Ladislav Novotny

Determination of diclofenac sodium, flufenamic acid, indomethacin and ketoprofen by LC-APCI-MS.

A sensitive, selective and accurate high-performance liquid chromatography-mass spectrometry (LC-MS) assay for the determination of selected non-steroidal anti-inflammatory drugs (NSAIDs), namely diclofenac sodium (DIC), flufenamic acid (FLU), indomethacin (IND) and ketoprofen (KET), either individually or in mixtures, was developed. The examined drugs were injected onto Shim-pack GLC-CN column and were eluted with a mobile phase consisting of acetonitrile and 20 mM ammonium acetate solution (5:1 v/v)/pH 7.4 at a flow rate l ml min(-1). The mass spectrometer, operated in the single ion monitoring mode, was programmed to admit the negative ions [M-H] at m/z 295.9 (DIC), 280.1 (FLU), 355.8 (IND) and 252.9 (KET), respectively. The calibration curves were linear (r > or = 0.9993) over the concentration range 50-300 ng ml(-1) (FLU, DIC) and 100-500 ng ml(-1) (KET, IND) with detection limits of 0.5-4.0 ng. The mean predicted concentrations for the analytes were in the range -5.9 and 5.2% of the nominal concentrations. Within-day and between-day precision were in the range of 0.8-9.1% of the R.S.D. Mean recovery percentages of the individual compounds from laboratory-made mixtures and pharmaceutical formulations were (99.5-101.5%) and (100.6-102.2%), respectively.

Dual activity of triterpenoids: apoptotic versus antidifferentiation effects

Triterpenoids are natural, biologically active compounds extracted from many plants. They possess antiinflammatory, anticancer, and antioxidant properties. In the report presented, antiproliferative effects and leukemia cell growth and apoptosis modulating activities of ursolic acid (UA) and oleanolic acid (OA) were investigated. Both triterpenoids are inhibitors of leukemia cell growth and inductors of apoptosis. However, when applied in combination with anthracycline antitumor antibiotic doxorubicin (Dox), UA and OA diversely modulate therapeutic efficacy of Dox, due to different antioxidant activities. Compare to OA showing synergism/additive effect with Dox, UA (stronger antioxidant) acts antagonistically and reduces leukemia cell growth inhibiting and differentiation effects induced by Dox. In conclusion, these findings suggest that although triterpenoids UA and OA can induce apoptosis, their antioxidant activities can interfere with the therapeutic effect of antitumor antibiotic Dox which mechanism of action is attributed to the production of reactive oxygen species.

Liquid chromatographic-mass spectrometric determination of celecoxib in plasma using single-ion monitoring and its use in clinical pharmacokinetics.

Celecoxib is a cyclooxygenase-2 specific inhibitor, that has been recently and intensively prescribed as an anti-inflammatory drug in rheumatic osteoarthritis. A robust, highly reliable and reproducible liquid chromatographic-mass spectrometric assay is developed for the determination of celecoxib in human plasma using sulindac as an internal standard. The run cycle-time is <4 min. The assay method involved extraction of the analytes from plasma samples at pH 5 with ethyl acetate and evaporation of the organic layer. The reconstituted solution of the residue was injected onto a Shim Pack GLC-CN, C18 column and chromatographed with a mobile phase comprised of acetonitrile-1% acetic acid solution (4:1) at a flow-rate of 1 ml/min. The mass spectrometer (LCQ Finnigan Mat) was programmed in the positive single-ion monitoring mode to permit the detection and quantitation of the molecular ions of celecoxib and sulindac at m/z 382 and 357, respectively. The peak area ratio of celecoxib/sulindac and concentration are linear (r2>0.994) over the concentration range 50-1000 ng/ml with a lowest detection limit of 20 ng/ml of celecoxib. Within- and between-day precision are within 1.58-4.0% relative standard deviation and the accuracy is 99.4-107.3% deviation of the nominal concentrations. The relative recoveries of celecoxib from human plasma ranged from 102.4 to 103.3% indicating the suitability of the method for the extraction of celecoxib and I.S. from plasma samples. The validated LC-MS method has been utilized to establish various pharmacokinetic parameters of celecoxib following a single oral dose administration of celecoxib capsules in two selected volunteers.

Development of LC–MS method for determination of ursolic acid: application to the analysis of ursolic acid in Staphylea holocarpa Hemsl.

Ursolic acid is a hydroxy pentacyclic triterpene, which has a chemoprotective activity in human. A reliable and reproducible liquid chromatography-mass spectrometric assay (LC-MS) was developed for the determination of ursolic acid in laboratory-made mixtures and in leaves and twigs extracts of Staphylea holocarpa Hemsl. The methanolic solution of the extracted ursolic acid was chromatographically analyzed using Shim Pack CLC-CN, C18 (150 x 6 mm, 5 mu) column and a mobile consisting of methanol-1% acetic acid solution (4:1) at a flow rate of 1.0 ml min(-1). The mass spectrometer (LCQ-Finnigan) was programmed in the positive single ion monitoring (SIM) to permit detection and quantitation of ursolic acid in MS-SIM mode at m/z 439.2, 411.2 and 390.9. Linear correlation (r > 0.99) of the peak area and the concentration of ursolic acid over the concentration range 0.25-10 microg ml(-1) was obtained. The relative standard deviation (%R.S.D.) and percentage deviation from the nominal concentrations (%DEV) were found to be 3.03-3.59% and -4.5 to +6.2%, respectively. Analysis of laboratory-made mixtures containing known concentrations of ursolic acid, as quality control samples, gave a mean recovery percentage of 97.8%. Application of the proposed method for the analysis of leaves and twigs extracts of S. holocarpa Hemsl. gave mean percentage contents of ursolic acid of 0.95 and 0.25%, respectively.

Enhanced effects of adriamycin by combination with a new ribonucleotide reductase inhibitor, trimidox, in murine leukemia

Ribonucleotide reductase is the rate limiting enzyme of de novo DNA synthesis; its activity is significantly increased in tumor cells related to the proliferation rate. Therefore the enzyme is considered to be an excellent target for cancer chemotherapy. In the present study we tested the in vitro and in vivo antitumor effects of a drug combination using trimidox (3,4,5-trihydroxybenzamidoxime), a novel inhibitor of ribonucleotide reductase with adriamycin, a widely used anticancer drug. This combination was selected because adriamycin generates free radicals being responsible for cardiotoxic side effects; trimidox has been shown to be a good free radical scavenger. The in vitro cytotoxic effect of the drug combination was examined in L1210 mouse leukemia cells employing a MTT chemosensitivity assay. Incubation of these cells with adriamycin and trimidox together yielded less than additive cytotoxic effects compared to either drug alone. These effects were not caused by the involvement of p-glycoprotein mediated drug efflux. However, when the effect of trimidox and adriamycin in combination was examined in L1210 leukemia bearing mice antitumor effects of adriamycin could be enhanced by the presence of trimidox. Our data indicate, that the in vivo combination of adriamycin together with trimidox might be beneficial for the treatment of malignancies.

Iron binding capacity of trimidox (3,4,5-trihydroxybenzamidoxime), a new inhibitor of the enzyme ribonucleotide reductase

Ribonucleotide reductase is the rate limiting enzyme of deoxynucleoside triphosphate synthesis and is considered to be an excellent target of cancer chemotherapy. Trimidox, a newly synthesized compound, inhibits this enzyme and has in vitro and in vivo antitumour activity. As trimidox was able to upregulate the expression of the transferrin receptor in HL-60 human promyelocytic leukaemia cells, we have now investigated the capability of trimidox to interfere with iron metabolism. We show by photometric and polarographic methods that trimidox is able for form an iron complex. However, its cytotoxic action cannot be circumvented by addition of iron-saturated transferrin or iron-ammonium citrate, indicating that the iron complexing capacity is not responsible for the mechanism of action of this compound. When HL-60, K562 or L1210 leukaemia cells were incubated with the trimidox-iron complex itself, we could observe increases of the 50% growth inhibitory capacity of the complex in comparison with trimidox alone. We conclude that trimidox is able to form an iron complex, but in contrast to other agents, the anticancer activity cannot be contributed to this effect alone. Further studies will have to elucidate the molecular mechanism of action of this new and promising anticancer agent.

Partition of bispyridinium oximes (trimedoxime and K074) administered in therapeutic doses into different parts of the rat brain

The penetration of acetylcholinesterase reactivators (oximes) into the central nervous system is typically restricted by the blood-brain barrier. Although oximes are highly hydrophilic compounds, some contradictory results confirming permeation into the brain exist. The aim of this study is to verify the penetration of oximes through the blood-brain barrier and to detect their levels achieved in different brain regions 60 min after the administration. It was confirmed that oximes are able to penetrate into the brain after injection of therapeutic doses corresponding with 5% of LD(50). The level in whole brain was 0.58% for trimedoxime and 0.85% for the experimental drug oxime K074 as the percentage of their plasma concentration. The highest concentration was found in frontal cortex (trimedoxime 2.27%; oxime K074 0.95%) and lowest in basal ganglia (trimedoxime 0.86%; oxime K074 0.42%). Entry of oximes into the brain is minimal, but some low reactivation effect should be expected. The reactivation potency of oximes might be higher or lower, depending on the real oxime concentration in a given area.

Benzamide Riboside, a Recent Inhibitor of Inosine 5-Monophosphate Dehydrogenase Induces Transferrin Receptors in Cancer Cells

Benzamide riboside, a recently discovered inhibitor of IMP dehydrogenase (IMPDH) exhibits oncolytic activity. IMPDH is the key enzyme of de novo guanylate biosynthesis and was shown to be linked with proliferation. Therefore, IMPDH is a very good target for antitumor therapy. In order to be active, benzamide riboside has to be converted to BAD, an NAD analogue that binds to the NAD site on IMPDH. Inhibition of the enzyme by benzamide riboside selectively inhibits tumor cell growth and induces apoptosis in various human tumor cell lines. In this manuscript we describe the induction of the CD71 transferrin receptor in human promyelocytic leukemia HL-60 cells following treatment with benzamide riboside. The results indicate a possible involvement of the iron metabolism in the action of this new compound. Benzamide riboside might be clinically used in the treatment of leukemia and solid tumors, alone or as part of combination therapy. Since transferrin receptors are overexpressed in certain cancers, such as glioma and colon cancer, a combination therapy that includes benzamide riboside in transferrin-coupled liposomes will not only target cancer cells but also leads to suicidal action because benzamide riboside will upregulate transferrin receptors on cancer cells thereby make it accessible to dose-intensive chemotherapy. We therefore believe that benzamide riboside itself or derivatives of benzamide riboside might become an important addition for the treatment to diseases that are otherwise fatal.

Effects of protein kinase C inhibitor, staurosporine derivative CGP 41 251, on cell cycle, DNA synthesis and drug uptake in neoplastic cell lines.

The protein kinase C inhibitor, staurosporine derivative CGP 41 251, was more efficient than staurosporine in the reversal of decreased anthracycline uptake in the anthracycline-resistant cell subline (A2780/ADR) of ovarian carcinoma. Staurosporine was more efficient than CGP 41 251 in the induction of cytometrically determined DNA fragmentation (cytofluorometric equivalent of apoptosis) in A2780 parental human ovarian carcino-ma cells compared with the drug-resistant A2780/ADR subline and in both human leukemia K-562 cells as well as mouse leukemia L1210 compared with the araC-resistant L1210 cells. Staurosporine was a more potent inhibitor than CGP 41 251 of DNA synthesis in both araC-sensitive and -resistant mouse leukemia L1210 cells. CGP 41 251 was a slightly more efficient inhibitor of thymidlne incorporation than staurosporine in human leukemia K-562 cells and its combination with araC had a higher inhibitory effect on the DNA synthesis in this cell line than staurosporine. CGP 41 251 exerted DNA synthesis inhibitory effects on both araC-sensitive and -resistant L1210 cells. Staurosporine-induced DNA synthesis inhibition in both araC-resistant and -sensitive L1210 mouse leukemia cells was decreased after combined administration with araC.

Antitumor activity of benzamide riboside and its combination with cisplatin and staurosporine

Benzamide riboside (BR), a new synthetic nucleoside analogue, has demonstrated a potent cytotoxic activity in murine leukemia in vitro. The purpose of the present investigation was to examine the antitumor activity of BR in mice bearing leukemia L1210. The results revealed that BR possesses a potent antitumor activity in vivo. It increases life-span of mice with leukemia. Synergistic cytotoxicity of BR with select DNA damaging agents, cisplatin (cis-Pt) and staurosporine (STP) was examined in MTT chemosensitivity assay, FACS analyses and apoptotic DNA fragmentation on L1210 cells in culture. A simultaneous treatment of leukemia L1210 cells with the combination of BR and STP resulted in synergistic cytotoxicity that correlated with increased apoptotic activity in those cells. On the other hand, treatment of L1210 cells with combination of BR and cis-Pt resulted in antagonistic cytotoxic effect. Finally, to elucidate the synergistic effect of BR and STP in inducing apoptosis, the attention was directed to the activation of cell death processes through various cell cycle signals. This is the first report describing in vivo antitumor activity of BR and its utilization in combination chemotherapy.