PvD1 defensin, a plant antimicrobial peptide with inhibitory activity against Leishmania amazonensis.

Plant defensins are small cysteine-rich peptides and exhibit antimicrobial activity against a variety of both plant and human pathogens. Despite the broad inhibitory activity that plant defensins exhibit against different micro-organisms, little is known about their activity against protozoa. In a previous study, we isolated a plant defensin named PvD1 from Phaseolus vulgaris (cv. Pérola) seeds, which was seen to be deleterious against different yeast cells and filamentous fungi. It exerted its effects by causing an increase in the endogenous production of ROS (reactive oxygen species) and NO (nitric oxide), plasma membrane permeabilization and the inhibition of medium acidification. In the present study, we investigated whether PvD1 could act against the protozoan Leishmania amazonensis. Our results show that, besides inhibiting the proliferation of L. amazonensis promastigotes, the PvD1 defensin was able to cause cytoplasmic fragmentation, formation of multiple cytoplasmic vacuoles and membrane permeabilization in the cells of this organism. Furthermore, we show, for the first time, that PvD1 defensin was located within the L. amazonensis cells, suggesting the existence of a possible intracellular target.

Highly efficient synthetic iron-dependent nucleases activate both intrinsic and extrinsic apoptotic death pathways in leukemia cancer cells.

The nuclease activity and the cytotoxicity toward human leukemia cancer cells of iron complexes, [Fe(HPClNOL)Cl2]NO3 (1), [Cl(HPClNOL)Fe(µ-O)Fe(HPClNOL)Cl]Cl2·2H2O (2), and [(SO4)(HPClNOL)Fe(µ-O)Fe(HPClNOL)(SO4)]·6H2O (3) (HPClNOL=1-(bis-pyridin-2-ylmethyl-amino)-3-chloropropan-2-ol), were investigated. Each complex was able to promote plasmid DNA cleavage and change the supercoiled form of the plasmid to circular and linear ones. Kinetic data revealed that (1), (2) and (3) increase the rate of DNA hydrolysis about 278, 192 and 339 million-fold, respectively. The activity of the complexes was inhibited by distamycin, indicating that they interact with the minor groove of the DNA. The cytotoxic activity of the complexes toward U937, HL-60, Jukart and THP-1 leukemia cancer cells was studied employing 3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), fluorescence and electronic transmission microscopies, flow cytometry and a cytochrome C release assay. Compound (2) has the highest activity toward cancer cells and is the least toxic for normal ones (i.e. peripheral blood mononuclear cells (PBMCs)). In contrast, compound (1) is the least active toward cancer cells but displays the highest toxicity toward normal cells. Transmission electronic microscopy indicates that cell death shows features typical of apoptotic cells, which was confirmed using the annexin V-FITC/PI (fluorescein isothiocyanate/propidium iodide) assay. Furthermore, our data demonstrate that at an early stage during the treatment with complex (2) mitochondria lose their transmembrane potential, resulting in cytochrome C release. A quantification of caspases 3, 9 (intrinsic apoptosis pathway) and caspase 8 (extrinsic apoptosis pathway) indicated that both the intrinsic (via mitochondria) and extrinsic (via death receptors) pathways are involved in the apoptotic stimuli.

[Study of the effect of thiosemicarbazones against Toxoplasma gondii]. / Étude de l'effet des thiosemicarbazones sur Toxoplasma gondii.

Toxoplasmosis is a neglected disease, with an estimated occurrence of one-third of the population worldwide. Research in medicinal chemistry has for some years been pursuing the development of new drugs against toxoplasmosis, because current treatments cause serious side effects in the patient. The use of thiosemicarbazones as an alternative option for the treatment of various diseases has been published in recent years, due to their, among others, anticancer, antimalarial, antitrypanosomal, antibacterial, and antitoxoplasmosis activities, the latter being the subject of this study, which is based upon biological analyses and tests of the response of Toxoplasma gondii in the presence of thiosemicarbazones.

Synthesis and evaluation of anti-Toxoplasma gondii and antimicrobial activities of thiosemicarbazides, 4-thiazolidinones and 1,3,4-thiadiazoles.

In this work we reported the synthesis and evaluation of anti-Toxoplasma gondii and antimicrobial activities in vitro of three new compound series obtained from ethyl(5-methyl-1-H-imidazole-4-carboxylate): acylthiosemicarbazide analogues 3a-d, 4-thiazolidinone analogues 4a-d and 1,3,4-thiadiazole analogues 5a-d. All synthesized compounds were characterized by IR, (1)H, (13)C NMR and HRMS. The majority of the tested compounds show excellent anti-T. gondii activity when compared to hydroxyurea and sulfadiazine. In addition it was also shown that most of the compounds in this study have a better performance against intracellular tachyzoites. The results for antimicrobial activity evaluation showed weak antibacterial and antifungal activities for all the tested molecules, when compared with the standard drugs (chloramphenicol and rifampicin for antibacterial activity; nistatin and ketoconazole for antifungal activity).

Synthesis, anti-Toxoplasma gondii and antimicrobial activities of benzaldehyde 4-phenyl-3-thiosemicarbazones and 2-[(phenylmethylene)hydrazono]-4-oxo-3-phenyl-5-thiazolidineacetic acids.

In the present communication, a new series of 2-[(phenylmethylene)hydrazono]-4-oxo-3-phenyl-5-thiazolidineacetic acids (2a-p) have been synthesized. Benzaldehyde 4-phenyl-3-thiosemicarbazones substituted (1a-p) were also obtained and used as intermediate to give the title compounds. All synthesized compounds were characterized by IR, (1)H and (13)C NMR. The in vitro anti-Toxoplasma gondii activity of 1a-p and 2a-p was evaluated. The 4-thiazolidinones (2a-p) were screened for their in vitro antimicrobial activity. For anti-Toxoplasma gondii activity, in general, all compounds promoted decreases in the percentage of infected cells leading to parasite elimination. These effects on intracellular parasites also caused a decrease in the mean number of tachyzoites. In addition, most of the 4-thiazolidinones showed more effective toxicity against intracellular parasites, with IC(50) values ranging from 0.05 to 1 mM. According to results of antimicrobial activity, compounds 2f, 2l, and 2p showed best activity against Mycobacterium luteus, 2c was more active against Mycobacterium tuberculosis, and 2g, 2l, and 2n showed same activity as nistatin (standard drug) against Candida sp. (4249).

Synthesis of thiosemicarbazone and 4-thiazolidinone derivatives and their in vitro anti-Toxoplasma gondii activity.

Thiosemicarbazone and 4-thiazolidinone derivatives were synthesized in one and two step, respectively, from thiosemicarbazide, in satisfactory yields. Then, the synthesized compounds were submitted to evaluation against host cells infected with Toxoplasma gondii. The present studies showed that thiosemicarbazones 2 and 4-thiazolidinone derivatives 3 were effective against intracellular T. gondii.