New antimalarial agents derived from nonlinear phenoxazine ring system

  • Mercy A. EzeokonkwoEmail author
  • Sunday N. Okafor
  • Onyinyechi N. Ogbonna
  • Efeturi A. Onoabedje
  • Fidelia N. Ibeanu
  • Evelyn U. Godwin-Nwakwasi
  • Benjamin E. Ezema
Original Research


In vivo antimalarial screening of nine nonlinear phenoxazine compounds was carried out on the blood stages of Plasmodium berghei using standard methods. The activities of the compounds were compared with that of quinine as a standard antimalarial drug. LD50 and histopathological studies were also done. Molecular docking studies were carried out on four different protein targets of Plasmodium spp. The effects of these compounds on the hematological parameters (Hemoglobin, Hb; packed cell volume, PCV; white blood cells, WBC; and red blood cells, RBC) were also evaluated. The in vivo antimalarial studies showed that all the synthesized compounds had significant parasitaemia load reduction (89.00–94.05%) at 200 mg/ml when compared with the control, with (2-aminophenoxyl)benzo[a]phenoxazin-5-one 3b showing the highest activity. There was no significant difference in the activities of these compounds compared with the standard drug used (96%). The LD50 was found to be ≥5000 mg/kg. Histopathological studies showed a significant restoration of the liver intoxicated with malaria parasite after 5 days. The hematological analysis showed normal values for Hb, PCV, WBC, and RBC in the course of the treatment. The compounds showed more binding affinities for the P. falciparum receptors than the standard drug. The nine synthesized nonliner phenoxazine compounds had significant antimalarial activities and did not significantly affect the hematological parameters. They showed strong binding affinity to the parasite receptors. Hence, they are good candidates for antimalarial drugs. More preclinical investigations are needed.


Nonlinear phenoxazine Plasmodium spp Binding affinity Molecular docking Antimalarial Parasitaemia 



lactate dehydrogenase


plasmepsin I


plasmepsin II


plasmepsin IV


standard drug


molecular weight


number of rotatable bonds


partition coefficient


number of hydrogen bond acceptors


number of hydrogen bond donors


number of violation


total polar surface area


normal control


no parasitaemia


untreated group




packed cell volume


red blood cell


white blood cell



The authors are grateful to the faculty of Veterinary Medicine Department of University of Nigeria, Nsukka for providing the malaria parasite—Plasmodium berghei used in the study.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conlict of interest.

Ethics approval

The ethical clearance to use rats was in accordance with the University of Nigeria Ethics Committee on the use of laboratory animals, registered by the National Health Research Ethics Committee (NHREC) of Nigeria, with the number; NHREC/05/01/2008B.


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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  • Mercy A. Ezeokonkwo
    • 1
    Email author
  • Sunday N. Okafor
    • 2
  • Onyinyechi N. Ogbonna
    • 3
  • Efeturi A. Onoabedje
    • 1
  • Fidelia N. Ibeanu
    • 4
  • Evelyn U. Godwin-Nwakwasi
    • 5
  • Benjamin E. Ezema
    • 1
  1. 1.Department of Pure and Industrial ChemistryUniversity of NigeriaNsukkaNigeria
  2. 2.Department of Pharmaceutical and Medicinal ChemistryUniversity of NigeriaNsukkaNigeria
  3. 3.Evangel UniversityAkaezeNigeria
  4. 4.Natural Science Unit, School of General StudiesUniversity of NigeriaNsukkaNigeria
  5. 5.Department of ChemistryGregory UniversityUturuNigeria

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