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Previous studies on the anticancer activity of protoberberine alkaloids against a variety of cancer cell lines were extended to human tumour HeLa and murine leukemia L1210 cell lines. An attempt was also made to investigate the relationship between the cytotoxic activity of berberine and its molecular mechanism of action. Cytotoxicity was measured in-vitro using a primary biochemical screening according to Oyama and Eagle, and the growth inhibition assay. The in-vitro cytotoxic techniques were complemented by cell cycle analysis and determination of apoptotic DNA fragmentation in L1210 cells. Berberine acted cytotoxically on both tumour cell lines. The sensitivity of leukemia L1210 cells to the berberine was higher than that of HeLa cells. The IC(100) was below 100 microg mL(-1) for HeLa cells and approached a 10 microg mL(-1) limit for the leukemia L1210 cells. For both cell lines the IC(50) was found to be less than 4 microg mL(-1), a limit put forward by the National Cancer Institute (NCI) for classification of the compound as a potential anticancer drug. In L1210 cells treated with 10-50 microg mL(-1) berberine, G(0)/G(1) cell cycle arrest was observed. Furthermore, a concentration-dependent decrease of cells in S phase and increase in G(2)/M phase was detected. In addition, apoptosis detected as sub-G(0) cell population in cell cycle measurement was proved in 25-100 microg mL(-1) berberine-treated cells by monitoring the apoptotic DNA fragmentation (DNA ladder) using agarose gel electrophoresis.

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Novel 7-substituted 6-oxo-6,9-dihydro[1,2,5]selenadiazolo[3,4-h]quinoline (SeQ(1-6)) and 8-substituted 9-oxo-6,9-dihydro[1,2,5]selenadiazolo[3,4-f ]quinoline derivatives (SeQN(1-5)) with R(7), R(8) =H, COOC(2) H(5), COOCH(3), COOH, COCH(3) or CN were synthesized and their spectral characteristics were obtained by UV/Vis spectroscopy. Ultraviolet A photoexcitation of the selenadiazoloquinolones in dimethylsulfoxide or acetonitrile resulted in the formation of paramagnetic species coupled with molecular oxygen activation generating the superoxide radical anion or singlet oxygen, evidenced by electron paramagnetic resonance spectroscopy. The cytotoxic/photocytotoxic impact of selenadiazoloquinolones on murine and human cancer cell lines was demonstrated using the derivative SeQ5 (with R(7)=COCH(3)).

Quercetin is a natural polyphenol with proven health beneficial activities. In this study 15 new quercetin derivatives were prepared with the aim to enhance their bioavailability. Modification of their physicochemical properties could herewith improve the action in cells. The prepared compounds were tested for their antioxidant and cytotoxic activity. The ability to scavenge free radicals as well as ferric reducing antioxidant power of the new derivatives was not better than that of unmodified quercetin. But for acetylated esters a better cytotoxic activity was found on human cervical cancer cells HeLa than for the initial molecule. The best effect revealed chloronaphtoquinone quercetin (IC50=13.2 µM). For this compound comparable cytotoxic action on non-cancer murine fibroblast cells was detected (IC50=16.5 µM). The obtained results indicate that appropriate lipophilization of the quercetin molecule could improve its cytotoxic action in cells, probably due to its enhanced bioavailability.