Interactions between Bio-Based Compounds and Cyclodextrins

Bio-based compounds, such as “green” surfactants and phytochemicals, are regarded as future sustainable resources for a vast range of applications in a modern society increasingly demanding economical, social, and environmental awareness. Natural compounds from plants (phytochemicals) are very sought by the pharmaceutical, cosmetic, and food industries. On the other hand, the growing interest in “green” surfactants (e.g., carbohydrate-based) is due to, inter alia, their preparation from renewable raw materials, ready biodegradability, and biocompatibility, among other reasons of fundamental, practical, economical, and environmental orders. Despite the wide range of potential applications of these bio-based compounds, their practical use is still limited due to many reasons such as poor aqueous solubility, volatility, reactivity, etc. Generally, when complexed with cyclodextrins, these bio-based compounds enhance considerably their performance and potential applications. Thus, this chapter aims at recalling some general fundamental aspects of phytochemicals and “green” surfactants, such as structure, function, and applications. In addition, their interactions with cyclodextrins are discussed from a physicochemical point of view with special focus on the techniques, mathematic modeling, and thermodynamic parameters (e.g., interactions, stoichiometries, association constants, etc.)

Release and antioxidant activity of carvacrol and thymol from polypropylene active packaging films

The migration of antioxidant (AO) agents, carvacrol and thymol, from polypropylene (PP) packaging films containing the studied compounds at 80 g/kg separately and an equimolar mixture of them into food simulants was investigated. Fast and reliable analytical procedures were developed and validated for the analysis of the studied AOs in food simulants. For aqueous food simulants, solid phase extraction followed by GC–MS analysis was performed. Fatty food simulants were directly analysed by GC–MS and HPLC-UV for isooctane and ethanol 950 mL/L, respectively. The release of AOs from the films was dependent on the type of food stimulant and AO incorporated. In particular, high levels of migration were obtained for both AOs into isooctane, showing thymol higher migration. The release kinetics of AOs from PP films showed a Fichian behaviour with diffusion coefficients ranging from 1 to 2 × 10−14 m2/s; except for the diffusion into isooctane where 4-6 higher values were obtained. The antioxidant activity of migration extracts was confirmed by the DPPH method, showing thymol a higher antioxidant capacity especially into isooctane with a 42.2% of inhibition. The obtained results suggest that carvacrol and thymol show a potential use as AOs for active packaging for extending the shelf-life of food products.Spanish Ministry of Economy and Competitiveness (MAT-2011-28640-C02-01). Marina Ramos would like to thank University of Alicante (Spain) for UAFPU2011-48539721S predoctoral research grant

Aggregation of Cyclodextrins: Fundamental Issues and Applications

The aggregation of cyclodextrins (CD) in aqueous solution is an old, yet still vastly unexplored topic that has been studied at least since the 1980s. At that time, few authors took into consideration the possibility of formation of aggregates for the interpretation of thermodynamic and thermophysical properties of CDs in aqueous solution. The aggregates appear at quite low CD concentrations and seem to encompass only a small number of CD molecules. They also occur in water in the presence of hydrophobic or amphiphilic moieties, including surfactants, assuming a preassembled state with the hydrophobic chains threading through one or two CDs. After a long period in which it has been neglected, CD aggregation is now a hot topic and one far from gathering consensus. In this chapter, a timely and critical review on the phenomenon of CD aggregation and the respective supramolecular properties, including some computational rationales, will be presented. A comprehensive summary of CD aggregates studied to date, indicating the formation conditions, characterization techniques, and applications, is also provided

Controlled Release of Thymol from Poly(Lactic Acid)-Based Silver Nanocomposite Films with Antibacterial and Antioxidant Activity

Thymol and silver nanoparticles (Ag-NPs) were used to develop poly(lactic acid) (PLA)-based films with antioxidant and antibacterial performance. Different amounts of thymol (6 and 8 wt%) and 1 wt% Ag-NPs were added to PLA to produce the active films. Ag-NPs and thymol were successfully identified in the nanocomposite structures using spectroscopic techniques. A kinetic study was performed to evaluate the release of thymol and Ag-NPs from the nanocomposites to an aqueous food simulant (ethanol 10%, v/v) at 40 °C. The diffusion of thymol from the polymer matrix was affected by the presence of non-migrating Ag-NPs, which showed non-Fickian release behavior. The ternary system including 1 wt% Ag-NPs and 8 wt% thymol showed clear antibacterial performance by reducing the cell viability of Escherichia coli and Staphylococcus aureus by around 40% after 3 and 24 h of storage at 4, 25, and 37 °C compared to neat PLA. Significant antioxidant behavior of all active films was also confirmed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. The obtained nanocomposite films based on PLA and the addition of Ag-NPs and thymol were proven to have combined antioxidant and antibacterial performance, with controlled release of thymol. These formulations have potential applications in the development of innovative and customized active packaging systems to increase the shelf-life of food products.Authors would like to thank Spanish Ministry of Economy and Competitiveness (MAT-2015-59242-C2-2-R) and Generalitat Valenciana (IDIFEDER/2018/007) for their support of this research. Marina Ramos would like to thank University of Alicante (Spain) for the UAFPU2011-48539721S predoctoral research grant

Controlled Release, Disintegration, Antioxidant, and Antimicrobial Properties of Poly (Lactic Acid)/Thymol/Nanoclay Composites

Nano-biocomposite films based on poly (lactic acid) (PLA) were prepared by adding thymol (8 wt.%) and a commercial montmorillonite (D43B) at different concentrations (2.5 and 5 wt.%). The antioxidant, antimicrobial, and disintegration properties of all films were determined. A kinetic study was carried out to evaluate the thymol release from the polymer matrix into ethanol 10% (v/v) as food simulant. The nanostructured networks formed in binary and ternary systems were of interest in controlling the release of thymol into the food simulant. The results indicated that the diffusion of thymol through the PLA matrix was influenced by the presence of the nanoclay. Disintegration tests demonstrated that the incorporation of both additives promoted the breakdown of the polymer matrix due to the presence of the reactive hydroxyl group in the thymol structure and ammonium groups in D43B. Active films containing thymol and D43B efficiently enhanced the antioxidant activity (inhibition values higher than 77%) of the nano-biocomposites. Finally, the addition of 8 wt.% thymol and 2.5 wt.% D43B significantly increased the antibacterial activity against Escherichia coli and Staphylococcus aureus 8325-4, resulting in a clear advantage to improve the shelf-life of perishable packaged food.Authors would like to thank Spanish Ministry of Economy and Competitiveness (MAT2017-84909-C2-1-R) and Generalitat Valenciana (IDIFEDER/2018/007) for their support of this research. Marina Ramos would like to thank University of Alicante (Spain) for the UAFPU2011-48539721S predoctoral research grant. AJMV thanks ´Coimbra Chemistry Center and Fundação para a Ciência e Tecnologia (FCT) for the financial support through the programmes UID/QUI/UI0313/2020 and COMPETE

Functional properties of sodium and calcium caseinate antimicrobial active films containing carvacrol

Active edible films were prepared by adding carvacrol into sodium caseinate (SC) and calcium caseinate (CC) matrices plasticized with two different glycerol concentrations (25 and 35 wt%) prepared by solvent casting. Functional characterisation of these bio-films was carried out by determination of some of their physico-chemical properties, such as colour, transparency, oxygen barrier, wettability, dye permeation properties and antibacterial effectiveness against Gram negative and Gram positive bacteria. All films exhibited good performance in terms of optical properties in the CIELab space showing high transparency. Carvacrol was able to reduce CC oxygen permeability and slightly increased the surface hydrophobicity. Dye diffusion experiments were performed to evaluate permeation properties. The diffusion of dye through films revealed that SC was more permeable than CC. The agar diffusion method was used for the evaluation of the films antimicrobial effectiveness against Escherichia cell and Staphylococcus aureus. Both SC and CC edible films with carvacrol showed inhibitory effects on both bacteria. (C) 2013 Elsevier Ltd. All rights reserved.This research was supported by the Ministry of Science and Innovation of Spain through the projects MAT2011-28468-C02-01, MAT2011-28468-C02-02 and HP2008-0080. M.P. Arrieta thanks Fundacion MAPFRE for "Ignacio Hernando de Larramendi 2009-Medio Ambiente" fellowship (MAPFRE-IHL-01). Authors thank Ferrer Alimentacion S.A., for providing the caseinates powders.Arrieta, MP.; Peltzer, MA.; López Martínez, J.; Garrigós Selva, MDC.; Valente, AJM.; Jimenez Migallon, A. (2014). Functional properties of sodium and calcium caseinate antimicrobial active films containing carvacrol. Journal of Food Engineering. 121:94-101. https://doi.org/10.1016/j.jfoodeng.2013.08.015S9410112

Effect of hofmeister ions on transport properties of aqueous solutions of sodium hyaluronate

Tracer diffusion coefficients obtained from the Taylor dispersion technique at 25.0◦C were measured to study the influence of sodium, ammonium and magnesium salts at 0.01 and 0.1 mol dm−3 on the transport behavior of sodium hyaluronate (NaHy, 0.1%). The selection of these salts was based on their position in Hofmeister series, which describe the specific influence of different ions (cations and anions) on some physicochemical properties of a system that can be interpreted as a salting-in or salting-out effect. In our case, in general, an increase in the ionic strength (i.e., concentrations at 0.01 mol dm−3 ) led to a significant decrease in the limiting diffusion coefficient of the NaHy 0.1%, indicating, in those circumstances, the presence of salting-in effects. However, the opposite effect (salting-out) was verified with the increase in concentration of some salts, mainly for NH4SCN at 0.1 mol dm−3 . In this particular salt, the cation is weakly hydrated and, consequently, its presence does not favor interactions between NaHy and water molecules, promoting, in those circumstances, less resistance to the movement of NaHy and thus to the increase of its diffusion (19%). These data, complemented by viscosity measurements, permit us to have a better understanding about the effect of these salts on the transport behaviour of NaHy. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Fundacao para a Ciencia e a Tecnologia (FCT) through COMPETE Programme (Operational Programme for Competitiveness) [UIDB/QUI/00313/2020]; Ministry of Education, Youth and Sports of the Czech Republic DKRVO [RP/CPS/2020/003]Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT: RP/CPS/2020/003; Fundação para a Ciência e a Tecnologia, FCT: UIDB/QUI/00313/202

Do the solvent properties affect the propensity for self-association of α-cyclodextrin? Insights from NMR self-diffusion

Whether cyclodextrins (CDs) self-aggregate or not in solution is an interesting and timely scientific question. Yet, we are far from a scientific consensus as regards the nature of the phenomenon. Those who are in favor of the formation of CD aggregates justify the phenomenon by the presence of H-bonds, occurring between the hydroxyl groups located at both rims of cyclodextrins. To gain further insight with regard to the importance of these intermolecular CD-CD interactions, a systematic study of 1H NMR self-diffusion of α-cyclodextrin in binary mixtures of deuterated DMSO and water, at different mole fractions, has been carried out. The choice of these solvents was made based on their different degree of polarity and the fact that they are miscible at any molar ratio. The experimental α-CD diffusion coefficients scale with the solution viscosity. Moreover, hydrodynamic radii of α-CD are independent of the solvent composition. No evidence of α-cyclodextrin aggregation at any DMSO mole fraction is found. Finally, experimental diffusion data are compared with those obtained from atomic level hydrodynamic calculations. In addition, diffusion coefficients of heavy water and DMSO in binary mixed solvents are also measured and analyzed. The obtained diffusion coefficients for DMSOd6 and D2O show a minimum at the eutectic composition and depend on the solution viscosity. The experimental results are compared with published molecular dynamic simulations

α-Cyclodextrin affects the acid-base properties of octanoic acid/sodium octanoate

The interaction of octanoic acid and its conjugate base sodium octanoate with α-cyclodextrin was studied by 1H NMR and isothermal titration calorimetry, respectively, at 298.15 K. The results are in agreement with a 1:1 stoichiometry in the complex. The binding of octanoate with α-cyclodextrin is characterized by a positive entropy, stressing the relevance of hydrophobic interactions. Based on the host-guest complex formation, the effect of α-cyclodextrin on the acidity behavior of the acid was evaluated by potentiometric titration. The results are interpreted in terms of the Henderson-Hasselbalch equation and by using an analytical equation for the titration curve. The apparent ionization constants of the complexes are higher than those obtained in water, indicating that octanoic acid becomes a weaker acid after complexation

Advances in kinetics and mechanism of chemical reactions

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