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101 105 J.B. Harborne and T.J. Mabry , The Flavonoids: Advances in Research, Chapman and Hall, London, 1982. Mabry

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12 404 421 Ř.M. Andersen, K.R. Markham , Flavonoids. Chemistry, Biochemistry and Applications, CRS Press, Taylor & Francis Group

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202 C.A. Rice-Evans and L. Packer (Eds) Flavonoids in Health and Disease, Marcel Dekker, New York, 1998. Flavonoids

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The flowering tops of Hypericum hirsutum, H. montanum, H. perforatum subsp. angustifolium, H. perforatum subsp. perforatum , and H. perforatum subsp. veronense , collected from different locations in Croatia, were investigated to determine their flavonoid, phenolic acid, and amino acid composition. Thin-layer chromatography (TLC) on silica gel was used for separation and identification of the flavonoids and phenolic acids and TLC on cellulose was used for investigation of the amino acids. By use of these procedures ten flavonoids, three phenolic acids, and sixteen amino acids were detected and identified in the samples investigated. The composition of these compounds depended on the taxa investigated and the locality. Spectrophotometric analysis of the flavonoid content indicated that the three subspecies of H. perforatum are richer in flavonoids than H. hirsutum and H. montanum. H. perforatum subsp. perforatum is the richest in flavonoids, phenolic acids, and amino acids. This is the first time these biologically active compounds have been identified in the some Hypericum taxa.

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A study of quantitative analysis of some flavonoids in Satureja hortensis L. extracts is presented. The HPTLC analyses were performed in a normal chromatographic chamber on silica gel plates, with an appropriate mobile phase. Photodensitometric evaluation of the chromatographic plates was performed by UV-visible absorbance at 320 nm for rosmarinic acid and 349 nm for luteoline, after pulverizing with NTS reagent (diphenylboryloxyethylamine). Quantitative analyses of flavonoids were performed by use of calibration curves. The quantity of compounds extracted depends on the composition of the extraction solvent and on the extraction technique. The best results were obtained by heating under reflux with systems that contained 60–70% ethanol. Under these conditions it was found that this plant contained approximately 34 mg g −1 rosmarinic acid and 30 mg g −1 luteoline. The results obtained were compared and correlated with extraction method and confirm this plant contains important amounts of flavonoids and phenolic acids.

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Stachys is a large genus belonging to the family Lamiaceae . In common with many other representatives of this family, the aerial parts of plants belonging to this genus have been used in folk medicine and phytotherapy for many years. The aim of this work was to determine the amounts of biologically active compounds (flavonoids and phenolic acids) present in seven Croatian Stachys taxa ( S. alpina, S. officinalis, S. palustris, S. recta subsp. recta, S. recta subsp. subcrenata, S. salviifolia , and S. sylvatica ). This was achieved by establishing an appropriate extraction procedure and by analyzing the samples by HPTLC with densitometric evaluation. Plant extracts and standard solutions of flavonoids and phenolic acids were applied to silica gel 60 F 254 HPTLC plates as 10 mm bands. Plates were developed in vertical glass chambers previously saturated with the mobile phase, ethyl acetate-acetic acid-formic acid-water, 100 + 11 + 11 + 26 ( v/v ). After drying and spraying with NP/PEG reagent, the bands were visualized under short and long-wavelength UV light. By use of standard solutions, R F values and fluorescence colors of the investigated compounds were determined. Concentrations of the standard solutions were adjusted to the amounts in the samples and again chromatographed with Stachys samples. The Camag Reprostar 3 Videosystem was used for quantitative evaluation. The compound occurring in most of the samples investigated was found to be chlorogenic acid (it was not present in S. recta subsp. recta only); isoquercitrin, luteolin 7- O glucoside, rutin, and quercitrin were present in several of the samples. Although S. recta subsp. recta did not contain chlorogenic acid, it was found to be richest in the flavonoids whose presence was determined.This HPTLC method was found to be simple and convenient for rapid screening of active compounds and quantification of the investigated flavonoids and phenolic acids in Stachys taxa.

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Flavonoids and phenolic acids with a variety of biological activity are considered to be the main compounds in propolis — a natural product produced by the honey bee. TLC can be used for rapid screening of pharmacologically active components and to establish the difference between different propolis samples. Our goal was to optimize chromatographic conditions for separation of flavonoids and phenolic acids and to apply the optimized method for analysis of propolis samples from different geographic regions of Croatia. For chromatographic analysis we used 20 cm × 20 cm glass-backed TLC plates coated with 0.25 mm layers of silica gel 60 F 254 . Ethanolic standard solutions (80%) of the flavonoids and phenolic acids (10 μL) were applied to the plates. Chromatograms were developed at room temperature by ascending development in previously saturated vertical, flat-bottomed glass chambers with glass lids. Visualization was performed in short-and long-wavelength UV light and in long-wavelength UV light after spraying with different reagents. After calculation of R F values numerical taxonomy methods were used 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-(98–100%) formic acid, 44.1 + 3 + 2.35, and n -hexane-ethyl acetate-glacial acetic acid, 31 + 14 + 5) for separation of standards. The results obtained were used for analysis of propolis samples. TLC was shown to be a highly suitable method for rapid analysis of propolis samples. It can be used to establish differences between the amounts of pharmacologically active compounds in propolis from different geographic regions of Croatia.

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The flavonoid and triterpenoid soyasaponin content of the aerial parts of Desmodium adscendens from four geographical origins of Africa (Ghana, Nigeria, Sierra Leone, and Togo) has been studied by planar chromatography, because the species is supposed to have hepato-protective activity. Comparative study of these compounds revealed the presence of flavonoids such as vitexine and isovitexine and soyasaponins such as soyasaponin I. The study proves the suitability of TLC analysis of soyasaponins for fingerprinting of this genus.

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Separation and quantitative analysis of quercetin glycosides in methanolic and aqueous extracts of Epilobii angustifolii herba have been achieved by HPTLC with densitometric detection. The compounds were separated on silica gel 60F 254 HPTLC plates with ethyl acetate-formic acid-water, 68 + 2.5 + 3 ( v/v ), as mobile phase; densitometric detection of the flavonoids was performed at λ = 350 nm. The amounts of the compounds were calculated by use of regression equations obtained from calibration plots. The flavonoids were more abundant in the aqueous extract than in the methanolic extract. Quercetin glucuronide was the most abundant compound in both extracts (21.22 mg g −1 and 17.85 mg g −1 , respectively). The method is rapid, easy, and selective, particularly for quercetin glucuronide analysis.

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Caffeetannins and flavonoid glycosides have been analyzed in polar solvent extracts from leaves of Mentha piperita (Lamiaceae) . Peppermint extracts and individual compounds isolated from the leaves were investigated by TLC with horizontal development on unmodified silica gel (HPTLC Si 60, HPTLC LiChrospher Si 60) and on silica gel chemically modified with polar (HPTLC NH 2 , HPTLC CN) and non-polar groups (HPTLC RP-18W). The mobile phase acetone-acetic acid, 85 + 15 ( v/v ), enabled successful separation on the aminopropyl adsorbent; water-methanol, 60 + 40 ( v/v ), was best on the octadecyl adsorbent. These simple methods can be very useful for rapid estimation of components of peppermint leaves or extracts.

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