Abstract
The global burdens of trypanosomiasis, malaria and leishmaniasis have continued to impoverish the developing countries. These protozoan parasitic diseases are still endemic in sub-Saharan Africa; and drug resistance and toxicities have further aggravated this situation. The aim of the study is to validate some folkloric claims on the uses of the selected plants in ethnomedicine in Nigeria. The study selected eight plants based on their use in the management of parasitic protozoan diseases and evaluated their antiprotozoal as well as cytotoxic activities. The methanol extracts of the plants were tested for in-vitro activities against Trypanosoma brucei rhodesiense (Tbr), Trypanosoma cruzi (Tcr), Leishmania donovani (Ldon) and Plasmodium falciparium as well as mammalian skeletal L6 myoblast for cytotoxicity. The results showed moderate to low in-vitro antiprotozoal and cytotoxic activities. Aspilia africana (IC50 8.15 ?g/mL) and Caesalpinia pulcherrima (IC50, 3.98 ?g/mL) showed significant in-vitro anti-Tbr activity with selectivity indices of 6 and 9.7 respectively. C. pulcherrima (IC50: 12.14 ?g/mL, Ldon; 14.0, Pfc), Dissotis rontundifolia (IC50: 18.45 ?g/mL, Tbr), Ficus glumosa flower (IC50: 16.05 ?g/mL, Tbr), Morinda morindiodes (IC50: 13.46 ?g/mL, Tbr), Senna alata (IC50: 10.51 ?g/mL, Tbr; 18.07 ?g/mL, Ldon) and Sphenocentrum jollyannum (IC50: 11.53 ?gmL, Tbr; 18.30 ?g/mL, Ldon; 13.26 ?g/mL, Pfc) showed moderate activities. Further separation of C. pulcherrima extract resulted in improved antileishmanial (IC50, SI: 4.57 ?g/mL, 4.6) and antiplasmodial (IC50, SI: 3.80 ?g/mL, 5.6) activities. This study has shown that some plants used in folk medicine in Nigeria could be potential sources of lead compounds for parasitic infection.
Highlights
The importance of plants as a source of new chemical entities in drug discovery can never be overemphasized
Moderate to low antiprotozoal activities were observed in extracts with IC50 < 20 μg/mL which included C. pulcherrima (Ldon and Pfc), D. rotundifolia (Tbr), F. glumosa fruits (Tbr), M. morindiodes (Tbr), S. alata (Tbr and Leishmania donovani (Ldon)) and S. jollyannum (Tbr, Ldon and Pfc)
Our study showed that A. aspilia, S. alata, F. glumosa and B. buonopozense elicited low in-vitro antiplasmodial activity (IC50 > 20); M. morindiodes was inactive (IC50 > 50) while S. jollyannum showed moderate antiplasmodial activity (10 < IC50 < 20)
Summary
The importance of plants as a source of new chemical entities in drug discovery can never be overemphasized. Plant-based natural products are still an important lead to the discovery and design of new biologically active molecules.[1] Over 51 % of new small molecule drugs (molecular weight < 500) are natural compounds; natural products derived or inspired by structures of active natural compounds and have yet to be minded from many plants, marine environments, microbial world, toxins, venoms and animals.[1] Rural dwellers still rely on folk medicines for the treatment of infectious diseases. The claimed safety and efficacy need to be validated. It is, necessary to scientifically validate the potential use of folk medicines for the treatment of parasitic infections, which plants present a good alterna-
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