RESUMO
TLC-DPPH(â¢) test belongs to a group of frequently performed assays aimed at detection of compounds with desired activity (effect directed analysis). Despite its popularity a standard procedure has not been elaborated so far causing difficulties in comparing results obtained in different laboratories. Thus the aim of the presented research was an approach to develop a standardized procedure for assessing free radical scavenging properties of plant polyphenols. It was observed that specifically positive adsorbent (silica gel) strengthened the observed result of radical-antioxidant reaction, while polar bonded stationary phase CN-silica weakened it. Based on the observed results it was concluded that the TLC-DPPH(â¢) assay should be preferably performed on the surface of non-specific adsorbents (e.g.: RP-18) with the use of n-hexane for DPPH(â¢) dissolution. It is also proposed to document the results every 5 min after staining, as they change in time.
Assuntos
Compostos de Bifenilo/química , Cromatografia em Camada Fina/métodos , Sequestradores de Radicais Livres/química , Picratos/química , Polifenóis/química , Adsorção , Calibragem , Cromatografia em Camada Fina/normas , Hexanos/química , Padrões de Referência , Sílica Gel/química , Solventes/química , Propriedades de Superfície , Fatores de TempoRESUMO
The purpose of the research was to recommend a unified procedure of image preprocessing of 2D thin layer videoscans for further supervised or unsupervised chemometric analysis. All work was done with open source software. The videoscans saved as JPG files underwent the following procedures: denoising using a median filter, baseline removal with the rollerball algorithm and nonlinear warping using spline functions. The application of the proposed procedure enabled filtration of random difference between images (background intensity changes and spatial differences of the spots location). After the preprocessing only spot intensities have an influence on the performed PCA or other techniques. The proposed technique was successfully applied to recognize the differences between three Carex species from the 2D videoscans of the extracts. The proposed solution may be of value for the any chemometric task--both unsupervised and supervised.
