Cells were incubated for 24 h at standard conditions this website and then cytotoxicity was estimated once more. Whereas, in the second approach cells were incubated with various concentrations of tested samples diluted in DMEM containing 1 % FBS for 24 h in standard conditions. After that time surviving fraction was determined by MTT assay. MTT assay Briefly, a solution of 3–(4,5–dimethylthiazo1–2–y1)–2,5–diphenyltetrazolium bromide (MTT, Sigma) was prepared at 5 mg/mL in PBS and was diluted

1:10 in DMEM without FBS. 200 μL of this solution was added to each well. After 4 h of incubation at 37 °C in a humidified incubator with 5 % CO2, the medium/MTT mixtures were removed, and the formazan crystals formed by the mitochondrial dehydrogenase activity of vital cells were dissolved in 100 μL of DMSO:CH3OH

dilution (1:1). The absorbance of soluble product was read with a microplate reader (Infinite 200 M PRO NanoQuant, Tecan, Switzerland) at 565 nm. NVP-BGJ398 chemical structure Data analysis Cell viability was calculated using cells treated with DMEM containing 1 % FBS as control. Cell surviving fraction (%) was calculated using the formula: S/S0 (%) = [abs565nm of treated cells/abs565nm of untreated cells (control)] × 100. Each experiment was done in triplicate and was repeated at least twice. The inhibitory concentration (IC) values were calculated from a dose–response curve. IC50 values were determined from the fitting curve by calculating the concentration of agent that reduced the surviving fraction of treated cells by 50 %, compared to control cells. IC50 data are expressed as mean values ± standard deviation

(SD) and they are the average of two independent experiments, done in triplicate. Fluorescence microscopy Viable and dead cells were Cisplatin supplier detected by staining with AO (5 mg/L) and PI (5 mg/L) for 20 min and examined using fluorescence- inverted microscope (Olympus IX51, Japan) with an excitation filter of 470/20 nm. Photographs of the cells after treatment with the tested compounds were taken under magnification 20.00×. Results and discussion The acid–base chemistry of methotrexate MTX molecule contains a 2,4-diaminopteridine ring and N,N-dimethyl-p-aminobenzoic acid residue linked with glutamic acid by a peptide bond (Fig. 1). It exists in Sinomenine water solution in a fully protonated form as a H3L ligand. The acid–base properties of the moieties, which can be deprotonated with a rise of pH value, were determined using potentiometric measurements (Table 1). The first two obtained pK a values: 2.89 and 4.56 correspond to the deprotonation of carboxylic groups from glutamic acid, α-COOH and γ-COOH, respectively (Poe, 1973, 1977; Meloun et al., 2010). The highest value of pK a = 5.65 corresponds to the deprotonation process of the heterocyclic nitrogen (N1)H+ from the pteridine ring. The resulting pK a values are quite consistent with the literature data.