Synthesis, Antimalarial Activity Evaluation and Molecular Docking Studies of Some New Substituted Spiro-1,2,4,5-Tetraoxane Derivatives

Eight new substituted spiro-1,2,4,5-tetraoxane derivatives were synthesized and characterized by a number of analytical and spectroscopic techniques. The molecules were subsequently screened for in vitro antimalarial activity against chloroquine sensitive (3D7) and chloroquine resistant (RKL-9) strains of Plasmodium falciparum. These substituted spiro-1,2,4,5-tetraoxane derivatives were studied by molecular docking analysis in the active site of Falcipain-2 as a putative protein. Most of the synthesized compounds exhibited moderate to very good activity toward the parasite in comparison to the standard drug, chloroquine. Three compounds showed potent antimalarial activity against chloroquine sensitive strain of P. falciparum (3D7). One compound 5b (3-ethyl-3-methyl-1,2,4,5-tetraoxa-spiro[5.5]undecane) showed a very good activity against both chloroquine sensitive strain (3D7) with MIC = 1.95 +/- 0.06 mu g/mL and IC50 = 1.95 +/- 0.06 mu g/mL compared to chloroquine (MIC = 0.4 +/- 0.10 mu g/mL, IC50 = 0.04 +/- 0.01 mu g/mL) as well as chloroquine-resistant strain of P. falciparum (RKL-9) with MIC = 15.63 +/- 0.70 mu g/mL and IC50 = 3.90 +/- 0.09 mu g/mL compared to chloroquine (MIC = 25.00 +/- 0.20 mu g/mL, IC50 = 0.39 +/- 0.02 mu g/mL). The top scored compounds having low binding energy interact with the active site of Falcipain-2 in molecular docking studies.