Dual-Stage Picolinic Acid-Derived Inhibitors of Toxoplasma gondii

Synthesis and Evaluation of Benzylamine Inhibitors of Neuropathogenic Naegleria fowleri "Brain-Eating" Amoeba

Current therapy for primary amoebic meningoencephalitis (PAM), a highly lethal brain infection in humans caused by Naegleria fowleri amoeba, is restricted to repurposed drugs with limited efficacy and success. Discovery of an antiamoebic benzylamine scaffold 2 precipitated a medicinal chemistry effort to improve potency, cytotoxicity profile, and drug-like properties. Thirty-four compounds were prepared, leading to compound 28 with significant gains in potency (EC50 = 0.92 μM), solubility, and microsomal stability and a demonstrated absence of cytotoxicity in SH-SY5Y human neuroblastoma cells (CC50 > 20 μM). The compounds demonstrated excellent blood-brain barrier permeability in an in vitro assay, thereby providing a new structural scaffold that inhibits N. fowleri viability and permits the investigation of therapeutic interventions in an understudied neglected disease.

Evaluation of Zamia floridana A. DC. Leaves and Its Isolated Secondary Metabolites as Natural Anti-Toxoplasma and Anti-Cancer Agents Using In Vitro and In Silico Studies

Toxoplasmosis and cancer are life-threatening diseases with worldwide distribution. However, currently used chemosynthetic treatments are not devoid of their own intrinsic problems. Natural metabolites are gaining attention due to their lower side effects. In this study, we investigated for the first time Zamia floridana leaves extract and its different fractions for their toxoplasmocidal activity, using Virulent RH Toxoplasma gondii, and cytotoxic activity against MCF-7 and HCT-116 cancer cell lines using MTT assay. The n-butanol fraction was the most potent fraction against T. gondii with an EC50 of 7.16 ± 0.4 µg/mL compared to cotrimoxazole (4.18 ± 0.3 µg/mL). In addition, the n-BuOH fraction showed a significant cytotoxicity against MCF-7 and HCT-116 with IC50 of 12.33 ± 1.1 and 17.88 ± 1.4 µg/mL, respectively, compared to doxorubicin (4.17 ± 0.2 and 5.23 ± 0.3 µg/mL, respectively), with higher safety index against normal cell line (WISH). Therefore, the n-BuOH fraction was investigated for its phytochemicals using extensive chromatographic techniques, which led to the isolation of six compounds that were fully characterized using different spectroscopic techniques. Three biflavonoids (1, 2 and 4) in addition to two phenolic acid derivatives (3 and 5) and a flavonoid glycoside (6) were isolated. Compounds (1, 3, 5 and 6) were reported for the first time from Z. floridana. In silico docking studies for toxoplasmocidal and cytotoxic effects of these compounds revealed that compounds (1, 2, 4 and 6) have promising inhibition potential of either thymidylate synthase-dihydrofolate reductase (TS-DHFR) or cyclin dependent kinase 2 (CDK2) target proteins. This study is considered the first report of chemical and biological investigation of Z. floridana leaves.

Characterization of Glucokinases from Pathogenic Free-Living Amoebae

Infection with pathogenic free-living amoebae, including Naegleria fowleri, Acanthamoeba spp., and Balamuthia mandrillaris, can lead to life-threatening illnesses, primarily because of catastrophic central nervous system involvement. Efficacious treatment options for these infections are lacking, and the mortality rate due to infection is high. Previously, we evaluated the N. fowleri glucokinase (NfGlck) as a potential target for therapeutic intervention, as glucose metabolism is critical for in vitro viability. Here, we extended these studies to the glucokinases from two other pathogenic free-living amoebae, including Acanthamoeba castellanii (AcGlck) and B. mandrillaris (BmGlck). While these enzymes are similar (49.3% identical at the amino acid level), they have distinct kinetic properties that distinguish them from each other. For ATP, AcGlck and BmGlck have apparent Km values of 472.5 and 41.0 μM, while Homo sapiens Glck (HsGlck) has a value of 310 μM. Both parasite enzymes also have a higher apparent affinity for glucose than the human counterpart, with apparent Km values of 45.9 μM (AcGlck) and 124 μM (BmGlck) compared to ~8 mM for HsGlck. Additionally, AcGlck and BmGlck differ from each other and other Glcks in their sensitivity to small molecule inhibitors, suggesting that inhibitors with pan-amoebic activity could be challenging to generate.