In vitro leishmanicidal activity of imidazole- or pyrazole-based benzo[g]phthalazine derivatives against Leishmania infantum and Leishmania braziliensis species.

OBJECTIVES: To evaluate the in vitro leishmanicidal activity of imidazole-based (1-4) and pyrazole-based (5-6) benzo[g]phthalazine derivatives against Leishmania infantum and Leishmania braziliensis. METHODS: The in vitro activity of compounds 1-6 was assayed on extracellular promastigote and axenic amastigote forms, and on intracellular amastigote forms of the parasites. Infectivity and cytotoxicity tests were performed on J774.2 macrophage cells using meglumine antimoniate (Glucantime) as the reference drug. The mechanisms of action were analysed by iron superoxide dismutase (Fe-SOD) and copper/zinc superoxide dismutase (CuZn-SOD) inhibition, metabolite excretion and transmission electronic microscopy (TEM). RESULTS: Compounds 1-6 were more active and less toxic than meglumine antimoniate. Data on infection rates and amastigote mean numbers showed that 2, 4 and 6 were more active than 1, 3 and 5 in both L. infantum and L. braziliensis. The inhibitory effect of these compounds on the antioxidant enzyme Fe-SOD of promastigote forms of the parasites was remarkable, whereas inhibition of human CuZn-SOD was negligible. The ultrastructural alterations observed in treated promastigote forms confirmed the greater cell damage caused by the most active compounds 2, 4 and 6. The modifications observed by (1)H-NMR in the nature and amounts of catabolites excreted by the parasites after treatment with 1-6 suggested that the catabolic mechanisms could depend on the structure of the side chains linked to the benzo[g]phthalazine moiety. CONCLUSIONS: All the compounds assayed were active in vitro against the two Leishmania species and were less toxic against mammalian cells than the reference drug, but the monosubstituted compounds were significantly more effective and less toxic than their disubstituted counterparts.

Synthesis and cytotoxic activity of a new potential DNA bisintercalator: 1,4-Bis{3-[N-(4-chlorobenzo[g]phthalazin-1-yl)aminopropyl]}piperazine.

The synthesis of new 1,4-bisalkylamino (2-4) and 1-alkylamino-4-chloro (5-6) substituted benzo[g]phthalazines is reported. Compounds 2-4 and 6 were prepared both in the free and heteroaromatic ring protonated forms. Bifunctional 6 contains the 1,4-bisaminopropylpiperazine chain as a linker between the two heteroaromatic units, whereas 5 is its monofunctional analogue. The in vitro antitumour activity of the synthesized compounds has been tested against human colon, breast and lung carcinoma cells, and also against human glioblastoma cells. Results obtained show that all of them are active in all cases, but bifunctional 6.2HCl is remarkably effective against the four cell lines tested, exhibiting IC50 values in the range of 10(-7) M, similar to those found for doxorubicin. The bifunctional structure of 6.2HCl enhances activity with respect to the monofunctional related compounds 5 and 7, leading to the highest activity among all the compounds tested. Molecular modelling of 6 suggests that those results could be indicative of DNA bisintercalation, which should be specially favoured in the diprotonated form 6.2HCl, a compound suitable for being studied more in depth in further biological tests. Measure of the DNA thermal melting curves show that the linear rise in Tm for bifunctional 6.2HCl is nearly twice than that one obtained for monofunctional 5, and supports the DNA-binding hypothesis.

Efficient inhibition of iron superoxide dismutase and of Trypanosoma cruzi growth by benzo[g]phthalazine derivatives functionalized with one or two imidazole rings.

The synthesis and trypanosomatic behavior of a new series of 1,4-bis(alkylamino)benzo[g]phthalazines 1- 4 containing the biologically significant imidazole ring are reported. In vitro antiparasitic activity against Trypanosoma cruzi epimastigotes is remarkable, especially for compound 2, whereas toxicity against Vero cells is very low. Conversion of epimastigotes to metacyclic forms in the presence of the tested compounds causes significant decreases in the amastigote and trypomastigote numbers. Fe-SOD inhibition is noteworthy, whereas effect on human Cu/Zn-SOD is negligible.

Synthesis and evaluation of in vitro and in vivo trypanocidal properties of a new imidazole-containing nitrophthalazine derivative.

A series of new phthalazine derivatives (1-4) containing imidazole rings and functionalized with nitro groups in the benzene ring of the phthalazine moiety were prepared and identified on the basis of their MS, elemental analyses and bidimensional (1)H and (13)C NMR data, and their trypanocidal activity was tested. The 8-nitrosubstituted compound (3) was more active in vitro against Trypanosoma cruzi and less toxic against Vero cells than the reference drug benznidazole, and showed a SI value that was 47-fold better than the reference drug in amastigote forms. It also remarkably reduced the infectivity rate in Vero cells and decreased the reactivation of parasitemia in immunodeficient mice. Ultrastructural alterations found in epimastigotes treated with 3 confirmed extensive cytoplasm destruction in the parasites, whereas histopathological analysis of the hearts of mice infected and treated with 3 resulted in a decrease in cardiac damage. Biochemical markers showed that livers, hearts, and kidneys of treated mice were substantially unaffected by the administration of 3, despite the presence of the potentially toxic nitro group. It was also found that this compound selectively inhibited the antioxidant parasite enzyme Fe-superoxide dismutase (Fe-SOD) in comparison with human CuZn-SOD, and molecular modeling suggested interaction with the H-bonding system of the iron-based moiety as a feasible mechanism of action against the enzyme.

Phthalazine derivatives containing imidazole rings behave as Fe-SOD inhibitors and show remarkable anti-T. cruzi activity in immunodeficient-mouse mode of infection.

A series of new phthalazine derivatives 1-4 containing imidazole rings were prepared. The monoalkylamino substituted derivatives 2 and 4 were more active in vitro against T. cruzi and less toxic against Vero cells than both their disubstituted analogues and the reference drug benznidazole. Compounds 2 and 4 highly inhibited the antioxidant parasite enzyme Fe-SOD, and molecular modeling suggested that they interact with the H-bonding system of the iron atom moiety. In vivo tests on the acute phase of Chagas disease gave parasitemia inhibition values twice those of benznidazole, and a remarkable decrease in the reactivation of parasitemia was found in the chronic phase for immunodeficient mice. Glucose metabolism studies showed that compounds 1-4 did not affect the succinate pathway but originated important changes in the excretion of pyruvate metabolites. The morphological alterations found in epimastigotes treated with 1-4 confirmed extensive cytoplasm damage and a high mortality rate of parasites.

In vitro and in vivo trypanosomicidal activity of pyrazole-containing macrocyclic and macrobicyclic polyamines: their action on acute and chronic phases of Chagas disease.

The in vitro and in vivo anti- Trypanosoma cruzi activity of the pyrazole-containing macrobicyclic polyamine 1 and N-methyl- and N-benzyl-substituted monocyclic polyamines 2 and 3 was studied. Activity against both the acute and chronic phases of Chagas disease was considered. The compounds were more active against the parasite and less toxic against Vero cells than the reference drug benznidazole, but 1 and 2 were especially effective, where cryptand 1 was the most active, particularly in the chronic phase. The activity results found for these compounds were complemented and discussed by considering their inhibitory effect on the iron superoxide dismutase enzyme of the parasite, the nature of the metabolites excreted after treatment, and the ultrastructural alterations produced. A complementary histopathological analysis confirmed that the compounds tested were significantly less toxic to mammals than the reference drug and that 1 and 2 exhibited lower levels of damage than 3.

In vivo trypanosomicidal activity of imidazole- or pyrazole-based benzo[g]phthalazine derivatives against acute and chronic phases of Chagas disease.

The in vivo trypanosomicidal activity of the imidazole-based benzo[g]phthalazine derivatives 1-4 and of the new related pyrazole-based compounds 5 and 6 has been studied in both the acute and chronic phases of Chagas disease. As a rule, compounds 1-6 were more active and less toxic than benznidazole in the two stages of the disease, and the monosubstituted derivatives 2, 4, and 6 were more effective than their disubstituted analogs. Feasible mechanisms of action of compounds 1-6 against the parasite have been explored by considering their inhibitory effect on the Fe-SOD enzyme, the nature of the excreted metabolites and the ultrastructural alterations produced. A complementary histopathological analysis has confirmed that the monosubstituted derivatives are less toxic than the reference drug, with the behavior of the imidazole-based compound 4 being especially noteworthy.

1,4-Bis(alkylamino)benzo[g]phthalazines able to form dinuclear complexes of Cu(II) which as free ligands behave as SOD inhibitors and show efficient in vitro activity against Trypanosoma cruzi.

The synthesis of a new series of 1,4-bis(alkylamino)benzo[g]phthalazines 1-3 is reported, and their ability to form dinuclear complexes with Cu(II) assayed. The geometry of the complexes is dependent on the nature of the electron-donor sites at the sidechains. Compounds 1 and 2, that contain sp3 or sp2 nitrogens at the end of the alkylamino groups, originate monopodal dinuclear complexes which seem to include endogenous OH bridges, and the sidechains seem to actively participate in complexation. However, the substitution of nitrogen by oxygen in 3 leads to a tripodal dinuclear complex in which the sidechains are not involved. The in vitro antiparasitic activity on Trypanosoma cruzi epimastigotes and amastigotes and the SOD activity inhibition have been evaluated for compounds 1-3, and, as expected, 1 and 2 show in all cases relevant results, whereas 3 is always the less active among the three substrates tested.

Synthesis and cytotoxic activity of N,N-bis-(3-[N-(4-chlorobenzo[g]-phthalazin-1-yl)]aminopropyl)-N-methylamine: a new potential DNA bisintercalator.

The synthesis of a new series of mono- and dinuclear 1-alkylamino-4-chlorobenzo[g]phthalazine derivatives 7-10 containing flexible polyaminic chains is reported. It has been achieved by the reaction of 1,4-dichlorobenzo[g]phthalazine with the corresponding polyamines. In vitro antitumoral activity against HT-29 human colon carcinoma cells was evaluated and showed best results for compound 10, in which two heteroaromatic units are linked by a N-methylsubstituted polyaminic chain. Molecular modelling of the complexes of 9 and 10 with DNA strongly suggests the possibility of bisintercalation, and also that the N-methyl group of 10 plays an important role in the formation of a specially stable DNA complex.