Abstract:
The emergence and spread of drug-recalcitrant Plasmodium falciparum parasites threaten to reverse the gains
made in the fight against malaria. Urgent measures need to be taken to curb this impending challenge. The higher
plant-derived sesquiterpene, quinoline alkaloids, and naphthoquinone natural product classes of compounds have
previously served as phenomenal chemical scaffolds from which integral antimalarial drugs were developed. Historical
successes serve as an inspiration for the continued investigation of plant-derived natural products compounds
in search of novel molecular templates from which new antimalarial drugs could be developed. The aim of this study
was to identify potential chemical scaffolds for malaria drug discovery following analysis of historical data on phytochemicals
screened in vitro against P. falciparum. To identify these novel scaffolds, we queried an in-house manually
curated database of plant-derived natural product compounds and their in vitro biological data. Natural products
were assigned to different structural classes using NPClassifier. To identify the most promising chemical scaffolds, we
then correlated natural compound class with bioactivity and other data, namely (i) potency, (ii) resistance index, (iii)
selectivity index and (iv) physicochemical properties. We used an unbiased scoring system to rank the different natural
product classes based on the assessment of their bioactivity data. From this analysis we identified the top-ranked
natural product pathway as the alkaloids. The top three ranked super classes identified were (i) pseudoalkaloids, (ii)
naphthalenes and (iii) tyrosine alkaloids and the top five ranked classes (i) quassinoids (of super class triterpenoids), (ii)
steroidal alkaloids (of super class pseudoalkaloids) (iii) cycloeudesmane sesquiterpenoids (of super class triterpenoids)
(iv) isoquinoline alkaloids (of super class tyrosine alkaloids) and (v) naphthoquinones (of super class naphthalenes).
Launched chemical space of these identified classes of compounds was, by and large, distinct from that of ‘legacy’
antimalarial drugs. Our study was able to identify chemical scaffolds with acceptable biological properties that are
structurally different from current and previously used antimalarial drugs. These molecules have the potential to be
developed into new antimalarial drugs.
