Search Results

You are looking at 1 - 6 of 6 items for :

  • Author or Editor: Gábor Tóth x
  • Chemistry and Chemical Engineering x
  • All content x
Clear All Modify Search

Most of the beneficial biological effects (e.g. neurosedative, antioxidant, and antimicrobial) of black horehound ( Ballota nigra L.) are because of its phenylpropanoid glycoside content. A rapid TLC-densitometric method with acceptable accuracy has been established for quantitative analysis of the most characteristic components of black horehound. Experiments were performed to establish the optimum conditions for densitometric measurement and for storage of extracts. Practical application of the elaborated method is reported for five plant extracts.

Restricted access

Different parts of three Ballota species ( B. nigra, B. hirsuta , and B. rupestris ) have been analyzed for phenylpropanoid content by means of a simple extraction technique and a newly established TLC-densitometric method. The compounds studied were verbascoside (VE), forsythoside B (FB), and caffeoyl-malic acid (CM). The largest amounts were detected in B. rupestris - CM (0.30%) and VE (4.58%) in the leaves and FB (3.0%) in the roots, followed by B. nigra ; the smallest amounts were found in B. hirsuta - 0.08% CM, 1.64% VE, and 0.91% FB in the leaves. The absence of caffeoylmalic acid was characteristic of the roots only. B. nigra , the common representative of the genus in Hungary, was chosen for thorough study of variation of phenylpropanoids during the vegetative period. Amounts of the phenylpropanoids increased during the main and secondary flowering periods in June (FB, 6.00%; VE, 8.50%; CM, 0.45% in the leaves) and September (FB, 3.80%; VE, 7.00%;, CM, 0.35% in the leaves).

Restricted access
Restricted access

Stachys palustris L. (Lamiaceae) contains the iridoids harpagide and acetylharpagide. The presence of other components, for example aucubin, can be revealed by TLC and RP HPLC. A readily applicable simple TLC-densitometric method for analysis of aqueous extracts of the plants has been established for comparative studies of aucubin-like iridoids in Stachys palustris .

Restricted access

Abstract

Intercalation complexes of three different Hungarian kaolinites with hydrazine and potassium acetate were investigated by FT-IR (DRIFT) spectrometry, X-ray diffraction, and thermogravimetry combined with mass spectrometry. Differences were found in the thermal behaviour of the complexes as well as in the rehydration — reexpansion patterns of the heated intercalates. An XRD method is proposed for the distinction of kaolinite and 7.2 Å halloysite present in the same mineral.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: Imre Szilágyi, István Sajó, Péter Király, Gábor Tárkányi, Attila Tóth, András Szabó, Katalin Varga-Josepovits, János Madarász, and György Pokol

Abstract  

This article discusses the formation and structure of ammonium tungsten bronzes, (NH4)xWO3−y. As analytical tools, TG/DTA-MS, XRD, SEM, Raman, XPS, and 1H-MAS NMR were used. The well-known α-hexagonal ammonium tungsten bronze (α-HATB, ICDD 42-0452) was thermally reduced and around 550 °C a hexagonal ammonium tungsten bronze formed, whose structure was similar to α-HATB, but the hexagonal channels were almost completely empty; thus, this phase was called reduced hexagonal (h-) WO3. In contrast with earlier considerations, it was found that the oxidation state of W atoms influenced at least as much the cell parameters of α-HATB and h-WO3, as the packing of the hexagonal channels. Between 600 and 650 °C reduced h-WO3 transformed into another ammonium tungsten bronze, whose structure was disputed in the literature. It was found that the structure of this phase—called β-HATB, (NH4)0.001WO2.79—was hexagonal.

Restricted access