L. Novotný

Contribution to the chemotaxonomy of some european Petasites species

Abstract Thin-layer chromatography of certain chemical components of some species of Petasites can be used for quick and reliable identification of non-flowering individuals and interspecific hybrids. The substances are: furanopetasin in P. hybridus (L.) Gaertn., Meyer et Scherb., petasalbin in P. albus (L.) Gaertn., and kablicin in P. kablikianus Tausch. ex Bercht. The phylogenetic position of P. kablikianus is discussed and it is concluded that this taxon should be considered as an independent species of hybrid origin, which underwent a speciation process of its own. Evidence is presented concerning the occurrence of two chemovars for P. hybridus and P. albus.

The method of interrupted convection for measurements of adsorption equilibrium

Abstract The method of interrupted convection for equilibrium adsorption measurements in very dilute solutions of strongly adsorptive compounds has been described, using the modified drop-time technique. The testing of the method was performed by recording a set of electrocapillary curves going down to extreme dilutions (10−7 mol dm−3) of dextrane and tetrabutylammonium perchlorate in 0.1 M NaClO4, which had not been possible by the previous techniques.

Electrocapillary studies of fluoride solutions on mercury using polyethylene capillary

Abstract The electrocapillary curves in concentration range 0.001 M to 1 M in sodium and potassium fluoride solutions and in 12.25 M potassium fluoride were measured using a glass capillary with a polyethylene tip. In very dilute solutions the lowering of the interfacial tension at potentials more positive than p.z.c. described several times in experiments with glass capillary electrometer was not observed, and the electrocapillary curves coincided very well with those obtained from double integration of capacitance data. At large concentration of fluoride an increase of maximum interfacial tension was noticed. The fabrication of polyethylene capillary electrode is described and its advantages discussed.

Terpenoids of the Petasites paradoxus and Petasites kablikianus in relation to their phylogeny

Abstract In addition to a hydrocarbon fraction identical with those of other Petasites species, the light petroleum extract of Petasites paradoxus contained: kablicin, angelyljaponicin, kablikopetasin, furoeremophilane and a hitherto unidentified triterpenic alcohol C 30 H 50 O. These substances are identical with those encountered in Petasites kablikianus . The assumed parallel phylogenetic origin of both species, and their hybrid origin from the same parent taxa, seems to be confirmed.

Structure-intestinal transport and structure-metabolism correlations of some potential cancerostatic pyrimidine nucleosides in isolated rat jejunum

SummaryBoth transport and biotransformation processes for a series of pyrimidine nucleobases, ribonucleosides, 2′-deoxyribonucleosides, and acetyl and 5′-substituted derivatives of the cancerostatic agent araC were studied in the isolated everted rat jejunum with a continuous perfusion technique. Metabolic alterations during penetration were assessed by HPLC. 5′-Halogeno and 5′-deoxy derivatives of cytosine nucleosides exhibited higher transport rates and higher stability towards the deamination reaction than did unsubstituted derivatives. Octanol-buffer partition coefficients were estimated for the study compounds, and fragmental constants for the sugar moieties of nucleosides were assessed. With the present study compounds there was no correlation between lipophilicity and transport rate, as previously reported, but there was a correlation between lipophilicity and metabolic alteration of araC derivatives (r=0.99, n=5).

Occurrence of betulinic acid in different callus cultures of Solanum aviculare

Abstract Betulinic acid (3β-hydroxy-lup-20(29)-en-28-oic acid) was obtained from in vitro cultures of Solanum aviculare in yields up to 3% of the dry weight. This is a further example of overproduction by cells cultured in vitro of a product not found in the original parent plant.

Kinetics of transport and metabolism of 1-β-d-arabinofuranosylcytosine and structural analogs by everted perfused rat jejunum

Few reports have dealt with the kinetics and metabolism of AraC and analogs by rat intestine. Using everted rat jejunum with continuous perfusion, it was possible to demonstrate that AraC and Cyd cross the intestinal barrier(s) by a carrier mediated process which was saturable and exhibited fairly good fitting of the flux rate by Michaelis-Menten equation. The transport rate of different analogs was not consistent with the pH-partition theory of membrane transport of drugs being rather dependent on the chemical structure of the nucleoside. A free amino group of cytosine increased the rate of transport within the present series of AraC analogs. There was a detectable deaminase as well as esterase activity towards AraC and its analogs in rat jejunum.