In vitro antiplasmodial, cytotoxic and antioxidant effects, and phytochemical constituents of eleven plants used in the traditional treatment of malaria in Akwa Ibom State, Nigeria

Abstract

Purpose: To evaluate the antiplasmodial effects of eleven plants (Bombax buonopozense, Carica papaya, Anthocleista djalonensis, Milicia excelsa, Heterotis rotundifolia, Homalim letestui, Starchystarpheta cayennnensis, Ocimum gratissimum, Cleistopholis patens, Chromolaena odorata and Hippocratea africana) reportedly used in the treatment of malaria in Akwa Ibom State of Nigeria. Methods: Phytochemical analysis was done by standard methods, while in vitro antiplasmodial evaluation was carried out using Plasmodium falciparum chloroquine-sensitive and chloroquineresistant strains using lactate dehydrogenase (pLDH) assay. Cytotoxicity test was undertaken by MTT assay on LLC-MK2 cells and the concentration killing 50 % of the cells (CC50) was calculated. Antioxidant activity of the ethanol extract was evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Results: Milicia excelsa, Heterotis rotundifolia and Chromolaena odorata had moderate antiplasmodial activity. Ocimum gratissimum and Hippocratea africana were weakly active. Milicia excelsa showed a considerable level of cytotoxicity, while Bombax buonopozense exhibited moderate cytotoxicity. Bombax buonopozense (95.3 %) and Ocimum gratissimum (92.0 %) exhibited high DPPH scavenging effect comparable to Vitamin C (98.7 %). There was a significant correlation (p < 0.05) between DPPH inhibition and the total phenolic contents of the eleven plants studied (r2 = 0.6616), between DPPH inhibition and flavonoids (r2 = 0.3553), between antiplasmodial activity and saponin content (r2 = 0.3992), and between the two antiplasmodial evaluation assay methods (r2 = 0.614). Conclusion: The results of this work provide some justification for the use of Milicia excelsa, Heterotis rotundifolia, Chromolaena odorata, Ocimum gratissimum and Hippocratea africana in the treatment of malaria.