein were confirmed through molecular docking study. Various spectroscopic techniques like 1H NMR, 13C NMR, and EI-MS were used for characterization of all synthesized analogs. These derivatives were synthesized by simple mode of synthesis like heterocyclic ring formation.
Over-expression of α-amylase enzyme causes hyperglycemia which lead to many physiological complications including oxidative stress, one of the most commonly associated problem with diabetes mellitus. Marketed α-amylase inhibitors such as acarbose, voglibose, and miglitol used to treat type-II diabetes mellitus, but also linked to several harmful effects. Therefore, it is essential to explore new and nontoxic antidiabetic agents with additional antioxidant properties. In this connection, a series of new N-sulfonohydrazide substituted indazoles 1-19 were synthesized by multistep reaction scheme and assessed for in vitro α-amylase inhibitory and radical (DPPH and ABTS) scavenging properties. All compounds were fully characterized by different spectroscopic techniques including 1H, 13C NMR, EI-MS, HREI-MS, ESI-MS, and HRESI-MS. Compounds showed promising α-amylase inhibitory activities (IC50 = 1.23 ± 0.06-4.5 ± 0.03 µM) as compared to the standard acarbose (IC50 1.20 ± 0.09 µM). In addition to that all derivatives were found good to moderate scavengers of DPPH (IC50 2.01 ± 0.13-5.3 ± 0.11) and ABTS (IC50 = 2.34 ± 0.07-5.5 ± 0.07 µM) radicals, in comparison with standard ascorbic acid having scavenging activities with IC50 = 1.99 ± 0.09 µM, and IC50 2.03 ± 0.11 µM for DPPH and ABTS radicals. In silico molecular docking study was conducted to rationalize the binding interaction of α-amylase enzyme with ligands. Compounds were observed as mixed type inhibitors in enzyme kinetic characterization.
Peptides are distinctive biomacromolecules that demonstrate potential cytotoxicity and diversified bioactivities against a variety of microorganisms including bacteria, mycobacteria, and fungi via their unique mechanisms of action. Among broad-ranging pharmacologically active peptides, natural marine-originated thiazole-based oligopeptides possess peculiar structural features along with a wide spectrum of exceptional and potent bioproperties. Because of their complex nature and size divergence, thiazole-based peptides (TBPs) bestow a pivotal chemical platform in drug discovery processes to generate competent scaffolds for regulating allosteric binding sites and peptide-peptide interactions. The present study dissertates on the natural reservoirs and exclusive structural components of marine-originated TBPs, with a special focus on their most pertinent pharmacological profiles, which may impart vital resources for the development of novel peptide-based therapeutic agents.
Ergosterol is the main component of the fungal membrane and is not found in plants or other microbial cells. Therefore, it can be a useful biomarker for the quantification of fungal biomass. We are now reporting the first isolation and characterisation of ergosterol from the mycelium of G. boninense. The ergosterol structure was detected by Thin Liquid Chromatography (TLC) and Ultra Performance Liquid Chromatography (UPLC) and confirmed with Gas Chromatography coupled with Mass Spectrometry (GCMS) and Nuclear Magnetic Resonance (NMR) analysis.