Fig. 2

In vitro cytotoxicity of flavonoids and inhibition of DNA synthesis on cultured L. donovani AG83 promastigotes. (A) L. donovani promastigotes were cultured in M199 medium for 24 hr at 22°C with increasing concentrations of quercetin (-□-), rutin (-▲-), luteolin (-■-), flavone A (-△-) and isoorientin (-●-). Cell numbers determined by microscopic counting are expressed as percentages of those determined for cells grown in presence of 0.5% DMSO used as drug vehicle. All measurements were made in triplicate. (B-D) Micrographs of Giemsa stained L. donovani AG83 promastigotes in culture media containing 0.5% DMSO (B), 50 µM quercetin (C), or 20 µM luteolin (D). Note the healthy promastigotes in cultures containing 0.5% DMSO, and the lysed or round-shaped cells with degranulated nuclei in cultures containing quercetin or luteolin. Magnification 1000X. (E) Incorporation of [³H] thymidine (100 µCi/ml) into DNA of L. donovani AG83 promastigotes was monitored following addition of [³H] thymidine and 0.25% DMSO (-□-); 12.5 µM luteolin 50 µM luteolin (-△-); 40 µM quercetin (-■-) or 100 µM quercetin (-●-) to parasite cultures (3 × 10⁶ cells / ml; 22°C) at time 0. Aliquots of 100 µl each were withdrawn from the cultures at indicated time intervals and processed to determine the incorporation of label into acid precipitable DNA. All measurements were done in triplicate.