No abstract

The direct acylation of quercetin (I) with 3-chloro-2,2-dimethylpropanoyl chloride (II) gives a complex reaction mixture. The synthesis of different acylated quercetin with from mono- to tetra-O-substituted functions was achieved in a simple procedure wherein the yield of isomers depended on the stoichiometric ratio of reagents. The crude reaction mixtures were analysed (LC-MS) and compared with the isolated products. Unambiguous structural characterisation of isomeric quercetin derivatives was confirmed by NMR analysis. In addition, the quercetin dimer can be obtained in a high yield in the simple procedure. The anti-oxidant activity and aldose reductase inhibition of the compounds were screened with the aim of providing bi-functional remedies to treat diabetic complications and other diseases where oxidative stress and the polyol pathway are key etiological factors.

No abstract

The group of 21 novel semi-synthetic derivatives of quercetin was screened for the antiradical efficiency in a DPPH assay. The initial fast absorbance decrease of DPPH, corresponding to the transfer of the most labile H atoms, was followed by a much slower absorbance decline representing the residual antiradical activity of the antioxidant degradation products. Initial velocity of DPPH decolorization determined for the first 75-s interval was used as a marker of the antiradical activity. Application of the kinetic parameter allowed good discrimination between the polyphenolic compounds studied. The most efficient chloronaphthoquinone derivative (compound Ia) was characterized by antiradical activity higher than that of quercetin and comparable with that of trolox. Under the experimental conditions used, one molecule of Ia was found to quench 2.6±0.1 DPPH radicals.

Drug-drug cocrystals of imatinib mesylate with several cocrystal formers, i.e. 5-chlorouracil, 5-fluorouracil, hydroxyurea, 5-fluorocytosine, N-acetylcytosine, chlorogenic acid, dacarbazine, curcumin, creatine, orotic acid, L-cysteine, glutathione, and caffeic acid, were prepared from mixtures by cogrinding or solvent cocrystallization. The samples prepared were analyzed by FTIR, DSC, and XRPD. Formation of cocrystals with different stoichiometry was observed. Novel cocrystals of imatinib mesylate with 5-fluorouracil or hydroxyurea were identified, characterized, and selected by the solid form screening approach. These cocrystals were non-hygroscopic and chemically and physically stable to thermal stress under the testing conditions.