Phytochemistry of Thai Plants and their Antiprotozoal Activities

Abstract

The in vitro antiprotozoal activities of 12 chloroform extracts from 6 species of Thai
plants were evaluated by three strains of protozoa including Crithidia fasciculata,
Plasmodium falciparum chloroquine sensitive strain (3D7) and chloroquine resistant strain
(K1). Anticrithidial activity of the chloroform extracts was studies by treatment of cultured
promastigotes with various concentrations of the chloroform extracts. Growth inhibition by
the sample was measured by microculture tetrazolium (MTT) assay. The antiplasmodial
activity was determined by using SYBR Green I against the chloroquine-resistance K1 strain
and chloroquine-sensitive strain of Plasmodium falciparum. In each assay, the 50% inhibitory
concentration (IC50) value for each sample was derived by the drug concentration-response
curves.
The results were demonstrated that, the leaf extracts from Aglaia odorata
(Meliaceae) and Azadirachta indica (Meliaceae) showed good active results against all of
selected protozoa. The highest anticrithidial activity was found in leaf extract of Azadirachta
indica (IC50 < 7.8125 μg/ml). While the highest antiplasmodial activity 3D7 strain was found
in leaf extracts of Aglaia odorata and Azadirachta indica (IC50 < 7.8125 μg/ml). It was
shown that the leaf extract of Azadirachta indica (IC50 3.846 μg/ml) gave the highest
antiplasmodial activity in K1 strain. The plant extracts which showed the most and moderate
activities have potential to be developed for antiprotozoal drugs in the future.