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In recent years, the growth of the functional foods industry has increased research into new compounds with high added value for use in the fortification of traditional products. One of the most promising functional food groups is those enriched in antioxidant compounds of a lipophilic nature. In spite of the numerous advantages reported for such antioxidant molecules, they may also have disadvantages that impede their use in functional foods, although these problems may well avoided by the use of encapsulant agents such as cyclodextrins. This explains the recent increase in the number of research papers dealing with the complexation of different guest molecules possesing important antioxidant properties using natural and modified cyclodextrins. This paper presents a review of the most recent studies on the complexes formed between several important types of antioxidant compounds and cyclodextrins, focusing on the contradictory data reported in the literature concerning to the antioxidant activity of the host/guest molecule complexes, the different complexation constants reported for identical complexes, the bioavailability of the antioxidant compound in the presence of cyclodextrins and recommendation concerning the use of natural or modified cyclodextrins. Moreover, the use of cyclodextrins as antibrowning agents to prevent enzymatic browning in different foods is revised. Finally, we look at studies which suggest that cyclodextrins act as ''secondary antioxidants," enhancing the ability of traditional antioxidants to prevent enzymatic browning.

Polyphenol content, free radical scavenging capacity, and changes during storage over 7 months in the dark were studied in ecological and conventional red and white wines. In red wines, the most changeable components during storage were the anthocyanins since during storage anthocyanins content decreased 88% in conventional wine and 91% in ecological wine. Initially, the total flavonol contents of the conventional and ecological red wines were 163.88 +/- 2.69 and 153.58 +/- 1.71 mg/L, respectively, and no significant variations occurred during storage. No differences in hydroxycinnamic acid derivatives content between conventional and ecological red and white wines were observed. The flavonol level in white wines was very low, as expected since these compounds are found in grape skin. The initial antioxidant activity was 5.37 +/- 0.14 and 5.82 +/- 0.31 mM equivalents Trolox for conventional and ecological red wines, respectively; no significant differences were observed (p = 0.2831), and these values were 7-8 times higher than the antioxidant activity observed in conventional and ecological white wine. In contrast with other studies, the total concentrations of phenolic compounds in conventional and ecological red and white wines were not related to antioxidant activity (p > 0.05). In red wines, no significant differences were observed in the antioxidant activity of ecological and conventional red wine (p = 0.28), while in white wine significant differences were observed in the antioxidant activity between conventional and ecological white wine (p = 0.006).

Neochlorogenic acid, a less-studied isomer of chlorogenic acid, has been seen to posses antioxidant, antifungal, anti-inflammatory and anticarcinogenic effects, which makes it an interesting candidate for incorporation in functional foods. However, its poor solubility in water and susceptibility to oxidation make such a task difficult. To overcome that, its encapsulation in cyclodextrins (CDs) is proposed. The fluorescence of neochlorogenic acid in different pH conditions was analyzed, and caffeic acid was proved to be the fluorescent moiety in the molecule. An encapsulation model whereby the ligand poses two potential complexation sites (caffeic and D-(-)-quinic moieties), showed that α-CD and HP-β-CD formed the best inclusion complexes with neochlorogenic acid, followed by M-β-CD, β-CD and γ-CD. Molecular docking with the two best CDs gave better scores for α-CD, despite HP-β-CD providing stabilization through H-bonds. The encapsulation of chlorogenic acid led to a similar CD order and scores, although constants were higher for α-CD, β-CD and M-β-CD, lower for HP-β-CD, and negligible for γ-CD. The protonation state affected these results leading to a different order of CD preference. The solubility and the susceptibility to oxidation of neochlorogenic acid improved after complexation with α-CD and HP-β-CD, while the antioxidant activity of both isomers was maintained. [ABSTRACT FROM AUTHOR]

The commercial value of Terfezia claveryi, an edible desert truffle with important gastronomic, nutritional, and antioxidant properties, has led to growing interest in its cultivation. The erratic and slow growth of T. claveryi mycelium in vitro represents an impairment to obtain mycorrhizal plants, and it makes necessary to find a new culture medium able to overcome these drawbacks. In this work, we analyze the effect of cyclodextrins (CDs) on the growth of T. claveryi mycelium. Different parameters, including colony diameter, growth rate, and colony fresh weight, were evaluated, both in the presence and absence of these encapsulant agents. The results obtained confirm the ability of CDs to stimulate the growth of T. claveryi mycelium when present in the culture medium. A similar effect was observed when CDs were added to the culture medium of Tuber melanosporum. Three natural (α-, β-, and γ) and two modified (hydroxypropil-β and methyl-β) CDs were assayed. The best results were obtained with β-cyclodextrin, but no improvement was observed with its chemically modified derivatives. CDs complex the different compounds present in the culture medium which impair mycelial growth. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:1558-1564, 2013 [ABSTRACT FROM AUTHOR]

Abstract: The aggregation state of (E)-resveratrol was studied in the presence and absence of hydroxypropyl-β-cyclodextrin (HP-β-CD) using absorption and steady-state fluorescence at different pH values. The results revealed that this potent antioxidant shows a monomer/aggregate equilibrium which is dependent on the protonation state of (E)-resveratrol. This equilibrium can be modified by the presence of HP-β-CD, which reduces the aggregation of the (E)-resveratrol molecules, producing individual molecules of the solute and preventing side effects due to aggregation phenomena. At pH values higher than the pK a1 of (E)-resveratrol, the coexistence of different protonated/deprotonated forms of this antioxidant does not permit the fluorimetric determination of the complexation constant (K F) of (E)-resveratrol with HP-β-CD. However, when the Hildebrand–Benesi equation was used to calculate this constant at physiological pH, this problem was resolved, with a K F value of 14490±723M−1 and the stoichiometry of the complexation process 1:1 for all the cases tested. The results obtained in this paper resolve the contradictory data published about the complexation process of (E)-resveratrol by cyclodextrins. [Copyright &y& Elsevier]

Abstract: The study of the complexation of trans-resveratrol with natural cyclodextrins (CDs) in aqueous medium under different physico-chemical conditions of pH or temperature is essential if this antioxidant compound is to be used successfully in the food industry as ingredient of functional foods, due its poor stability, bioavailability and solubility. In this paper, a rapid, simple and sensitive determination of the apparent formation constant of trans-resveratrol/CD complexes by HPLC in aqueous medium has been investigated for first time. It can be observed that trans-resveratrol forms a 1:1 complex with α-, β- and γ-CD. The highest value of the apparent formation constant (K F =1922±89M−1) was found for β-CD and a strong dependence of K F on pH can be seen in the region where the trans-resveratrol begins the deprotonation of their hydroxyl groups. Moreover, an increase in the system’s temperature produced a decrease in the values of K F. Finally, to gain information on the mechanism of the trans-resveratrol affinity for CD, the thermodynamic parameters of the complexation were obtained. [Copyright &y& Elsevier]

The ability of cyclodextrins to enhance the water solubility of lipophilic compounds is used to modify the water-based Oxygen Radical Absorbance Capacity (ORAC) method to measure antioxidant activity in vitro. However, the use of these solubility enhancers may alter fluorescent readings, which has led to contradictory results being described in the literature. The low specificity of these oligosaccharides and their controlled release effect can result in cyclodextrins forming inclusion complexes with other reagents in the assay, changing the kinetics. In this study, the cause of cyclodextrins' interference in the ORAC method is evaluated through a physicochemical and computational approach. Cyclodextrins showed a clear increase in the fluorescent signal both in the presence and absence of the antioxidant oxyresveratrol, the precise effect being dependent on the type and concentration of cyclodextrin. Although the glucidic nature of cyclodextrins could play a minimal role in this effect, it seems that the main cause was the encapsulation of other substrates in the reaction, fluorescein and AAPH. [Display omitted] • Different types of cyclodextrins can modify ORAC readings in a dose-dependent manner. • This effect is mainly due to the ability of cyclodextrins to encapsulate other molecules. • Fluorescein and AAPH can be trapped in the cyclodextrin cavity, as well as the antioxidant. • The use of cyclodextrins as solubility enhancers in the ORAC method is discouraged. [ABSTRACT FROM AUTHOR]