Betulinic acid purified from Alstonia boonei inhibits folate biosynthesis in malarial Plasmodium, enhances mitochondrial pore opening and F1F0 ATPase in mice

Abstract Activity-guided assay of antimalarial properties of Alstonia boonei led to the purification of betulinic acid from the chloroform fraction of the methanol stem bark extract. The structure and stereochemistry of betulinic acid from A. boonei was established by 1H, 13C, COSY, HMBC, HSQC, LC-MS and DEPT techniques. This compound demonstrated antiplasmodial activities using chloroquine susceptible (NK 65) and resistant (ANKA) strains of Plasmodium berghei. Betulinic acid (BA) opens mitochondrial permeability transition pore (mPT), increased mitochondrial F1F0 ATPase activity, decreased lipid peroxidation and prevented DNA fragmentation. Molecular dynamics simulation studies against falcipain-2, dihydrofolate reductase, dihydropteroate synthase and mitochondrial F1F0 ATPase (F-2-BA, DHFR-BA, DHPS-BA and mATPase-BA, respectively) revealed that betulinic acid (BA) mechanistically disrupted the secondary structure of mATPase (mouse) with RMSD > 2 (RMSD=2.34 A). Binding effects of BA was more prominent on DHFR as evidenced by high structural deviations (RMSD = 2.24 A). However, Falcipain-2 had the least deviation (RMSD = 1.77 A) correlative with the reduced activity of the compound. DHPS, on the other hand, had a mean RMSD value of 1.93 A. The disruption of mATPase could explain the effect of the compound on the opening of mPT as experimentally reported.