Readily accessible azido-alkyne-functionalized monomers for the synthesis of cyclodextrin analogues using click chemistry.

A set of linear and cyclic oligomers were synthesized starting from a suitable azido-alkyne monomer through click oligomerization. The synthesis of these monomers starting from bromobenzene features an enzymatic dihydroxylation and the regio- and stereoselective installation of the azide and alkyne functionalities. Optimization of the click reaction was accomplished using dimerization as the model reaction. The product distribution of the oligomerization could be modulated by the monomer concentration and the use of additives, generating mainly cyclic oligomers consisting of tetramers, pentamers and hexamers.

KR12 peptide associated with cyclodextrin: Antimicrobial and antitumor activities.

The aim of this study was to determine the physical properties and antimicrobial and antiproliferative effects of the KR12 peptide complexed with 2-hydroxypropyl-ß-cyclodextrin (Hp-ßCd) in vitro. The KR12:Hp-ßCd composition was evaluated for particle size and its zeta (ζ)-potential in the presence and absence of cells. Antimicrobial activity against Streptococcus mutans, Actinobacillus actinomycetemcomitans, and Porphyromonas gingivalis for the peptide alone or associated was evaluated by minimal inhibitory concentration. The cytotoxicity of the peptide and composition toward fibroblasts, Caco-2 cells, and A431 cells was determined using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide; thiazolyl blue assay and hemolysis assay. Membrane integrity was analyzed by the lactate dehydrogenase assay. KR12:Hp-ßCd decreased the peptide concentration required for the antimicrobial effect. Moreover, this composition was able to modify cell surface parameters, such as ζ-potential, and alter the degree of hemolysis induced by KR12. However, the KR12:Hp-ßCd and KR12 alone alter the zeta potential of cells to a similar extent, suggesting a similar level of membrane interaction. The peptide alone inhibited the proliferation of Caco-2 and A431 cells more efficiently than KR12:Hp-ßCd (p < 0.001), but did not show significant cytotoxic effects via the dehydrogenase lactate assay. Both substances were effective in inhibiting the growth of odontopathogenic bacteria, as well as inhibiting Caco-2 epithelial cells. These observations highlight the potential antimicrobial and antiproliferative effects of KR12 peptide alone or associated with Hp-ßCd.

Production of cyclodextrins by CGTase from Bacillus clausii using different starches as substrates.

Cyclodextrins (CDs) are cyclic oligasaccharides composed by D-glucose monomers joined by alpha-1,4-D glicosidic linkages. The main types of CDs are alpha-, beta- and gamma-CDs consisting of cycles of six, seven, and eight glucose monomers, respectively. Their ability to form inclusion complexes is the most important characteristic, allowing their wide industrial application. The physical property of the CD-complexed compound can be altered to improve stability, volatility, solubility, or bio-availability. The cyclomaltodextrin glucanotransferase (CGTase, EC 2.4.1.19) is an enzyme capable of converting starch into CD molecules. In this work, the CGTase produced by Bacillus clausii strain E16 was used to produce CD from maltodextrin and different starches (commercial soluble starch, corn, cassava, sweet potato, and waxy corn starches) as substrates. It was observed that the substrate sources influence the kind of CD obtained and that this CGTase displays a beta-CGTase action, presenting a better conversion of soluble starch at 1.0%, of which 80% was converted in CDs. The ratio of total CD produced was 0:0.89:0.11 for alpha/beta/gamma. It was also observed that root and tuber starches were more accessible to CGTase action than seed starch under the studied conditions.

Synthesis and characterization of an amphiphilic cyclodextrin, a micelle with two recognition sites.

A cyclodextrin derivative (Mod-CD) was synthesized through the monoesterification of beta-cyclodextrin (beta-CD) with 3-((E)-dec-2-enyl)-dihydrofuran-2,5-dione. The compound is an interesting surfactant that can form large aggregates not only through the interaction of the hydrophobic tails as in common amphiphilic compounds but also through the inclusion of the alkenyl chain into the cavity of another Mod-CD molecule. The self-inclusion of the chain in the cavity of cyclodextrin as well as the intermolecular inclusion was demonstrated by 1H NMR measurements that were able to detect methyl groups in three different environments. Besides, in the aggregates of Mod-CD, the cavity is available to interact with external guests such as phenolphthalein, 1-amino adamantane, and Prodan. Phenolphthalein has the same binding constant with Mod-CD and beta-CD, but the equilibrium constant for the interaction with Prodan is about 2 times larger for Mod-CD than for beta-CD. The latter result is attributed to the fact that this probe interacts with the micelle in two binding sites: the cavity of the cyclodextrin and the apolar heart of the micelle as evidenced by the spectrofluorimetric behavior of Prodan in solutions containing different concentrations of Mod-CD.

Improved pharmacological properties for superoxide dismutase modified with beta-cyclodextrin-carboxymethylcellulose polymer.

Superoxide dismutase was glycosidated with cyclodextrin-branched carboxymethylcellulose. The modified enzyme contained 1.4 mol polymer per mol protein and retained 87% of the initial activity. The anti-inflammatory activity of superoxide dismutase was 2.2-times increased after conjugation and its plasma half-life time was prolonged from 4.8 min to 7.2 h.

(trans-1,4-bis[(4-pyridyl)ethenyl]benzene)(2,2'-bipyridine)ruthenium(II) complexes and their supramolecular assemblies with beta-cyclodextrin.

Two novel ruthenium polypyridine complexes, [Ru(bpy)(2)Cl(BPEB)](PF(6)) and ([Ru(bpy)(2)Cl](2)(BPEB))(PF(6))(2) (BPEB = trans-1,4-bis[2-(4-pyridyl)ethenyl]benzene), were synthesized and their characterization carried out by means of elemental analysis, UV-visible spectroscopy, positive ion electrospray (ESI-MS), and tandem mass (ESI-MS/MS) spectrometry, as well as by NMR spectroscopy and cyclic voltammetry. Cyclic and differential pulse voltammetry for the mononuclear complex showed three set of waves around 1.2 V (Ru(2+/3+)), -1.0 V (BPEB(0/)(-)), and -1.15 (BPEB(-/2-)). This complex exhibited aggregation phenomena in aqueous solution, involving pi-pi stacking of the planar, hydrophobic BPEB ligands. According to NMR measurements and variable-temperature experiments, the addition of beta-cyclodextrin (betaCD) to [Ru(bpy)(2)Cl(BPEB)](+) leads to an inclusion complex, breaking down the aggregated array.

Thermal stabilization of trypsin by enzymic modification with beta-cyclodextrin derivatives.

Streptoverticillum sp. transglutaminase was used as catalyst for the attachment of several beta-cyclodextrin derivatives to the glutamine residues in bovine pancreatic trypsin. The modifying agents used were mono-6-ethylenediamino-6-deoxy-beta-cyclodextrin, mono-6-propylenediamino-6-deoxy-beta-cyclodextrin, mono-6-butylenediamino-6-deoxy-beta-cyclodextrin and mono-6-hexylenediamino-6-deoxy-beta-cyclodextrin. The transformed trypsin preparations contained about 3 mol of oligosaccharides/mol of protein. The specific esterolytic activity of trypsin was increased by about 4-21% after conjugation. The K (m) values for cyclodextrin-trypsin complexes represented about 58-87% of that corresponding to the native enzyme. The optimum temperature for esterolytic activity of trypsin was increased by about 5-10 degrees C after enzymic modification with the cyclodextrin derivatives. The thermostability was increased by 16 degrees C for the modified trypsin. Thermal inactivation at different temperatures ranging from 45 to 60 degrees C was markedly increased for the oligosaccharide-trypsin complexes. This modification also protected the enzyme against autolysis at alkaline pH.

Enhancement of selectivity for producing gamma-cyclodextrin.

The production of cyclodextrins (CDs) by cyclodextrin-glycosyl-transferase (CGTase) from Bacillus firmus was studied, with respect to the effect of the source of starch upon CD yield and on the selectivity for producing gamma-CD. Cyclodextrin production tests were run for 24 h at 50 degrees C, pH 8.0, and 1 mg/L of CGTase, and substrates were maltodextrin or the starches of rice, potato, cassava, and corn hydrolyzed up to D.E. 10. Cornstarch was the best substrate for producing gamma-CD. Later, glycyrrhizin (2.5% [w/v]), which forms a stable complex with gamma-CD, was added to the cornstarch reaction medium and increased the yield of gamma-CD to about four times that produced with only maltodextrin, but the total yield of CDs remained practically unchanged. Therefore, the results showed that the studied CGTase is capable of giving relatively high yield of gamma-CD in the presence of glycyrrhizin as complexant and cornstarch as substrate.