Hybrid PABA-glutamic acid conjugated 1,3,5-triazine derivatives: Design, synthesis, and antimalarial activity screening targeting Plasmodium falciparum dihydro folate reductase enzyme

Despite the successful reduction in the malaria health burden in recent years, it continues to remain a significant global health problem mainly because of the emerging resistance to first-line treatments. Also because of the disruption in malaria prevention services during the COVID-19 pandemic, there was an increase in malaria cases in 2021 compared to 2020. Hence, the present study outlined the in silico study, synthesis, and antimalarial evaluation of 1,3,5-triazine hybrids conjugated with PABA-glutamic acid. Docking study revealed higher binding energy compared to the originally bound ligand WR99210, predominant hydrogen bond interaction, and involvement of key amino acid residues, like Arg122, Ser120, and Arg59. Fourteen compounds were synthesized using traditional and microwave synthesis. The in vitro antimalarial evaluation against chloroquine-sensitive 3D7 and resistant Dd2 strain of Plasmodium falciparum showed a high to moderate activity range. Compounds C1 and B4 showed high efficacy against both strains and a further study revealed that compound C1 is non-cytotoxic against the HEK293 cell line with no acute oral toxicity. In vivo, study was performed for the most potent antimalarial compound C1 to optimize the research work and found to be effectively suppressing parasitemia of Plasmodium berghei strain in the Swiss albino mice model.

Microwave-assisted synthesis of hybrid PABA-1,3,5-triazine derivatives as an antimalarial agent

The present manuscript deals with the development of novel p-aminobenzoic acid (PABA) associated 1,3,5-triazine derivatives as antimalarial agents. The molecules were developed via microwave-assisted synthesis and structures of compounds were ascertained via numerous analytical and spectroscopic techniques. The synthesized compounds were also subjected to ADMET analysis. In a docking analysis, the title compounds showed high and diverse binding affinities towards wild (-162.45 to -369.38 kcal/mol) and quadruple mutant (-165.36 to -209.47 kcal/mol) Pf-DHFR-TS via interacting with Phe58, Arg59, Ser111, Ile112, Phe116. The in vitro antimalarial activity suggested that compounds 4e, 4b, and 4h showed IC₅₀ ranging from 4.18 to 8.66 μg/ml against the chloroquine-sensitive (3D7) strain of Plasmodium falciparum. Moreover, compounds 4g, 4b, 4e, and 4c showed IC₅₀ ranging from 8.12 to 12.09 μg/ml against chloroquine-resistant (Dd2) strain. In conclusion, our study demonstrated the development of hybrid PABA substituted 1,3,5-triazines as a novel class of Pf-DHFR inhibitor for antimalarial drug discovery.

Diarylpyrazole Ligated Dihydropyrimidine Hybrids as Potent Non-Classical Antifolates and Their Efficacy Against Plasmodium falciparum

A series of diarylpyrazole clubbed dihydropyrimidine derivatives (J1-J30) was synthesized under microwave-assisted heating conditions by employing Biginelli reaction methodology and utilizing triethylammonium acetate both as a catalyst and as reaction medium, leading towards a greener reaction pathway. The synthesized entities were screened for their antimalarial efficacy against a Plasmodium falciparum strain in vitro. The active entities (J9, J15, J21, J25, and J27) obtained out of the in vitro screening were further evaluated for their enzyme inhibitory potency against the Pf-DHFR enzyme in vitro as well as in silico using Glide. Furthermore, the active scaffolds were tested for their cytotoxicity against Vero cells, proving their nontoxic behavior and selectivity. The ADME parameters were also evaluated and predicted in silico, indicating good oral bioavailability of the compounds.

Microwave Assisted Synthesis of Pyrimidines in Ionic Liquid and Their Potency as Non-Classical Malarial Antifolates

Synthesis of pyrazole-linked triazolo-pyrimidine hybrids was achieved by employing Biginelli-type reaction methodology in an ionic liquid (triethylammonium acetate) under microwave irradiation. This method proved to be highly efficient and the ionic liquid employed was found recyclable for up to five consecutive cycles. The synthesized molecules were further screened for their antimalarial efficacy screening out the active scaffolds J15, J18, J21, J24, J27, and J30. The active molecules were evaluated in an enzyme inhibition study against the active Plasmodium falciparum dihydrofolate reductase (Pf-DHFR), computationally as well as in vitro, demonstrating their potency as DHFR inhibitors. The active entities were also investigated for their oral bioavailability by predicting ADME properties in silico, indicating good bioavailability.