title: Plasmodium transmission blocking activities of Vernonia amygdalina extracts and isolated compounds.
abstract: BACKGROUND
  Medicinal 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 Vernonia amygdalina leaf extracts and isolated compounds against gametocytes and sporogonic stages of Plasmodium berghei and to validate the findings on field isolates of Plasmodium falciparum.
  
  
  METHODS
  Aqueous (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.
  
  
  RESULTS
  Ver-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.
  
  
  CONCLUSIONS
  Vernonia 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.
authors.affiliation: School of Pharmacy, University of Camerino, Piazza dei Costanti, 62032, Camerino, MC, Italy. solomonabay@gmail.com.|School of Medicine, College of Health Sciences, Addis Ababa University, Addis Ababa, Ethiopia. solomonabay@gmail.com.
authors.forename: Solomon M
authors.initials: SM
authors.lastname: Abay
authors.affiliation: School of Pharmacy, University of Camerino, Piazza dei Costanti, 62032, Camerino, MC, Italy. l.lucantoni@griffith.edu.au.|Discovery Biology, Eskitis Institute for Drug Discovery, Griffith University, Nathan, QLD, 4111, Australia. l.lucantoni@griffith.edu.au.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Lucantoni
authors.affiliation: School of Pharmacy, University of Camerino, Piazza dei Costanti, 62032, Camerino, MC, Italy. nisha.dahiya@unicam.it.
authors.forename: Nisha
authors.initials: N
authors.lastname: Dahiya
authors.affiliation: School of Pharmacy, University of Camerino, Piazza dei Costanti, 62032, Camerino, MC, Italy. gemeurge@yahoo.com.
authors.forename: Geme
authors.initials: G
authors.lastname: Dori
authors.affiliation: School of Pharmacy, University of Camerino, Piazza dei Costanti, 62032, Camerino, MC, Italy. edembo@gmail.com.
authors.forename: Edson G
authors.initials: EG
authors.lastname: Dembo
authors.affiliation: School of Pharmacy, University of Camerino, Piazza dei Costanti, 62032, Camerino, MC, Italy. fulvio.esposito@unicam.it.
authors.forename: Fulvio
authors.initials: F
authors.lastname: Esposito
authors.affiliation: School of Pharmacy, University of Camerino, Piazza dei Costanti, 62032, Camerino, MC, Italy. giulio.lupidi@unicam.it.
authors.forename: Guilio
authors.initials: G
authors.lastname: Lupidi
authors.affiliation: School of Pharmacy, University of Camerino, Piazza dei Costanti, 62032, Camerino, MC, Italy. ogboijb@yahoo.com.
authors.forename: Sonny
authors.initials: S
authors.lastname: Ogboi
authors.affiliation: School of Pharmacy, University of Camerino, Piazza dei Costanti, 62032, Camerino, MC, Italy. oued.kossivi.robert@gmail.com.|Institut de Recherche enSciences de la Santé, Direction Régionale de l'Ouest, Bobo-Dioulasso, Burkina Faso. oued.kossivi.robert@gmail.com.
authors.forename: Robert K
authors.initials: RK
authors.lastname: Ouédraogo
authors.affiliation: Department of Pharmacy, University of Naples Federico II, Via Montesano 49, 80131, Naples, Italy. annamaria.sinisi@unina.it.
authors.forename: Annamaria
authors.initials: A
authors.lastname: Sinisi
authors.affiliation: Department of Pharmacy, University of Naples Federico II, Via Montesano 49, 80131, Naples, Italy. scatagli@unina.it.
authors.forename: Orazio
authors.initials: O
authors.lastname: Taglialatela-Scafati
authors.affiliation: Institut de Recherche enSciences de la Santé, Direction Régionale de l'Ouest, Bobo-Dioulasso, Burkina Faso. yrserge@yahoo.fr.
authors.forename: R Serge
authors.initials: RS
authors.lastname: Yerbanga
authors.affiliation: School of Pharmacy, University of Camerino, Piazza dei Costanti, 62032, Camerino, MC, Italy. massimo.bramucci@unicam.it.
authors.forename: Massimo
authors.initials: M
authors.lastname: Bramucci
authors.affiliation: School of Pharmacy, University of Camerino, Piazza dei Costanti, 62032, Camerino, MC, Italy. luana.quassinti@unicam.it.
authors.forename: Luana
authors.initials: L
authors.lastname: Quassinti
authors.affiliation: Institut de Recherche enSciences de la Santé, Direction Régionale de l'Ouest, Bobo-Dioulasso, Burkina Faso. jbouedraogo@gmail.com.
authors.forename: Jean Bosco
authors.initials: JB
authors.lastname: Ouédraogo
authors.affiliation: Department of Life Sciences, Imperial College London, London, UK. g.christophides@imperial.ac.uk.
authors.forename: George
authors.initials: G
authors.lastname: Christophides
authors.affiliation: School of Pharmacy, University of Camerino, Piazza dei Costanti, 62032, Camerino, MC, Italy. annette.habluetzel@unicam.it.
authors.forename: Annette
authors.initials: A
authors.lastname: Habluetzel
mesh_terms: D000818:Animals; D000852:Anopheles / Q000469:parasitology; D000962:Antimalarials / Q000494:pharmacology* / Q000627:therapeutic use / Q000633:toxicity; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D005260:Female; D006801:Humans; D008288:Malaria / Q000188:drug therapy / Q000469:parasitology / Q000517:prevention & control / Q000635:transmission*; D008297:Male; D051379:Mice; D010936:Plant Extracts / Q000494:pharmacology* / Q000627:therapeutic use / Q000633:toxicity; D010962:Plasmodium berghei / Q000187:drug effects*; D035741:Vernonia / Q000737:chemistry*
chemical_list: D000962:Antimalarials; D010936:Plant Extracts