A new flavane acid from the fruits of Illicium verum

A new compound, illiciumflavane acid (1), along with 13 known compounds (2–14), were isolated from the fruits of Illicium verum Hook. F. Their structures were elucidated through various spectroscopic methods, including 1D NMR (¹H NMR, ¹³C NMR), 2D NMR (HMQC, HMBC and NOESY) and HRMS. The stereochemistry at the chiral centres was determined using CD spectrum as well as analyses of coupling constants and optical rotation data. Cytotoxicity evaluation of four compounds showed that illiciumflavane acid and (E)-1,2-bis(4-methoxyphenyl)ethene exhibited potential against A549 activities with IC₅₀ values of 4.63 μM and 9.17 μM, respectively.     

Synthesis,characterization and antimicrobial activity of maltol functionalized chitosan derivatives

Chitin was isolated from prawn shell powder through demineralization and deproteinization process. Chitosan was synthesized from isolated chitin by deacetylation process and characterized by Fourier Transform Infrared (FTIR) spectra which showed close agreement with commercial chitosan. Physicochemical features such as moisture content, ash content, degree of deacetylation and molecular weight has been measured. The prepared chitosan was found to have comparatively higher molecular weight than the commercial chitosan. Functionalization of NH₂ group of chitosan with C?=?O group of maltol and ethyl maltol by refluxing equimolar quantities of respective ketones was performed. These synthesized derivatives of chitosan were characterized by their FTIR, ¹³C-Nuclear magnetic resonance (NMR) spectroscopy, elemental analysis, X-Ray Diffraction (XRD), Thermogravimetric analysis (TGA) and Differential thermal analysis (DTA) instrumental techniques. Antibacterial screening results of the synthesized chitosan and its derivatives indicate that these compounds are active against Escherichia coli bacteria.     

Spectroscopic studies of water-soluble superstructured iron(III) porphyrin. Interaction with the bovine serum albumin protein

Abstract

Acid-base equilibrium of the “one-face”-hindered sulfonated porphyrin, α5,15-[2,2′(dodecamethyleneoxy),(5-sulfonato)diphenyl]-10,20-bis(2-hydroxy,5-sulfonatophenyl)porphyrinato iron(III), has been studied by paramagnetic ¹H NMR. The isotropically shifted signals change in a fast exchange regime on the NMR time-scale. ¹H longitudinal relaxation times and temperature dependence of the chemical shifts were measured and analyzed. The electronic structure of hydroxo specie is characteristic of a six- or five-coordinate high-spin iron(III) porphyrin with an S = 5/2 ground state. The ¹H NMR titration allowed determination of the acidity constant, pK_a 6.2 (0.1 M KNO₃, 25 °C). In addition, we also report the interaction between the monohydroxo iron(III) porphyrin and the bovine serum albumin protein. From a ¹H NMR titration, we have determined the affinity apparent constant, log K_ap 3.2 (pH 7, KNO₃ 0.1 M, 25 °C). The formation of superstructured iron porphyrin-albumin protein adduct was confirmed by electronic absorption spectroscopy and electron paramagnetic resonance.     

Extraction and Characterization of Chitin,Chitosan, and Protein Hydrolysates Prepared from Shrimp Waste by Treatment with Crude Protease from <Emphasis Type="Italic">Bacillus cereus</Emphasis> SV1

Chitin is a polysaccharide found in abundance in the shell of crustaceans. In this study, the protease from Bacillus cereus SV1 was applied for chitin extraction from shrimp waste material of Metapenaeus monoceros. A high level of deproteinization 88.8% ± 0.4 was recorded with an E/S ratio of 20. The demineralization was completely achieved within 6 h at room temperature in HCl 1.25 M, and the residual content of calcium in chitin was below 0.01%. ¹³C CP/MAS-NMR spectral analysis of chitin prepared by the enzymatic deproteinization of shrimp wastes was found to be similar to that obtained by alkaline treatment and to the commercial α-chitin. The degree of N-acetylation, calculated from the spectrum, was 89.5%. Chitin obtained by treatment with crude protease from B. cereus was converted to chitosan by N-deacetylation, and the antibacterial activity of chitosan solution against different bacteria was investigated. Results showed that chitosan solution at 50 mg/mL markedly inhibited the growth of most Gram-negative and Gram-positive bacteria tested. Furthermore, the antioxidant potential of the protein hydrolysates obtained during enzymatic isolation of chitin was evaluated using various in vitro assays. All the samples exerted remarkable antioxidant activities. These results suggest that enzymatic deproteinization of the shrimp shell wastes, using B. cereus SV1 protease, could be applicable to the chitin production process.     

Synthesis of a tetrazine-based catecholamide derivative and its evaluation as a chelating agent for removal of Cd(II), Co(II), and Cu(II)

The synthesis and structural characterization of a tetrazine-based catecholamide (CAM) ligand, N,N′-bis(N″-(aminoethyl)-2,3-bis(hydroxy)benzamide)-1,2,4,5-tetrazine-3,6-diamine (5), were investigated. All compounds were characterized by ¹H NMR spectroscopy, ¹³C NMR spectroscopy, and FTIR spectroscopy. The protonation equilibria of 5 and complexation capacities (log β_pqr) of Cd²⁺, Co²⁺, and Cu²⁺ complexes of 5 were evaluated through potentiometric titration and spectrophotometric titration, respectively. Species independent pM value (=?log [M]_free) was used to compare metal affinities with the final sequence Cu²⁺ > Cd²⁺ > Co²⁺. Results show that 5 has potential for heavy metal removal.     

A novel diarylheptanoid-bearing sesquiterpene moiety from the rhizomes of Alpinia officinarum

A new diarylheptanoid analogue-bearing sesquiterpene moiety, named Alpinisin A, was isolated from the rhizomes of Alpinia officinarum Hance. The new structure was determined by various spectroscopic techniques ¹H-nuclear magnetic resonance (¹H NMR), ¹³C-attached proton test (¹³C-APT), heteronuclear single quantum coherence (HSQC), heteronuclear multiple bond correlation (HMBC), ¹H-¹H correlation spectroscopy (¹H–¹HCOSY), nuclear overhauser effect spectroscopy (NOESY) and high resolution electrospray ionization mass spectrometry (HR–ESI–MS). The compound was tested for cytotoxic activity in vitro against human tumour cell lines (gastric carcinoma cell -7901 (SGC-7901), Michigan Cancer Foundation-7 (MCF-7) and Caski), which showed significant inhibitory effects with IC₅₀ levels of 11.42, 15.14 and 14.78 μM, respectively. The novel chemical structure characterised with a diarylheptanoid linked to a chain-like sesquiterpenoid should be highlighted.     

Purification and Characterization of Thermostable Chitinase from <Emphasis Type="Italic">Bacillus licheniformis</Emphasis> SK-1

Chitinase was purified from the culture medium of Bacillus licheniformis SK-1 by colloidal chitin affinity adsorption followed by diethylamino ethanol-cellulose column chromatography. The purified enzyme showed a single band on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The molecular size and pI of chitinase 72 (Chi72) were 72 kDa and 4.62 (Chi72) kDa, respectively. The purified chitinase revealed two activity optima at pH 6 and 8 when colloidal chitin was used as substrate. The enzyme exhibited activity in broad temperature range, from 40 to 70°C, with optimum at 55°C. It was stable for 2 h at temperatures below 60°C and stable over a broad pH range of 4.0–9.0 for 24 h. The apparent K _m and V _max of Chi72 for colloidal chitin were 0.23 mg ml⁻¹ and 7.03 U/mg, respectively. The chitinase activity was high on colloidal chitin, regenerated chitin, partially N-acetylated chitin, and chitosan. N-bromosuccinamide completely inhibited the enzyme activity. This enzyme should be a good candidate for applications in the recycling of chitin waste.     

The use of DSC curves to determine the acetylation degree of chitin/chitosan samples

The use of DSC curves is proposed as an alternative method to determine the degree of N-acetylation (DA) in chitin/chitosan samples, based in both peak area and height of the decomposition signal. Samples with DA from 74 to 16% were prepared from a chitin commercial sample and the DA was determined by ¹H NMR, ¹³C CP/MAS NMR and IR spectra. The effect of water content, heating rate, sample mass and gas flow on the DSC peaks were evaluated and optimized. Using optimized conditions a linear relationship between peak area and height with the DA could be achieved with linear correlation coefficients of −0.998 and −0.999 (n = 7), respectively. The calibration graphs were used to determine the DA of a commercial chitosan sample with relative errors ranging from 2 to 3% for both peak area and peak height, when compared with the DA determined by ¹H NMR method.     

Enantiopure cryptophane-129Xe nuclear magnetic resonance biosensors targeting carbonic anhydrase

The (+) and ( ? ) enantiomers for a cryptophane-7-bond-linker-benzenesulfonamide biosensor (C7B) were synthesised and their chirality was confirmed by electronic circular dichroism spectroscopy. Biosensor binding to carbonic anhydrase II (CAII) was characterised for both enantiomers by hyperpolarised (HP) ¹²⁹Xe NMR spectroscopy. Our previous study of the racemic ( ± ) C7B biosensor–CAII complex [Chambers, J.M.; Hill, P.A.; Aaron, J.A.; Han, Z.H.; Christianson, D.W.; Kuzma, N.N.; Dmochowski, I.J. J. Am. Chem. Soc.2009, 131, 563–569] identified two ‘bound’ ¹²⁹Xe@C7B peaks by HP ¹²⁹Xe NMR (at 71 and 67 ppm, relative to ‘free’ biosensor at 64 ppm), which led to the initial hypothesis that (+) and ( ? ) enantiomers produce diastereomeric peaks when coordinated to Zn²⁺ at the chiral CAII active site. Unexpectedly, the single enantiomers complexed with CAII also identified two ‘bound’ ¹²⁹Xe@C7B peaks: (+) 72, 68 ppm and ( ? ) 68, 67 ppm. These results are consistent with X-ray crystallographic evidence for benzenesulfonamide inhibitors occupying a second site near the CAII surface. As illustrated by our studies of this model protein–ligand interaction, HP ¹²⁹Xe NMR spectroscopy can be useful for identifying supramolecular assemblies in solution.     

Spectroscopic characterisation of the inclusion complexes between the antifungal drugs naftifine and terbinafine and cyclodextrins

The complexation of naftifine (NF) and terbinafine (TB) with cyclodextrins (CDs) has been investigated by UV/visible and ¹H NMR spectroscopy, ROESY techniques and also ESI-MS. Both drugs form 1:1 inclusion complexes with all the CDs tested except with α-CD, as deduced from the Benesi–Hildebrand plots and confirmed by ESI-MS and NMR spectroscopy (Job plot method). The K ₁₁ values for NF decrease in the order β-CD > methylated β-CD > 2-hydroxypropyl-β-CD >γ-CD. The determination of the enthalpy and entropy provides information about the main driving forces in the process. The stability constants of the complexes NF–β-CD, TB–β-CD and TB–γ-CD determined by ¹H NMR spectroscopy are in agreement with the values obtained by UV. For TB–β-CD, the value is higher, due to the fact that the length of the TB aliphatic chain allows a deeper inclusion of the naphthalene group inside the corresponding β-CD molecule, according to the 2D ROESY experiments.     

Determination of Pyrethroids in Environmental Waters Using Magnetic Chitosan Extraction Coupled with High Performance Liquid Chromatography Detection

The magnetic chitosan was prepared by adding chitosan, Fe²⁺ and Fe³⁺ into a basic precipitant of NaOH solution. The synthetic magnetic chitosan was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and physical properties. The adsorption characteristics of magnetic chitosan for extracting pyrethroids from water samples were investigated. The analytes were separated by magnetic solid phase extraction and determined by high performance liquid chromatography. The optimum conditions of adsorption experiments were obtained: the amount of sorbent was 80 mg, the extraction time was 20 min, the washing solvent was 50% aqueous methanol, and the eluent was acetonitrile-acetic acid (99: 1, v/v). The obtained linearity of three pyrethroids was in the range of 30–3000 ng L^?1. The detection limits of beta-cyfluthrin, cyhalothrin, and cyphenothrin were 7.5, 5.6, and 6.1 ng L^?1, respectively. The intra-day and inter-day precisions of three pyrethroids were in the range of 3.6–5.2% and 5.9–8.6%, respectively. In the optimized conditions, three water samples were analyzed, and the recoveries of pyrethroids obtained were 83.2–95.2%.     

Antiplasmodial prenylated flavanonols from Tephrosia subtriflora

The CH₂Cl₂/MeOH (1:1) extract of the aerial parts of Tephrosia subtriflora afforded a new flavanonol, named subtriflavanonol (1), along with the known flavanone spinoflavanone B, and the known flavanonols MS-II (2) and mundulinol. The structures were elucidated by the use of NMR spectroscopy and mass spectrometry. The absolute configuration of the flavanonols was determined based on quantum chemical ECD calculations. In the antiplasmodial assay, compound 2 showed the highest activity against chloroquine-sensitive Plasmodium falciparum reference clones (D6 and 3D7), artemisinin-sensitive isolate (F32-TEM) as well as field isolate (KSM 009) with IC₅₀ values 1.4–4.6 μM without significant cytotoxicity against Vero and HEp2 cell lines (IC₅₀ > 100 μM). The new compound (1) showed weak antiplasmodial activity, IC₅₀ 12.5–24.2 μM, but also showed selective anticancer activity against HEp2 cell line (CC₅₀ 16.9 μM).     

Preparation and properties of chitin and chitosan from a hydroid polyp

The chemical composition of Obelia longissima hydroid polyp from mariculture system fouling community was examined. Conditions for chitin recovery and chitosan preparation thereof were developed. The initial raw material, chitin, and chitosan were characterized by electron microscopy, infrared spectroscopy, and X-ray diffraction analysis. Also, certain qualitative characteristics of these materials were determined.     

Anticancer activity of Ophiobolin A,isolated from the endophytic fungus Bipolaris setariae

The present work describes the anticancer activity of Ophiobolin A isolated from the endophytic fungus Bipolaris setariae. Ophiobolin A was isolated using preparative HPLC and its structure was confirmed by HRMS, ¹H NMR, ¹³C NMR, COSY, DEPT, HSQC and HMBC. It inhibited solid and haematological cancer cell proliferation with IC₅₀ of 0.4–4.3 μM. In comparison, IC₅₀ against normal cells was 20.9 μM. It was found to inhibit the phosphorylation of S6 (IC₅₀ = 1.9 ± 0.2 μM), ERK (IC₅₀ = 0.28 ± 0.02 μM) and RB (IC₅₀ = 1.42 ± 0.1 μM), the effector proteins of PI3K/mTOR, Ras/Raf/ERK and CDK/RB pathways, respectively. It induced apoptosis and inhibited cell cycle progression in MDA-MB-231 cancer cells with concomitant inhibition of signalling proteins. Thus, this study reveals that anticancer activity of Ophiobolin A is associated with simultaneous inhibition of multiple oncogenic signalling pathways namely PI3K/mTOR, Ras/Raf/ERK and CDK/RB.     

Westerdijkin A,a new hydroxyphenylacetic acid derivative from deep sea fungus Aspergillus westerdijkiae SCSIO 05233

A new methyl 2-(4-((2-hydroxy-3-methylbut-3-en-1-yl)oxy)phenyl) acetate 1, together with five known compounds 2–6, was isolated from the culture of the deep sea-derived fungus Aspergillus westerdijkiae SCSIO 05233. The new structure was determined by NMR (¹H and ¹³C NMR, HSQC, HMBC and MS) and optical rotation analysis. Compound 5 displayed weak inhibitory activities towards K562 and promyelocytic HL-60 with IC₅₀ values of 25.8 and 44.9 μM, and compound 6 showed strong antifouling activity with EC₅₀ value 8.81 μg/mL.     

Binding cellulose and chitosan via click chemistry: Synthesis,characterization, and formation of some hollow tubes

A novel cellulose‐click‐chitosan polymer was prepared successfully in three steps: (1) propargyl cellulose with degrees of substitution (DS) from 0.25 to 1.24 was synthesized by etherification of bamboo Phyllostachys bambusoide cellulose with propargyl chloride in DMA/LiCl in the presence of NaH. The regioselectivity of propargylation on anhydrous glucose unit determined by GC‐MS was in the order of 2 >> 6 > 3; (2) the functional azide groups were introduced onto the chitosan chains by reacting chitosan with 4‐azidobenzoic acid in [Amim]Cl/DMF and the DS ranged from 0.02 to 0.46; (3) thus, the cellulose‐click‐chitosan polymer was obtained via click reaction, that is, the Cu(I)‐catalyzed Huisgen 1,3‐dipolar cycloaddition reaction, between the terminal alkyne groups of cellulose and the azide groups on the chitosan backbone at room temperature. The successful binding of cellulose and chitosan was confirmed and characterized by FTIR and CP/MAS ¹³C NMR spectroscopy. TGA analyses indicated that the cellulose‐click‐chitosan polymer had a higher thermal stability than that of cellulose and chitosan as well as cellulose–chitosan complex. More interestingly, some hollow tubes with near millimeter length were also observed by SEM. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

LC Determination of Clindamycin Phosphate from Chitosan Microspheres

A simple, rapid and precise reverse phase LC method was adopted, modified and validated for the determination of clindamycin phosphate from chitosan microspheres prepared by spray drying method. Separation was performed using ACE5 C18 reversed phase column (150 mm × 4.6 mm, 5 μm) with acetonitrile:phosphate buffer at pH 2.5 (25:75 v/v) as mobile phase. The limit of detection was 46.43 × 10^?3 μg mL^?1, with UV detection at 210 nm. No interference from chitosan and other excipients was observed. Therefore an incorporation efficiency of microspheres could be determined accurately and specifically.     

Sorption of Cu2+ ions by chitin and chitosan from aqueous solutions. Molecular structure of complexes formed

The sorption of Cu²⁺ ions by chitin and chitosan from aqueous solutions has been investigated, as well as the molecular structure of the complexes formed. The static exchange capacities have been determined, equal to 3.5 and 0.25 mmole/g for chitosan and chitin, respectively, and the partition coefficients (5000 and 70 g/ml). It has been shown that in complex formation a bond with the amino group is formed as the result of the substitution of a proton in the latter. The EPR spectra of these complexes have been obtained and their radiospectroscopic parameters determined (g = 2.334,g = 2.054,A = 0.0156 cm^–1, andB = 0.0028 cm^–1 for chitin, andg = 2.231,g = 2.048,A = 0.0192 cm^–1, andB = 0.0025 cm^–1 for chitosan). For chitosan the ligands are two nitrogen atoms of the amino groups and two oxygen atoms of the hydroxyl groups in the position C³ of adjacent glucosamine rings; for chitin, the oxygen atoms of the acetyl groups take part in addition in the complex formation. The analysis of the radiospectroscopic parameters and their comparison with published data lead to the conclusion that the Cu²⁺ complex with chitosan has a tetragonal symmetry, while the complex with chitin most probably has an octahedral structure.Institute of Physical Chemistry, Russian Academy of Sciences, 117915 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2305–2311, October, 1992.     

Kinetic and thermodynamic inclusion complexes of symmetric teramethyl-substituted cucurbit[6]uril with HCl salts of N,N′-bis(pyridylmethyl)-1,6-hexanediamine

The host–guest interaction of symmetrical α,α′,δ,δ′-tetramethyl-cucurbit[6]uril (TMeQ[6]) with the hydrochloride salts of N,N′-bis(4-pyridylmethyl)-1,6-hexanediamine (P6), N,N′-bis(3-pyridyl-methyl)-1,6-hexanediamine (M6) and N,N′-bis(2-pyridylmethyl)-1,6-hexanediamine (O6) was investigated via single crystal X-ray diffraction, ¹H NMR spectroscopy, electronic absorption spectroscopy and fluorescence spectroscopy. Single crystal X-ray diffraction showed that the hexyl moiety of P6 or M6 was incorporated in the cavity of TMeQ[6], while the two pyridylmethyl moieties of O6 were incorporated in the TMeQ[6] cavity in the solid state. The ¹H NMR results in aqueous solution revealed that the TMeQ[6]-P6 and TMeQ[6]-M6 host–guest interaction systems produce a kinetic dumbbell-shaped inclusion complex at the initial stage and then an equilibrium pseudorotaxane-shaped inclusion complex as the only product after heating. However, only the pseudorotaxane-shaped inclusion complex was observed for the TMeQ[6]-O6 host–guest interaction system. Aqueous absorption spectrophotometric analysis showed that the dumbbell-shaped inclusion complexes were stable at pH 5.6, had a host–guest ratio of 2:1 and formed quantitatively at ～10¹¹ l²/mol² for the TMeQ[6]-M6 and TMeQ[6]-O6 systems. The transformation from dumbbell to pseudorotaxane-shaped inclusion complexes for the TMeQ[6]-P6 and TMeQ[6]-M6 host–guest systems yielded activation energies of 59.35 ± 1.55 and 78.7 ± 3.45 kJ/mol, respectively. The pseudorotaxane-shaped inclusion complexes were stable at pH 5.6, had a host–guest ratio of 1:1 and formed quantitatively at ～10⁷ l/mol for the TMeQ[6]-M6 and TMeQ[6]-P6 systems.     

Proton mobility and copper coordination in polysaccharide- and gelatin-based bioblends and polyblends

Polysaccharide- and gelatin-based bioblends and polyblends were synthesized and characterized by complex impedance spectroscopy, proton nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR). Higher ionic conductivities of 7.9 × 10^?5 S/cm at room temperature and 2.5 × 10^?3 S/cm at 80 °C were obtained for the agar-chitosan polyblends. For all samples, the activation energies, calculated from the Arrhenius plot of ionic conductivity and from the onset of NMR line narrowing, are in the range 0.30–0.86 and 0.38–0.57 eV, respectively. The glass transition temperatures (T _g ^NMR ) varied from 200 to 215 K, depending on the sample composition. The temperature dependence of the ¹H spin–lattice relaxation revealed two distinct proton dynamics. The EPR spectra are characteristic of Cu² ions in tetragonally distorted octahedral sites. Quantitative analysis of the EPR spin Hamiltonian g _|| and A _|| parameters revealed copper ions complexed by nitrogens and oxygens in the samples containing chitosan or gelatin and only by oxygens in agar-based ones. The in-plane π bonding is less covalent for the gelatin and chitosan blends. Results suggest that natural bioblends and polyblends are interesting systems to be used in materials science engineering.