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

Area of Science:

• Microbiology
• Pharmacology
• Natural Products Chemistry

Background:

• Traditional Chinese Medicines (TCMs) have a long history of use in treating bacterial infections.
• The specific active compounds and mechanisms underlying TCMs' anti-infective properties remain largely unknown.
• Bacterial type III secretion systems (T3SS) are critical virulence factors enabling pathogen invasion of host cells.

Purpose of the Study:

• To identify molecules from TCMs that can inhibit bacterial virulence pathways.
• To elucidate the mechanism by which active TCM compounds interfere with bacterial pathogenesis.
• To investigate the potential of plant-derived metabolites as novel anti-infective agents.

Main Methods:

• A high-throughput screening assay was employed to assess the impact of TCMs on Salmonella enterica serovar Typhimurium T3SS.
• The effect of active TCMs on bacterial growth and epithelial cell invasion was evaluated.
• Specific compounds, such as baicalein and quercetin, were identified and their targets within the T3SS were investigated.

Main Results:

• Several TCMs were found to attenuate the Salmonella T3SS without affecting bacterial viability.
• Baicalein, a flavonoid from Scutellaria baicalensis, was identified as a key inhibitor, targeting SPI-1 T3SS effectors and translocases.
• Baicalein and related flavonoids, like quercetin, effectively inhibited bacterial invasion of epithelial cells.

Conclusions:

• Specific plant metabolites within TCMs can directly target and inhibit critical bacterial virulence mechanisms, such as the T3SS.
• Flavonoids like baicalein represent a promising class of compounds for developing new anti-infective strategies.
• This study reveals a novel mechanism of action for anti-infective medicinal plants, highlighting their potential in modern medicine.