Zebrafish-based identification of the antiseizure nucleoside inosine from the marine diatom Skeletonema marinoi

PLoS One. 2018 Apr 24;13(4):e0196195. doi: 10.1371/journal.pone.0196195. eCollection 2018.

Abstract

With the goal of identifying neuroactive secondary metabolites from microalgae, a microscale in vivo zebrafish bioassay for antiseizure activity was used to evaluate bioactivities of the diatom Skeletonema marinoi, which was recently revealed as being a promising source of drug-like small molecules. A freeze-dried culture of S. marinoi was extracted by solvents with increasing polarities (hexane, dichloromethane, methanol and water) and these extracts were screened for anticonvulsant activity using a larval zebrafish epilepsy model with seizures induced by the GABAA antagonist pentylenetetrazole. The methanolic extract of S. marinoi exhibited significant anticonvulsant activity and was chosen for bioassay-guided fractionation, which associated the bioactivity with minor constituents. The key anticonvulsant constituent was identified as the nucleoside inosine, a well-known adenosine receptor agonist with previously reported antiseizure activities in mice and rat epilepsy models, but not reported to date as a bioactive constituent of microalgae. In addition, a UHPLC-HRMS metabolite profiling was used for dereplication of the other constituents of S. marinoi. Structures of the isolated compounds were elucidated by nuclear magnetic resonance and high-resolution spectrometry. These results highlight the potential of zebrafish-based screening and bioassay-guided fractionation to identify neuroactive marine natural products.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anticonvulsants / chemistry
  • Anticonvulsants / isolation & purification
  • Anticonvulsants / therapeutic use*
  • Chemical Fractionation
  • Diatoms / chemistry*
  • Disease Models, Animal
  • Inosine / chemistry
  • Inosine / isolation & purification
  • Inosine / therapeutic use*
  • Magnetic Resonance Spectroscopy
  • Molecular Structure
  • Pentylenetetrazole / adverse effects*
  • Seizures / chemically induced
  • Seizures / drug therapy*
  • Zebrafish

Substances

  • Anticonvulsants
  • Inosine
  • Pentylenetetrazole

Grant support

The research leading to these results was part of the PHARMASEA project (312184) which received funding from the European Union 7th Framework Program. The School of Pharmaceutical Sciences of the University of Geneva (Prof. J-L. Wolfender) is thankful to the Swiss National Science Foundation for the support in the acquisition of the NMR 600 MHz (SNF R’Equip grant 316030_164095). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.