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The complexation of kaempferol with cyclodextrins (CDs) (beta-, G(2)-beta-, and HP-beta-CDs) in basic medium was studied, and the complexation constants (K(c)) were calculated by using enzymatic, solubility, and fluorometric methods. This is the first time that a decrease in fluorescence has been observed as result of the analyte complexation by CDs. The highest K(c) value for kaempferol complexation was obtained for HP-beta-CDs. To establish the validity of the fluorometric method for determining the K(c) between kaempferol and CDs, the same parameters were also determined by enzymatic and solubility methods. The enzymatic method was carried out by using horseradish peroxidase as oxidative enzyme, and the K(c) values obtained were similar to those obtained by using the solubility method. However, the fluorometric method underestimated the K(c) value by about 1.2-fold with respect to the other methods used. In all cases HP-beta-CDs showed the highest K(c) value, indicating that they are more efficient in the formation of inclusion complexes with kaempferol.

BACKGROUND: The aims of the present study were to obtain a stable dry powder formulation of cyclodextrins (CDs) encapsulating thymol, for successful use as an ingredient on an industrial scale, and to characterize the thymol‐CDs complexes using different techniques. RESULTS: Thymol was successfully solubilized in aqueous solutions and the Kc value increased with the pH of the media until the pH was neutral, giving the highest values (2583 ± 176 L mol−1) for HP‐β‐cyclodextrins (HP‐β‐CDs). The best encapsulation efficiency of thymol in solid complexes was obtained using the microwave (MWI) encapsulation method. The different characterization techniques have demonstrated the affinity of HP‐β‐CDs for thymol molecules, forming stable complexes. CONCLUSIONS: The results support the use of the MWI method in the preparation of solid HP‐β‐CD‐thymol complexes, due to greater encapsulation efficiency and technological and economic advantages for industrial applications. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The effects of the addition of cyclodextrins (CDs), β-CD, or HP-β-CD (1%), on the protection of antioxidant compounds of mandarin juices enriched with pomegranate extract and goji berries juice, was studied. Juices were prepared and after their thermal treatment (98 °C, 30 s) they were stored at 4 °C during 75 d. Vitamin C content, CIE L*a*b* color, antioxidant capacity, retinol equivalents, and sensory properties were studied. Losses on vitamin C were higher (6%) for juices with β-CD than juices with HP-β-CD. Retinol equivalents degradation was lower (3.4%) in juices with HP-β-cyclodextrins than in those treated with β-CD. Lower losses were observed for the instrumental and sensory color intensity in juices with HP-β-CD addition. Finally, the antioxidant capacity was also higher in juices treated with HP-β-CD. Finally, the overall sensory quality of juices with HP-β-CD was the best one after 30 d of cold storage. Even though β-CD addition did not cause any improvement compared with control juice (without CD addition), the benefits of adding HP-β-CD to this particular juice were shown in almost all parameters under study. The present study deals with the practical aspects of the utilization of CDs and CD-complexes in the food industry. The molecular encapsulation of lipophilic food ingredients with CD are supposed to improve the stability of flavors, vitamins, colorants, and antioxidant activity, leading to extended product shelf life. The HP-β-CD treated mandarin juice enriched with pomegranate extract and juice of goji berries will have a more intense color, higher vitamin C content, retinol equivalents, and antioxidant activity during storage and shelf life than control juices, with no CD addition. [ABSTRACT FROM AUTHOR]

β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) were used to prepare insoluble polymers using epichlorohydrin as a cross-linking agent and the azo dye Direct Red 83:1 was used as target adsorbate. The preliminary study related to adsorbent dosage, pH, agitation or dye concentration allowed us to select the best conditions to carry out the rest of experiments. The kinetics was evaluated by Elovich, pseudo first order, pseudo second order, and intra-particle diffusion models. The results indicated that the pseudo second order model presented the best fit to the experimental data, indicating that chemisorption is controlling the process. The results were also evaluated by Freundlich, Langmuir and Temkin isotherms. According to the determination coefficient (R2), Freunlich gave the best results, which indicates that the adsorption process is happening on heterogeneous surfaces. One interesting parameter obtained from Langmuir isotherm is qmax (maximum adsorption capacity). This value was six times higher when a β-CDs-EPI polymer was employed. The cross-linked polymers were fully characterized by nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA). Also, morphology and particle size distribution were both assessed. Under optimized conditions, the β-CDs-EPI polymer seems to be a useful device for removing Direct Red 83:1 (close 90%), from aqueous solutions and industrial effluents. Complementarily, non-adsorbed dye was photolyzed by a pulsed light driven advanced oxidation process. The proposed methodology is environmental and economically advantageous, considering the point of view of a sustainable recycling economy in the textile dyeing process. [ABSTRACT FROM AUTHOR]

The adsorption properties of two cyclodextrin-epichlorohydrin polymers to remove Direct Red 83:1 textile dye from wastewater solutions was evaluated. Adsorption studies were performed in a batch reactor, and the efficiency of the polymers under different parametric values such as contact time, adsorbent dosage, initial dye concentration, pH of initial solution and temperature was followed by spectrophotometry. Both Langmuir and Freundlich equations were used to fit the equilibrium isotherms and the kinetic data were analyzed by the pseudo-first-order and pseudo-second-order models. Adsorption process follows a pseudo-second-order kinetic and was influenced by intraparticle diffusion model, dye concentration and contact time, reaching equilibrium within the first 30 min. Experimental data were better fitted to Freundlich isotherm model than to Langmuir and Temkin isotherms. Since about 93% of dye removal was achieved under optimized conditions, the α-cyclodextrin-epichlorohydrin polymer seems to be a useful device for removing Direct Red 83:1 from aqueous solutions and industrial effluents. [ABSTRACT FROM AUTHOR]