A solid-state NMR study of cellulose degradation

A series of laboratory-aged transformer insulating papers were investigated using solid-state NMR spectroscopy. Carbon-13 CPMAS, and proton MAS experiments were carried out along with static proton relaxation (T₁, and T₁) and free induction decay (FID) measurements. Some proton CRAMPS and proton-carbon-13 correlation (WISE) experiments were also undertaken. A change in the proton T₁ and FID with ageing was detected. No detectable change was found in the proton T₁. Some amorphous cellulose was detected in the carbon-13 spectrum. There was, however, no evidence for a substantial change in the nature of the cellulose with ageing. The carbon-13 spectra from some aged samples showed signals not present in the spectrum from an unaged sample. This was taken to be evidence of chemical degradation. Proton MAS and the WISE exeriment gave some information about the nature of the water in the sample.     

Photochemical and oxidative degradation of the solid-state tretinoin tocoferil

The photostability of tretinoin tocoferil was investigated under irradiation with three kinds of lamps, i.e., a cool white fluorescent lamp, a UV-A fluorescent lamp and a D65 fluorescent lamp. A combination of the cool white fluorescent lamp and the UV-A fluorescent lamp, and the D65 lamp having relative spectral power distribution similar to that of direct daylight, correspond to options 2 and 1 in ICH Guidelines, respectively. The photodegradation apparently followed second-order kinetics under these light sources and the degradation rate constant under exposure by the D65 lamp was larger than that by the cool white fluorescent lamp. The drug was susceptible to degradation by visible and UV light below 480 nm and was degraded most remarkably at around 420 nm, showing a wavelength-dependency. The semi-logarithmic plots of apparent degradation rate constant against the reciprocal of illuminance showed a good linear relationship in the Arrhenius-type fashion, and the photostability under ordinary illumination conditions could be predicted from the data obtained under the accelerated illumination conditions. The rate of oxidative degradation was slightly accelerated with the rise of temperature. Thermodynamic parameter was calculated from the Arrhenius plot. The degradation rate constant rapidly increased in proportion to partial pressure of oxygen below 20 kPa.     

The thermal degradation of polyoxymethylene produced by solid-state polymerization

The thermal degradation of polyoxymethylene produced by the solid-state polymerization of trioxane crystals has been studied. Changes in small-angle and wide-angle x-ray patterns, weight loss, and density have been measured in specimens heated in air at 175°C, 185°C, and 195°C. The polyoxymethylene contained material in two different crystallographic orientations, which behaved differently. Material in the so-called “twin” orientation melted preferentially at 185°C and 195°C, and at 185°C resolidified on cooling in parallel to the main orientation, in a lamellar structure. At 195°C, randomly oriented material was produced on resolidification. At 175°C, there was no evidence of melting or the formation of a lamellar structure, but the twin material was preferentially degraded so that only material in the main orientation remained after a time of 1500 min. The more rapid loss by degradation of the twin material was attributed to its having a lower molecular weight than the material in the main orientation.     

Advanced isoconversional and master plot analyses on solid-state degradation kinetics of a novel nanocomposite

The decomposition kinetics of glycerol diglycidyl ether (GDE)/3,3-dimethylglutaric anhydride/nanoalumina composite have been investigated by thermogravimetry analysis under nonisothermal mode. The activation energy, E _a, of the solid-state decomposition process was evaluated using the advanced isoconversional method. From the experimental data, the dependence of conversion on temperature and activation energy was constructed allowing calculating the master plots. Our results showed that the decomposition mechanism at temperatures below 400 °C could be fitted by R2 kinetic model with E _a = 143 kJ mol^?1. The information about the kinetic parameters based only on thermal degradation data has been used for quick lifetime estimation at different temperatures. The Vyazovkin method was also employed to predict the times to reach α = 0.5 at isothermal mode using the activation energy calculated by the advanced isoconversional approaches. Scanning electron microscopy (SEM) analysis was carried out to investigate the fracture surface morphology. It was revealed from the SEM images that the presence of nanoalumina results in reinforcement of GDE matrix.     

Four new andrographolide metabolites in rats

Four new sulfonate metabolites of andrographolide, 14-deoxy-12(R)-sulfo andrographolide (Metabolite 1), 14-deoxy-12(S)-sulfo andrographolide (Metabolite 2), 14-deoxy-12(R)-sulfo-9(S)-andrographolide (Metabolite 3) and 14-sulfo isoandrographolide (Metabolite 4), were isolated from urine and feces in rats. Their structures were elucidated by chemical and spectroscopic analyses. These four metabolites were formed through a rare metabolic reaction and were all new compounds.     

Six new andrographolide metabolites in rats

Six new andrographolide metabolites M-5-M-10 were isolated from rat urine, feces, and the contents of the small intestine. Three (M-5-M-7) as sulfate ester compounds were identified as new compounds. The structures of these six metabolites were determined to be 14-deoxy-12(R)-sulfo andrographolide 3-sulfate (M-5), 14-deoxy-12(S)-sulfo andrographolide 3-sulfate (M-6), 14-sulfo isoandrographolide 3-sulfate (M-7), 14-deoxy-11,12-didehydroandrographolide (M-8), isoandrographolide (M-9), and 14-deoxy andrographolide (M-10), respectively, based on chemical evidence and spectroscopic analysis.     

HPLC determination of andrographolide in rat whole blood: study on the pharmacokinetics of andrographolide incorporated in liposomes and tablets

A sensitive and simple high-performance liquid chromatographic method with UV detection was developed and validated for the determination of andrographolide in rat whole blood. Carbamazepine was employed as internal standard and the blood sample was extracted with chloroform. Chromatographic separations were achieved on a Chromasil ODS column (250 x 4.6 mm, 5 microm). The mobile phase was consisted of methanol-water (52:48, v/v) and delivered at 0.8 mL/min. The detection wavelength was set at 225 nm. The calibration curve had a good linearity in the range 0.053-530 microg/mL in rat whole blood with its correlation coefficient being 0.996. The extraction recovery of andrographolide was ranged from 65.7 to 72.6%. The intra-day and inter-days repeatabilities were below 4.2% in terms of the percentage of relative standard deviation (RSD). The method was used to provide data on the pharmacokinetics of the drug in rats. The data obtained was processed using the 3P87 pharmacokinetic program. The results showed that the disposition of andrographolide after intravenous administration of liposomal andrographolide conformed to a two-compartment open model with alpha = 4.75 x 10(-2) +/- 2.41 x 10(-3) min(-1), beta = 3.16 x 10(-3) +/- 1.58 x 10(-4) min(-1), V(c) = 174.67 +/- 13.97 mL, k(21) = 1.60 x 10(-2) +/- 8.12 x 10(-4) min(-1), k(10) = 9.38 x 10(-3) +/- 5.62 x 10(-4) min(-1), k(12) = 2.53 x 10(-2) +/- 1.27 x 10(-3) min(-1) and AUC(0-infinity) = 1525.47 +/- 92.35 microg min/mL. For the intragastric administration of andrographolide tablets, the disposition of andrographolide followed a one-compartment open model with k(e) = 6.78 x 10(-3) +/- 3.53 x 10(-4) min(-1), k(a) = 3.69 x 10(-2) +/- 4.68 x 10(-3) min(-1), T(max) = 59.69 +/- 3.61 min, C(max) = 1.62 +/- 0.11 microg/mL, V(c) = 1056.90 +/- 83.42 mL, AUC(0-infinity) = 348.75 +/- 24.41 microg min/mL.     

Probing the surface adsorption and photocatalytic degradation of catechols on TiO2 by solid-state NMR spectroscopy

The local structure of the TiO2 surface modified with electron-donating bidentate ligands, such as catechols, has been investigated by solid-state NMR spectroscopy. The adsorption and degradation processes of catechols at the TiO2 surface were observed. The photocatalytic degradation mechanism of catechols at the TiO2 surface was interpreted in terms of the interfacial charge recombination reaction with conduction band electrons.     

Relationship between coffee husk caffeine degradation and respiration of Aspergillus sp. LPBx in solid-state fermentation

Studies were carried out in a packed-bed column fermentor using coffee husk as substrate in order to verify a relationship between caffeine degradation and the respiration of Aspergillus sp. LPBx. Fermentation conditions were optimized by using factorial design experiments. The kinetic study showed that the caffeine degradation was related to the development of mold and its respiration and also with the consumption of reducing sugars present in coffee husk. From the values obtained experimentally for oxygen uptake rate and CO₂ evolved, we determined a biomass yield of 3.811 g of biomass/g of consumed O₂ and a maintenance coefficient of 0.0031 g of consumed O₂/(g of biomass·h). The maximum caffeine degradation achieved was 90%.     

Four new andrographolide metabolites in human urine

Andrographolide is one of principal components of a famous traditional Chinese herbal medicine Andrographis paniculate (BURM) NEES. Four new metabolites of andrographolide were isolated from human urine. All of them were characterized as sulfate and one of them also as a cysteine S-conjugate. The structures were determined to be andrographolide-3-O-sulfate (M-1), isoandrographolide-3-O-sulfate (M-2), 14-deoxyandrographolide-3-O-sulfate (M-3), 14-deoxy-12-(cysteine-S-yl)-andrographolide-3-O-sulfate (M-4), respectively, based on chemical evidence and spectroscopic analyses.     

Flow injection spectrophotometric determination of andrographolide from Andrographis paniculata

A simple flow injection colourimetric procedure for determining andrographolide was proposed. It is based on the reaction between andrographolide with 3,5-dinitrobenzoic acid, resulting in an intense purplish red complex with a suitable absorption at 536 nm. A standard or sample solution was injected into the 3,5-dinitrobenzoic acid stream (flow rate of 1.0 ml min⁻¹) which was then merged with potassium hydroxide stream with the same flow rate. Optimum conditions for determining andrographolide were investigated by univariate method. Under the optimum conditions, a linear calibration graph was obtained over the range 5.0-150.0 μg ml⁻¹ and the detection limit was 1.50 μg ml⁻¹ (3σ). The relatives standard deviation of the proposed method calculated from 10 replicate injections of 10.0 and 80.0 μg ml⁻¹ andrographolide were 0.66% and 1.64%, respectively. The sample throughput was 50 h⁻¹. The proposed method has been satisfactorily applied to the determination of andrographolide in herb plant samples.     

Effect of andrographolide on cysteamine-induced duodenal ulcer in rats

The aim of this study was to evaluate the gastroprotective efficacy of andrographolide isolated from Andrographis paniculata in rats induced with duodenal ulcers. Duodenal ulcers were induced by cysteamine administration in rats pretreated with 3?mg?kg?1 BW?day?1 of andrographolide for 30 days. Ulcer score, myeloperoxidase activity, TBARS level, GSH/GSSG ratio and enzyme antioxidants were measured in the duodenal tissue. Brush border and basolateral membranes were isolated to assay sucrase, maltase, alkaline phosphatase and total ATPases. Ulcer score was significantly minimised in rats pretreated with andrographolide. Elevation in myeloperoxidase and TBARS levels were found to be minimised significantly due to andrographolide treatment. Membrane-bound enzyme activities and the thiol redox status of glutathione were significantly maintained in duodenal mucosa of rats that received andrographolide. This study reveals that the major component of A. paniculata, andrographolide, has potent antiulcer properties that are most likely caused by minimising inflammatory changes, counteracting free radical formation and maintaining the thiol redox status in the duodenum.     

Development of andrographolide molecularly imprinted polymer for solid-phase extraction

A method employing molecularly imprinted polymer (MIP) as selective sorbent for solid-phase extraction (SPE) to pretreat samples was developed. The polymers were prepared by precipitation polymerization with andrographolide as template molecule. The structure of MIP was characterized and its static adsorption capacity was measured by the Scatchard equation. In comparison with C(18)-SPE and non-imprinted polymer (NIP) SPE column, MIP-SPE column displays high selectivity and good affinity for andrographolide and dehydroandrographolide for extract of herb Andrographis paniculata (Burm.f.) Nees (APN). MIP-SPE column capacity was 11.9±0.6 μmol/g and 12.1±0.5 μmol/g for andrographolide and dehydroandrographolide, respectively and was 2-3 times higher than that of other two columns. The precision and accuracy of the method developed were satisfactory with recoveries between 96.4% and 103.8% (RSD 3.1-4.3%, n=5) and 96.0% and 104.2% (RSD 2.9-3.7%, n=5) for andrographolide and dehydroandrographolide, respectively. Various real samples were employed to confirm the feasibility of method. This developed method demonstrates the potential of molecularly imprinted solid phase extraction for rapid, selective, and effective sample pretreatment.     

The synthesis,characterization and effect of molar mass distribution on solid-state degradation kinetics of oligo(orcinol)

Journal of Thermal Analysis and Calorimetry - In this study, the oxidative polymerization of orcinol monohydrate using different oxidants such as NaOCl, H2O2, and air was investigated....     

Computational study on the molecular inclusion of andrographolide by cyclodextrin

Due to the poor water solubility of andrographolide (andro), an inclusion technique has been developed to modify its physical and chemical properties so as to improve its bioavailability. In contrast with the immense experimental studies on the inclusion complexes of andro:cyclodextrin, no computational study has so far been carried out on this system. In this work, preliminary docking experiments with AutoDock were performed. Density Functional Theory (DFT) and Austin Model 1 (AM1) calculations upon the docking instances were applied to investigate the two possible modes of molecular inclusions between andro and x-cyclodextrin (xCD, where x is alpha, beta or gamma). Atoms-in-Molecules (AIM) analysis based on the B3LYP/cc-pVDZ wavefunction was applied to verify the existence of the intermolecular hydrogen bonds. It was found that the most stable complex among the six possible inclusion complexes was the one formed between andro and betaCD with andro's decalin ring moiety wrapped by CD at a ratio of 1:1. The hydrogen bonds between andro and CD were responsible for the stability of the inclusion complexes. The calculated data were found to be consistent with the experimental results. Thus, the results of this study can aid new drug design processes.     

正交试验法优选穿心莲内酯硫酸酯化反应工艺

硫酸酯化反应以分子结构中的羟基为反应位点,向有机分子中引入硫酸酯基,是一种有效改善天然产物水溶性的结构修饰途径[1]。有些药物因水溶性差,致使其在临床应用中存在一些问题,如生物利用度不高,服用量大,制成的片剂或胶囊体内吸收缓慢等。这类化合物经硫酸酯化后不但可以增加     

Synthesis and structure anti-inflammatory activity relationships studies of andrographolide derivatives

Abstract

Andrographolide is a main bioactive diterpene lactone in A. paniculata with anti-inflammatory activity. In this study, a series of andrographolide derivatives were synthesized and evaluated for their structure-anti-inflammatory activity relationships in vivo. Among all compounds, isoandrographolide and 14-deoxyandrographolide showed stronger anti-inflammatory activity than andrographolide. The results indicated that the introduction of tetrahydrofuran ring and cyclic olefinic bond plays an important role in enhancing the anti-inflammatory activity of andrographolide derivatives. Isoandrographolide and 14-deoxyandrographolide are potent inhibitor of inflammation.

     

Synthesis and biological evaluation of andrographolide derivatives as potent anti-HIV agents

A series of Andro derivatives were described and evaluated for their anti-HIV activity in vitro.Compound 10 and 16b,of which TI were>10,had some anti-HTV-l activity in vitro.Therein,compound 10 which was the best potent compound,could serve as a new lead for further development of anti-AIDS agents.