engleski

Investigation of the Flavonoids in Croatian Propolis by Thin-Layer Chromatography

Flavonoids and phenolic acids, with various biological activities, are considered to be main compounds in propolis - a natural product produced by the honeybee. TLC can be used for rapid screening of pharmacologically active components and for establishing the difference between different propolis samples. Our goal was to optimize chromatographic conditions for separation of flavonoids and phenolic acids and to apply optimized method in analysis of propolis samples from different geographic regions of Croatia. For chromatographic analysis we used 20 x 20 cm glass-backed TLC plates coated with 0.25 mm layers of silica gel 60 F254 (Merck). 10 μ l of 80% ethanolic standard solutions (flavonoids and phenolic acids) was applied to TLC plates. Chromatograms were developed at the room temperature by ascendenting development in previously saturated vertical flat-bottom glass chambers with glass lid (CAMAG, Switzerland). Visualization was performed under short and long wave UV light and in long wave UV light after spraying with different reagents. After calculating RF values, we used the numerical taxonomy methods to test the efficiency of 11 mobile phases and to optimize chromatographic conditions for separation of 19 standard solutions. We established the most appropriate mobile phases (chloroform : methanol : formic acid (conc., 98% - 100%), 44.1:3:2.35 and n-hexane : ethyl acetate : glacial acetic acid, 31:14:5) for the separation of standards. Obtained results were used in analysis of propolis samples. As we predicted, TLC is shown to be highly suitable method for rapid analysis of propolis samples. It can be used to establish the difference in composition of pharmacologically active compounds in propolis from different geographic regions of Croatia.

Propolis; Flavonoids; Phenolic acids; Numerical taxonomy; TLC

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