Roseoflavin, a natural riboflavin analogue, possesses in vitro and in vivo antiplasmodial activity

The ability of the human malaria parasite Plasmodium falciparum to access and utilise vital nutrients is critical to its growth and proliferation. Molecules that interfere with these process could potentially serve as antimalarials. We found that two riboflavin analogues, roseoflavin and 8-aminoriboflavin, inhibit malaria parasite proliferation by targeting riboflavin metabolism and/or the utilisation of the riboflavin metabolites flavin mononucleotide and flavin adenine dinucleotide. An additional eight riboflavin analogues were evaluated, but none were found to be more potent than roseoflavin, nor was their activity on target. Focussing on roseoflavin, we tested its antimalarial activity in vivo against Plasmodium vinckei vinckei in mice. We found that roseoflavin decreased the parasitemia by 46-fold following a 4 day suppression test and, on average, increased the survival of mice by 4-5 days. Our data are consistent with riboflavin metabolism and/or the utilisation of riboflavin-derived cofactors being viable drug targets for the development of new antimalarials and that roseoflavin could serve as a potential starting point.