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Resveratrol and cyclodextrins: Recent advances in encapsulation
Abstract
Resveratrol (3,5,4'-trihydroxy-trans-stilbene), which naturally occurs in peanuts, grapes, and grape-derived foodstuffs such as red wine, has been reported to exert many different health-promoting effects including antioxidant, anti-inflamatory, antitumor, antiplatelet aggregation, cardioprotective and aging-delay effects. However, despiste the huge number of studies regarding the health-beneficial effects of resveratrol, its effectiveness from a dietary point of view is not clear. The dietary intake can be increased through resveratrol-enriched functional foods. The use of resveratrol as functional ingredient in novel foods (as a fortifier and nutraceutical compound) has been restricted to date. The high hydrophobicity of resveratrol and its sensitivity to external agents such us air, light and oxidative enzymes may constitute a serious problem for its bioavailability, formulation and manipulation in the elaboration of functional foods. In order to avoid this limitation, inclusion of resveratrol in cyclodextrins has recently been suggested by our group. Cyclodextrins (CDs) are a group of naturally occurring cyclic oligosaccharides derived from starch with six, seven or eight glucose residues linked by α(1-4) glycosidic bonds in a cylinder-shaped structure, and denominated α-, β-and γ-CDs, respectively. The central cavity of these molecules is hydrophobic, while the rims of the surrounding walls are hydrophilic. This hydrophobic cavity forms inclusion complexes with resveratrol, increasing its solubility, stability, bioavailability and antioxidant activity. The complexation of resveratrol in CDs increase its antioxidant activity, with CDs acting as a controlled dosage reservoir that protects resveratrol against its rapid oxidation by free radicals. Future research should focus on translating in vitro findings regarding potential benefits into in vivo models. In addition, further understanding of the potential toxicity, health effects, bioavailability, and metabolism of resveratrol is necessary before dietary and supplements recommendations can be made. Scientific information summarized in this review supports the many potential health benefits of resveratrol and the future mechanisms for the functional foods and nutraceuticals elaboration.
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A study was carried out on the acid denitrosation of N-methyl-N-nitroso-p-toluenesulfonamide (MNTS) in mixed systems made up of linear (geminal and terminal) alkyl diols and β-cyclodextrin (CD). The alkyl diols used allowed us to vary the length of the hydrocarbon chain from 2 to 6 carbon atoms. The observed rate constant, k
obs, decreases in the presence of CD. The inhibition profile decreases as the as the number of carbons in the chain is increased. This behaviour can be interpreted as a consequence of a balance between the complexation processes of MNTS and the alkyl diols by the CD. At a constant CD concentration and increase in the diols concentration decreases the concentration of free cyclodextrin available to complex with MNTS molecules and therefore produces an increases in the observed rate constant. The results were interpreted in terms of two different models; trough the presupposition and non-presupposition of a stoichiometry for the CD-diols complex. Both models agreed quite well and allow us to determine the uncomplexed cyclodextrin concentration in each case as well as the stoichiometry of the complexes. The binding constant for both types of alkane diols increase with increasing the number of carbon in the chain. Besides, the binding constant of the α,ω-alkane diols is higher than for the analog α,β-alkane diols. One of the main consequences of this study is that the acid denitrosation of MNTS can be use to obtain the stochiometry of the CD-diol complexes and to monitor the free cyclodextrin concentration.
The paper provides data on the practical utilization of the benefits of the molecular encapsulation of natural colorants by cyclodextrins. Experimental results on the stability of cyclodextrin complexed curcumin, curcuma oleoresin, -carotene and carotenoid oleoresins against light-, heat- and oxygen prove the benefits of molecular encapsulation of colorants. The parent -cyclodextrin stabilized most effectively the curcumines, while the stability of carotenoids was most effectively achieved by -cyclodextrin complexation. Methylated -cyclodextrin was found to be the most potent solubilizing agent for both carotenoids and curcuminoids.
Solid inclusion complex of rutin with β-cyclodextrin (β-CD) was prepared by coprecipitate method. The formation of inclusion complex was confirmed by differential scanning calorimetry (DSC) and X-ray diffraction. The formation constant was obtained by steady-state fluorescence measurements and the result suggested the complex preferred 1:1 (rutin:CD) stoichiometry. Furthermore, the spatial configuration of the complex has been proposed based on NMR and molecular modeling.
The complexation of resveratrol with native α-, β- and γ-cyclodextrins (CDs) and modified CDs (hydroxypropyl-β-(HP-β-CDs), maltosyl-β-(G2-β-CDs), methyl-β-, carboxymethyl-β- and acetyl-β-cyclodextrins) was studied, and the complexation constants (Kc) were compared. The complexation constant between resveratrol and each type of CD was calculated using three different methods: enzymatic, solubility and fluorimetric. The Kc values obtained showed that HP-β-CDs with their very high Kc of 18,048±625M−1, were the most effective for complexing resveratrol. Moreover, comparison of the results obtained by the three methods revealed that the fluorimetric method undervalued the Kc between resveratrol and all cyclodextrins, while the enzymatic and solubility methods were more precise for calculating the Kc between resveratrol and CDs, as demonstrated by the cyclodextrin-assay.
The antioxidant activity of resveratrol in the absence and presence of increasing concentrations of HP-β-CDs was determined using three different methods: ORAC, ABTS and DPPH. The three methods were validated and compared for their linearity, precision and accuracy in measuring resveratrol antioxidant activity. The results indicated that the most sensitive method is the ORAC assay, which can measure the lowest resveratrol concentration (0.15-2 μM) with the highest precision. In the presence of increasing concentrations of HP-β-CDs, the antioxidant activity of resveratrol was seen to increase when it was measured by the ORAC and ABTS assays. However, no increase was observed when the DPPH assay was used. With the ORAC assay, the antioxidant activity increased until all the resveratrol had been included in HP-β-CDs (0.4 mM CDs), whereas in the case of ABTS assay the plateau in antioxidant activity was reached after 2 mM HP-β-CDs, suggesting that the CDs interferences in the measurement method. When the DPPH assay was used, no effect was observed when increasing concentrations of HP-β-CDs, indicating that in a methanolic medium resveratrol is free. Therefore, so this method cannot be used to measure the effect of resveratrol complexation with CDs on its antioxidant activity.
In this work the oxidative degradation of resveratrol catalyzed by lipoxygenase-1 (LOX-1) has been studied. The process has been characterized by spectroscopic and polarographic measurements. The oxidation of resveratrol was dependent on the concentration of resveratrol and the enzyme. When resveratrol was incubated in the presence of lipoxygenase at pH 9.0, the reaction displayed a k(M) value of 18.6 x 10(-)(6) M and a catalytic efficiency (k(cat)/k(M)) of 4.3 x 10(4) s(-)(1) M(-)(1). These values are close to those shown by the enzyme when linoleic acid is used as the substrate. The effect of lipoxygenase inhibitors on the lipoxygenase-catalyzed resveratrol oxidation was also evaluated. The rate of resveratrol oxidation was markedly decreased by the presence of NDGA in the incubation mixture. From HPLC measurements, it can be deduced that resveratrol is oxidatively decomposed to a complex mixture of products similar to those obtained when the molecule is oxidized by hydrogen peroxide.
This study was designed to determine the optimum conditions of three different factors (mixing time, mixing temperature, and
tube size) in reduction of cholesterol in milk using immobilized β-CD beads. Immobilized β-CD glass beads were prepared at
different conditions of silanization and β-CD immobilization reactions. In result, the glass beads (diameter 1 mm) at 20 mM
3-isocyanatopropyltriethoxysilane and 30 mM β-CD without base showed the highest cholesterol removal rate as 41%. Using above
immobilized β-CD glass beads, the cholesterol removal rate was 40.2% with 6 h of mixing time in 7 mm diameter tube at 10°C.
After cholesterol removal from milk, the glass beads were washed for cholesterol dissociation and reused. In recycling study,
the cholesterol removal rate was 41%, which was mostly same as that using new glass beads. These results indicated that cholesterol
removal rate was about 40% with β-CD immobilized glass beads, however, the recycling efficiency was almost 100%.
Dominga grape polyphenol oxidase (PPO) was extracted using phase partitioning with Triton X-114. The enzyme was obtained in latent state and could be optimally activated by the presence of 0.2% sodium dodecyl sulfate (SDS) at pH 6.0. In the absence of SDS, the enzyme showed maximum activity at acid pH. The kinetic parameters of the enzyme at pH 3.0 and 6.0 in the presence of SDS were calculated. The effect of several inhibitors was studied, tropolone being the most effective with a K(i) value of 18 muM. The effect of cyclodextrins was also studied, and the complexation constant K(c) between G(2)-beta-cyclodextrins and 4-tert-butylcatechol was calculated using the enzymatic method (K(c) = 13960 M(-)(1)). The evolution of the color parameters (L, a, b) of liquefied grape berries was inhibited by inhibitors of PPO activity, such as diethyldithiocarbamate, metabisulfite, and G(2)-beta-cyclodextrins, indicating that enzymatic browning by PPO is the main process involved in the browning of Dominga grape juice at room temperature.