Derivatization of the natural flavonoid dihydroquercetin with p-aminobenzoic acid was carried out in an ethyl acetate/citric buffer biphasic system using laccase from the fungus Trametes hirsuta. The main reaction product yield was ~68 mol %. The product was characterized by 1H NMR, 13C NMR, and liquid chromatography-mass spectroscopy, and its structure was elucidated. The reaction product affected viability of cultured human rhabdomyosarcoma cells (RD cell line) in a dose-dependent manner and, therefore, can be of interest to pharmaceutical industry.

Introduction. Heterogeneous nuclear ribonucleoprotein A1 (hnRNP А1) and other RNA-binding proteins involved in splicing participate in realization of genetic information and can be greatly changed in pathological conditions including tumors. Objective. Proteomic study of hnRNP A1 and other RNA-binding splicing proteins in 10 human malignant and non-malignant cultured cell lines of mesenchymal and epithelial origin. Materials and methods. Two-dimensional gel electrophoresis of adenocarcinomas (LNCaP, DU-145, PC-3, 769-P) and sarcomas (U2-OS, SK-UT-1B, RD) cell lines with following protein identification by matrix-assisted laser desorption ionization mass spectrometry have been carried out. Results. HnRNP А1 has been identified as an abundant protein in all studied malignant cell lines. It has been revealed in lower amount in normal mesenchymal cells compared to malignant cultured cells and achieved undetectable levels in myoblasts after induction of differentiation. Conclusion. High cellular level of hnRNP А1 can suggest high proliferative activity of cells including malignant those. Hence, hnRNP А1 and other RNA-binding splicing proteins hold promise to its further investigation in human transformed cells.