High-Throughput Screening of a Marine Compound Library Identifies Anti-Cryptosporidium Activity of Leiodolide A

Rachel M. Bone Relat, Priscilla L. Winder, Gregory D. Bowden, Esther A. Guzmán, Tara A. Peterson, Shirley A. Pomponi, Jill C. Roberts, Amy E. Wright, Roberta M. O’connor

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Cryptosporidium sp. are apicomplexan parasites that cause significant morbidity and possible mortality in humans and valuable livestock. There are no drugs on the market that are effective in the population most severely affected by this parasite. This study is the first highthroughput screen for potent anti-Cryptosporidium natural products sourced from a unique marine compound library. The Harbor Branch Oceanographic Institute at Florida Atlantic University has a collection of diverse marine organisms some of which have been subjected to medium pressure liquid chromatography to create an enriched fraction library. Numerous active compounds have been discovered from this library, but it has not been tested against Cryptosporidium parvum. A highthroughput in vitro growth inhibition assay was used to test 3764 fractions in the library, leading to the identification of 23 fractions that potently inhibited the growth of Cryptosporidium parvum. Bioassay guided fractionation of active fractions from a deep-sea sponge, Leiodermatium sp., resulted in the purification of leiodolide A, the major active compound in the organism. Leiodolide A displayed specific anti-Cryptosporidium activity at a half maximal effective concentration of 103.5 nM with selectivity indexes (SI) of 45.1, 11.9, 19.6 and 14.3 for human ileocecal colorectal adenocarcinoma cells (HCT-8), human hepatocellular carcinoma cells (Hep G2), human neuroblastoma cells (SH-SY5Y) and green monkey kidney cells (Vero), respectively. The unique structure of leiodolide A provides a valuable drug scaffold on which to develop new anti-Cryptosporidium compounds and supports the importance of screening natural product libraries for new chemical scaffolds.

Original languageEnglish (US)
Article number240
JournalMarine Drugs
Issue number4
StatePublished - Apr 2022

Bibliographical note

Funding Information:
Funding: This research was funded by the National Institutes of Health, National Institute of Allergy and Infectious Diseases grant number R21 AI138774. Support for preparation of the enriched fraction library was provided by grant number 1RC2AT005917 from The National Institutes of Health, National Center for Complementary and Integrative Health and the Harbor Branch Oceanographic Institute Foundation (HBOIF). Support for testing against Hep G2, SH-SY5Y and Vero cells was provided in part by a Research Excellence Grant to E.A.G. from the HBOIF. Support for bioassays involving C. parvum was provided in part by the Poncin Fellowship Fund to R.M.B.R. Partial stipend costs of R.M.B.R were covered by the Seattle Chapter of ARCS and the Washington Research Foundation.

Publisher Copyright:
© 2022 by the authors. Licensee MDPI, Basel, Switzerland.


  • Cryptosporidium
  • anti-protozoal compounds
  • apicomplexan
  • high-throughput screen
  • leiodolide A
  • marine natural products


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