Plasmodium transmission blocking activities of Vernonia amygdalina extracts and isolated compounds

Abstract

BackgroundMedicinal plants are a validated source for discovery of new leads and standardized herbal medicines. The aim of this study was to assess the activity of Vernoniaamygdalina leaf extracts and isolated compounds against gametocytes and sporogonic stages of Plasmodiumberghei and to validate the findings on field isolates of Plasmodium falciparum.MethodsAqueous (Ver-H2O) and ethanolic (Ver-EtOH) leaf extracts were tested in vivo for activity against sexual and asexual blood stage P. berghei parasites. In vivo transmission blocking effects of Ver-EtOH and Ver-H2O were estimated by assessing P. berghei oocyst prevalence and density in Anopheles stephensi mosquitoes. Activity targeting early sporogonic stages (ESS), namely gametes, zygotes and ookinetes was assessed in vitro using P. berghei CTRPp.GFP strain. Bioassay guided fractionation was performed to characterize V.amygdalina fractions and molecules for anti-ESS activity. Fractions active against ESS of the murine parasite were tested for ex vivo transmission blocking activity on P.falciparum field isolates. Cytotoxic effects of extracts and isolated compounds vernolide and vernodalol were evaluated on the human cell lines HCT116 and EA.hy926.ResultsVer-H2O reduced the P. berghei macrogametocyte density in mice by about 50% and Ver-EtOH reduced P. berghei oocyst prevalence and density by 27 and 90%, respectively, in An.stephensi mosquitoes. Ver-EtOH inhibited almost completely (>90%) ESS development in vitro at 50 μg/mL. At this concentration, four fractions obtained from the ethylacetate phase of the methanol extract displayed inhibitory activity >90% against ESS. Three tested fractions were also found active against field isolates of the human parasite P. falciparum, reducing oocyst prevalence in Anopheles coluzzii mosquitoes to one-half and oocyst density to one-fourth of controls. The molecules and fractions displayed considerable cytotoxicity on the two tested cell-lines.ConclusionsVernonia amygdalina leaves contain molecules affecting multiple stages of Plasmodium, evidencing its potential for drug discovery. Chemical modification of the identified hit molecules, in particular vernodalol, could generate a library of druggable sesquiterpene lactones. The development of a multistage phytomedicine designed as preventive treatment to complement existing malaria control tools appears a challenging but feasible goal.Electronic supplementary materialThe online version of this article (doi:10.1186/s12936-015-0812-2) contains supplementary material, which is available to authorized users.

Insecticidal activity of Tithonia diversifolia and Vernonia amygdalina

“…Our research showed that methanol extracts of both plant species were equally effective against bruchids whereas earlier work (Mkenda et al 2015a) Furthermore, there is evidence that extracts are useful as antimicrobials (Erasto et al 2006;Orsomando et al 2016) and are toxic to parasitic protozoa (de Toledo et al 2014;Abay et al 2015) which would make them more useful to rural communities, particularly as they are easily cultivated. T. diversifolia is a globally invasive weed (Yang et al 2012) and a particular problem in Africa (Henderson 2007) where its collection and use as a pesticide could help reduce its environmental impacts.…”

Green synthesis and characterization of silver nanoparticles using leaves extracts of neem (<i>Azadirachta indica</i>) and bitter leaf (<i>Vernonia amygdalina</i>)

“…The objective also includes the characterization of the as-synthesized nanoparticles. Both plants are known to be medicinal with various therapeutic benefits (Abay et al, 2015;Asante et al, 2016;Luo et al, 2011;Sinisi et al, 2016;Subarpriya, 2005). The synthesized silver nanoparticles were characterized by UV-Vis spectroscopy, FTIR and powder X-ray diffraction (PXRD).…”

Transmission blocking effects of neem (Azadirachta indica) seed kernel limonoids on Plasmodium berghei early sporogonic development

“…To assess in vitro transmission blocking (TB) activity of fractions and compounds targeted to early sporogonic development, the ookinete development assay (ODA) was employed as described in [19]. .…”

“…Mice with parasitemia around 5% and with mature gametocytes were assessed for microgamete exflagellation. A drop of blood was taken from the mouse tail tip and diluted in exflagellation medium[19]; ookinete medium was prepared by adjusting exflagellation medium to pH 7.4 and by adding 20% heatinactivated fetal bovine serum and 1% penicillin (10.000 U) /streptomycin (10 mg/ml) before use. Blood samples diluted in exflagellation medium (1:25) were placed in hand-made coverslip glass slide chambers and incubated for 20 minutes at 19 °C.…”