Phytochemical and pharmacological studies on Orthosiphon stamineus Benth. (Lamiaceae) hydroalcoholic extracts.

The main components of Orthosiphon stamineus Benth. leaves and extracts are the pharmacologically active polyphenols: the polymethoxylated flavonoids and the caffeic acid derivatives. Two tinctures, having different alcohol concentration, were studied from phytochemical and pharmacological point of view. The main polyphenols were identified and quantitatively determined by HPLC. Comparison of the retention parameters and UV-Vis spectra of standards and those of the separated compounds performed the identification of caffeic-, cichoric- and rosmarinic acids, respectively, of sinesetine and eupatorine. The quantitative determination was performed by external standard method. The diuretic, saluretic and uricosuric actions of the studied tinctures were compared by experiments on rats.

Stationary phases for thin-layer chromatography.

This paper presents a review of the literature concerning development of the stationary phases for thin-layer chromatography (TLC) in the last ten years. The silica gel remains the most important adsorbent for TLC separation. The kinetic properties of the silica-gel thin layer and the new TLC plates have been presented. Other materials used as stationary phase were alumina, zirconium oxide, Florisil, and ion-exchanger. Chemically new bonded stationary phase development is also discussed. The improvement of the separations of some organic mixtures by impregnation of silica gel, cellulose, or polyamide plates (with transition metal ions and silver salts) and their applications is presented. The impregnation of the thin layer with organic stationary phase and inclusion complexes is another method used for the enhancement of the separation efficiences. Another modality to improve the selectivity in TLC using ion-pairing as reagent of impregnation is described as well. The actual state of chiral separation by TLC is discussed with concrete references to recent advances in chiral stationary phases. The use of nonpolar chemically bonded stationary phases impregnated with transitional metal ions is presented as chiral stationary phases. The cellulose, modified cellulose, chitin, chitosan, and their derivatives are presented and their potential for the analysis of the racemates is discussed. The cyclodextrines and macrocyclic antibiotics were used with very good results for enantiomeric separation by TLC. A new separation approach with molecular imprinting polymers was reported as a chiral stationary phase in TLC. The examples provide a wide range of structural types that can be readily resolved enantiomerically by TLC.