Background: A diverse library of pre-fractionated plant extracts, generated by an automated high-throughput system, was tested using an in vitro anti-malarial screening platform to identify known or new natural products for lead development. The platform identifies hits on the basis of in vitro growth inhibition of Plasmodium falciparum and counter-screens for cytotoxicity to human foreskin fibroblast or embryonic kidney cell lines. The physical library was supplemented by early-stage collection of analytical data for each fraction to aid rapid identification of the active components within each screening hit. Results: A total of 16,177 fractions from 1300 plants were screened, identifying several P. falciparum inhibitory fractions from 35 plants. Although individual fractions were screened for bioactivity to ensure adequate signal in the analytical characterizations, fractions containing less than 2.0 mg of dry weight were combined to produce combined fractions (COMBIs). Fractions of active COMBIs had EC50 values of 0.21-50.28 and 0.08-20.04 μg/mL against chloroquine-sensitive and -resistant strains, respectively. In Berberis thunbergii, eight known alkaloids were dereplicated quickly from its COMBIs, but berberine was the most-active constituent against P. falciparum. The triterpenoids α-betulinic acid and β-betulinic acid of Eugenia rigida were also isolated as hits. Validation of the anti-malarial discovery platform was confirmed by these scaled isolations from B. thunbergii and E. rigida. Conclusions: These results demonstrate the value of curating and exploring a library of natural products for small molecule drug discovery. Attention given to the diversity of plant species represented in the library, focus on practical analytical data collection, and the use of counter-screens all facilitate the identification of anti-malarial compounds for lead development or new tools for chemical biology.
|State||Published - May 10 2016|
Bibliographical noteFunding Information:
The authors thank Dr. Vijayasankar Raman for providing plant collection, Dr. Bhar-athi Avula for recording mass spectra, Mr. Frank Wiggers for collecting NMR data, Mr. John Trott for anti-malarial assay support, and Ms. Maria Bennett for extract preparation. This work was supported, in part, by the USDA Agricultural Research Service Specific Cooperative Agreement No. 58-6408-1-603 and by ALSAC. MZ was supported by a scholarship from the Ministry of Higher Education of the Egyptian Government.
© 2016 Zhang et al.
- Berberis thunbergii
- Drug discovery
- Eugenia rigida
- Natural products
- Plasmodium falciparum
ASJC Scopus subject areas
- Infectious Diseases