Selective cytotoxicity and apoptosis induction in glioma cell lines by 5-oxygenated-6,7-methylenedioxycoumarins from Pterocaulon species.

The coumarins 5-methoxy-6,7-methylenedioxycoumarin 1 5-(3-methyl-2-butenyloxy)-6,7-methylenedioxycoumarin 2 and 5-(2,3-dihydroxy-3-methylbutyloxy)-6,7-methylenedioxycoumarin 3 isolated from Pterocaulon species showed significant cytotoxicity against two glioma cells lines. Compound 1 presented IC(50) values of 34.6 µM and 31.6 µM against human (U138-MG) and rat (C6) glioma cells, respectively, and this compound was at least two times more potent than compounds 2 and 3. This result could be explained by the planar conformation adopted by 1 through a non-classical hydrogen bond between a hydrogen of the methoxy and the oxygen of the methylenedioxy groups. Another important finding was that the cytotoxic effect induced by 1 in glioma cells was not observed in organotypic cultures, indicating a selective cytotoxicity for tumor cells.

Validated HPLC method for determination of LASSBio-581, a new heterocyclic N-phenylpiperazine derivative, in rat plasma.

A rapid, simple and accurate high performance liquid chromatography (HPLC) method was developed and validated for the determination of LASSBio-581 (1-[1-(4-chloro-phenyl)-1H-[1,2,3]triazol-4-ylmethyl]-4-phenyl-piperazine) in rat plasma using ketoconazole as internal standard. Plasma samples were deproteinized with methanol. A good chromatographic separation was achieved using a reversed phase C18 column. Mobile phase consisting of sodium dihydrogen phosphate monohydrate (pH 4.5, 0.02 M) and methanol mixture (35:65, v/v) was used at a flow rate of 1.0 ml/min. The eluate was monitored using a UV detector at 248 nm. The retention times of LASSBio-581 and the internal standard were approximately 3.8 and 5.6 min, respectively. The calibration curves were linear over the concentration range of 0.25-8.0 microg/ml with correlation coefficients >0.99. The limit of quantitation was 0.25 microg/ml. The accuracy of the method was >90%. The intra-day relative standard deviation (R.S.D.) ranged from 6.15 to 10.52% at 0.4 microg/ml, 7.44 to 13.81% at 1.5 microg/ml and 6.10 to 13.94% at 6.0 microg/ml. The inter-day R.S.D. were 9.54, 8.42 and 8.25% at 0.4, 1.5 and 6.0 microg/ml, respectively. No interference from endogenous substances or metabolites were observed. The method has been used to measure plasma concentrations of LASSBio-581 in pharmacokinetic studies in rats.

Ofloxacin/beta-cyclodextrin complexation.

Ofloxacin (OFX) is a fluorquinolone characterized by photochemical instability. With the goal to improve its photostability in aqueous solutions, the complexation of ofloxacin with beta-cyclodextrin was investigated. The complexes showed a water solubility enhancement of approximately 2.6 times; nevertheless, the photodegradation of ofloxacin was not reduced. The complexes obtained were characterized by thermal and 1H nuclear magnetic resonance (NMR) analysis, which revealed an interaction between ofloxacin and beta-cyclodextrin. The last analysis indicated that only partial inclusion of the N-methylpiperazinyl moiety occurred, which can explain the fact that photostabilization was not improved. This partial inclusion phenomenon could be explained also by computer-aided molecular modeling.

Inhibition of tumor growth and polyamine uptake by tetracyclic amidines bearing a putrescine moiety.

Tetracyclic amidines (tetrahydroquino[4.3-b][l]benzazepine: compound 11 and tetrahydrobenzo[k]naphthyridine: compound 12) bearing a putrescine moiety possess significant DNA-binding affinity. We report here that these compounds and their a and b isomers inhibit tumor cell growth and putrescine uptake in 3LL carcinoma cells in vitro. Moreover, compound 11 reduced by 50% the accumulation of putrescine in intestinal brush border membrane vesicles. In CHO-MG, a cell line deficient for the specific polyamine uptake system, the cytotoxicity of these compounds was significantly reduced compared to the CHO wild cell line. The IC50 for CHO-MG was significantly higher than for CHO, demonstrating that the polyamine transport system increased the efficacy of these compounds. The efficacy of compounds 11 and 12 might therefore be related to their ability to interact with DNA as well as their structural analogy with polyamines. Moreover, we clearly show that DFMO enhances the efficacy of these tetracyclic amidines in vivo. Potential mechanisms include: a) lower intracellular polyamine levels reduces polyamine DNA-stabilizing functions, increasing accessibility for DNA-binding drugs; b) DFMO enhances the polyamine uptake system in tumor cells, increasing the entry of tetracyclic amidines bearing a putrescine moiety as well as their accessibility to final DNA-binding sites. The fact that natural polyamine uptake is reduced by the same compounds constitutes an additive mechanism for antitumoral efficiency.