Persea americana seeds are widely used in traditional Mexican medicine to treat rheumatism, asthma, infectious processes as well as diarrhea and dysentery caused by intestinal parasites. The chloroformic and ethanolic extracts of P. americana seeds were prepared by maceration and their amoebicidal, giardicidal and trichomonicidal activity was evaluated. These extracts were also tested against Mycobacterium tuberculosis H37Rv, four mono-resistant and two multidrug resistant strains of M. tuberculosis as well as five non tuberculosis mycobacterium strains by MABA assay. The chloroformic and ethanolic extracts of P. americana seeds showed significant activity against E. histolytica, G. lamblia and T. vaginalis (IC50 <0.634 μg/ml). The chloroformic extract inhibited the growth of M. tuberculosis H37Rv, M. tuberculosis MDR SIN 4 isolate, three M. tuberculosis H37Rv mono-resistant reference strains and four non tuberculosis mycobacteria (M. fortuitum, M. avium, M. smegmatis and M. absessus) showing MIC values ≤50 μg/ml. Contrariwise, the ethanolic extract affected only the growth of two mono-resistant strains of M. tuberculosis H37Rv and M. smegmatis (MIC ≤50 μg/ml). The CHCl3 and EtOH seed extracts from P. americana showed amoebicidal and giardicidal activity. Importantly, the CHCl3 extract inhibited the growth of a MDR M. tuberculosis isolate and three out of four mono-resistant reference strains of M. tuberculosis H37Rv, showing a MIC = 50 μg/ml. This extract was also active against the NTM strains, M. fortuitum, M. avium, M. smegmatis and M. abscessus, with MIC values <50 μg/ml.

Indazole is considered a very important scaffold in medicinal chemistry. It is commonly found in compounds with diverse biological activities, e.g., antimicrobial and anti-inflammatory agents. Considering that infectious diseases are associated to an inflammatory response, we designed a set of 2H-indazole derivatives by hybridization of cyclic systems commonly found in antimicrobial and anti-inflammatory compounds. The derivatives were synthesized and tested against selected intestinal and vaginal pathogens, including the protozoa Giardia intestinalis, Entamoeba histolytica, and Trichomonas vaginalis; the bacteria Escherichia coli and Salmonella enterica serovar Typhi; and the yeasts Candida albicans and Candida glabrata. Biological evaluations revealed that synthesized compounds have antiprotozoal activity and, in most cases, are more potent than the reference drug metronidazole, e.g., compound 18 is 12.8 times more active than metronidazole against G. intestinalis. Furthermore, two 2,3-diphenyl-2H-indazole derivatives (18 and 23) showed in vitro growth inhibition against Candida albicans and Candida glabrata. In addition to their antimicrobial activity, the anti-inflammatory potential for selected compounds was evaluated in silico and in vitro against human cyclooxygenase-2 (COX-2). The results showed that compounds 18, 21, 23, and 26 display in vitro inhibitory activity against COX-2, whereas docking calculations suggest a similar binding mode as compared to rofecoxib, the crystallographic reference.

Protease secretion by Giardia duodenalis trophozoites upon interaction with epithelial cells and its association with the parasite adhesion was studied in co-cultures of parasites with IEC6 epithelial cell monolayers in the presence or absence of protease inhibitors. Proteolytic activity in supernatants from trophozoites was enhanced when they were co-cultured with IEC6 cells. This activity was strongly inhibited by pre-incubation of live trophozoites with E-64 and TPCK and a concomitant inhibition of parasite adhesion to IEC6 cells was observed. These data suggest that trophozoites secrete cysteine-type proteases that play a role in the adhesion of G. duodenalis to epithelial cells.

Chagas disease, caused by the parasite Trypanosoma cruzi, affects millions of people in South America. The current treatments are limited, have severe side effects, and are only partially effective. Drug repositioning, defined as finding new indications for already approved drugs, has the potential to provide new therapeutic options for Chagas. In this work, we conducted a structure-based drug repositioning approach with over 130,000 3D protein structures to identify drugs that bind therapeutic Chagas targets and thus represent potential new Chagas treatments. The screening yielded over 500 molecules as hits, out of which 38 drugs were prioritized following a rigorous filtering process. About half of the latter were already known to have trypanocidal activity, while the others are novel to Chagas disease. Three of the new drug candidates—ciprofloxacin, naproxen, and folic acid—showed a growth inhibitory activity in the micromolar range when tested ex vivo on T. cruzi trypomastigotes, validating the prediction. We show that our drug repositioning approach is able to pinpoint relevant drug candidates at a fraction of the time and cost of a conventional screening. Furthermore, our results demonstrate the power and potential of structure-based drug repositioning in the context of neglected tropical diseases where the pharmaceutical industry has little financial interest in the development of new drugs.

Leishmanicidal drugs have many side effects, and drug resistance to all of them has been documented. Therefore, the development of new drugs and the identification of novel therapeutic targets are urgently needed. Leishmania mexicana trypanothione reductase (LmTR), a NADPH-dependent flavoprotein oxidoreductase important to thiol metabolism, is essential for parasite viability. Its absence in the mammalian host makes this enzyme an attractive target for the development of new anti-Leishmania drugs. Herein, a tridimensional model of LmTR was constructed and the molecular docking of 20 molecules from a ZINC database was performed. Five compounds (ZINC04684558, ZINC09642432, ZINC12151998, ZINC14970552, and ZINC11841871) were selected (docking scores −10.27 kcal/mol to −5.29 kcal/mol and structurally different) and evaluated against recombinant LmTR (rLmTR) and L. mexicana promastigote. Additionally, molecular dynamics simulation of LmTR-selected compound complexes was achieved. The five selected compounds inhibited rLmTR activity in the range of 32.9% to 40.1%. The binding of selected compounds to LmTR involving different hydrogen bonds with distinct residues of the molecule monomers A and B is described. Compound ZINC12151998 (docking score −10.27 kcal/mol) inhibited 32.9% the enzyme activity (100 µM) and showed the highest leishmanicidal activity (IC₅₀ = 58 µM) of all the selected compounds. It was more active than glucantime, and although its half-maximal cytotoxicity concentration (CC₅₀ = 53 µM) was higher than that of the other four compounds, it was less cytotoxic than amphotericin B. Therefore, compound ZINC12151998 provides a promising starting point for a hit-to-lead process in our search for new anti-Leishmania drugs that are more potent and less cytotoxic.