Leishmanicidal Potential of Hardwickiic Acid Isolated From Croton sylvaticus

Justice Afrifa Crentsil; Lauve Rachel Tchokouaha Yamthe; Barbara Zenabu Anibea; Emmanuel Broni; Samuel Kojo Kwofie; John Kweku Amissah Tetteh; Dorcas Osei-Safo

doi:10.3389/fphar.2020.00753

Leishmanicidal Potential of Hardwickiic Acid Isolated From Croton sylvaticus

Front Pharmacol. 2020 May 25:11:753. doi: 10.3389/fphar.2020.00753. eCollection 2020.

Authors

Justice Afrifa Crentsil¹, Lauve Rachel Tchokouaha Yamthe^{2

3

4}, Barbara Zenabu Anibea¹, Emmanuel Broni⁵, Samuel Kojo Kwofie^{5

6

7

8}, John Kweku Amissah Tetteh⁹, Dorcas Osei-Safo¹

Affiliations

¹ Department of Chemistry, School of Physical and Mathematical Sciences, College of Basic and Applied Sciences (CBAS), University of Ghana, Accra, Ghana.
² Institute for Medical Research and Medicinal Plants Studies, Yaoundé, Cameroon.
³ Department of Parasitology, College of Health Sciences, Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana.
⁴ Antimicrobial and Biocontrol Agents Unit, Laboratory for Phytobiochemistry and Medicinal Plants Studies, Faculty of Science, University of Yaoundé I, Yaoundé, Cameroon.
⁵ Department of Biomedical Engineering, School of Engineering Sciences, CBAS, University of Ghana, Accra, Ghana.
⁶ West African Centre for Cell Biology of Infectious Pathogens, Department of Biochemistry, Cell and Molecular Biology, CBAS, University of Ghana, Accra, Ghana.
⁷ Department of Medicine, Loyola University Medical Center, Maywood, IL, United States.
⁸ Department of Physics and Engineering Science, Coastal Carolina University, Conway, SC, United States.
⁹ Department of Immunology, College of Health Sciences, Noguchi Memorial Institute for Medical Research, University of Ghana, Accra, Ghana.

Abstract

Leishmania is a parasitic protozoon responsible for the neglected tropical disease Leishmaniasis. Approximately, 350 million people are susceptible and close to 70,000 death cases globally are reported annually. The lack of effective leishmanicides, the emergence of drug resistance and toxicity concerns necessitate the pursuit for effective antileishmanial drugs. Natural compounds serve as reservoirs for discovering new drugs due to their chemical diversity. Hardwickiic acid (HA) isolated from the stembark of Croton sylvaticus was evaluated for its leishmanicidal potential against Leishmania donovani and L. major promastigotes. The susceptibility of the promastigotes to HA was determined using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide/phenazine methosulfate colorimetric assay with Amphotericin B serving as positive control. HA showed a significant antileishmanial activity on L. donovani promastigotes with an IC₅₀ value of 31.57± 0.06 µM with respect to the control drug, amphotericin B with IC₅₀ of 3.35 ± 0.14 µM). The cytotoxic activity was observed to be CC₅₀ = 247.83 ± 6.32 µM against 29.99 ± 2.82 µM for curcumin, the control, resulting in a selectivity index of SI = 7.85. Molecular modeling, docking and dynamics simulations of selected drug targets corroborated the observed antileishmanial activity of HA. Novel insights into the mechanisms of binding were obtained for trypanothione reductase (TR), pteridine reductase 1 (PTR1), and glutamate cysteine ligase (GCL). The binding affinity of HA to the drug targets LmGCL, LmPTR1, LdTR, LmTR, LdGCL, and LdPTR1 were obtained as -8.0, -7.8, -7.6, -7.5, -7.4 and -7.1 kcal/mol, respectively. The role of Lys16, Ser111, and Arg17 as critical residues required for binding to LdPTR1 was reinforced. HA was predicted as a Caspase-3 stimulant and Caspase-8 stimulant, implying a possible role in apoptosis, which was shown experimentally that HA induced parasite death by loss of membrane integrity. HA was also predicted as antileishmanial molecule corroborating the experimental activity. Therefore, HA is a promising antileishmanial molecule worthy of further development as a biotherapeutic agent.

Keywords: Croton sylvaticus; glutamate cysteine ligase; hardwickiic acid; leishmaniasis; molecular docking; pteridine reductase 1; structural modeling; trypanothione reductase.