Inclusion complexes of rosmarinic acid and cyclodextrins: stoichiometry,association constants,and antioxidant potential

The interaction between β-cyclodextrin (β-CD) and the polyphenol rosmarinic acid (RA) is here reported by ¹H NMR titration experiments. The formation of an aqueous soluble inclusion complex is confirmed and valuable information regarding mode of penetration of guest into β-CD, stoichiometry, and stability of the complex is obtained. The analysis by the continuous variation method shows the undoubted formation of 1:1 β-CD/RA complex. Additionally, the estimated apparent association constants reveal the importance of the asymmetry of the RA in the complexation; the incorporation of the catechol moiety closer to the carboxylic group is more favorable (K?=?2,028 M^?1) than from the other end of the RA molecule (K?=?1,184 M^?1). Finally, we have also investigated the antioxidant activity and storage stability of the β-CD/RA complexed system; the presence of β-CD was found to produce a remarkable enhancement on the antioxidant activity.     

The Influence of Polyols on the Process Kinetics and Bioactive Substance Content in Osmotic Dehydrated Organic Strawberries

In recent years, an increasing interest in reducing sugar consumption has been observed and many studies are conducted on the use of polyols in the osmotic dehydration process to obtain candied or dried fruits. The studies in the literature have focused on the kinetics of the process as well as the basic physical properties. In the scientific literature, there is a lack of investigation of the influence of such polyol solutions such as sorbitol and mannitol used as osmotic substances during the osmotic dehydration process on the contents of bioactive components, including natural colourants. Thus, the aim of the study was to evaluate the impact of polyols (mannitol and sorbitol) in different concentrations on the process kinetics and on chosen physical (colour and structural changes) as well as chemical (sugars and polyol content, total anthocyanin content, total polyphenol content, vitamin C, antioxidant activity) properties of osmotic-dehydrated organic strawberries. Generally, the results showed that the best solution for osmotic dehydration is 30% or 40% sorbitol solutions, while mannitol solution is not recommended due to difficulties with preparing a high-concentration solution and its crystallization in the tissue. In the case of sorbitol, the changes of bioactive compounds, as well as colour change, were similar to the sucrose solution. However, the profile of the sugar changed significantly, in which sucrose, glucose, and fructose were reduced in organic strawberries and were partially replaced by polyols.     

Syntheses of 5-hydroxy-2-(phenyl or styryl)chromones and of some halo derivatives

One-pot syntheses of 5-hydroxy-2-(phenyl or styryl)chromones and the corresponding 6- and 8-monoiodo- and 6,8-diiodochromones have been developed. The procedures involve oxidative cyclization of 2′-benzyloxy-6′-hydroxychalcones and 2′-benzyloxy-6′-hydroxy-2-cinnamylideneacetophenones and electrophilic substitution processes on the chromone moieties; such procedures were also applied to the syntheses of 6,8-dibromochromone derivatives.     

Evaluation of photodynamic therapy (PDT) procedures using microfluidic system

A hybrid PDMS/glass microfluidic system for evaluation of the efficiency of photodynamic therapy is presented. 5-aminolevulinic acid (ALA) was used as a precursor of photosensitizer. The geometry of the microdevice presented in this paper enables to test different concentrations of the photosensitizer in a single assay. The viability of the A549 cells was determined 24 h after PDT procedure (irradiation with light which induced a photosensitizer accumulated in carcinoma cells, λ = 625 nm). The presented results confirmed the possibility to perform the photodynamic therapy process in vitro in microscale and the possibility to assess its effectiveness. Moreover, because two identical microstructures on a single chip were performed, the microchip can be used for examination simultaneously various cell lines (carcinoma and normal) or various photosensitizers.     

Effect of Long-Term Potato Starch Retention with Citric Acid on Its Properties

The present study aimed to determine changes in the properties of starch triggered by its long-lasting (1, 2, 4, 7, 10, or 14 days) retention with citric acid (5 g/100 g) at a temperature of 40 °C. The starch citrates obtained under laboratory conditions had a low degree of substitution, as confirmed via NMR and HPSEC analyses. The prolonging time of starch retention with citric acid at 40 °C contributed to its increased esterification degree (0.05–0.11 g/100 g), swelling power (30–38 g/g), and solubility in water (19–35%) as well as to decreased viscosity of the starch pastes. Starch heating with citric acid under the applied laboratory conditions did not affect the course of DSC thermal characteristics of starch pasting. The low-substituted starch citrates exhibited approximately 15% resistance to amylolysis.     

Kinetics of the hydrogen abstraction R?OH + H → R?O• + H2 reaction class

This paper presents an application of the reaction class transition state theory (RC‐TST) to predict thermal rate constants for the hydrogen abstraction R? OH + H → R? O^? + H₂ reaction class, where R is an alkyl group. We have derived all parameters for the RC‐TST method for this reaction class from rate constants of 19 representative reactions, coupling with linear energy relationships (LERs) and the barrier height grouping (BHG) approach. Error analyses indicate that the RC‐TST/LER, where only reaction energy is needed, and RC‐TST/BHG, where no other information is needed, can predict rate constants for any reaction in this reaction class with satisfactory accuracy for combustion modeling. Specifically for this reaction class, the RC‐TST/LER method has less than 25% systematic errors in the predicted rate constants, whereas the RC‐TST/BHG method has less than 35% error when compared to explicit rate calculations. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 414–429, 2010     

Unprecedented Double aza‐Michael Addition within a Sapphyrin Core

A novel sapphyrin derivative was obtained from the reaction between a free‐base sapphyrin and dimethyl acetylenedicarboxylate (DMAD). The formation of the new compound involved a double aza‐Michael addition of two pyrrolic NH groups to a DMAD molecule, with the formation of a disubstituted ethano bridge. The NMR spectral data reveal a product with an unsymmetrical structure; DFT calculations provided support for a structure in which the ethano bridge links two adjacent pyrrole units. The present study provides a seemingly unprecedented example of an N,N′‐dinucleophile reacting with DMAD to form a heterocyclic compound in which the two N‐atoms are linked to the two sp³ carbon atoms derived from a substituted acetylene.     

On nondegenerate coupling forms

The aim of the present paper is to investigate new classes of symplectically fat fibre bundles. We prove a general existence theorem for fat vectors with respect to the canonical invariant connections. Based on this result we give new proofs of some constructions of symplectic structures. This includes twistor bundles and locally homogeneous complex manifolds. The proofs are conceptually simpler and allow for obtaining more general results.