Alejandra Gerpe

Pharmacological Properties of Indazole Derivatives: Recent Developments

The chemistry of indazole and its N-oxide derivatives is very well-known. Indazole derivatives were extensively studied as bioactive compounds, such as anti-aggregatory and vasorelaxant activity by NO release and increase of cGMP levels and anticancer effects, antimicrobial and antiparasitic properties, among others. Recently, the research and development in the medicinal chemistry of these systems have produced compounds with contraceptive activities for men, for the treatment of osteoporosis, inflammatory disorders and neurodegenerative diseases. On the other hand, indazole N-oxide derivatives were poorly studied as bioactive compounds, but recently compounds with antiparasitic properties were produced. In this presentation, recent developments in the chemistry and medicinal chemistry of indazole and its N-oxide derivatives will be reviewed.

5-Nitrofuranes and 5-nitrothiophenes with anti-Trypanosoma cruzi activity and ability to accumulate squalene

Chagas disease represents a serious public health problem in South America. The first line of treatment is Nifurtimox and Benznidazole which generate toxic effects in treated patients. We have recently shown that a number of 5-nitrofuranes possess activity against Trypanosoma cruzi through oxidative stress and inhibition of parasite ergosterol biosynthesis, specifically at the level of squalene epoxidase. Here, we identify new 5-nitrofuranes and the thia-analogues with excellent effects on the viability of T. cruzi and adequate parasite/mammal selectivity indexes. Analysis of the free sterols from parasite incubated, during 120h, with the compounds showed that some of them accumulated squalene suggesting the squalene epoxidase activity inhibition of the parasite. Nifurtimox was able to accumulate squalene only at lower incubation times. Due to this fact some derivatives were also tested as antifungal agents. Quantitative structure-activity relationship studies were also performed showing relevant features for further new derivatives design. Taken together, the results obtained in the present work point to a more general effect of 5-nitrofuranes and 5-nitrothiophenes in trypanosomatids, opening potential therapeutic possibilities of them for these infectious diseases.

Study of 5-nitroindazoles' anti-Trypanosoma cruzi mode of action: Electrochemical behaviour and ESR spectroscopic studies

New indazole derivatives have been developed to know about structural requirements for adequate anti-Trypanosoma cruzi activity. In relation to position 1 of indazole ring, we have observed that a butylaminopentyl substituent (14) affords good activity, but N-oxidation of omega-tertiary amino moiety yields completely inactive compounds (17, 18); the substituent at position 3 of indazole ring affects drastically the in vitro activity, 3-OH derivative 13 being completely inactive. On the other hand, since compound 22, denitro-analogue of active compound 4, does not show activity, the 5-nitro substituent of indazole ring seems to be essential. Intramolecular cyclization of side chain at position 1 also affords inactive compounds (19, 20). The electrochemical studies showed that the trypanocidal 5-nitroindazole derivatives yielded nitro-anion radical via one-electron process at physiological pH. This electrochemical behaviour occurs in the parasite according to ESR experiment with the T. cruzi microsomal fraction showing that 5-nitroindazole derivatives suffer bio-reduction without reactive oxygen species generation.

Naftifine-analogues as anti-Trypanosoma cruzi agents.

Chagas disease represents a relevant health problem in Central and South America. The first line of treatment is Nifurtimox and Benznidazole which have a great deal of disadvantages that demands the rapid generation of therapeutic alternatives. Based in our research on aza-thiaheterocycles as anti-Trypanosoma cruzi agents we identified pharmacophores that act through oxidative stress. Here, we describe the synthesis and the activity of new containing bioactive-heterocycles analogues of naftifine as potential T. cruzi membrane sterol biosynthesis inhibitors. Benzimidazole 1,3-dioxides (11 and 13) and quinoxaline 1,4-dioxides (22 and 23) displayed excellent parasite/mammal selectivity indexes. Analysis of the free sterols from parasite incubated with the compounds showed that any of them are able to accumulate squalene suggesting that in the anti-T. cruzi mechanism of action is not involved the inhibition of sterol biosynthesis. Some derivatives were also tested as antifungal agents. The results obtained in the present work open potential therapeutic possibilities of new compounds for these infectious diseases.

New heteroaryl nitrones with spin trap properties: Identification of a 4-furoxanyl derivative with excellent properties to be used in biological systems

A new series of heteroaryl nitrones, 1-7, bearing furoxanyl and thiadiazolyl moieties, were evaluated for their free radical-trapping properties. The physicochemical characterization by electron paramagnetic resonance (EPR) demonstrated its capability to trap and stabilize oxygen-, carbon-, sulfur-, and nitrogen-centered free radicals. The 4-furoxanyl nitrone 3 (FxBN), alpha(Z)-(3-methylfuroxan-4-yl)-N-tert-butylnitrone, showed appropriate solubility in aqueous solution and taking into account that this physicochemical property is very important for biological applications, we studied it deeply in terms of its trapping and kinetic behaviors. For this, kinetic studies of the hydroxyl adduct decay gave rate constants k(ST) of 1.22x10(10)dm(3)mol(-1)s(-1) and half-live up to 7200s at physiological pH, without any artifactual signals. The ability of FxBN to directly traps and stabilizes superoxide free radical, with a half-life of 1620s at physiological pH, was also demonstrated. Besides, FxBN-hydroxyl and -superoxide adducts exhibited distinct and characteristic EPR spectral patterns. Finally, we confirmed the ability of FxBN to act as spin trap in a specific biological system, that is, in the free radical production of experimental anti-trypanosomatid drugs using Trypanosoma cruzi microsomes as biological system. Moreover, previous observations of low FxBN toxicity transform it in a good candidate for in vivo spin trapping.

Development of a HPLC method for the determination of antichagasic phenylethenylbenzofuroxans and its major synthetic secondary products in the chemical production processes.

A simple isocratic reverse-phase HPLC method for the determination of six antichagasic phenylethenylbenzofuroxans and its major synthetic secondary products, the corresponding geometric isomers and the benzofurazans, was developed and validated for use in the analysis of pre-clinical studies. Separation was achieved on a reverse-phase Supelco LC-18 column using either methanol-acetonitrile-water or acetonitrile-water, in different proportions, as mobile phase. The compounds were eluted isocratically at a flow rate of either 0.8 or 1.0 mLmin(-1). The compounds were analyzed with UV detection at 210 and 300 nm. The validation characteristics included linearity, accuracy, precision, specificity, limit of detection and quantification and robustness. Validation acceptance criteria were met in all cases. This method was used successfully for the quality assessment of the drugs production in the scale-up procedures.

Convenient Route to Primary (Z)-Allyl Amines and Homologs

Abstract A convenient two-step procedure for the synthesis of primary (Z)-allyl amines, (Z)-homoallyl amines [(Z)-but-3-enylamines], and (Z)-pent-4-enylamines using the Wittig reaction was achieved. The use of nonstabilized ylides from triphenylphosphonium salt, potassium salt, and apolar solvent produced (Z/E)-geometric isomer ratios generally greater than 1.6. The amine moiety was masked using a phtalimide group that was removed successfully in the last step of the process in two different conditions, NH2NH2/EtOH/rt or CH3NH2/EtOH/rt. However, in some cases, reduction of the C = C double bond in the deprotection with hydrazine was concomitantly observed.