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J Am Chem Soc. 2016 Feb 24;138(7):2209-18. doi: 10.1021/jacs.5b11575. Epub 2016 Feb 16.

Antibacterial Flavonoids from Medicinal Plants Covalently Inactivate Type III Protein Secretion Substrates.

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Laboratory of Chemical Biology and Microbial Pathogenesis, The Rockefeller University , New York, New York 10065, United States.
Institute of Biotechnology and Pharmaceutical Research, National Health Research Institutes , Zhunan Town, Miaoli County 35053, Taiwan, R.O.C.
Department of Microbial Pathogenesis, Yale University School of Medicine , New Haven, Connecticut 06536, United States.
Department of Pharmacology, Yale University School of Medicine , New Haven, Connecticut 06520, United States.


Traditional Chinese Medicines (TCMs) have been historically used to treat bacterial infections. However, the molecules responsible for these anti-infective properties and their potential mechanisms of action have remained elusive. Using a high-throughput assay for type III protein secretion in Salmonella enterica serovar Typhimurium, we discovered that several TCMs can attenuate this key virulence pathway without affecting bacterial growth. Among the active TCMs, we discovered that baicalein, a specific flavonoid from Scutellaria baicalensis, targets S. Typhimurium pathogenicity island-1 (SPI-1) type III secretion system (T3SS) effectors and translocases to inhibit bacterial invasion of epithelial cells. Structurally related flavonoids present in other TCMs, such as quercetin, also inactivated the SPI-1 T3SS and attenuated S. Typhimurium invasion. Our results demonstrate that specific plant metabolites from TCMs can directly interfere with key bacterial virulence pathways and reveal a previously unappreciated mechanism of action for anti-infective medicinal plants.

[Available on 2017-02-24]
[Indexed for MEDLINE]
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