Synthetic Peroxides Promote Apoptosis of Cancer Cells by Inhibiting P-Glycoprotein ABCB5

This article discloses a new horizon for the application of peroxides in medical chemistry. Stable cyclic peroxides are demonstrated to have cytotoxic activity against cancer cells; in addition a mechanism of cytotoxic action is proposed. Synthetic bridged 1,2,4,5-tetraoxanes and ozonides were effective against HepG2 cancer cells and some ozonides selectively targeted liver cancer cells (the selectivity indexes for compounds 11 b and 12 a are 8 and 5, respectively). In some cases, tetraoxanes and ozonides were more selective than paclitaxel, artemisinin, and artesunic acid. Annexin V flow-cytometry analysis revealed that the active ozonides 22 a and 23 a induced cell death of HepG2 by apoptosis. Further study showed that compounds 22 a and 23 a exhibited a strong inhibitory effect on P-glycoprotein (P-gp/ABCB5)-overexpressing HepG2 cancer cells. ABCB5 is a key player in the multidrug-resistant phenotype of liver cancer. Peroxides failed to demonstrate a direct correlation between oxidative potential and their biological activity. To our knowledge this is the first time that peroxide diastereoisomers have been found to show stereospecific antimalarial action against the chloroquine-sensitive 3D7 strain of Plasmodium falciparum. Stereoisomeric ozonide 12 b is 11 times more active than stereoisomeric ozonide 12 a (IC₅₀=5.81 vs 65.18 μm ). Current findings mean that ozonides merit further investigation as potential therapeutic agents for drug-resistant hepatocellular carcinoma.     

Dyeing of cotton yarn with the aqueous extract of the leaves of Eupatorium odoratum L. in Thailand and associated extract toxicity studies

Flavonoid constituents from the aqueous extract of the leaves of Eupatorium odoratum, an invasive weed in Thailand, have potential use as dyestuffs for cotton dyeing. It was found that cotton yarn, which was pretreated with a chitosan solution (with and without a crosslinking glyoxal solution), followed by dyeing with E. odoratum extract in the presence of the inorganic mordant, alum, provided better depth of shade (K/S) and also gave better fastness to light and washing than the untreated cotton yarn. Pretreated cotton yarn with the biomordant solution from Memecylon scutellatum leaves gave relatively poor light and wash fastness of the resultant dyed cotton in the presence of alum. From the toxicity studies, the aqueous extract of the leaves of E. odoratum before and after dyeing showed a high toxicity level to the earthworm (Diplocardia communis) and the guppy fish (Poecilia reticulate). Therefore, it is strongly suggested that E. odoratum aqueous extract after dyeing should be significantly diluted before discharged into the environment.     

An avian influenza model with latency and vaccination

Avian influenza, caused by influenza A viruses, has received worldwide attention in recent years. The viruses can spread from birds to humans as well as transmit among human hosts. In this study, we formulate a mathematical model for avian influenza that includes bird-human interaction and that incorporates the effects of infection latency and human vaccination. We investigate the essential dynamics of the model through an equilibrium analysis. Meanwhile, we explore effective vaccination strategy to control avian influenza outbreaks using optimal control theory. Our results indicate that strategically deployed human vaccination can significantly reduce the numbers of exposed and infectious people.     

Thermal degradation kinetics of a commercial epoxy resin—Comparative analysis of parameter estimation methods

The thermal degradation behavior of a commercial epoxy resin, EpoFix® (Struers), has been investigated by thermogravimetry (TG), differential thermal gravimetry (DTG), and differential thermal analysis (DTA) under nonisothermal conditions in an argon atmosphere. Different methods (Kissinger, Flynn–Wall–Ozawa (FWO), Friedman isoconversion methods, and nonlinear least‐squares (NLSQ) estimation method) have been used to analyze the thermal degradation process and determine the apparent kinetic parameters. The methods produce similar results in terms of activation energy estimations. Nevertheless, the NLSQ method has several advantages over the other methods in terms of both characterizing the activation energy and modeling the thermal degradation—i.e., including this model in a resin degradation process simulation. However, it is interesting to combine the NLSQ method with other isoconversion methods: they can reflect the dependence and variability of the activation energies during pyrolysis processes, while providing a good starting point for a nonlinear procedure, especially with respect to the activation energy E. This work is the first step (apparent kinetic reaction) of complete simulation of experimental oven of degradation of epoxy resin coating of impregnate nuclear fuel sample. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42201.     

Biosorption of lac dye by the red marine alga Gracilaria tenuistipitata: biosorption kinetics,isotherms, and thermodynamic parameters

The hypothesis that the dried, ground biomass of the red marine alga Gracilaria tenuistipitata could be used for the efficient removal of lac dye from aqueous solution was assessed in this work. The effects of parameters such as initial pH, biosorbent dosage, contact time, initial dye concentration, and temperature on the biosorption capacity of the dye were investigated. Equilibrium data were analysed using Langmuir, Freundlich, and Temkin isotherm models, and the Freundlich model provided the highest coefficient of determination values. Biosorption kinetic data were successfully described with a pseudo‐second‐order model at initial dye concentrations of 50, 80, 100, and 120 mg l^?1. The thermodynamic parameters of biosorption – enthalpy change (?H° = ?30.64 kJ mol^?1), free energy change (?G° = 4.32 kJ mol^?1 at 303 K to 7.78 kJ mol^?1 at 333 K), and entropy change (?S° = ?115.38 J mol^?1 K^?1) – were determined. The negative value of the enthalpy change and positive values of the free energy change indicate that the biosorption process is exothermic and non‐spontaneous. The negative value of the entropy change is consistent with decreased randomness at the solid–liquid interface with dye biosorption. Attenuated total reflectance–Fourier transform infrared spectroscopic analysis confirmed the presence of lac dye on the G. tenuistipitata material. The efficiency of lac dye removal by this biomass material at 20 g l^?1 and with an initial dye concentration of 50 mg l^?1 in acidic solution was 71%, which indicated its potential usefulness as a new dye biosorbent.     

Application of ultrasonic incorporated with calcium gluconate maintains physicochemical quality of pink guavas during short-term storage at room temperature

Food Science and Biotechnology - The effectiveness of simultaneous calcium gluconate (0.5% w/v) (Ca-G) and ultrasonication (Ca-G + US) on physicochemical quality of pink guavas under...     

A kinetic and thermodynamic study of lac dye adsorption on silk yarn coated with microcrystalline chitosan

The coating of silk yarn with microcrystalline chitosan (MCCh) was carried out using the ultrasonic‐assisted method at a pulsed wave frequency of 80 kHz, which only had a slight impact on the yarn as measured by changes in Young's modulus and percentage of elongation compared with untreated silk. A significant enhancement of lac dye uptake onto MCCh‐coated silk yarn compared with the untreated silk was observed. The rate of dye uptake at different temperatures onto silk yarn coated with MCCh was investigated. It was found that the adsorption rate constant and diffusion coefficient both increased with increasing temperature, as a result of a diffusion kinetically controlled process with a diffusion activation energy of 9.40 kJ mol^?1. This suggests that dye adsorption on silk yarn coated with MCCh is a physisorption process. The free energy change (?G^○), enthalpy change (?H^○) and entropy change for dye adsorption were also determined, and the negative values of ?G^○ and ?H^○ obtained indicated that the lac dye adsorption process is both spontaneous and exothermic.     

Effects of additives on the dyeing of cotton yarn with the aqueous extract of Combretum latifolium Blume stems

Flavonoid constituents from the aqueous extract of the stems of Combretum latifolium Blume sourced in Thailand have potential use as dyestuffs for cotton dyeing. In an effort to improve current natural dyeing methods with this extract, further aspects of the process were studied. It was found that, before equilibrium was reached, an increase in temperature led to an increase in dye adsorption rate of the extract; the initial rate and extent of dye adsorption was further increased by the addition of sodium chloride to the dyebath. In addition, cotton yarn pretreated with a chitosan solution (with and without a crosslinking glyoxal solution), followed by dyeing with C. latifolium extract, provided better depth of shade and also gave better fastness to light and washing than the untreated cotton yarn. Post‐mordanting cotton yarn with a biomordant solution from Memecylon scutellatum leaves also gave good light and wash fastness of the resulting dyed cotton, comparable with the dyeing results with the less environmentally friendly alum as a mordant.     

Polydopamine‐coated silk yarn for improving the light fastness of natural dyes

One of the problems occasionally associated with the use of natural dyes in the dyeing of silk is the susceptibility of the dyed yarn to fading in light. While a number of approaches have been used to address this problem, the use of polydopamine (PDA), a known agent with photo‐protective properties, has not been assessed previously. In this study, silk was pretreated with nano‐particulate PDA formed in situ by oxidation of a dopamine solution, then dyed with lac dye or annatto dye as model natural dyes. Photofading rates were significantly reduced in the case of annatto‐dyed, PDA‐coated silk relative to uncoated silk, while wash fastness was unaffected and remained only moderately good. In contrast, no significant change was seen in photofading rates with treated or untreated lac‐dyed silk, and wash fastness was also unaffected. The PDA did not adversely affect resultant colour values if the concentration of the dopamine precursor was kept low. When this was done, acceptable colours were obtained in the dyed silk. Further investigation is warranted of PDA as a photofading protectant and mordant with other natural dyes on silk and other fibres.