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The great prevalence of thin‐layer chromatography over high‐performance liquid chromatography is connected with the possibility of analyzing many samples in parallel. Therefore, the method is often used in screening and/or effect directed analysis to compare composition and chemical/biological properties of many samples in one run. It was already proved, that high performance thin‐layer chromatography, in many cases, can replace high‐performance liquid chromatography for quantitative analysis. The main aim of the paper is to show that simple thin‐layer chromatography can also be used as a quantitative or at least as a semi‐quantitative method, even when it concerns effect directed analysis e.g. direct bioautography. Chlorogenic acid content was measured in four methanol extracts of various green coffees and in one extract of black coffee using thin‐layer chromatography with ultraviolet detection and thin‐layer chromatography with effect directed detection. High‐performance liquid chromatography was used as a reference method. Additionally, total contents of polyphenols and antioxidants were estimated using thin‐layer chromatography or dot‐blot on chromatography plates. These results were compared to spectrophotometric methods. It was proved that thin‐layer chromatography can be used as a quantitative (using densitometry) or semi‐quantitative method (using other detection methods including effect directed detection) as well as for estimating total antioxidants or polyphenols content. [ABSTRACT FROM AUTHOR]

A spectrophotometric technique after paper chromatography was found adequate for quantitatively determining chlorogenic and caffeic acids in the vegetative apical buds of Pyrus communis L., variety ‘Passe‐Crassane’, de ľOrléanais. Using this method, significant changes in these polyphenols were shown to occur both in tissue concentration and total amount per bud, in samples collected during winter 1973–1974. A close relationship between chlorogenic acid concentration and state of dormancy of excised twigs was found. [ABSTRACT FROM AUTHOR]

Through the use of paper chromatographic separation, and fluorometric and spectrophotometric analysis, three caffeoylquinic acid isomers and scopolin have been quantitated in tobacco as a function of age and chilling temperature. Cold-chilled plants exhibited nitrate deficiency symptoms and 4-5 fold increases over control plants in chlorogenic acid (CGA) concentration in all plant sections except the roots. Varying lesser increases in neochlorogenic acid, "Band 510", and scopolin concentration were also observed in the above ground sections of chilled Plants. hoots of cold-chilled plants contained lesser concentrations of CGA and scopolin than control plants after 15 days of treatment. Leaves from the same control plant were found to decrease in CGA, Band 510 and scopolin concentration with age, while neochlorogenic acid concentrations changed little. In stem sections CGA concern ration also decreased basipetally while the concentrations of scopolin increased. Similar leaf age studies done with cold -chilled plants revealed phenolic concentration changes comparable to those of control plants, even though their concentrations were appreciably higher. [ABSTRACT FROM AUTHOR]