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Abstract The effects of gamma radiation (0, 1, 2 and 3 kGy) were used to evaluate the stability and thermal degradation kinetics of anthocyanins, as well as the stability of total phenolic compounds (TPC) and antioxidant activity at different temperatures (4, 25, 35 and 45 °C) during the storage (0, 30, 60, 90 and 120 days) of black rice flour. This flour can be used as ingredient for gluten-free cereal products with higher nutritional value. For this it is necessary to preserve the anthocyanin content during thermal processing and shelf-life periods. At time 0, the dose of 3 kGy provided all of the most available bioactive compounds, raising their antioxidant potential, except for TPC. During the storage at different temperatures up to 120 days, gradual losses occurred in all the analysed parameters. Regarding the total anthocyanin content and TPC, the sample irradiated with a 1 kGy dose remained most stable. The analysis of kinetic data indicated a first-order reaction for the degradation of anthocyanins. The combination of irradiation with different temperatures may improve the shelf-life of black rice flour.
Subject(s)
Radiation , Oryza , Thermodynamics , Phytochemicals , Anthocyanins/chemistryABSTRACT
Isothermal titration calorimetry (ITC) is a real-time, quantitative, on-line, and dynamic thermal analysis technique for describing reaction processes. Some thermodynamic parameters, such as association constant, dissociation constant, stoichiometry ratio, enthalpy change, and entropy change of host and guest interaction, can be obtained in ITC analysis. This technique has the advantages of high calorimetric sensitivity and accurate measurement. In this paper, the principle and application characteristics of ITC technology are described, and the application of this technique in drug research are reviewed, including the interaction between drugs and proteins, the interaction between drugs and DNA molecules, clinical drug compatibility, the application in pharmaceutical preparations and the interaction between drugs and biomembrane. Lastly, the application of this technique in the nonspecific molecular interaction is prospected.
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In the pharmaceutical industry, the analysis of atropisomers is of considerable interest from both scientific and regulatory perspectives. The compound of interest contains two stereogenicaxes due to the hindered rotation around the single bonds connecting the aryl groups, which results in fourpotential configurational isomers (atropisomers). The separation of the four atropisomers was achieved on aderivatized β-cyclodextrin bonded stationary phase. Further investigation showed that low temperatureconditions, including sample preparation (?70 °C), sample storage (?70 °C), and chromatographic separation (6 °C),were critical to preventing interconversion. LC-UV-laser polarimetric analysis identified peaks 1 and 2as a pair of enantiomers and peaks 3 and 4 as another. Thermodynamic analysis of the retention data indicatedthat the separation of the pairs of enantiomers is primarily enthalpy controlled as indicated by the positiveslope of the van't Huff plot. The difference in absolute Δ (Δ H), ranged from 2.20 kJ/mol to 2.42 kJ/mol.
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Based on the basic theory of thermodynamics, the thermodynamic parameters and related equations in the process of water adsorption and desorption of Chinese herbal decoction pieces were established, and their water absorption and desorption characteristics were analyzed. The physical significance of the thermodynamic parameters, such as differential adsorption enthalpy, differential adsorption entropy, integral adsorption enthalpy, integral adsorption entropy and the free energy of adsorption, were discussed in this paper to provide theoretical basis for the research on the water adsorption and desorption mechanism, optimum drying process parameters, storage conditions and packaging methods of Chinese herbal decoction pieces.
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Aim To compare the interactions of baicalein and baicalin with bovine serum albumin (BSA) and their mechanism. Methods The binding reactions of baicalein and baicalin with BSA and the effects of glucose on them were studied by spectroscopy to compare the binding constants and binding distances of baicalein-BSA and baicalin-BSA,which were calculated according to Lineweaver-Burk equation and F?ster' energy transfer theory. Thermodynamic parameters were used to calculate the types of interaction force between BSA with baicalein or baicalin and the technique of synchronous fluorescence spectra was used to observe the effects of baicalein or baicalin on the conformation of BSA. Results Both the binding constants and binding distances of baicalein-BSA and baicalin-BSA decreased with temperature increasing and were increased by glucose. Relative to baicalein,the binding affinity of baicalin to BSA decreased obviously with an increase in binding distance. Both baicalein and baicalin could form non-covalent compounds with BSA mainly to quench the intrinsic fluorescence of BSA through a static quenching procedure. Baicalein could interact with BSA through hydrogen bonds and Van der Waals force,and baicalin did it mainly through electrostatic force. Though baicalein or baicalin could induce the conformational changes of BSA by binding reaction,only the former reduced the hydrophobicity in microenvironment around the tryptophan moieties of BSA. Conclusions The glycosylation substitution of baicalein molecule can decrease the binding to BSA (baicalin-BSA) and change the types of interaction force. The physiological concentration of glucose increases the binding constants and the number of binding sites of baicalein and baicalin with BSA.