The difficulty of developing an efficient
malaria vaccine along
with increasing spread of multidrug resistant strain of Plasmodium falciparum to the available antimalarial
drugs poses the need to discover safe and efficacious antimalarial
drugs to control malaria. An alternative strategy is to synthesize
compounds possessing structures similar to the active natural products
or marketed drugs. Several biologically active natural products and
drugs contain β-carboline moiety. In the present study, few
selected β-carboline derivatives have been synthesized and tested
for their in vitro and in vivo antiplasmodial activity against the
rodent malaria parasite Plasmodium berghei (NK-65). The designed analogs exhibited considerable in vitro antimalarial
activity. Two compounds (1R,3S)-methyl
1-(benzo[d][1,3]dioxol-5-yl)-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole-3-carboxylate (9a) and (1R,3S)-methyl 1-(pyridin-3-yl)-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole-3-carboxylate (9b) were further selected for in vivo studies. Both the lead
compounds (9a and 9b) were observed to be
safe for oral administration. The therapeutic effective dose (ED50) for 9a and 9b were determined
and in the animal model, 9a (at 50 mg/kg dose) exhibited
better activity in terms of parasite clearance and enhancement of
host survival. Biochemical investigations also point toward the safety
of the compound to the hepatic and renal functions of the rodent host.
Further studies are underway to explore its activity alone as well
as in combination therapy with artesunate against the human malaria
parasite P. falciparum.