Amino acid profiling using HRGC-FTIR oftert.-Butyldimethylsilyl derivatives

Summary The use of N, O (S)-tert.-Butyldimethylsilyl derivatives of amino acids for capillary gas chromatography and FTIR identification of amino acids is described. Rapid identification is achieved by computerised comparison of FTIR spectra. Derivatives that are characterised by identical sets of ions in gas chromatography-mass spectrometry experiments are clearly distinguished and identified by means of their infrared spectra. This, for example, is the case with alanine, -alanine and sarcosine, which norvaline and valine, and with norleucine, leucine and isoleucine. Unknows are also promptly detected. This is especially useful in screening biological samples for less common amino acids. Screening of hemoglogin hydrolysates for amino acid adducts is exemplified.Presented at the 17th International Symposium on Chromatography, September 25–30, 1988, Vienna, Austria.     

Antibacterial activity of extract and fractions from branches of Protium spruceanum and cytotoxicity on fibroblasts

The crude ethanol extract (CEE) and fractions from branches of Protium spruceanum were subjected to antibacterial and cytotoxicity assays. Compounds of the most active fraction were identified by GC-MS and LC-MS. CEE was active against 19 bacteria and the ethyl acetate fraction (EAF) showed the lowest minimum bactericidal concentration (MBC 0.3–80.0 mg/mL). Through time-kill assay was observed that EAF induced rapid bactericidal effect against Staphylococcus saprophyticus. The cytotoxicity tests against L929 fibroblasts showed great potential of EAF on the treatment of infections caused by five bacteria (MBC < IC₅₀). The results provide in vitro scientific support to the possible application of branches of P. spruceanum as antimicrobial agent that may contribute for treatment of infections.     

Analysis of anatoxin-a in biological samples using liquid chromatography with fluorescence detection after solid phase extraction and solid phase microextraction

Anatoxin-a is a naturally occurring, potent neurotoxin produced by some species of cyanobacteria in freshwaters. This toxin, which is a potential health hazard, especially to animals, has been determined in different biological matrices such as several cyanobacterial cultures and water samples and carps and mussels tissue using a sensitive High Performance Liquid Chromatography with Fluorescence detection method. Sonication was the technique selected for the extraction of intracellular anatoxin-a and solid phase extraction using weak cation exchange was used for the concentration and purification of the samples. 4-Fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) was used to convert anatoxin into a highly fluorescent derivative. Recovery experiments were performed for each type of matrix used in this work, and adequate values were obtained (71-87%). Limits of detection for anatoxin-a were estimated to be in the ng/L and ng/g level for water and cyanobacterial samples, respectively. The results obtained were also compared with those obtained after using solid phase microextraction, as an alternative for the extraction and purification of the samples. Advantages and disadvantages regarding to the efficiency for impurities removal, simplicity and rapidity and the potential for concentration enhancement of using both methodologies have been also discussed.     

Antifungal Effect and Inhibition of the Virulence Mechanism of D-Limonene against Candida parapsilosis

Yeasts from the Candida parapsilosis complex are clinically relevant due to their high virulence and pathogenicity potential, such as adherence to epithelial cells and emission of filamentous structures, as well as their low susceptibility to antifungals. D-limonene, a natural compound, emerges as a promising alternative with previously described antibacterial, antiparasitic, and antifungal activity; however, its mechanisms of action and antivirulence activity against C. parapsilosis complex species have not been elucidated. Therefore, in the present study, we aimed to evaluate the antifungal and antivirulence action, as well as the mechanism of action of D-limonene against isolates from this complex. D-limonene exhibited relevant antifungal activity against C. parapsilosis complex yeasts, as well as excellent antivirulence activity by inhibiting yeast morphogenesis and adherence to the human epithelium. Furthermore, the apoptotic mechanism induced by this compound, which is not induced by oxidative stress, represents an important target for the development of new antifungal drugs.     

Study of the influence of some DCCAs on the structure of sol–gel silica membranes

We obtained silica gel membranes by sol–gel processing. In order to study the effect of some drying control chemical additives, we used an alkoxide/additive molar ratio of 1/1. The performance of the drying additives in obtaining crack-free gels was evaluated through monolithicity measurements. The structural evolution occurring in the interconnected network of the membranes during thermal treatment was monitored by Fourier transform infrared spectroscopy, structural density measurements and nitrogen gas sorption. The degree of cross-linking of the silica network was inferred from the frequency of the Si–O(Si) vibration in the range. We noted that in the presence of formamide and N,N-dimethylformamide, the Si–O–Si bonds are stronger and belong to a more cross-linked structure. Changes in the chemical properties of the membranes, evaluated by quantities of molecular water and silanol groups on their surface, were monitored by absorption bands in the range of 3800–3000 cm⁻¹. Membranes obtained with additives have surfaces covered by a large content of isolated silanol groups even when annealed at 800 °C. The membrane obtained in the presence of amide has larger pore volume and its pore structure is in the range of mesoporosity. The membranes without additive and with propylene carbonate are microporous. Formamide and N,N-dimethylformamide allowed the preparation of crack-free membranes stabilized at high temperatures.     

One-pot three-component synthesis of indole-3-glyoxyl derivatives and indole-3-glyoxyl triazoles

A general and efficient reaction of indole with oxalyl chloride and nucleophiles providing indole-3-glyoxyl derivatives has been developed in mild conditions. In the same fashion, the other reaction involved the addition of organic azides leading to the synthesis of indole-3-glyoxyl-1,2,3-triazoles, which proceeds smoothly generating the products in moderate to high yields.