Human African Trypanosomiasis (HAT), sleeping sickness, is a protozoan parasitic disease
caused by Trypanosoma brucei. The disease is endemic in regions of sub-Saharan Africa, covering 36 countries with
more than 60 million people at risk. There are only a few drugs that are available
for the treatment of HAT. Current therapies for HAT suffer from severe toxicities
and require intramuscular or intravenous administrations. This situation is further
aggravated due to the emergence of drug resistant variants. There is an urgent need
for new drugs that can be effective orally against both stages of HAT. Natural products
offer an unmatched source for bioactive molecules with new chemotypes. Extracts prepared
from more than 500 plants collected from various parts of the North America were screened
in vitro against blood stage forms of T. brucei. A significantly high number (153) of extracts showed >90% inhibition in proliferation
of trypomastigote forms of T. brucei at 20µg/mL concentration. Active extracts were screened at concentrations ranging
from 10–0.4µg/mL. Eight plant extracts were identified as potent antitrypanosomal
extracts with IC50 values <1µg/mL. Antitrypanosomal activity of these plants extracts was selective
as none of these were significantly active against Leishmania donovani, Plasmodium falciparum or transformed THP1 human macrophage cells. Four additional plant extracts with IC50's of <2 and >1mg/ml also represented new antitrypanosomal leads. Further evaluation
of these extracts is likely to yield new antitrypanosomal drug leads.
