Extraction and Planar Chromatographic Separation Techniques in the

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The suitability of a densitometer and video scanner in the detection of plant phenols by TLC
was studied and the optimum performance of the methods was assessed. A mixture of
phenolic acids and flavonoids, and of coumarins, were detected by UV irradiation at 254 nm
and 366 nm, respectively. The methods were found to be equivalent, on the basis of
repeatability, when the results from the densitometric measurements were compared with
those obtained with a video scanner. The advantages and limitations of the two systems were
discussed.
A method was developed to measure the radical scavenging activity of compounds separated
by reversed-phase thin-layer chromatography (RP-TLC) using phenolic acids as model
analytes. Thin-layer chromatographic separation was followed by derivatization of the
analytes with 1,1-diphenyl-2-picrylhydrazyl (DPPH) in methanol (0,04 %, w/v). The
compounds possessing radical scavenging activity were detected as bright yellow bands
against a purple background. A video documentation system utilizing a charged-coupled
device (CCD) video camera was used for the detection of the activity. The RP-TLC-DPPH
method correlated well with the widely used spectrophotometric DPPH assay. The results
from the measurement of the free radical scavenging activity of rapeseed meal fractions
indicated the potential of the method as a rapid alternative to some of the currently used
methods in the fractionation and analysis of potential antioxidative compounds in natural
extracts.