In silico evaluation and in vitro growth inhibition of Plasmodium falciparum by natural amides and synthetic analogs

In vitro anti-parasitic effect of the alkaloids harmaline and piperine on Toxoplasma gondii

Toxoplasma gondii is a coccidian protozoan of zoonotic importance that causes toxoplasmosis. Although the current treatments for toxoplasmosis may be associated with adverse effects and limited efficacy for different biological forms of the parasite, evidence suggests that alkaloid molecules such as harmaline and piperine exhibit antiparasitic effects against protozoa parasites. This investigation aimed to evaluate the in vitro effect of harmaline and piperine against T. gondii tachyzoites in infected Vero cell cultures. After 24 hours of host cell infection, the cultures were treated with harmaline or piperine (0.49 to 15.63 µg/mL). Negative and positive controls were RPMI/DMSO (0.1%) and sulfadiazine (200 µg/mL). Harmaline significantly reduced parasite multiplication by 20% compared to the negative control, while piperine decreased between 55.56% and 88.89% in a dose-dependent manner. According to an intracellular parasite proportion scale, it was observed that the Vero cells with low or moderate parasitic proliferation were more prevalent after the alkaloid treatment. The study demonstrated that the alkaloids had antiparasitic effects on T. gondii, with piperine being the most effective. Additional studies must be carried out to clarify other aspects of the action of the alkaloids on parasites.

Novel Baicalein-Derived Inhibitors of Plasmodium falciparum

Malaria, a life-threatening mosquito-borne disease caused by Plasmodium parasites, continues to pose a significant global health burden. Despite notable progress in combating the disease in recent years, malaria remains prevalent in many regions, particularly in Southeast Asia and most of sub-Saharan Africa, where it claims hundreds of thousands of lives annually. Flavonoids, such as the baicalein class of compounds, are known to have antimalarial properties. In this study, we rationally designed and synthesized a series of baicalein derivatives and identified a lead compound, FNDR-10132, that displayed potent in vitro antimalarial activity against Plasmodium falciparum (P. falciparum), both chloroquine-sensitive (60 nM) and chloroquine-resistant (177 nM) parasites. FNDR-10132 was evaluated for its antimalarial activity in vivo against the chloroquine-resistant strain Plasmodium yoelii N67 in Swiss mice. The oral administration of 100 mg/kg of FNDR-10132 showed 44% parasite suppression on day 4, with a mean survival time of 13.5 ± 2.3 days vs. 8.4 ± 2.3 days of control. Also, FNDR-10132 displayed equivalent activity against the resistant strains of P. falciparum in the 200-300 nM range. This study offers a novel series of antimalarial compounds that could be developed into potent drugs against chloroquine-resistant malarial parasites through further chemistry and DMPK optimization.

Antileishmanial activity evaluation of a natural amide and its synthetic analogs against Leishmania (V.) braziliensis: an integrated approach in vitro and in silico

Leishmaniasis is considered a neglected disease, which makes it an unattractive market for the pharmaceutical industry; hence, efforts in the search for biologically active substances are hampered by this lack of financial motivation. Thus, in the present study, we report the leishmanicidal activity and the possible mechanisms of action of compounds with promising activity against the species Leishmania (V.) braziliensis, the causative agent of the skin disease leishmaniasis. The natural compound 1a (piplartine) and the analog 2a were the most potent against promastigote forms with growth inhibition values for 50% of the parasite population (IC50) = 8.58 and 11.25 μM, respectively. For amastigote forms, the ICa50 values were 1.46 and 16.7 μM, respectively. In the molecular docking study, piplartine showed favorable binding energy (-7.13 kcal/mol) and with 50% inhibition of trypanothione reductase (IC50) = 91.1 μM. Preliminary investigations of the mechanism of action indicate that piplartine increased ROS levels, induced loss of cell membrane integrity, and caused accumulation of lipid bodies after 24 h of incubation at its lowest effective concentration (IC50), which was not observed for the synthetic analog 2a. The mode of action for the leishmanicidal activity of piplartine (1a) was assigned to involve affinity for the trypanothione reductase of Leishmania (V.) braziliensis TR.

In silico studies on stilbenolignan analogues as SARS-CoV-2 Mpro inhibitors

COVID-19, a new strain of coronavirus family, was identified at the end of 2019 in China. The COVID-19 virus spread rapidly all over the world. Scientists strive to find virus-specific antivirals for the treatment of COVID-19. The present study reports a molecular docking study of the stilbenolignans and SARS-CoV-2 main protease (SARS-CoV-2 Mpro) inhibitors. The detailed interactions between the stilbenolignan analogues and SARS-CoV-2 Mpro inhibitors were determined as hydrophobic bonds, hydrogen bonds and electronic bonds, inhibition activity, ligand efficiency, bonding type and distance and etc. The binding energies of the stilbenolignan analogues were obtained from the molecular docking of SARS-CoV-2 Mpro. Lehmbachol D, Maackolin, Gnetucleistol, Gnetifolin F, Gnetofuran A and Aiphanol were found to be -7.7, -8.2, -7.3, -8.5, -8.0 and -7.3 kcal/mol, respectively. Osirus, Molinspiration and SwissADME chemoinformatic tools were used to examine ADMET properties, pharmacokinetic parameters and toxicological characteristics of the stilbenolignan analogues. All analogues obey the Lipinski's rule of five. Furthermore, stilbenolignan analogues were studied to predict their binding affinities against SARS-CoV-2 Mpro using molecular modeling and simulation techniques, and the binding free energy calculations of all complexes were calculated using the molecular mechanics/Poisson-Boltzmann surface area (MM-PBSA) method. With the data presented here it has been observed that these analogues may be a good candidate for SARS-CoV-2 Mpro in vivo studies, so more research can be done on stilbenolignan analogues.