Burya Dimitrova

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The determination of 18 aromatic and arylaliphatic carboxylic acids in honey from different floral origin using solid-phase extraction (SPE) and reversed-phase high performance liquid chromatography (RP-HPLC) is reported. The behaviour of the solutes on SPE cartridges was predicted from preliminary calculations involving the pK(a) constants of the(More)
Two new triterpenoids, lup-20(29)-en-3 alpha, 28-diol (1) and lup-20(29)-en-3 alpha, 28,30-triol (2), have been isolated from aerial parts of Bupleurum flavum, a native plant of the Eastern Mediterranean area (Bulgaria, Greece, and Turkey). Their structures were elucidated by spectral analysis. The known compounds betulin, betulinic acid, jasminol, together(More)
The aim of this study was to assess the potency of the reversed-phase high-performance liquid chromatography (RP-HPLC) for in vitro evaluation of the distribution behavior of common drugs between one of the generally used suppository bases Witepsol H15 and the rectal liquid which is imitated by a phosphate buffer, pH 7.2. The distribution coefficients (log(More)
An isocratic reversed-phase high-performance liquid chromatographic procedure for the determination of all-trans-retinoic acid (all-trans-RA) and its metabolites, all-trans-4-oxo-RA, 5,6-epoxy-RA, 9-cis-RA and 13-cis-RA, in mouse plasma and embryo and in new in vitro potential test systems for developmental toxicology has been developed. These compounds,(More)
The separation of pyrazolone derivatives with different acid-base properties and polarities has been investigated in view of recent concepts about the retention mechanisms in reversed-phase liquid chromatography. It is shown that both the protonated (BH+) and uncharged (B) bases undergo a dual mechanism of retention due to solvophobic and silanophilic(More)
The activation of the catalytic persulphate oxidation of sulphanilic acid when the catalyst, silver(I), is suitably complexed, is discussed. 2,2'-Bipyridyl is proposed as activator as it accelerates the rate-determining step of the process-the oxidation of silver(I) to silver(II). The mechanism of activation is investigated and discussed in detail. On the(More)
A specific liquid chromatographic method for the determination of 4-[[(5,6,7,8,8-tetrahydro-5,5,8,8-tetramethyl-2- naphthalenyl)carbonyl]amino]benzoic acid (Am580) in rat plasma is described. The procedure includes one-step isolation of the compound and the internal standard (naphthol AS) from protein precipitated with acetonitrile, resolution on a(More)
All-trans-retinoic acid (RA) is used successfully in the treatment of acute promyelocytic leukaemia (APL), although unexplained relapses occur in many of the patients. Pharmacokinetic studies may help in understanding the mechanism of resistance to RA and a simple and rapid procedure for its determination in biological samples may be advantageous. A(More)
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