In vitro antiprotozoan activity and mechanisms of action of selected Ghanaian medicinal plants against Trypanosoma, Leishmania, and Plasmodium parasites

Abstract

Trypanosomiasis, leishmaniasis, and malaria are protozoan infections of public health importance with thousands of new cases recorded annually. Control of these infection(s) with existing chemotherapy is limited by drug toxicity, lengthy parenteral treatment, affordability, and/or the emergence of resistant strains. Medicinal plants on the other hand are used in the treatment of various infectious diseases although their chemical properties are not fully evaluated. In this study, we screened 112 crude extracts from 72 selected Ghanaian medicinal plants for anti-Trypanosoma, anti-Leishmania, and anti-Plasmodium activities in vitro and investigated their mechanisms of action. Twenty-three extracts from 20 plants showed significant antiprotozoan activity against at least 1 of 3 protozoan parasites screened with IC values less than 20 μg/ml. Eleven extracts showed high anti-Trypanosoma activity with Bidens pilosa whole plant and Morinda lucida leaf extracts recording the highest activities. Their IC (selectivity index [SI]) values were 5.51 μg/ml (35.00) and 5.96 μg/ml (13.09), respectively. Nine extracts had high anti-Leishmania activity with Annona senegalensis and Cassia alata leaf extracts as the most active. Their IC (SI) values were 10.8 μg/ml (1.50) and 10.1 μg/ml (0.37), respectively. Six extracts had high anti-Plasmodium activity with the leaf and stem-bark extracts of Terminalia ivorensis recording the highest activity. Their IC (SI) values were 7.26 μg/ml (129.36) and 17.45 μg/ml (17.17), respectively. Only M. lucida at 25 μg/ml induced significant apoptosis-like cell death in Trypanosoma parasites. Anti-Leishmania active extracts induced varying morphological changes in Leishmania parasites such as multiple nuclei and/or kinetoplast, incomplete flagella division, or nuclear fragmentation. Active extracts may be potential sources for developing new chemotherapy against these infections.

Terminalia albida treatment improves survival in experimental cerebral malaria through reactive oxygen species scavenging and anti-inflammatory properties

“…Terminalia species are rich sources of secondary metabolites including cyclic triterpenes and their derivatives, and polyphenols (flavonoids, phenolic acids and tannins). Several Terminalia extracts or fractions have been tested for their anti- Plasmodium activities [34–42] but most of these studies lack chemical characterization of the studied extracts, except Muganga et al [36] who isolated the active compounds, through a bioguided fractionation [36]. Among all the compounds isolated, ellagic acid, already know to have a strong anti-malarial activity (IC50 between 90 and 175 ng/mL) [43], was found to be the main antiplasmodial compound (IC 50 = 0.175 μg/mL) in Terminalia mollins , while ellagic acid derivatives were inactive, suggesting the crucial role of the free hydroxyl groups in antiplasmodial activity.…”

Antileishmanial activity of Annona species (Annonaceae)

“…The hydroalcoholic leaf extract of A. glabra was active against L. amazonensis promastigotes (IC 50 : 37.8 ± 0.1 µg/ mL) [17]. The extracts obtained from the leaves and branches of A. senegalensis also showed activity against another strain of Leishmania (L. donovani; IC 50 10.8 µg/mL and 27.8 µg/mL respectively) [18]. However, the two samples were moderately cytotoxic for human T-cell of acute leukemia (JURKAT; CC 50 : 273.49 µg/mL and 127.95 µg/mL respectively) [18] and the leaf extract showed best selectivity index (SI: 25.3; Table 1).…”

Anti-amebic effects of Chinese rhubarb (Rheum palmatum) leaves' extract, the anthraquinone rhein and related compounds

“…Several studies have reported antiparasitic effects of natural and isolated/synthetic anthraquinones on diverse pathogenic unicellular eukaryotes (Leishmania donovani, L. major, Plasmodium falciparum, Trypanosoma brucei), but the mechanism of action remains speculative [31,32,33,34,35,36]. When interacting with the cellular chemistry of the pathogen, these compounds seem to generate free oxygen metabolites (which are toxic), alter DNA replication/repair enzymes, or cause direct damage on the DNA [31,32,33,34,35,36].…”