Title:
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The synthesis and development of novel quinolone antimalarials targeting the bc1 protein complex of Plasmodium falciparum
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In recent years investigation of the biological mode of action of the
antimalarial compound atovaquone has validated the Plasmodium falciparum
bC1 protein complex as a target for the development of novel antimalarials.
This project is concerned with the design, synthesis and development of
quinolone based antimalarial compounds targeting the Qo site of the
Plasmodium falciparum bC1 protein complex.
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A small array of quinolone-based compounds, substituted at the 3 and 7
positions, has been developed utilising the Gould-Jacobs methodology. The
synthesised compounds express activity as low as 0.46 nM versus
Plasmodium falciparum malaria parasites in vitro. Activity at the bC1 protein
complex has been confirmed and selectivity for the parasite protein over the
mammalian equivalent has been demonstrated. Poor solubility has been
highlighted as a potential issue; however steps have been taken towards the
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development of carbamate prod rugs with encouraging results.
Docking studies performed in silico, using the crystallised structure of
yeast bC1 protein, demonstrate a key role for residues His181 and Glu272 in
the recognition of high potency inhibitors and have aided in the rationalisation
of the observed biological activities. The orientation of the quinolone group in
the active site and interaction of the inhibitors with the hydrophobic channel
leading to the active site have both been shown to be of significance for
biological potency.
Computer lead design of a new chemotype has resulted in the
development of a second array of quinolone based compounds synthesised
by a divergent method based on the Huisqen 1,3-dipolar cycloaddition.
Docking studies predicted the synthesised compounds to be potent inhibitors
of Plasmodium falciparum bC1. However, in vitro results for the array proved
disappointing, an outcome attributed to a failure to account for membrane
permeability and the physical location of the targeted bC1 protein complex.
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